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Kamille Herskind,1 Peter Bjødstrup Jensen,1 Christina Anne Vinter,2– 4 Lone Krebs,5,6 Lene Friis Eskildsen,5 Anne Broe,1,7 Anton Pottegård,1 Mette Bliddal1,8 1Clinical Pharmacology, Pharmacy, and Environmental Medicine, Department of Public Health, University of Southern Denmark, Odense, Denmark; 2Department of Gynaecology and Obstetrics, Odense University Hospital, Odense, Denmark; 3Department of Clinical Research, University of Southern Denmark, Odense, Denmark; 4Steno Diabetes Center Odense, Odense University Hospital, Odense, Denmark; 5Department of Obstetrics and Gynecology, Copenhagen University Hospital-Amager and Hvidovre, Copenhagen, Denmark; 6Department of Clinical Medicine, University of Copenhagen, Copenhagen, Denmark; 7IQVIA, London, UK; 8Research Unit OPEN, Department of Clinical Research, University of Southern Denmark, Odense, DenmarkCorrespondence: Mette Bliddal, OPEN, Heden 16, St.tv, Odense, 5000, Denmark, Tel +45 2943 7912, Email mette.bliddal@rsyd.dkPurpose: This study aimed to systematically evaluate the validity of variables related to pregnancy, delivery, and key characteristics of the infant in the Danish National Patient Register using maternal medical records as the reference standard.Patients and Methods: We reviewed medical records of 1264 women giving birth in the Region of Southern Denmark during 2017. We calculated positive (PPV) and negative (NPV) predictive values, sensitivity, and specificity to estimate the validity of 49 selected variables.Results: The PPV was ≥ 0.90 on most pregnancy-related variables including parity, pre-gestational BMI, diabetes disorders, and previous cesarean section, while it was lower for hypertensive disorders, especially mild to moderate preeclampsia (0.49, 95% CI 0.32– 0.66). Sensitivity ranged from 0.80 to 1.00 on all pregnancy-related variables, except hypertensive disorders (sensitivity 0.38– 0.71, lowest for severe preeclampsia). On most delivery-related variables including obstetric surgical procedures (eg cesarean section and induction of labor), pharmacological pain-relief, and gestational age at delivery, PPV’s ranged from 0.98 to 1.00 and the corresponding sensitivities from 0.87 to 1.00. Regarding infant-related variables, both the APGAR score registered five minutes after delivery and birthweight yielded a PPV of 1.00.Conclusion: Obstetric coding in the Danish National Patient Register shows very high validity and completeness making it a valuable source for epidemiologic research.Plain Language Summary: Danish register data are often used for epidemiological research in reproduction. The registers are based on coded information to the registers based on information from medical records. The quality of the register data is highly dependent of the validity of the codes. Yet there is a lack in our knowledge of the validity of data related to pregnancy, childbirth, and the characteristics of the newborn baby. We therefore aimed to validate the Danish National Patient Registry data related to pregnancy and childbirth by comparing the registered code with information from the medical records.We scrutinized medical records from 1264 women giving birth in the Region of Southern Denmark during 2017. We compared the registration in the medical record with the registered code in the Danish National Patient Registry by calculating how accurate the register data are according to 49 different variables.Results showed that registered codes in the Patient Registry for pregnancy- and childbirth-related conditions and key infant characteristics were to a high degree in agreement with the data from the medical report with few exceptions.In conclusion, the study revealed that the Danish National Patient Register provides highly accurate and comprehensive data for most pregnancy, delivery, and infant-related variables. This underscores the register’s value as a reliable source for epidemiologic research in reproductive health.Keywords: registries, sensitivity and specificity, validity, epidemiology, pregnancy, delivery

Kasper Bruun Kristensen,1 Lars Christian Lund,1 Peter Bjødstrup Jensen,1 Anne Broe,1 Emelie Rotbain,2 Per Damkier,1,3,4 Anton Pottegård,1 Jacob Harbo Andersen,1 Mikkel Højlund,1,5 Morten Olesen,1 Lotte Rasmussen,1 Morten Rix Hansen,1,3,4 Martin Thomsen Ernst,1 Rikke Wesselhoeft,1,6 Daniel Pilsgaard Henriksen,3 Mette Reilev,1 Mette Bliddal,1,7 Jesper Hallas1 1Clinical Pharmacology, Pharmacy and Environmental Medicine, Department of Public Health, University of Southern Denmark, Odense, Denmark; 2Department of Hematology, Odense University Hospital, Odense, Denmark; 3Department of Clinical Pharmacology, Odense University Hospital, Odense, Denmark; 4Department of Clinical Research, University of Southern Denmark, Odense, Denmark; 5Department of Psychiatry Aabenraa, Mental Health Services in the Region of Southern Denmark, Aabenraa, Denmark; 6Child and Adolescent Psychiatry Odense, Mental Health Services in the Region of Southern Denmark, Odense, Denmark; 7Research Unit OPEN, Department of Clinical Research, University of Southern Denmark, Odense, DenmarkCorrespondence: Jesper Hallas, Clinical Pharmacology, Pharmacy and Environmental Medicine, Department of Public Health, University of Southern Denmark, J.B. Winsløws Vej 19, 2, Odense, 5000, Denmark, Tel +4565503010, Email jhallas@health.sdu.dkPurpose: To develop the Nordic Multimorbidity Index (NMI), a multimorbidity measure specifically suited to the Nordic health and administrative registry data based on current diagnosis, treatment, and coding practices.Methods: The NMI was developed to predict 5-year mortality in a population-based cohort of randomly sampled Danish residents aged ≥ 40 years (n = 425,087) followed from 2013 to 2018. Included predictors were selected from hospital diagnoses and filled drug prescriptions based on a combination of subject matter knowledge and a data-driven approach using backwards elimination. The performance of the NMI was assessed in a temporal validation cohort of Danish residents followed from 2007 to 2012 and in six cohorts of new users of selected drugs. The discriminative performance of the NMI, Charlson Comorbidity Index (CCI) and the Elixhauser Comorbidity Index (ECI) was assessed using the c-statistic from logistic regression models with 5-year mortality as dependent variable and the multimorbidity index score, age, and sex as independent variables.Results: The NMI included 50 predictors. In the temporal validation cohort, the c-statistic of the NMI (0.887, 95% CI 0.883– 0.890) exceeded that of the CCI (0.871, 95% CI 0.868– 0.874) and ECI (0.866, 95% CI 0.863– 0.870). In all new user cohorts, the NMI outperformed the other indices with c-statistics ranging from 0.781 (95% CI 0.779– 0.784) to 0.838 (95% CI 0.834– 0.842).Conclusion: The NMI predicted 5-year mortality in a general Danish population and six cohorts of new users of selected drugs and was superior to the CCI and ECI. The NMI could be preferred over these indices to quantify the level of multimorbidity for, eg, descriptive purposes or confounding control. The NMI should be validated in other patient populations and other Nordic countries.Keywords: multimorbidity, comorbidity, pharmacoepidemiology, prognosis, risk score

Anne Broe,1,2 Per Damkier,1,2 Anton Pottegård,3 Jesper Hallas,1,3 Mette Bliddal3,4 1Department of Clinical Biochemistry and Pharmacology, Odense University Hospital, Odense, Denmark; 2Department of Clinical Research, University of Southern Denmark, Odense, Denmark; 3Department of Clinical Pharmacology, Pharmacy, and Environmental Medicine, University of Southern Denmark, Odense, Denmark; 4Department of Clinical Research, Open Patient Data Explorative Network, University of Southern Denmark and Odense University Hospital, Odense, DenmarkCorrespondence: Anne BroeDepartment of Clinical Biochemistry & Pharmacology, Odense University Hospital, JB Winsløwsvej 19, 2, Odense 5000 Odense C, DenmarkEmail anbroe@health.sdu.dkBackground: Danish health registers are used widely to examine associations between specific risk factors and congenital malformations. Various overall prevalence rates of malformations have been reported in Denmark indicating differences in the underlying data sources or malformation definitions. We described trends in registration of malformations in Denmark 1997– 2017 and identified potential caveats for the use of Danish health registries in epidemiological studies. We composed a Danish adaptation of EUROCATs definition of malformations.Methods: Using nationwide Danish health registries, we identified all recorded pregnancies and followed livebirths for up to 5 years. We described the different data sources, ways to identify malformations, the overall rate of malformations over time, and identified the 10 most common major malformations.Results: A total of 1,340,774 foetuses and infants from 1,313,281 pregnancies among 747,144 women from 1997 to 2017 were analysed. Using primary and secondary diagnoses from all available sources and restricting hip malformations to diagnoses after 6 weeks postpartum, we found that 65,411 (49/1000) foetuses or infants had at least one major malformation defined by our Danish translation of EUROCATs definition of malformations. The prevalence of major malformations increased over time from 39/1000 in 1997 to 53/1000 in 2017. The most common specific malformations were malformations of cardiac septa (Q21) and great arteries (Q25) with a peak of 10 and 6/1000 births in 2010 and 2009, respectively.Conclusion: Malformations should be identified using primary and secondary diagnoses from the Birth register, the Patient register, and the Cause of Death register. To increase transparency and external validity, classification of major malformations should be based on the Danish adaptation of EUROCATs classification of malformations.Keywords: malformations, anomalies, health registries, epidemiology, EUROCAT

Objective: To compare antidepressant utilization in individuals aged 5–19 years from the Scandinavian countries. Methods: A population‐based drug utilization study using publicly available data of antidepressant use from Denmark, Norway, and Sweden. Results: In the study period from 2007 to 2017, the proportion of antidepressant users increased markedly in Sweden (9.3–18.0/1000) compared to Norway (5.1–7.6/1000) and Denmark (9.3–7.5/1000). In 2017, the cumulated defined daily doses (DDD) of selective serotonin reuptake inhibitors were 5611/1000 inhabitants in Sweden, 2709/1000 in Denmark, and 1848/1000 in Norway. The use of 'other antidepressants' (ATC code N06AX) also increased in Sweden with a higher DDD in 2017 (497/1000) compared to Denmark (225/1000) and Norway (170/1000). The use of tricyclic antidepressants was generally low in 2017 with DDDs ranging between 30–42 per 1000. The proportion of antidepressant users was highest among 15‐ to 19‐year‐old individuals. Girls were more likely to receive treatment than boys, and the treated female/male ratios per 1000 were similar in Sweden (2.39), Denmark (2.44), and Norway (2.63). Conclusion: Even in highly comparable healthcare systems like the Scandinavian countries', variation in antidepressant use is considerable. Swedish children and adolescents have a markedly higher and still increasing use of antidepressants compared to Danish and Norwegian peers. [ABSTRACT FROM AUTHOR]

Background: Parents of twins appear to be at increased risk of postpartum depression (PPD), yet little is known about the magnitude and timing of onset in the postpartum period compared to singleton parents., Methods: We conducted a cohort study using the Danish nationwide health registers. We defined a study population of parents that is, mothers and fathers of all twin and singleton livebirths between 1997 and 2019. Postpartum depression was defined as incident depression diagnosis or a redeemed antidepressant prescription from childbirth through 365 days postpartum. We performed a parametric time-to-event analysis based on Poisson regression. The time scale was time since birth, modeled using restricted cubic splines. From this we estimated the hazard ratio (HR) representing the momentary risk, and the cumulative risk ratio (RR) over the first year postpartum, in twin compared to singleton parents., Results: The study population was based on 27,095 twin and 1,350,046 singleton births. In adjusted analyses, the HR of twins compared to singletons was highest around 2 months postpartum (HR 1.28, 95% CI 1.10-1.49) for mothers, and around 6 months (1.20, 95% CI 1.02-1.42) for fathers. The 6 months adjusted cumulative RR of PPD in twins compared to singletons was 1.24 (95% CI 1.10-1.40) for mothers and 1.11 (95% CI 0.95-1.30) for fathers., Conclusions: Twin mothers had increased risk of PPD compared to singleton mothers, which was driven by an immediate increase after childbirth. The risk among twin fathers was not increased immediately after childbirth, but we found slightly elevated risk around 6 months postpartum. This could suggest diverse patterns of PPD symptomatology in twin parents compared to singleton parents and between mothers and fathers. Our findings underline parents of twins as a potentially vulnerable group to PPD and emphasize the need for increased awareness of their mental health., (© 2024 The Author(s). Acta Psychiatrica Scandinavica published by John Wiley & Sons Ltd.)

Purpose: Infertility is common and an increasing number of women go through medically assisted reproduction (fertility treatment) to achieve pregnancy. This may affect mental health. We examined if fertility treatment and the specific fertility treatment method used (in vivo or in vitro) were associated with impaired mental health during or after pregnancy., Methods: Using self-reported data from the Odense Child Cohort, we assessed prenatal stress by the 10-item Cohen Perceived Stress Scale (PSS-10) during pregnancy at median gestational week 27 and postnatal depressive symptoms by the Edinburgh Postnatal Depression Scale (EPDS) at median postpartum week 15. We compared fertility-treated women overall and by fertility treatment method to women who conceived spontaneously. We conducted linear regression analyses to evaluate the PSS-10 score dimensionally and logistic regression to evaluate EPDS scores above cut-off (≥ 11)., Results: A total of 108 of 820 women (13%) gave birth after fertility treatment. Their prenatal mean stress (PSS-10) score was 11.38 compared to 11.78 for women who conceived spontaneously, leading to an adjusted mean difference of -0.09 points (95% confidence interval (CI): -1.88 to 1.69). In the fertility-treated group, 9.7% had EPDS scores ≥ 11 compared to 10.7% in the spontaneous conception group (adjusted odds ratio of 0.71 (95% CI: 0.26 to 1.91)). The MAR method (in vivo/vitro) did not influence these results., Conclusion: Women who gave birth after fertility treatment did not report higher levels of prenatal stress or postpartum depressive symptoms than women who conceived spontaneously., Competing Interests: Declarations. Ethical approval and consent: All participants in the OCC provided written consent for their participation (Kyhl et al. 2015). The data was pseudonymized and kept according to current legislation. The study was registered at the repository of the Region Southern Denmark (22/58886, December 13, 2022). Competing interests: None., (© 2024. The Author(s).)

Preclinical data suggest that gestational exposure to selective serotonin reuptake inhibitors (SSRI) alter gut innervation, and delays colonic motility. In this study we investigated associations between gestational SSRI exposure and offspring disorders of gut-brain interaction (DGBI). Using population-based registries, we included all single-birth Danish children born 1997-2015 with follow-up until outcome occurrence, age 15 years, death, emigration, or December 2018. Children to mothers who continued SSRIs during pregnancy and children to mothers who discontinued SSRI use before pregnancy were compared using Cox regression. Main outcomes were the first diagnosis of a childhood DGBI (functional nausea and vomiting, functional abdominal pain disorders, functional diarrhea, and functional constipation), or a physician-prescribed laxative. Among 1,158,560 children, 21,969 children (1.9%) were exposed to SSRIs prenatally and 30,174 children (2.6%) were born to mothers who discontinued SSRIs before pregnancy. Overall, the estimated 15-year cumulative incidence of any DGBI was 15.5% (95% CI, 14.9-16.2) in the SSRI-exposed group and 14.7% (14.0-15.3) in the unexposed group. SSRI-exposed children had an overall increased risk of DGBIs (HR 1.08, [1.02-1.14]), which was driven by functional constipation (HR 1.19, [1.10-1.28]) rather than functional nausea and vomiting (HR 0.97, [0.83-1.13]) or functional abdominal pain disorders (HR 0.90, [0.81-1.00]). These data suggest that prenatal SSRI exposure is associated with an increased risk of developing functional constipation. These findings are also consistent with extensive preclinical data supporting key roles for serotonin in gut development and function. Together findings support the need for further investigation of the long-term impact of maternal depression and SSRI exposure on development of common gastrointestinal disorders., Competing Interests: Competing interests: AP reports funds paid to his institution for participation in research projects funded by Alcon, Almirall, Astellas, AstraZeneca, Boehringer Ingelheim, Novo Nordisk, Servier, and LEO Pharma, outside the current work. All other authors have no disclosures., (© 2024. The Author(s), under exclusive licence to Springer Nature Limited.)

Importance: In pregnancy, the benefits of lithium treatment for relapse prevention in psychiatric conditions must be weighed against potential teratogenic effects. Currently, there is a paucity of information on how and when lithium is used by pregnant women., Objective: To examine lithium use in the perinatal period., Design, Setting, and Participants: This cohort study used individual-level data of pregnancies from January 1, 2000, to December 31, 2021, in Australia, Denmark, Finland, Germany, Hong Kong, Iceland, Israel, New Zealand, Norway, South Korea, Sweden, Taiwan, the UK, and 2 cohorts in the US. Analyses were performed from September 1 to November 30, 2023., Exposures: The prevalence of lithium use as the proportion of pregnancies with at least 1 prescription fill or prescription within 3 months before pregnancy until childbirth was estimated using a common protocol. Lithium use during pregnancy by trimester and in the 3 months before and after pregnancy was examined., Main Outcomes and Measures: Comparison of prevalence between the first and last 3-year periods of available data., Results: Among 21 659 454 pregnancies from all collaborating sites, the prevalence of lithium use ranged from 0.07 per 1000 pregnancies in Hong Kong to 1.56 per 1000 in the US publicly insured population. Lithium use increased per 1000 pregnancies in 10 populations (Australia [0.60 to 0.74], Denmark [0.09 to 0.51], Finland [0.10 to 0.29], Iceland [0.24 to 0.99], Israel [0.25 to 0.37], Norway [0.24 to 0.47], South Korea [0.30 to 0.44], Sweden [0.42 to 1.07], the UK [0.07 to 0.10], and Taiwan [0.15 to 0.19]), remained stable in 4 populations (Germany [0.17 to 0.16], Hong Kong [0.06 to 0.06], and the publicly [1.50 to 1.34] and commercially [0.38 to 0.36] insured US populations), and decreased in 1 population (New Zealand [0.54 to 0.39]). Use of lithium decreased with each trimester of pregnancy, while prevalence of postpartum use was similar to prepregnancy levels. The proportion of lithium use in the second trimester compared with the prepregnancy period ranged from 2% in South Korea to 80% in Denmark., Conclusions and Relevance: Prevalence of lithium use in pregnant women over the past 2 decades varied markedly between populations. Patterns of use before, during, and after pregnancy suggest that many women discontinued lithium use during pregnancy and reinitiated treatment after childbirth, with large variations between countries. These findings underscore the need for internationally harmonized guidelines, specifically for psychiatric conditions among pregnant women that may benefit from lithium treatment.

Background: Little is known about the time trends of postpartum depression (PPD) and whether they differ from time trends of depression among women in general., Methods: Using Danish health registers, we identified a postpartum population from all women who had a liveborn child from 2000-2022. We sampled a background population by matching five women for each delivery on age and date of childbirth. Depression and PPD were measured as incident depression diagnosis or redeemed antidepressant prescription within 180 days from childbirth/matching. We described incidence rates from 2000-2022 using Poisson regression with a restricted cubic spline., Results: The study population included 1,133,947 postpartum women (669,101 unique), matched to 5,669,735 women (1,165,505 unique). Overall IR per 10,000 person-years of diagnoses was 34.3 (95% CI: 32.8-35.9) for PPD and 18.9 (95% CI: 18.3-19.4) for depression. Both IRs increased similarly over time in the main analyses, but more pronounced for PPD in primiparous and older mothers. Correspondingly, IR for prescriptions was 135.7 (95% CI: 132.7-138.8) for PPD and 209.8 (95% CI: 208.1-211.5) for depression, and both groups had fluctuating time trends., Limitations: Depression measures were based on women who actively sought and received treatment, expectedly underestimating true disease incidence., Conclusions: Incidence rates of PPD and depression diagnoses increased over time, especially for PPD among primiparous and older mothers. These findings could suggest either increased vulnerability or increased awareness and detection over time in these groups. Fluctuating trends overserved from prescriptions could likely be driven by external factors and not a reflection of disease trends., Competing Interests: Declaration of competing interest Trine Munk-Olsen has received honorarium as a speaker for Lundbeck Pharma A/S. Remaining authors: Nothing to declare., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

Objectives: The Bacillus Calmette-Guérin (BCG) vaccine may induce non-specific protection against unrelated infections. We tested the effect of BCG on the risk of infections among Danish senior citizens., Methods: Single-blinded randomised controlled trial including 1676 volunteers >65 years. Participants were randomised 1:1 to BCG or placebo and followed for 12 months. The primary outcome was acute infection leading to medical contact. Secondary outcomes were verified SARS-CoV-2 infection, self-reported respiratory symptoms, and all-cause hospitalisation. Data was analysed using Cox regression models, estimating hazard ratios (HR) with 95% confidence intervals (CI)., Results: The incidence of acute infection was 52.1 and 58.2 per 100 person-years for BCG and placebo, respectively (HR=0.89, 95% CI=0.78-1.02). There was no effect of BCG on SARS-CoV-2 infections (0.97, 0.75-1.26) or all-cause hospitalisations (1.10, 0.80-1.50), but BCG was associated with more respiratory symptoms (1.21, 1.10-1.33). BCG reduced the incidence of acute infections among participants <75 years (0.82, 0.70-0.95) but not among those >75 years (1.14, 0.88-1.47). In participants, who were COVID-19 vaccinated before enrolment, BCG was associated with lower incidence of acute infections (0.65, 0.50-0.85)., Conclusion: BCG did not reduce risk of acute infections among Danish seniors overall, but the effect was modified by age group and COVID-19 vaccination., Trial Registration: ClinicalTrials.gov (NCT04542330) and EU Clinical Trials Register (EudraCT number 2020-003904-15). Full trial protocol is available at ClinicalTrials.gov., Summary: In a randomised clinical trial among Danish senior citizens, BCG vaccination did not reduce the overall risk of acute infection, but BCG was associated with reduced risk in participants <75 years and participants who received COVID-19 vaccines prior to enrolment., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Objective: To assess incidence rates of clinically diagnosed eating disorders among Danish youth before, during, and after the COVID-19 pandemic., Method: This study used a population-based time series analysis with individual-level data from Danish healthcare registries. Participants included all Danish individuals aged 6-24 years from January 1, 2015, to December 31, 2023. Monthly incident cases of any eating disorder, anorexia nervosa, and bulimia nervosa were analyzed using interrupted time-series analysis. We estimated the cumulative number of excess cases of incident eating disorder diagnoses and risk ratios (RR) associated with the pandemic and post-pandemic periods compared with pre-pandemic predictions., Results: The study population encountered a mean of 1,310,542 individuals during the study period. The study included 11,693 individuals diagnosed with an eating disorder, median age 17 (IQR 14-20 years). Incident cases increased during the pandemic (RR 1.29, 95% CI 1.15-1.45) and normalized post-pandemic (RR 1.07, 95% CI 0.91-1.25) compared with pre-pandemic predictions. Similar patterns were seen for anorexia and bulimia. Increases were significant for ages 13-16 (RR 1.19, 95% CI 1.02-1.38), 17-19 (RR 1.51, 95% CI 1.25-1.83), and 20-24 (RR 1.35, 95% CI 1.12-1.64). Post-pandemically, a continued increase was observed only for ages 20-24 (RR 1.32, 95% CI 1.02-1.71)., Conclusions: The study documents a temporary increase in diagnosed eating disorders among Danish youths during the COVID-19 pandemic, with rates later returning to pre-pandemic levels. These results provide insights into the pandemic's impact on adolescents and youths., (© 2024 The Author(s). International Journal of Eating Disorders published by Wiley Periodicals LLC.)

Purpose: The healthcare systems in Scandinavia inform nationwide registers and the Scandinavian populations are increasingly combined in research. We aimed to compare Norway (NO), Sweden (SE), and Denmark (DK) regarding sociodemographic factors and healthcare., Methods: In this cross-sectional study, we analyzed aggregated data from the nationwide Scandinavian registers. We calculated country-specific statistics on sociodemographic factors and healthcare use (general practitioner visits, admissions to somatic hospitals, and use of medicines)., Results: In 2018, population were 5295,619 (NO), 10,120,242 (SE), and 5781,190 (DK). The populations were comparable regarding sex, age, education, and income distribution. Overall, medication use was comparable, while there was more variation in hospital admissions and general practitioner visits. For example, per 1000 inhabitants, 703 (NO), 665 (SE), and 711 (DK) individuals redeemed a prescription, whereas there were 215 (NO), 134 (SE), and 228 (DK) somatic hospital admissions per 1000 inhabitants. General practitioner contacts per 1000 inhabitants were 7082 in DK and 5773 in NO (-data from SE)., Conclusion: The Scandinavian countries are comparable regarding aggregate-level sociodemographic factors and medication use. Variations are noted in healthcare utilisation as measured by visits to general practitioners and admissions to hospitals. This variation should be considered when comparing data from the Scandinavian countries., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

The HOPE cohort is a Danish nationwide cohort with ongoing follow-up, holding information on postpartum depression (PPD) symptoms and diagnoses on 170,218 childbirths (142,795 unique mothers). These data have been linked with extensive register data on health and socioeconomic information on the mothers, their partners, parents, and children. This cohort profile aimed to provide an overview of the data collection and content, describe characteristics, and evaluate potential selection bias. PPD screenings, using the Edinburgh Postnatal Depression Scale, were collected from 67 of the 98 Danish municipalities, covering the period January 2015 to December 2021. This data was linked with register data on PPD diagnoses (identified through medication prescriptions and hospital contacts) as well as background information. Cohort characteristics were compared to the source population, defined as all childbirths by women residing in Denmark during the same period (452,207 childbirths). Potential selection bias was evaluated by comparing odds ratios of five well-established associations between the cohort and the source population. The HOPE cohort holds information on 170,218 childbirths (38% of the source population) involving 142,795 unique mothers. The HOPE cohort only differed slightly from the source population on most characteristics examined, but larger differences were observed on specific characteristics with an underrepresentation of the youngest and oldest age groups, women with more than three children or twins/triplets, and women born outside Denmark. Similar associations were identified across the two populations within the five well-established associations. There was no indication of selection bias on the five examined associations, and the HOPE cohort is representative of the source population on important perinatal characteristics., (© 2024. The Author(s).)

The aim of this study was to examine variations in use of antidepressants among children and adolescents in the three Scandinavian countries (Sweden, Norway, and Denmark). We identified new users of antidepressants (5-17 years) during 2007-2018 and described the annual incidence rate, treatment duration, concomitant psychotropic drug use, and the clinical setting of the prescribing physician (in Sweden and Denmark). Incident use of antidepressants increased by a factor 1.9 in Sweden, 1.3 in Norway and decreased by a factor 0.6 in Denmark during the study period. In Sweden, 58% of antidepressant users were covered by a prescription 12 months after initiation compared to 40% in Norway and 49% in Denmark. Also, 34% of Swedish antidepressant users were in continuous treatment after 12 months compared to 26% in Norway and 31% in Denmark. Concomitant use of other psychotropics was more common in Sweden (57%) than in Norway (37%) and Denmark (27%). During 2007-2018, clinicians from psychiatry settings initiated 75% of antidepressant treatments in Sweden, while this was the case for 50% of prescriptions in Denmark, although the proportion increased over time. The number of new antidepressant users is high and still rising in Sweden compared to Norway and Denmark. Swedish antidepressant users are more likely to use other psychotropics and to be covered by an antidepressant prescription after one year. Most antidepressants in Sweden are prescribed by physicians within psychiatric settings suggesting that they are based on specialized psychiatric evaluation., (© 2024. The Author(s).)

Background: An increasing number of women of reproductive age are treated with attention-deficit hyperactivity disorder (ADHD) medication; however, patterns of ADHD medication use for women in the perinatal period have not been well described., Objective: This study aimed to describe ADHD medication use patterns from 1 year before pregnancy to 1 year after delivery, and to describe sociodemographic characteristics and clinical features by medication trajectories., Methods: The population-based cohort study included pregnancies in Denmark between 1997 and 2020, from the Medical Birth Register, by women who filled at least one prescription for ADHD medication from 12 months before pregnancy until 12 months after delivery. We applied group-based trajectory modeling to classify women into subgroups based on the identification of heterogeneous ADHD medication treatment patterns, and described the characteristics associated with these groups., Results: Overall, we included 4717 pregnancies leading to liveborn singletons by 4052 mothers with a mean (standard deviation) age of 27.5 (5.6) years. We identified four treatment trajectories across pregnancy and the postpartum period: continuers (23.3%), discontinuers (41.8%), interrupters who ceased filling prescriptions during pregnancy but resumed postpartum (17.2%), and postpartum initiators (17.7%). Continuers were older at the time of conception, gave birth in more recent years, were more likely to smoke during pregnancy, and used other psychotropic medications during pregnancy. A large proportion of continuers used methylphenidate (89.1%) compared with the other groups (75.9-84.1%) and had switched ADHD medication type during the whole period (16.4% vs. 7.4-14.8%)., Conclusion: We found that approximately 60% of women discontinued or interrupted their ADHD medication around pregnancy, and those who continued differed in sociodemographic and clinical factors that may reflect more severe ADHD., (© 2024. The Author(s).)

Background: Conduct disorders (CD) are among the most frequent psychiatric disorders in children and adolescents, with an estimated worldwide prevalence in the community of 2-4%. Evidence-based psychological outpatient treatment leads to significant improvement in about two-thirds of cases. However, there seems to be considerable variation in rates of CD diagnoses and implementation of evidence-based interventions between nations. The aim of this study was to compare administrative prevalence and treatment patterns for CD in children and adolescents seen in health care systems across four Western countries (Denmark, Germany, Norway, and the USA)., Methods: Cross-sectional observational study using healthcare data to identify children and adolescents (aged 0-19 years) with an ICD-10 code for CD within the calendar year 2018. Within each country's study population, the prevalence of CD, psychiatric comorbidity, psychopharmacological treatment, and psychiatric hospitalisation was calculated., Results: The prevalence of diagnosed CD differed 31-fold between countries: 0.1% (Denmark), 0.3% (Norway), 1.1% (USA) and 3.1% (Germany), with a male/female ratio of 2.0-2.5:1. The rate of psychiatric comorbidity ranged from 69.7 to 86.1%, with attention-deficit/hyperactivity disorder being most common. Between 4.0% (Germany) and 12.2% (USA) of youths with a CD diagnosis were prescribed antipsychotic medication, and 1.2% (Norway) to 12.5% (Germany) underwent psychiatric hospitalisation., Conclusion: Recognition and characteristics of youths diagnosed with CD varied greatly by country. In some countries, the administrative prevalence of diagnosed CD was markedly lower than the average estimated worldwide prevalence. This variation might reflect country-specific differences in CD prevalence, referral thresholds for mental health care, diagnostic tradition, and international variation in service organisation, CD recognition, and availability of treatment offers for youths with CD. The rather high rates of antipsychotic prescription and hospitalisation in some countries are remarkable, due to the lack of evidence for these therapeutic approaches. These findings stress the need of prioritising evidence-based treatment options in CD. Future research should focus on possible reasons for inter-country variation in recognition and management of CD, and also address possible differences in patient-level outcomes., (© 2024. The Author(s).)

We aimed to provide a detailed description of the use of melatonin in Danish children, adolescents, and young adults during 2012-2019. We identified melatonin users 0-24 years of age (n = 43,652; median age 16 years) via the Danish nationwide health registers. Melatonin is a prescription drug in Denmark. The incidence of melatonin use increased from 2.4 to 3.9/1000 person-years during 2012 to 2019. Among 6,557 incident users in 2019, 53% filled only a single prescription within the first 6 months. Long-term use was most common among the younger age groups, with 17% of 5-9-year-olds and 14% of 10-13-year-olds being in continued treatment (no treatment breaks) 12 months after their first melatonin prescription. Disregarding treatment breaks, 3 in 10 were using melatonin 12 months after their first melatonin prescription and this proportion was also highest among 5-9-year-olds (63%) and 10-13-year-olds (51%). Psychopathology was common among melatonin users with 75% registered with either a psychiatric disorder diagnosis (54%), a filled prescription for another psychotropic (58%), or a contact to a private practice psychiatrist (15%) within ± 12 months of treatment initiation. General practitioners authorized melatonin prescriptions to almost half of all new users (48%), while psychiatric specialists authorized 37% of first prescriptions. In conclusion, the incidence of melatonin use increased in Denmark from 2012 to 2019. A substantial proportion of users had concurrent psychopathology most likely explaining their use of melatonin. Long-term melatonin use was more common among the youngest age groups, which should be a focus of interest due to limited safety data., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany.)

Objective: Use of opioids in pregnancy is of concern yet little is known on opioid prescription patterns in Denmark. The aim of this drug utilization study was to describe prescription patterns for opioids during pregnancy in Denmark from 1997 to 2016., Study Design: Using the nationwide health care registers, we obtained information on all women with a registered pregnancy in the period 1 January 1997 to 31 December 2016. Opioids were grouped in four: opioids (N02A except codeines), opioid dependency medications (N07BC), cough medications (R05DA except codeines), and codeines (N02AJ06, N02AJ07, N02BA75, and R05DA04). We used logistic regression analyses to identify factors associated with opioid use in pregnancy and cumulative oral morphine equivalent (OMEQ) to estimate volume of use in pregnancy., Results: Prescription patterns were similar for women with live births, non-live births, and terminations. Total use of opioids among women with live born deliveries remained stable at 19.8 per 1000 pregnancies from 1997 to 2016. Codeine use declined from 2008 onwards, while use of other opioids increased from 2007 onwards. This was dominated by a threefold increase in tramadol use (2.0-7.6 per 1000 pregnancies with live births). Codeine was the most used opioid, followed by tramadol and codeine combined with paracetamol. The number of women, who used opioids before pregnancy and continued into their pregnancy, was reduced as the pregnancy progressed. The cumulative oral morphine equivalent during pregnancy was stable until 2007, after which, use prior to pregnancy and during the first two trimesters increased. The odds ratios for opioid use were higher in pregnancies of women of lower socioeconomic status or older age. For live births, odds ratios for opioid use in pregnancy were higher among women with obesity or smoking., Conclusions: Overall use of opioids was stable from 2007 to 2016. This covers a decline in the use of codeine, but a 3-fold increase in tramadol. The number of pregnant women who continued use throughout pregnancy decreased, while OMEQ among persistent users increased. The real-world data suggest an unmet need of specific focus in local Danish Outpatient Clinics and Multidisciplinary Pain Centers both pre-conceptionally and during pregnancy., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Author(s). Published by Elsevier B.V. All rights reserved.)

Background: The emergence of the COVID-19 pandemic and the derived changes in maternity care have created stress and anxiety among pregnant women in different parts of the world. In times of stress and crisis, spirituality, including spiritual and religious practices, may increase., Objective: To describe if the COVID-19 pandemic influenced pregnant women's considerations and practises of existential meaning-making and to investigate such considerations and practices during the early pandemic in a large nationwide sample., Methods: We used survey data from a nationwide cross-sectional study sent to all registered pregnant women in Denmark during April and May 2020. We used questions from four core items on prayer and meditation practices., Results: A total of 30,995 women were invited, of whom 16,380 participated (53%). Among respondents, we found that 44% considered themselves believers, 29% confirmed a specific form of prayer, and 18% confirmed a specific form of meditation. In addition, most respondents (88%) reported that the COVID-19 pandemic had not influenced their responses., Conclusion: In a nationwide Danish cohort of pregnant women, existential meaning-making considerations and practices were not changed due to the COVID-19 pandemic. Nearly one in two study participants described themselves as believers, and many practised prayer and/or meditation., Competing Interests: Declaration of Competing Interest None of the authors have financial or other conflicts of interests related to the subject of this study., (Copyright © 2023. Published by Elsevier Ltd.)

Background: Currently, melatonin is used to treat children and adolescents with insomnia without knowing the full extent of the short-term and long-term consequences. Our aim was to provide clinicians and guideline panels with a systematic assessment of serious-and non-serious adverse events seen in continuation of melatonin treatment and the impact on pubertal development and bone health following long-term administration in children and adolescents with chronic insomnia., Methods: We searched PubMed, Embase, Cinahl and PsycINFO via Ovid, up to March 17, 2023, for studies on melatonin treatment among children and adolescents (aged 5-20 years) with chronic insomnia. The language was restricted to English, Danish, Norwegian, and Swedish. Outcomes were non-serious adverse events and serious adverse events assessed 2-4 weeks after initiating treatment and pubertal development and bone health, with no restriction on definition or time of measurement. Observational studies were included for the assessment of long-term outcomes, and serious and non-serious adverse events were assessed via randomised studies. The certainty of the evidence was assessed using Grades of Recommendation, Assessment, Development and Evaluation (GRADE). The protocol is registered with the Danish Health Authority., Findings: We identified 22 randomised studies with 1350 patients reporting on serious-and non-serious adverse events and four observational studies with a total of 105 patients reporting on pubertal development. Melatonin was not associated with serious adverse events, yet the number of patients experiencing non-serious adverse events was increased (Relative risk 1.56, 95% CI 1.01-2.43, 17 studies, I 2  = 47%). Three studies reported little or no influence on pubertal development following 2-4 years of treatment, whereas one study registered a potential delay following longer treatment durations (>7 years). These findings need further evaluation due to several methodological limitations., Interpretation: Children who use melatonin are likely to experience non-serious adverse events, yet the actual extent to which melatonin leads to non-serious adverse events and the long-term consequences remain uncertain. This major gap of knowledge on safety calls for caution against complacent use of melatonin in children and adolescents with chronic insomnia and for more research to inform clinicians and guideline panels on this key issue., Funding: The Danish Health Authority. The Parker Institute, Bispebjerg and Frederiksberg Hospital, supported by the Oak Foundation., Competing Interests: LB is a member of the Danish medication reimbursement committee. AV has previously received honoraria for lectures at AGB pharma, Takeda & Medice, and holds stocks at Novo Nordisk. All other authors declare no competing interests. Statements of conflicts of interests can be found for all members of the guideline panel, the external reviewer of the national clinical guideline, the reference–and project group at the Danish Health Authority website (www.sst.dk)., (© 2023 The Authors.)

Background: Selective serotonin reuptake inhibitors (SSRIs) are the most frequently prescribed antidepressants in pregnancy. Animal and some clinical studies have suggested potential increases in depression and anxiety following prenatal SSRI exposure, but the extent to which these are driven by the medication remains unclear. We used Danish population data to test associations between maternal SSRI use during pregnancy and children outcomes up to age 22., Methods: We prospectively followed 1,094,202 single-birth Danish children born 1997-2015. The primary exposure was ≥ 1 SSRI prescription filled during pregnancy; the primary outcome, first diagnosis of a depressive, anxiety, or adjustment disorder, or redeemed prescription for an antidepressant medication. We used propensity score weights to adjust potential confounders, and incorporated data from the Danish National Birth Cohort (1997-2003) to further quantify potential residual confounding by subclinical factors., Results: The final dataset included 15,651 exposed and 896,818 unexposed, children. After adjustments, SSRI-exposed had higher rates of the primary outcome than those of mothers who either did not use an SSRI (HR = 1.55 [95%CI:1.44,1.67] or discontinued the SSRI use ≥ 3 months prior to conception (HR = 1.23 [1.13,1.34]). Age of onset was earlier among exposed (9 [IQR:7-13] years) versus unexposed (12 [IQR:12-17] years) children (p < 0.01). Paternal SSRI use in the absence of maternal use during the index pregnancy (HR = 1.46 [1.35,1.58]) and maternal SSRI use only after pregnancy (HR = 1.42 [1.35,1.49]) were each also associated with these outcomes., Conclusions: While SSRI exposure was associated with increased risk in the children, this risk may be driven at least partly by underlying severity of maternal illness or other confounding factors., (© 2023. The Author(s).)

Introduction: We identified risk factors and outcomes associated with SARS-CoV-2 infection in pregnancy in a universally tested population according to disease severity and validated information on SARS-CoV-2 during pregnancy in national health registers in Denmark., Material and Methods: Cohort study using data from national registers and medical records including all pregnancies between March 1, 2020 and February 28, 2021. We compared women with a validated positive SARS-CoV-2 test during pregnancy with non-infected pregnant women. Risk factors and pregnancy outcomes were assessed by Poisson and Cox regression models and stratified according to disease severity defined by hospital admission status and admission reason (COVID-19 symptoms or other). Using medical record data on actual period of pregnancy, we calculated predictive values of the SARS-CoV-2 diagnosis in pregnancy in the registers., Results: SARS-CoV-2 infection was detected in 1819 (1.6%) of 111 185 pregnancies. Asthma was associated with infection (relative risk [RR] 1.63, 95% confidence interval [CI] 1.28-2.07). Risk factors for severe COVID-19 disease requiring hospital admission were high body mass index (median ratio 1.06, 95% CI 1.04-1.09), asthma (RR 7.47, 95% CI 3.51-15.90) and gestational age at the time of infection (gestational age 28-36 vs < 22: RR 3.53, 95% CI 1.75-7.10). SARS-CoV-2-infected women more frequently had hypertensive disorders in pregnancy (adjusted hazard ratio [aHR] 1.31, 95% CI 1.04-1.64), early pregnancy loss (aHR 1.37, 95% CI 1.00-1.88), preterm delivery before gestational age 28 (aHR 2.31, 95% CI 1.01-5.26), iatrogenically preterm delivery before gestational age 37 (aHR 1.49, 95% CI 1.01-2.19) and small-for-gestational age children (aHR 1.28, 95% CI 1.05-1.54). The associations were stronger among women admitted to hospital for any reason. The validity of the SARS-CoV-2 diagnosis in relation to pregnancy in the registers compared with medical records showed a negative predictive value of 99.9 (95% CI 99.9-100.0) and a positive predictive value of 82.1 (95% CI 80.4-83.7)., Conclusions: Women infected with SARS-CoV-2 during pregnancy were at increased risk of hypertensive disorders in pregnancy, early pregnancy loss, preterm delivery and having children small for gestational age. The validity of Danish national registers was acceptable for identification of SARS-CoV-2 infection during pregnancy., (© 2023 The Authors. Acta Obstetricia et Gynecologica Scandinavica published by John Wiley & Sons Ltd on behalf of Nordic Federation of Societies of Obstetrics and Gynecology (NFOG).)

Importance: Existing observational data have indicated positive associations of acid-suppressive medication (ASM) use in prenatal and early life with allergic diseases in children; however, no study to date has accounted for confounding by indication or within-familial factors., Objective: To evaluate the association of prenatal or infant exposure to ASMs with risk of allergic diseases in children., Design, Setting, and Participants: This nationwide, cohort study included data from South Korea's National Health Insurance Service mother-child-linked database from January 1, 2007, to December 31, 2020. Participants included mother-child pairs of neonates born from April 1, 2008, to December 31, 2019., Exposures: Prenatal and infant exposure to ASMs (histamine 2 receptor antagonists [H2RAs] and proton pump inhibitors [PPIs])., Main Outcomes and Measures: Composite and individual outcomes of allergic diseases (asthma, allergic rhinitis, atopic dermatitis, and food allergy) in children (followed up to 13 years of age) were assessed. The ASM-exposed individuals were compared with unexposed individuals in propensity score (PS)-matched and sibling-matched analyses to control for various potential confounders and within-familial factors. Hazard ratios (HRs) with 95% CIs were estimated using Cox proportional hazards regression models., Results: The study included 4 149 257 mother-child pairs. Prenatal exposure analyses included 808 067 PS-matched pairs (763 755 received H2RAs, 36 529 received PPIs) among women with a mean (SD) age of 31.8 (4.2) years. The PS-matched HR was 1.01 (95% CI, 1.01-1.02) for allergic diseases overall (asthma: HR, 1.02 [95% CI, 1.01-1.03]; allergic rhinitis: HR, 1.02 [95% CI, 1.01-1.02]; atopic dermatitis: HR, 1.02 [95% CI, 1.01-1.02]; food allergy: HR, 1.03 [95% CI, 0.98-1.07]); in sibling-matched analyses, the HRs were similar to those of PS-matched analyses but were not significant (allergic diseases: HR, 1.01; 95% CI, 0.997-1.01). Infant exposure analyses included 84 263 PS-matched pairs (74 188 received H2RAs, 7496 received PPIs). The PS-matched HR was 1.06 (95% CI, 1.05-1.07) for allergic diseases overall (asthma: HR, 1.16 [95% CI, 1.14-1.18]; allergic rhinitis: HR, 1.02 [95% CI, 1.01-1.03]; atopic dermatitis: HR, 1.05 [95% CI, 1.02-1.08]; food allergy: HR, 1.28 [95% CI, 1.10-1.49]); asthma risk (HR, 1.13; 95% CI, 1.09-1.17) remained significantly higher among children exposed to ASMs during infancy in sibling-matched analyses. The findings were similar for H2RAs and PPIs analyzed separately and were robust across all sensitivity analyses., Conclusions and Relevance: The findings of this cohort study suggest that there is no association between prenatal exposure to ASMs and allergic diseases in offspring. However, infant exposure to ASMs was associated with a higher risk of developing asthma, although the magnitude was more modest than previously reported. Clinicians should carefully weigh the benefits of prescribing ASMs to children, accompanied by subsequent close monitoring for any clinically relevant safety signals.

Objective: To study patterns of antidepressant, anxiolytic, and hypnotic drug utilization in Denmark, Norway, and Sweden during the first year of the COVID-19 pandemic., Methods: The monthly observed number of prescription fills of antidepressants, benzodiazepines and benzodiazepine-related hypnotics (BZ), and other anxiolytics and hypnotics (OAH) per population in 2020 were compared with predicted numbers based on analysis of covariance of prescription fills during 2015-2019., Results: In March 2020, there was an increased number of prescription fills for antidepressants, anxiolytics, and hypnotics in youths and adults aged 20-59 years in Denmark, Norway, and Sweden. Antidepressant prescription fills increased between 13.5 % and 31.3 % at the end of 2020 in all age groups in Denmark and 17.4 % in youths in Norway. BZ drug prescription fills increased by 20.8 % at the end of 2020 in the 20-59 year age group in Denmark and decreased by 16.7 % in youths in Sweden. A general increase of prescription fills of OAH at the end of 2020 was observed in all countries (range 24.0-80.0 % in Denmark, 11.5-30.8 % in Norway, and 9.1-12.1 % in Sweden). Increases of prescription fills of OAH occurred earlier in Denmark., Limitations: Aggregated data with lack of information on indications., Conclusions: Peaks of utilization of antidepressants, anxiolytics, and hypnotics observed in March 2020 may reflect medication stock piling. Increased antidepressant drug utilization in Denmark and in Norwegian youths together with the general increase in OAH utilization in the Scandinavian countries in late 2020 may indicate an increase of symptoms of depression and anxiety, as well as disturbed sleep., Competing Interests: Conflict of interest CEC, PK, and JR are employed at the Centre for Pharmacoepidemiology, Karolinska Institutet, which receives grants from several entities (pharmaceutical companies, regulatory authorities, and contract research organizations) for performance of drug safety and drug utilization studies, with no relation to the work reported in this paper. MT, MB, SS, RW, and MH declare no conflict of interest., (Copyright © 2022 The Authors. Published by Elsevier B.V. All rights reserved.)

Importance: The direct and indirect implications of the COVID-19 pandemic have been associated with the mental health of children and adolescents, but it is uncertain whether these implications have been associated with changes in prescribing and diagnosis patterns., Objective: To examine psychotropic medication use and rates of psychiatric disorders in Danish children, adolescents, and young adults during the COVID-19 pandemic., Design, Setting, and Participants: This population-based, descriptive register-based cohort study included all Danish individuals aged 5 to 24 years from January 1, 2017, until June 30, 2022., Main Outcomes and Measures: Rates of filled prescriptions of psychotropic medications, including antipsychotics, anxiolytics, hypnotics, sedatives, antidepressants, and psychostimulants, and all inpatient and outpatient contacts with mental and behavioral disorders. Rates of new (incident) and total (prevalent) psychotropic medication use and psychiatric diagnoses were estimated. Rate ratios (RRs) were assessed between observed and expected numbers of incident psychotropic medication use or psychiatric diagnoses from March 2020 to June 30, 2022, comparing observed numbers with expected numbers predicted from the modeled prepandemic trend., Results: The study identified 108 840 (58 856 female individuals [54%]; median [IQR] age, 18 [14-22] years) incident psychotropic medication users. From March 2020 (first national lockdown) to June 2022, the rate of incident users of any psychotropic medication showed a relative increase of 18% (RR, 1.18; CI, 1.17-1.20) compared with expected numbers, which was primarily associated with an increase among those aged 12 to 17 years of 37% (RR, 1.37; 95% CI, 1.34-1.41). Similarly, there was an overall relative increase of incident psychiatric disorders of 5% (incidence rate, 1.05; CI, 1.04-1.07) (incident cases, 114 048 [58 708 female individuals (51%)]), which was associated with an increase in hyperkinetic disorders (RR, 1.13; CI, 1.09-1.18) and anxiety disorders (RR, 1.04; CI, 1.02-1.06). Prevalence patterns showed similar trends of an overall increase in psychotropic medication use and psychiatric disorders. One of 3 new users of an individual drug group had filled a prescription for a drug from another psychotropic medication group within the prior 6 months., Conclusions and Relevance: The results of this cohort study suggest that Danish youths experienced an increase in rates of psychotropic treatment and psychiatric disorder diagnoses during the COVID-19 pandemic, which was most pronounced among those aged 12 to 17 years. The increase was observed for children and adolescents with and without a psychiatric history within the last 5 years.

It remains unclear whether the rate of fetal death has changed during the COVID-19 pandemic. We assessed the impact of COVID-19 mitigation measures on fetal death in Sweden (449,347 births), Denmark (290,857 pregnancies) and Norway (261,057 pregnancies) using robust population-based registry data. We used Cox regression to assess the impact of the implementation of pandemic mitigation measures on March 12th, 2020, on miscarriage (fetal loss before gestational week 22) and stillbirth (fetal loss after gestational week 22). A total of 11% of 551,914 pregnancies in Denmark and Norway ended in miscarriage, while the proportion of stillbirths among 937,174 births across the three countries was 0.3%. There was no difference in the risk of fetal death during the year following pandemic mitigation measures. For miscarriage, the combined hazard ratio (HR) for Norway and Denmark was 1.01 (95% CI 0.98, 1.03), and for stillbirth, the combined HR for all three countries was 0.99 (95% CI 0.89, 1.09). We observed a slightly decreased risk of miscarriage during the first 4 months, with an HR of 0.94 (95% CI 0.90, 0.99) after lockdown. In conclusion, the risk of fetal death did not change after the implementation of COVID-19 pandemic mitigation measures in the three Scandinavian countries., (© 2022. The Author(s).)

Aim: We aimed to describe the aim, data collection and content from a survey completed among pregnant women during the first peak of the COVID-19 pandemic in Denmark., Methods: The declaration of the COVID-19 pandemic in early 2020 challenged pregnant women's mental well-being due to a concern for their unborn child and their need for healthcare services through pregnancy and birth. To explore how the COVID-19 pandemic and the intensified measures such as the lockdown of Denmark impacted pregnant women's well-being and mental health, we conducted a questionnaire survey in the spring of 2020 when the COVID-19 pandemic was at its first peak, and the consequences for pregnant women and the unborn child were very uncertain. All women residing in Denmark and registered with an ongoing pregnancy on 24 April 2020 were invited to participate. The questionnaire included background information, variables on COVID-19 symptoms and validated batteries of questions on loneliness, anxiety, stress, quality of life, meditation and prayers. Additional questions were included to examine concerns related to pregnancy and childbirth during the pandemic., Cohort Characteristics: Almost 18,000 women answered the questionnaire, which represents 60% of all invited women who experienced a national lockdown for the first time. Their median age was 30 years, and they were more likely to be multiparous., Conclusions: Data from the COVIDPregDK Study will enable us to gain valuable knowledge on how the pandemic, the intensified measures from the health authorities and the national lockdown affected pregnant women's mental health and their concerns during the COVID-19 pandemic.

Confounding by comorbidities is of concern in many epidemiological studies. To take this into account a common strategy is to calculate each participant's Charlson Comorbidity Index (CCI) and use this for adjustment in regression analyses. Various CCI adjustment strategies are possible, and it is unclear, which is preferable. In this simulation study, we compared common adjustment strategies in Cox regression analyses to determine to which degree they mitigate confounding and conservative bias caused by missing adjustment for independent predictors. We found that adjustment for each comorbidity as separate dichotomous covariate is the preferable adjustment strategy in samples of sufficient size as this mitigates both bias sources to the largest degree. If this is impractical in smaller studies adjustment for CCI split into multiple categories is preferable. In conclusion, the choice of CCI adjustment strategy impacts mitigation of bias in this simulation study, and suboptimal adjustment strategies can cause an observable bias, although of quite limited magnitude of only a few percent in this simulation example. Researcher should be careful when deciding on the adjustment strategies applied to ensure that the desired mitigation of bias sources is achieved., (© 2021. Springer Nature B.V.)