Search

Background: Postinfectious autoimmune processes have been proposed as potential causal factors for obsessive-compulsive disorder (OCD). This large population-based study aimed to clarify the co-aggregation pattern between severe infections and OCD across clusters of relatives with varying degrees of relatedness., Methods: We identified 4,916,898 individuals born in Sweden between 1960 and 2008 and followed them until 2020. Each individual was linked to their first- and second-degree relatives, including monozygotic (MZ) and dizygotic (DZ) twins, mothers, fathers, full siblings, maternal and paternal half siblings, aunts, uncles, and cousins. OCD and infection diagnoses from inpatient and specialized outpatient units were retrieved from the Swedish National Patient Register. We compared the risk of OCD in relatives of probands with severe infections to those of probands without severe infections. Cox proportional hazard regression models, incorporating time-varying exposures, were used to estimate hazard ratios (HRs). Dose-response associations were examined using logistic regression models., Results: Relatives of probands with severe infections exhibited a higher risk of OCD, increasing with genetic relatedness, with HRs (95% CI) ranging from 1.46 (1.07-1.98) in MZ twins to 1.10 (1.09-1.11) in cousins. The results remained robust after adjusting for severe infections among relatives, OCD in probands, and comorbid autoimmune disorders in both probands and relatives. A dose-response association was observed between the number of infections in the probands and their odds of OCD, as well as in their relatives., Conclusions: The results strongly suggest that the association between severe infections and OCD may be largely driven by shared genetic factors., (Copyright © 2024. Published by Elsevier Inc.)

Body dysmorphic disorder (BDD) is a relatively common and highly impairing mental disorder that is strikingly underdiagnosed and undertreated in Child and Adolescent Mental Health Services (CAMHS). The only clinical guidelines for the management of BDD in youth were published nearly 20 years ago, when empirical knowledge was sparse. Fortunately, there has been a surge in research into BDD over the last 10 years, shedding important insights into the phenomenology, epidemiology, assessment and treatment of the disorder in young people. This review aimed to provide an overview of recent research developments of relevance to clinicians and healthcare policymakers. We summarise key findings regarding the epidemiology of BDD in youth, which indicate that the disorder usually develops during teenage years and affects approximately 2% of adolescents at any one point in time. We provide an overview of aetiological research, highlighting that BDD arises from an interplay between genetic and environmental influences. We then focus on screening and assessment strategies, arguing that these are crucial to promote detection and diagnosis of this under-recognised condition. Additionally, we summarise the recommended treatment approaches for BDD in youth, namely cognitive behaviour therapy with or without selective serotonin reuptake inhibitors. The review concludes by highlighting key knowledge gaps and priorities for future research including, but not limited to, better understanding aetiological factors, long-term consequences and treatment., (© 2024 The Authors. Journal of Child Psychology and Psychiatry published by John Wiley & Sons Ltd on behalf of Association for Child and Adolescent Mental Health.)

Family accommodation might play a crucial role in obsessive-compulsive disorder (OCD). Previous systematic reviews on family accommodation in OCD have focused on specific populations or variables or are outdated. We conducted a preregistered systematic review and meta-analysis on family accommodation in adults, children, and adolescents with OCD (CRD42021264461). We searched PubMed, Scopus, and Web of Science using the keywords "family accommodation" and "obsessive-compulsive disorder. One hundred-eight studies involving 8928 individuals with OCD were included. Our results indicate that levels of family accommodation in OCD are moderate, that there is a significant positive correlation between family accommodation and OCD severity (r = 0.42), that baseline family accommodation does not predict pre- to post-treatment change in OCD severity (g = -0.03), and that family accommodation decreases as a result of both individual and family-focused cognitive behavioral therapy for OCD (g = 2.00 and g = 1.17, respectively). Our findings highlight the relevance of family accommodation in OCD and may help guide assessment and treatment., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Background: Body dysmorphic disorder (BDD) is thought to be associated with considerable suicide risk. This nationwide cohort study quantified the risks of intentional self-harm-including nonsuicidal self-injuries and suicide attempts-and death by suicide in BDD., Methods: Individuals with a validated ICD-10 diagnosis of BDD in the Swedish National Patient Register, registered between January 1, 1997, and December 31, 2020, were matched with 10 unexposed individuals (i.e., without BDD) from the general population on birth year, sex, and county of residence. Conditional Poisson regression models estimated incidence rate ratios and 95% CIs for intentional self-harm. Stratified Cox proportional hazards models estimated hazard ratios and 95% CIs for death by suicide. Models adjusted for sociodemographic variables and lifetime psychiatric comorbidities., Results: Among 2833 individuals with BDD and 28,330 unexposed matched individuals, 466 (16.45%) and 1071 (3.78%), respectively, had at least 1 record of intentional self-harm during the study period (incidence rate ratio = 3.37; 95% CI, 3.02-3.76). In the BDD group, about two-thirds (n = 314; 67%) had their first recorded self-harm event before their first BDD diagnosis. A total of 17 (0.60%) individuals with BDD and 27 (0.10%) unexposed individuals died by suicide (hazard ratio = 3.47; 95% CI, 1.76-6.85). All results remained robust to additional adjustment for lifetime psychiatric comorbidities. A higher proportion of individuals with BDD who died by suicide had at least 1 previous record of intentional self-harm compared with unexposed individuals (52.94% vs. 22.22%; p = .036)., Conclusions: BDD was associated with a 3-fold increased risk of intentional self-harm and death by suicide., (Copyright © 2024 Society of Biological Psychiatry. Published by Elsevier Inc. All rights reserved.)

Importance: Behavior therapy is a recommended intervention for Tourette syndrome (TS) and chronic tic disorder (CTD), but availability is limited and long-term effects are uncertain., Objective: To investigate the long-term efficacy and cost-effectiveness of therapist-supported, internet-delivered exposure and response prevention (ERP) vs psychoeducation for youths with TS or CTD., Design, Setting, and Participants: This 12-month controlled follow-up of a parallel group, superiority randomized clinical trial was conducted at a research clinic in Stockholm, Sweden, with nationwide recruitment. In total, 221 participants aged 9 to 17 years with TS or CTD were enrolled between April 26, 2019, and April 9, 2021, of whom 208 (94%) provided 12-month follow-up data. Final follow-up data were collected on June 29, 2022. Outcome assessors were masked to treatment allocation throughout the study., Interventions: A total of 111 participants were originally randomly allocated to 10 weeks of therapist-supported, internet-delivered ERP and 110 participants to therapist-supported, internet-delivered psychoeducation., Main Outcomes and Measures: The primary outcome was within-group change in tic severity, measured by the Total Tic Severity Score of the Yale Global Tic Severity Scale (YGTSS-TTSS), from the 3-month follow-up to the 12-month follow-up. Treatment response was defined as 1 (very much improved) or 2 (much improved) on the Clinical Global Impression-Improvement scale. Analyses were intention-to-treat and followed the plan prespecified in the published study protocol. A health economic evaluation was performed from 3 perspectives: health care organization (including direct costs for treatment provided in the study), health care sector (additionally including health care resource use outside of the study), and societal (additionally including costs beyond health care [eg, parent's absenteeism from work])., Results: In total, 221 participants were recruited (mean [SD] age, 12.1 [2.3] years; 152 [69%] male). According to the YGTSS-TTSS, there were no statistically significant changes in tic severity from the 3-month to the 12-month follow-up in either group (ERP coefficient, -0.52 [95% CI, -1.26 to 0.21]; P = .16; psychoeducation coefficient, 0.00 [95% CI, -0.78 to 0.78]; P > .99). A secondary analysis including all assessment points (baseline to 12-month follow-up) showed no statistically significant between-group difference in tic severity from baseline to the 12-month follow-up (coefficient, -0.38 [95% CI, -1.11 to 0.35]; P = .30). Treatment response rates were similar in both groups (55% in ERP and 50% in psychoeducation; odds ratio, 1.25 [95% CI, 0.73-2.16]; P = .42) at the 12-month follow-up. The health economic evaluation showed that, from a health care sector perspective, ERP produced more quality-adjusted life years (0.01 [95% CI, -0.01 to 0.03]) and lower costs (adjusted mean difference -$84.48 [95% CI, -$440.20 to $977.60]) than psychoeducation at the 12-month follow-up. From the health care organization and societal perspectives, ERP produced more quality-adjusted life years at higher costs, with 65% to 78% probability of ERP being cost-effective compared with psychoeducation when using a willingness-to-pay threshold of US $79 000., Conclusions and Relevance: There were no statistically significant changes in tic severity from the 3-month through to the 12-month follow-up in either group. The ERP intervention was not superior to psychoeducation at any time point. While ERP was not superior to psychoeducation alone in reducing tic severity at the end of the follow-up period, ERP is recommended for clinical implementation due to its likely cost-effectiveness and support from previous literature., Trial Registration: ClinicalTrials.gov Identifier: NCT03916055.

The Appearance Anxiety Inventory (AAI) is a self-report measure assessing the typical cognitions and behaviours of body dysmorphic disorder (BDD). Despite its use in research and clinical settings, its psychometric properties have not been evaluated in young people with BDD. We examined the factor structure, reliability, validity, and sensitivity to change of the AAI in 182 youths with BDD (82.9% girls; M age  = 15.56, SD  = 1.37) consecutively referred to two specialist outpatient clinics in Stockholm, Sweden ( n  = 97) and London, England ( n  = 85). An exploratory factor analysis identified three factors, namely "threat monitoring", "camouflaging", and "avoidance", explaining 48.15% of the variance. The scale showed good internal consistency (McDonalds omega = 0.83) and adequate convergent validity with the Yale-Brown Obsessive-Compulsive Scale Modified for Body Dysmorphic Disorder for Adolescents (BDD-YBOCS-A; r s  = 0.42) and the Clinical Global Impression-Severity Scale ( r s  = 0.32). Sensitivity to change was adequate, with AAI total scores and individual factor scores significantly decreasing over time in the subgroup of participants receiving multimodal treatment for BDD ( n  = 79). Change of AAI scores over treatment showed a positive statistically significant moderate-to-good correlation ( r  = 0.55) with changes in BDD symptom severity, measured by the BDD-YBOCS-A. The study provides empirical support for the use of the AAI in young people with BDD in clinical settings.

Body-focused repetitive behavior disorders, including trichotillomania (hair-pulling disorder) and excoriation (skin picking) disorder, typically emerge in early adolescence, but little is known about the clinical characteristics and treatment outcomes of these disorders in young people, particularly in real-world clinical settings. Participants were 63 children and adolescents (51 girls; age range 9-17) with a diagnosis of trichotillomania (n = 33) and/or skin-picking disorder (n = 33) attending a specialist outpatient clinic in Stockholm, Sweden. Demographic and clinical characteristics were gathered at the initial assessment. Of the 63 assessed youths, 56 received manual-based behavior therapy mainly focusing on habit reversal training, which was combined with medication when deemed appropriate. The mean clinician-reported trichotillomania and skin-picking disorder symptom severity at baseline (n = 63) was in the moderate range. We observed high rates of psychiatric comorbidity (63.5%) and use of psychiatric medication (54.8%). For the 56 individuals undertaking treatment at the clinic, mixed-effects regression models showed a significant decrease in symptom severity from baseline to posttreatment, with gains maintained up to the 12-month follow-up. Substantial and durable improvements were also seen on self-reported symptoms, self-reported depression, and global functioning. Specialist care should be made more widely available to improve the prognosis and quality of life of young people with trichotillomania and skin-picking disorder., (Copyright © 2023 Association for Behavioral and Cognitive Therapies. Published by Elsevier Ltd. All rights reserved.)

Importance: Hypochondriasis, also known as health anxiety disorder, is a prevalent, yet underdiagnosed psychiatric disorder characterized by persistent preoccupation about having serious and progressive physical disorders. The risk of mortality among individuals with hypochondriasis is unknown., Objective: To investigate all-cause and cause-specific mortality among a large cohort of individuals with hypochondriasis., Design, Setting, and Participants: This Swedish nationwide matched-cohort study included 4129 individuals with a validated International Statistical Classification of Diseases and Related Health Problems, Tenth Revision (ICD-10) diagnosis of hypochondriasis assigned between January 1, 1997, and December 31, 2020, and 41 290 demographically matched individuals without hypochondriasis. Individuals with diagnoses of dysmorphophobia (body dysmorphic disorder) assigned during the same period were excluded from the cohort. Statistical analyses were conducted between May 5 and September 27, 2023., Exposure: Validated ICD-10 diagnoses of hypochondriasis in the National Patient Register., Main Outcome and Measures: All-cause and cause-specific mortality in the Cause of Death Register. Covariates included birth year, sex, county of residence, country of birth (Sweden vs abroad), latest recorded education, civil status, family income, and lifetime psychiatric comorbidities. Stratified Cox proportional hazards regression models were used to estimate the hazard ratios (HRs) and 95% CIs of all-cause and cause-specific mortality., Results: Of the 4129 individuals with hypochondriasis (2342 women [56.7%]; median age at first diagnosis, 34.5 years [IQR, 26.3-46.1 years]) and 41 290 demographically matched individuals without hypochondriasis (23 420 women [56.7%]; median age at matching, 34.5 years [IQR, 26.4-46.2 years]) in the study, 268 individuals with hypochondriasis and 1761 individuals without hypochondriasis died during the study period, corresponding to crude mortality rates of 8.5 and 5.5 per 1000 person-years, respectively. In models adjusted for sociodemographic variables, an increased rate of all-cause mortality was observed among individuals with hypochondriasis compared with individuals without hypochondriasis (HR, 1.69; 95% CI, 1.47-1.93). An increased rate was observed for both natural (HR, 1.60; 95% CI, 1.38-1.85) and unnatural (HR, 2.43; 95% CI, 1.61-3.68) causes of death. Most deaths from unnatural causes were attributed to suicide (HR, 4.14; 95% CI, 2.44-7.03). The results were generally robust to additional adjustment for lifetime psychiatric disorders., Conclusions and Relevance: This cohort study suggests that individuals with hypochondriasis have an increased risk of death from both natural and unnatural causes, particularly suicide, compared with individuals from the general population without hypochondriasis. Improved detection and access to evidence-based care should be prioritized.

Background: Obsessive-compulsive disorder (OCD) has been associated with a broad range of health-related issues. Unhealthy lifestyle habits such as physical inactivity, an unhealthy diet, smoking, and alcohol consumption are hypothesized to contribute to this association. However, the lifestyle habits of individuals with OCD have been scarcely investigated. In this international survey, we explored the physical health and lifestyle habits of adults with a self-reported diagnosis of OCD., Methods: An online global survey available in seven languages was disseminated through interest organizations and social media between July 2021 and March 2022. The survey included questions relating to socio-demographic variables and clinical characteristics (including OCD symptom severity - as measured with the 12-item self-report scale Obsessive-Compulsive Inventory [OCI-12] - and psychotropic medication), physical health, and lifestyle habits. Frequencies and percentages, or means and standard deviations, as appropriate, were calculated. Subgroup analyses by OCD symptom severity, gender, and age group were performed., Results: A total of 496 individuals with OCD completed the survey and were included in the analyses (mean age = 36.0 years, SD = 12.5, range 18-79; 78.8% women). Most participants were from Europe (n = 245, 49.4%) and North America (n = 187, 37.7%). OCD symptom severity scores were on the moderate range (OCI-12 mean score = 21.2, SD = 9.1). A majority (n = 354, 71.4%) reported having comorbid somatic health issues, mainly allergies, gastrointestinal conditions, and cardiometabolic conditions. Nearly half of the sample (n = 236, 47.6%) reported a body mass index ≥ 25, corresponding to at least overweight. A significant proportion of the participants reported low physical activity (n = 271, 55.0%), unhealthy dietary habits (n = 182, 36.7%), risk consumption of alcohol (n = 111, 22.3%), and non-restorative sleep (n = 268, 54.0%). Subgroup analyses showed overall similar results across groups, with some exceptions., Conclusions: In this sample, individuals with OCD self-reported a range of health-related issues and a number of unhealthy lifestyle behaviors, most prominently a lack of physical activity. Interventions aimed at modifying unhealthy lifestyles to prevent or improve health conditions beyond the psychiatric symptoms should be considered., (© 2024. The Author(s).)

Objective: To estimate the risk of all cause and cause specific mortality in people with obsessive-compulsive disorder (OCD) compared with matched unaffected people from the general population and with their unaffected siblings., Design: Population based matched cohort and sibling cohort study., Setting: Register linkage in Sweden., Participants: Population based cohort including 61 378 people with OCD and 613 780 unaffected people matched (1:10) on sex, birth year, and county of residence; sibling cohort consisting of 34 085 people with OCD and 47 874 unaffected full siblings. Cohorts were followed up for a median time of 8.1 years during the period from 1 January 1973 to 31 December 2020., Main Outcome Measures: All cause and cause specific mortality., Results: 4787 people with OCD and 30 619 unaffected people died during the study period (crude mortality rate 8.1 and 5.1 per 1000 person years, respectively). In stratified Cox proportional hazards models adjusted for birth year, sex, county, migrant status (born in Sweden versus abroad), and sociodemographic variables (latest recorded education, civil status, and family income), people with OCD had an increased risk of all cause mortality (hazard ratio 1.82, 95% confidence interval 1.76 to 1.89) and mortality due to natural causes (1.31, 1.27 to 1.37) and unnatural causes (3.30, 3.05 to 3.57). Among the natural causes of death, those due to endocrine, nutritional, and metabolic diseases, mental and behavioural disorders, and diseases of the nervous, circulatory, respiratory, digestive, and genitourinary systems were higher in the OCD cohort. Conversely, the risk of death due to neoplasms was lower in the OCD cohort compared with the unaffected cohort. Among the unnatural causes, suicide showed the highest hazard ratio, followed by accidents. The results were robust to adjustment for psychiatric comorbidities and familial confounding., Conclusions: Non-communicable diseases and external causes of death, including suicides and accidents, were major contributors to the risk of mortality in people with OCD. Better surveillance, prevention, and early intervention strategies should be implemented to reduce the risk of fatal outcomes in people with OCD., Competing Interests: Competing interests: All authors have completed the ICMJE uniform disclosure form at www.icmje.org/disclosure-of-interest/ and declare: support from the Swedish Research Council for Health, Working Life and Welfare, Region Stockholm, the Swedish Society of Medicine, and Karolinska Institutet; LFC receives royalties for contributing articles to UpToDate and Wolters Kluwer Health and for editorial work from Elsevier, outside the submitted work; HL has received additional grants from Shire/Takeda in the previous three years and receives personal fees from Shire and Takeda, Evolan, and Medici, all outside the submitted work; CR receives royalties for books or book chapters to Natur och Kultur, Studentlitteratur, and Albert Bonniers Förlag, outside the submitted work; DMC receives royalties for contributing articles to UpToDate and Wolters Kluwer Health, receives occasional payments from funding agencies as an external grant reviewer, and is part owner of Scandinavian E-Health, AB, all outside the submitted work; no other relationships or activities that could appear to have influenced the submitted work., (© Author(s) (or their employer(s)) 2019. Re-use permitted under CC BY. No commercial re-use. See rights and permissions. Published by BMJ.)

The Yale-Brown Obsessive-Compulsive Scale Modified for Body Dysmorphic Disorder for Adolescents (BDD-YBOCS-A) is a clinician-rated measure of BDD symptom severity in youth. Despite widespread use in both research and clinical practice, its psychometric properties have not been formally evaluated. The current study examined the factor structure, reliability, validity, and sensitivity to change of the BDD-YBOCS-A in 251 youths with BDD attending two specialist clinics. A principal component analysis identified two factors, explaining 56% of the variance. The scale showed good internal consistency (Cronbach's alpha = 0.87) and adequate convergent and divergent validity. In a subgroup of participants receiving BDD treatment (n = 175), BDD-YBOCS-A scores significantly decreased over time, demonstrating sensitivity to change. BDD-YBOCS-A change scores over treatment were highly correlated with severity changes measured by the Clinical Global Impression - Severity scale (r = .84). The study provides empirical support for the use of the BDD-YBOCS-A in children and adolescents with BDD., (© 2022. The Author(s).)

Body dysmorphic disorder (BDD) is a prevalent and impairing psychiatric condition that typically debuts in adolescence and is associated with risky behaviours. The disorder can be effectively treated with cognitive behaviour therapy (CBT). However, CBT for BDD is seldom available primarily due to a shortage of trained therapists. Internet-delivered CBT (ICBT) can be a way to increase treatment availability. The aim of this feasibility trial was to evaluate the feasibility, safety, and preliminary efficacy of a CBT protocol for adolescents with BDD, adapted to be delivered over the Internet with minimal therapist support. A total of 20 participants (12-17-year-olds) meeting criteria for BDD were recruited nationally to a specialist outpatient clinic in Stockholm, Sweden. One participant withdrew consent and their data could not be analysed. Nineteen participants were offered 12 modules of therapist-guided ICBT for BDD and were followed up to 12 months post-treatment. Preliminary efficacy was measured at the a priori primary endpoint (3-month follow-up) and at the 12-month follow-up with the clinician-rated Yale-Brown Obsessive Compulsive Scale Modified for BDD for Adolescents. The treatment was rated as both credible and satisfactory and was associated with a large and statistically significant reduction in BDD symptom severity ( d  = 2.94). The proportion of participants classified as responders at the primary endpoint was 73.7%, and the proportion of full or partial remitters was 63.2%. The average therapist support time was 8 min per participant per week. Treatment gains continued to accrue up to the 12-month follow-up. Two participants attempted suicide and another two reported non-suicidal self-injuries during the study period. ICBT with minimal therapist support is a feasible, potentially efficacious, and durable treatment for adolescents with BDD. Risky behaviours typical of this patient group should be carefully monitored during treatment., Competing Interests: David Mataix-Cols receives royalties for contributing articles to UpToDate, Wolters Kluwer Health. Lorena Fernández de la Cruz receives royalties for contributing articles to UpToDate, Wolters Kluwer Health and for editorial work from Elsevier. All other authors report no conflicts of interest., (© 2023 The Authors.)

Purpose: Depression and anxiety afflict millions worldwide causing considerable disability. MULTI-PSYCH is a longitudinal cohort of genotyped and phenotyped individuals with depression or anxiety disorders who have undergone highly structured internet-based cognitive-behaviour therapy (ICBT). The overarching purpose of MULTI-PSYCH is to improve risk stratification, outcome prediction and secondary preventive interventions. MULTI-PSYCH is a precision medicine initiative that combines clinical, genetic and nationwide register data., Participants: MULTI-PSYCH includes 2668 clinically well-characterised adults with major depressive disorder (MDD) (n=1300), social anxiety disorder (n=640) or panic disorder (n=728) assessed before, during and after 12 weeks of ICBT at the internet psychiatry clinic in Stockholm, Sweden. All patients have been blood sampled and genotyped. Clinical and genetic data have been linked to several Swedish registers containing a wide range of variables from patient birth up to 10 years after the end of ICBT. These variable types include perinatal complications, school grades, psychiatric and somatic comorbidity, dispensed medications, medical interventions and diagnoses, healthcare and social benefits, demographics, income and more. Long-term follow-up data will be collected through 2029., Findings to Date: Initial uses of MULTI-PSYCH include the discovery of an association between PRS for autism spectrum disorder and response to ICBT, the development of a machine learning model for baseline prediction of remission status after ICBT in MDD and data contributions to genome wide association studies for ICBT outcome. Other projects have been launched or are in the planning phase., Future Plans: The MULTI-PSYCH cohort provides a unique infrastructure to study not only predictors or short-term treatment outcomes, but also longer term medical and socioeconomic outcomes in patients treated with ICBT for depression or anxiety. MULTI-PSYCH is well positioned for research collaboration., Competing Interests: Competing interests: DMC receives royalties for contributing articles to UpToDate, Inc, outside this work. LFC receives royalties for contributing articles to UpToDate, Wolters Kluwer Health and for editorial work from Elsevier, outside the submitted work., (© Author(s) (or their employer(s)) 2023. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Background: Many children with tic disorders outgrow their tics, but little is known about the proportion of individuals who will continue to require specialist services in adulthood and which variables are associated with tic persistence., Objectives: The aims were to estimate the proportion of individuals first diagnosed with tic disorders in childhood who continued to receive tic disorder diagnoses after age 18 years and to identify risk factors for persistence., Methods: In this Swedish nationwide cohort study including 3761 individuals diagnosed with tic disorders in childhood, we calculated the proportion of individuals whose diagnoses persisted into adulthood. Minimally adjusted logistic regression models examined the associations between sociodemographic, clinical, and family variables and tic disorder persistence. A multivariable model was then fitted, including only variables that were statistically significant in the minimally adjusted models., Results: Seven hundred and fifty-four (20%) children with tic disorders received a diagnosis of a chronic tic disorder in adulthood. Psychiatric comorbidity in childhood (particularly attention-deficit hyperactivity disorder, obsessive-compulsive disorder, pervasive developmental disorders, and anxiety disorders) and psychiatric disorders in first-degree relatives (particularly tic and anxiety disorders) were the strongest risk factors for persistence. We did not observe statistically significant associations with socioeconomic variables, perinatal complications, comorbid autoimmune diseases, or family history of autoimmune diseases. All statistically significant variables combined explained approximately 10% of the variance in tic disorder persistence (P < 0.0001)., Conclusions: Childhood psychiatric comorbidities and family history of psychiatric disorders were the strongest risk factors associated with tic disorder persistence into adulthood. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society., (© 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.)

Background: Cognitive behavioral therapy (CBT) is a moderately efficacious treatment for hoarding disorder (HD), with most individuals remaining symptomatic after treatment. The Joining Forces Trial will evaluate whether 10 weeks of in-home decluttering can significantly augment the outcomes of group CBT., Methods: A randomized controlled trial of in-home decluttering augmentation of group CBT for HD. Adult participants with HD (N = 90) will receive 12 weeks of protocol-based group CBT for HD. After group CBT, participants will be randomized to either 10 weeks of in-home decluttering led by a social services team or a waitlist. The primary endpoint is 10 weeks post-randomization. The primary outcome measures are the self-reported Saving Inventory-Revised and the blind assessor-rated Clutter Image Rating. Participants on the waitlist will cross over to receive the in-home decluttering intervention after the primary endpoint. Data will be analyzed according to intention-to-treat principles. We will also evaluate the cost-effectiveness of this intervention from both healthcare and societal perspectives., Discussion: HD is challenging to treat with conventional psychological treatments. We hypothesize that in-home decluttering sessions carried out by personnel in social services will be an efficacious and cost-effective augmentation strategy of group CBT for HD. Recruitment started in January 2021, and the final participant is expected to reach the primary endpoint in December 2024., Trail Registration: ClinicalTrials.gov NCT04712474. Registered on 15 January 2021., (© 2023. The Author(s).)

Background: The causes of obsessive-compulsive disorder (OCD) remain unknown. Gene-searching efforts are well underway, but the identification of environmental risk factors is at least as important and should be a priority because some of them may be amenable to prevention or early intervention strategies. Genetically informative studies, particularly those employing the discordant monozygotic (MZ) twin design, are ideally suited to study environmental risk factors. This protocol paper describes the study rationale, aims, and methods of OCDTWIN, an open cohort of MZ twin pairs who are discordant for the diagnosis of OCD., Methods: OCDTWIN has two broad aims. In Aim 1, we are recruiting MZ twin pairs from across Sweden, conducting thorough clinical assessments, and building a biobank of biological specimens, including blood, saliva, urine, stool, hair, nails, and multimodal brain imaging. A wealth of early life exposures (e.g., perinatal variables, health-related information, psychosocial stressors) are available through linkage with the nationwide registers and the Swedish Twin Registry. Blood spots stored in the Swedish phenylketonuria (PKU) biobank will be available to extract DNA, proteins, and metabolites, providing an invaluable source of biomaterial taken at birth. In Aim 2, we will perform within-pair comparisons of discordant MZ twins, which will allow us to isolate unique environmental risk factors that are in the causal pathway to OCD, while strictly controlling for genetic and early shared environmental influences. To date (May 2023), 43 pairs of twins (21 discordant for OCD) have been recruited., Discussion: OCDTWIN hopes to generate unique insights into environmental risk factors that are in the causal pathway to OCD, some of which have the potential of being actionable targets., (© 2023. The Author(s).)

Background: Postinfectious autoimmune processes are hypothesized to be causally related to both obsessive-compulsive disorder (OCD) and tic disorders, but current evidence is conflicting. This study examined whether prenatal maternal (and paternal, as an internal control) infections and early childhood infections in the offspring (i.e., during the first 3 years of life) were associated with a subsequent risk of OCD and Tourette syndrome or chronic tic disorder (TS/CTD)., Methods: Individuals exposed to any prenatal maternal infection (n = 16,743) and early childhood infection (n = 264,346) were identified from a population-based birth cohort consisting of 2,949,080 singletons born in Sweden between 1973 and 2003 and were followed through 2013. Cox proportional hazard regression models were used to estimate hazard ratios (HRs). Sibling analyses were performed to control for familial confounding., Results: At the population level, and after adjusting for parental psychiatric history and autoimmune diseases, a significantly increased risk of OCD and TS/CTD was found in individuals exposed to prenatal maternal (but not paternal) infections (OCD: HR, 1.33; 95% CI, 1.12-1.57; TS/CTD: HR, 1.60; 95% CI, 1.23-2.09) and early childhood infections (OCD: HR, 1.19; 95% CI, 1.14-1.25; TS/CTD: HR, 1.34; 95% CI, 1.24-1.44). However, these associations were no longer significant in the sibling analyses., Conclusions: The results do not support the hypothesis that prenatal maternal or early-life infections play a direct causal role in the etiology of either OCD or TS/CTD. Instead, familial factors (e.g., genetic pleiotropy) may explain both the propensity to infections and the liability to OCD and TS/CTD., (Copyright © 2022 Society of Biological Psychiatry. Published by Elsevier Inc. All rights reserved.)

Importance: Obsessive-compulsive disorder (OCD) is associated with adverse health-related outcomes. However, pregnancy and neonatal outcomes among women with OCD have been sparsely studied., Objective: To evaluate associations of maternal OCD with pregnancy, delivery, and neonatal outcomes., Design, Setting, and Participants: Two register-based cohort studies in Sweden and British Columbia (BC), Canada, included all singleton births at 22 weeks or more of gestation between January 1, 1999 (Sweden), or April 1, 2000 (BC), and December 31, 2019. Statistical analyses were conducted between August 1, 2022, and February 14, 2023., Exposure: Maternal OCD diagnosis recorded before childbirth and use of serotonin reuptake inhibitors (SRIs) during pregnancy., Main Outcomes and Measures: Pregnancy and delivery outcomes examined were gestational diabetes, preeclampsia, maternal infection, antepartum hemorrhage or placental abruption, premature rupture of membranes, induction of labor, mode of delivery, and postpartum hemorrhage. Neonatal outcomes included perinatal death, preterm birth, small for gestational age, low birth weight (<2500 g), low 5-minute Apgar score, neonatal hypoglycemia, neonatal jaundice, neonatal respiratory distress, neonatal infections, and congenital malformations. Multivariable Poisson log-linear regressions estimated crude and adjusted risk ratios (aRRs). In the Swedish cohort, sister and cousin analyses were performed to account for familial confounding., Results: In the Swedish cohort, 8312 pregnancies in women with OCD (mean [SD] age at delivery, 30.2 [5.1] years) were compared with 2 137 348 pregnancies in unexposed women (mean [SD] age at delivery, 30.2 [5.1] years). In the BC cohort, 2341 pregnancies in women with OCD (mean [SD] age at delivery, 31.0 [5.4] years) were compared with 821 759 pregnancies in unexposed women (mean [SD] age at delivery, 31.3 [5.5] years). In Sweden, maternal OCD was associated with increased risks of gestational diabetes (aRR, 1.40; 95% CI, 1.19-1.65) and elective cesarean delivery (aRR, 1.39; 95% CI, 1.30-1.49), as well as preeclampsia (aRR, 1.14; 95% CI, 1.01-1.29), induction of labor (aRR, 1.12; 95% CI, 1.06-1.18), emergency cesarean delivery (aRR, 1.16; 95% CI, 1.08-1.25), and postpartum hemorrhage (aRR, 1.13; 95% CI, 1.04-1.22). In BC, only emergency cesarean delivery (aRR, 1.15; 95% CI, 1.01-1.31) and antepartum hemorrhage or placental abruption (aRR, 1.48; 95% CI, 1.03-2.14) were associated with significantly higher risk. In both cohorts, offspring of women with OCD were at elevated risk of low Apgar score at 5 minutes (Sweden: aRR, 1.62; 95% CI, 1.42-1.85; BC: aRR, 2.30; 95% CI, 1.74-3.04), as well as preterm birth (Sweden: aRR, 1.33; 95% CI, 1.21-1.45; BC: aRR, 1.58; 95% CI, 1.32-1.87), low birth weight (Sweden: aRR, 1.28; 95% CI, 1.14-1.44; BC: aRR, 1.40; 95% CI, 1.07-1.82), and neonatal respiratory distress (Sweden: aRR, 1.63; 95% CI, 1.49-1.79; BC: aRR, 1.47; 95% CI, 1.20-1.80). Women with OCD taking SRIs during pregnancy had an overall increased risk of these outcomes, compared with those not taking SRIs. However, women with OCD not taking SRIs still had increased risks compared with women without OCD. Sister and cousin analyses showed that at least some of the associations were not influenced by familial confounding., Conclusion and Relevance: These cohort studies suggest that maternal OCD was associated with an increased risk of adverse pregnancy, delivery, and neonatal outcomes. Improved collaboration between psychiatry and obstetric services and improved maternal and neonatal care for women with OCD and their children is warranted.

Background: Cesarean delivery (CD) has been associated with postpartum psychiatric disorders, but less is known about the risk of suicidal behaviors. We estimated the incidence and risk of suicide attempts and deaths during the first postpartum year in mothers who delivered via CD v. vaginally., Method: All deliveries in Sweden between 1973 and 2012 were identified. The mothers were followed since delivery for 12 months or until the date of one of the outcomes (i.e. suicide attempt or death by suicide), death by other causes or emigration. Associations were estimated using Cox proportional hazards regression models., Results: Of 4 016 789 identified deliveries, 514 113 (12.8%) were CDs and 3 502 676 (87.2%) were vaginal deliveries. During the 12-month follow-up, 504 (0.098%) suicide attempts were observed in the CD group and 2240 (0.064%) in the vaginal delivery group (risk difference: 0.034%), while 11 (0.0037%) deaths by suicide were registered in the CD group and 109 (0.0029%) in the vaginal delivery group (risk difference: 0.008%). Compared to vaginal delivery, CD was associated with an increased risk of suicide attempts [hazard ratio (HR) 1.46; 95% CI 1.32-1.60], but not of deaths by suicide (HR 1.44; 95% CI 0.88-2.36)., Conclusions: Maternal suicidal behaviors during the first postpartum year were uncommon in Sweden. Compared to vaginal delivery, CD was associated with a small increased risk of suicide attempts, but not death by suicide. Improved understanding of the association between CD and maternal suicidal behaviors may promote more appropriate measures to improve maternal mental well-being and further reduce suicidal risks.

Importance: Maternal immune activation (MIA) leading to altered neurodevelopment in utero is a hypothesized risk factor for psychiatric outcomes in offspring. Primary antibody immunodeficiencies (PIDs) constitute a unique natural experiment to test the MIA hypothesis of mental disorders., Objective: To assess the association of maternal and paternal PIDs with psychiatric disorders and suicidal behavior in offspring., Design, Setting, and Participants: Cohort study of 4 294 169 offspring of parents with and without PIDs living in Sweden at any time between 1973 and 2013. Data were extracted from Swedish nationwide health and administrative registers and were analyzed from May 5 to September 30, 2022. All individuals with diagnoses of PIDs identified between 1973 and 2013 from the National Patient Register were included. Offspring were included if born before 2003. Parent-offspring pairs in which both parents had a history of PIDs were excluded., Exposures: Lifetime records of parental PIDs according to the International Classification of Diseases, Eighth Revision (ICD-8); International Classification of Diseases, Ninth Revision (ICD-9); and International Statistical Classification of Diseases and Related Health Problems, Tenth Revision (ICD-10) diagnostic codes., Main Outcomes and Measures: Lifetime records of 10 psychiatric disorders and suicidal behavior identified using ICD-8, ICD-9, and ICD-10 diagnostic codes, including suicide attempts and death by suicide, among offspring. Covariates included sex, birth year, parental psychopathology, suicide attempts, and autoimmune diseases. Additional analyses excluded offspring with their own PIDs and autoimmune diseases. Poisson regression models were fitted separately for mothers and fathers to estimate incidence rate ratios (IRRs) and 95% CIs for the risk of psychiatric and suicidal behavior outcomes in the offspring of PID-exposed vs PID-unexposed mothers or fathers., Results: The cohort included 4 294 169 offspring (2 207 651 males [51.4%]) and 3 954 937 parents (1 987 972 females [50.3%]). A total of 7270 offspring (0.17%) had parents with PIDs, and 4 286 899 offspring had parents without PIDs. In fully adjusted models, offspring of mothers with PIDs had an increased risk of any psychiatric disorder, while no such risks were observed in offspring of fathers with PIDs (IRR, 1.17; 95% CI, 1.10-1.25 vs IRR, 1.03; 95% CI, 0.94-1.14; P < .001). Likewise, an increased risk of suicidal behavior was observed among offspring of mothers with PIDs but not offspring of fathers with PIDs (IRR, 1.20; 95% CI, 1.06-1.36 vs IRR, 1.10; 95% CI, 0.91-1.34; P = .01). For the offspring of mothers with PIDs, the risk of developing any psychiatric disorder was significantly higher for those with mothers with 6 of 10 individual disorders, with IRRs ranging from 1.15 (95% CI, 1.04-1.26) for anxiety and stress-related disorders and 1.15 (95% CI, 1.03-1.30) for substance use disorders to 1.71 (95% CI, 1.37-2.14) for bipolar disorders. Offspring of mothers with both PIDs and autoimmune diseases had the highest risk for any psychiatric disorder (IRR, 1.24; 95% CI, 1.11-1.38) and suicidal behavior (IRR, 1.44; 95% CI, 1.17-1.78)., Conclusions and Relevance: Findings of this cohort study suggest that maternal, but not paternal, PIDs were associated with a statistically significant increased risk of psychiatric disorders and suicidal behavior in the offspring, particularly when PIDs co-occur with autoimmune diseases. These findings align with the MIA hypothesis of mental disorders, but the precise mechanisms remain to be elucidated.

In clinical trials of obsessive-compulsive disorder (OCD), clinical outcomes are generally measured using lengthy clinician-administered interviews. However, in routine clinical practice, many clinicians lack the time to administer such instruments. This study evaluated cutoffs for treatment response and remission in OCD using the self-rated Obsessive-Compulsive Inventory-Revised (OCI-R). Data from 349 patients in three clinical trials of cognitive-behavioral therapy for OCD were pooled for analysis. The OCI-R was compared to gold-standard criteria for response and remission based on the clinician-administered Yale-Brown Obsessive Compulsive Scale and the Clinical Global Impression Scale. The results showed that a ≥40% reduction on the OCI-R was the optimal cutoff for treatment response, with a sensitivity of 0.72 and a specificity of 0.79. For remission status, the optimal cutoff was ≤8 points on the OCI-R, with a sensitivity of 0.57 and specificity of 0.83. Results from additional analyses using the 12-item version of the OCI were similar. These cutoffs provide a simple and time-efficient way to help determine treatment response and remission in OCD when the administration of clinician-administered instruments is unfeasible., (Copyright © 2022 Association for Behavioral and Cognitive Therapies. Published by Elsevier Ltd. All rights reserved.)

Individuals with obsessive-compulsive disorder (OCD) more often think about, attempt, and die by suicide than individuals from the general population. Sexual and religious obsessions (i.e., taboo obsessions) have been linked to increased risk of suicidality, but it is unclear if they explain additional risk over and above other risk factors. We refined the recently proposed multidimensional hierarchical model of OCD and explored how each symptom dimension in the model was associated with suicidality in a random half (n = 500) of a well-characterized cohort of patients with OCD. Symptom dimensions and other risk factors significantly associated with suicidality were included in a confirmatory multivariable model conducted with the other half of the sample (n = 501). The predictive confirmatory model accounted for 19% of the variance in suicidality. Taboo obsessions, the general OCD factor (i.e., having many different OCD symptoms at the same time), lifetime major depression, and lifetime substance use disorders significantly predicted suicidality in this model. Lifetime major depression explained most unique variance in suicidality (5.6%) followed by taboo obsessions and the general OCD factor (1.9% each). Taboo obsessions explain a small but significant proportion of variance in suicidality and should be considered an independent risk factor for suicidality in patients with OCD., (Copyright © 2022 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

Purpose: Individuals with obsessive-compulsive disorder (OCD) often report driving-related obsessions, such as fears of causing accidents, but the risk of transport accidents in OCD is unknown. We investigated whether individuals with OCD have an increased risk of serious transport accidents and convictions due to traffic offenses and explored the role of psychiatric comorbidities., Methods: We included all individuals ≥ 18 years living in Sweden between 1997 and 2013 (N = 5,760,734). A total of 23,126 individuals had a diagnosis of OCD in the National Patient Register. We also identified 16,607 families with full siblings discordant for OCD. Cox proportional hazards regression models estimated hazard ratios (HRs) with 95% confidence intervals (CIs) for the risk of three outcomes in individuals with OCD, compared to unexposed individuals and their unexposed full siblings: injuries or deaths due to transport accidents, injuries or deaths due to motor vehicle accidents, and convictions related to traffic offenses. Psychiatric comorbidities were systematically adjusted for., Results: Women, but not men, with OCD had a marginally increased risk of serious transport accidents (adjusted HR = 1.20 [95% CI 1.13-1.28]) and motor vehicle accidents (adjusted HR = 1.20 [95% CI 1.09-1.31]), compared to unaffected individuals. Neither women nor men with OCD had a significantly increased risk of convictions. The sibling comparisons showed no significant associations. When psychiatric comorbidities were adjusted for, several observed associations became non-significant or inversed (HRs and 95% CIs below one)., Conclusion: The risks of serious transport accidents and driving-related criminal convictions in OCD are negligible and heavily influenced by psychiatric comorbidity., (© 2021. The Author(s).)

Body dysmorphic disorder (BDD) typically originates in adolescence and is associated with considerable adversity. Evidence-based treatments exist but research on clinical outcomes in naturalistic settings is extremely scarce. We evaluated the short- and long-term outcomes of a large cohort of adolescents with BDD receiving specialist multimodal treatment and examined predictors of symptom improvement. We followed 140 young people (age range 10-18) with a diagnosis of BDD treated at two national and specialist outpatient clinics in Stockholm, Sweden (n = 96) and London, England (n = 44), between January 2015 and April 2021. Participants received multimodal treatment consisting of cognitive behavior therapy and, in 72% of cases, medication (primarily selective serotonin reuptake inhibitors). Data were collected at baseline, posttreatment, and 3, 6, and 12 months after treatment.The primary outcome measure was the clinician-rated Yale-Brown Obsessive-Compulsive Scale Modified for BDD, Adolescent version (BDD-YBOCS-A). Secondary outcomes included self-reported measures of BDD symptoms, depressive symptoms, and global functioning. Mixed-effects regression models showed that BDD-YBOCS-A scores decreased significantly from baseline to posttreatment (coefficient [95% confidence interval] = -16.33 [-17.90 to -14.76], p<0.001; within-group effect size (Cohen's d) = 2.08 (95% confidence interval, 1.81 to 2.35). At the end of the treatment, 79% of the participants were classified as responders and 59% as full or partial remitters. BDD symptoms continued to improve throughout the follow-up. Improvement was also seen on all secondary outcome measures. Linear regression models identified baseline BDD symptom severity as a predictor of treatment outcome at posttreatment, but no consistent predictors were found at the 12-month follow-up. To conclude, multimodal treatment for adolescent BDD is effective in both the short- and long-term when provided flexibly within a specialist setting. Considering the high personal and societal costs of BDD, specialist care should be made more widely available., (Copyright © 2022. Published by Elsevier Ltd.)

Importance: The availability of behavior therapy for individuals with Tourette syndrome (TS) and chronic tic disorder (CTD) is limited., Objective: To determine the efficacy and cost-effectiveness of internet-delivered exposure and response prevention (ERP) for children and adolescents with TS or CTD., Design, Setting, and Participants: This single-masked, parallel group, superiority randomized clinical trial with nationwide recruitment was conducted at a research clinic in Stockholm, Sweden. Out of 615 individuals assessed for eligibility, 221 participants meeting diagnostic criteria for TS or CTD and aged 9 to 17 years were included in the study. Enrollment began in April 2019 and ended in April 2021. Data were analyzed between October 2021 and March 2022., Interventions: Participants were randomized to 10 weeks of therapist-supported internet-delivered ERP for tics (111 participants) or to therapist-supported internet-delivered education for tics (comparator group, 110 participants)., Main Outcomes and Measures: The primary outcome was change in tic severity from baseline to the 3-month follow-up as measured by the Total Tic Severity Score of the Yale Global Tic Severity Scale (YGTSS-TTSS). YGTSS-TTSS assessors were masked to treatment allocation. Treatment response was operationalized as a score of 1 ("Very much improved") or 2 ("Much improved") on the Clinical Global Impression-Improvement scale., Results: Data loss was minimal, with 216 of 221 participants (97.7%) providing primary outcome data. Among randomized participants (152 [68.8%] boys; mean [SD] age, 12.1 [2.3] years), tic severity improved significantly, with a mean reduction of 6.08 points on the YGTSS-TTSS in the ERP group (mean [SD] at baseline, 22.25 [5.60]; at 3-month follow-up, 16.17 [6.82]) and 5.29 in the comparator (mean [SD] at baseline, 23.01 [5.92]; at 3-month follow-up, 17.72 [7.11]). Intention-to-treat analyses showed that the 2 groups improved similarly over time (interaction effect, -0.53; 95% CI, -1.28 to 0.22; P = .17). Significantly more participants were classified as treatment responders in the ERP group (51 of 108 [47.2%]) than in the comparator group (31 of 108 [28.7%]) at the 3-month follow-up (odds ratio, 2.22; 95% CI, 1.27 to 3.90). ERP resulted in more treatment responders at little additional cost compared with structured education. The incremental cost per quality-adjusted life-year gained was below the Swedish willingness-to-pay threshold, at which ERP had a 66% to 76% probability of being cost-effective., Conclusions and Relevance: Both interventions were associated with clinically meaningful improvements in tic severity, but ERP led to higher response rates at little additional cost., Trial Registration: ClinicalTrials.gov identifier: NCT03916055.

Importance: Neurobiological models have postulated shared neural mechanisms between obsessive-compulsive disorder (OCD) and substance use disorders, but results from clinical and epidemiological studies are conflicting or even suggest that OCD may be protective against substance misuse., Objective: To investigate whether OCD and obsessive-compulsive symptoms are associated with substance misuse and the extent to which shared genetic and/or environmental factors account for this association., Design, Setting, and Participants: In this cohort study, individuals in the general population of Sweden born between January 1, 1932, and December 31, 1997 (population cohort), were followed up through Swedish nationwide registers from January 1, 1997, to December 31, 2013. The second cohort included twin participants in the Child and Adolescent Twin Study in Sweden (CATSS) followed up from ages 18 to 24 years. Data were analyzed from March 1, 2021, to March 31, 2022., Exposures: Lifetime International Statistical Classification of Diseases and Related Health Problems, Tenth Revision, diagnosis of OCD in the National Patient Register (population cohort 1), and self-reported obsessive-compulsive symptoms at 18 years of age (CATSS cohort)., Main Outcomes and Measures: Substance misuse was defined as registered substance use-related disorder, criminal conviction, or death (population cohort), and self-reported alcohol and drug dependence symptoms at 18 and 24 years of age (CATSS cohort)., Results: The general population cohort included 6 304 188 individuals (48.9% women and 51.1% men; median baseline age, 30.5 [IQR, 15.0-46.4] years), of whom 27 342 had an OCD diagnosis. Obsessive-compulsive disorder was associated with an elevated risk of substance misuse (hazard ratio, 3.68 [95% CI, 3.52-3.85]). In the 9230 individuals in the CATSS cohort (5551 women [60.1%] and 3679 men [39.9%]), obsessive-compulsive symptoms at 18 years of age were associated with increased symptoms of alcohol dependence (concurrent [n = 9219], β = 0.18 [95% CI, 0.16-0.20]; longitudinal [n = 3381], β = 0.10 [95% CI, 0.06-0.14]) and drug dependence (concurrent [n = 749], β = 0.19 [95% CI, 0.11-0.27]; longitudinal [n = 452], β = 0.15 [95% CI, 0.04-0.25]). Comorbid anxiety and depression did not entirely explain the associations in either cohort. Using data from full siblings and maternal half-siblings (population cohort) and monozygotic and dizygotic twins (CATSS cohort) provided estimates of the relative contribution of genetic and environmental influences to the covariance between OCD and obsessive-compulsive symptoms and substance misuse or dependence. The associations were explained by genetic (56%-68%) and nonshared environmental (32%-44%) factors., Conclusions and Relevance: The findings of this Swedish population-based cohort study challenge the notion that OCD is protective against developing substance misuse. The association of OCD and obsessive-compulsive symptoms with substance misuse was largely explained by shared genetics but was also compatible with partial environmental mediation.