Search

Background Previous studies suggest a protective effect of parenthood on suicide, but little is known about how the association may change across the lifespan, or in relation to sex, marital status or occurrence of psychiatric disorders. Methods We followed a cohort of over 5 million Swedish women and men, from 1991 to 2011, up to max. age 75, for death by suicide using national registers. Information on childbirths/adoptions, potential confounders and modifying factors were obtained from national registers. We assessed the associations between parenthood and suicide across adulthood using within time-stratified Cox regression models, with parenthood as a time-dependent exposure. Results Parents had a lower risk of suicide than non-parents across the lifespan, after adjusting for sociodemographic factors. The association was most pronounced in young adults, especially young women, but attenuated with increasing age and converged between sexes in older age groups. The lower risk of suicide over the life course was similar whether parents were married, unmarried or divorced, apart from married men; among them, parents only had a lower risk above age 55. The lower risk in parents was also evident in people with a history of psychiatric hospitalizations, but disappeared from age 55 in this population. Conclusion The lower risk of suicide was present in both parents, was most pronounced in young adulthood and weakened with increasing age. Our results are consistent with a plausible mechanism where feelings of responsibility and connectedness are protective against suicide in parents.

Objective To investigate whether patients with clozapine treatment are at an increased risk of a more severe COVID-19 infection as compared with patients on other antipsychotic drugs. Methods In this register-based cohort study, all residents (age 18 or older) in the Stockholm Region with a psychotic disorder diagnosis and antipsychotic treatment were included (N = 8 233) and followed from March 1, 2020 to January 14, 2021. The exposure was defined as clozapine treatment and the outcome measures (indicating a more severe COVID-19 infection) were: inpatient care, care within intensive care unit or death due to COVID-19 infection. Differences in outcome rates between exposed (n = 966) and unexposed (other antipsychotics; n = 7 267) were examined using Cox proportional hazards models and expressed as hazard ratios (HR) with 95% confidence intervals (CI). Results No statistically significant differences in outcome rates were found between the two groups of patients after adjusting for age, sex, and residence in retirement homes. The adjusted HR for the exposed compared to the unexposed was 0.96 (95% CI: 0.54, 1.70) for inpatient care; 1.69 (0.48, 5.93) for care in intensive care unit (ICU); and 0.86 (0.26, 2.80) for death. Regarding inpatient care, additional adjusting for country of birth, living in socioeconomically vulnerable areas, number of care visits during the previous year, and comorbid medical illnesses did not alter the results. Conclusions Our results may add support to the present guidelines, recommending sustained clozapine treatment during the current COVID-19 pandemic with careful monitoring and readiness to alter drug doses as needed.

Objective To determine whether parenthood among 25‐ to 44‐year‐olds is associated with a lower suicide rate in men and women in Sweden, and whether this is explained by selection into parenthood. Methods In total, 1,582,360 Swedish women and men, born between 1967 and 1985, and childless at their 25th birthday, were followed from 1992 to 2011. All data originated from linkage to national Swedish registers. Cox regression models were used with time‐varying parenthood status to estimate adjusted hazard ratios and 95% confidence intervals (aHR;CI) for suicide. Results Having one, two, three or more children was associated with 64%, 79% and 78% lower suicide rate, respectively, compared with having no children, in models with basic adjustments. When a wide range of indicators of selection into parenthood were taken into account, the suicide rate was 58% lower in parents with one child and 70% lower in parents with two or more children compared with childless individuals (aHR 0.42 [95% CI 0.36‐0.48]; 0.30 [95% CI 0.25‐0.35]; 0.30 [95% CI 0.21‐0.42]). In fathers with one, two, three or more children suicide rate was 54%, 64% and 59% lower, respectively, compared with non‐fathers whereas in mothers was 70%, 83% and 93% lower, respectively, compared with non‐mothers. Conclusion Parenthood among 25‐to 44‐year‐olds is associated with a lower suicide risk in both men and women but to a larger extent among women, and particularly in parents with two or more children. Although selection into parenthood is possible, a protective effect of parenthood on suicide is likely in both men and women.

Background Psychosocial workplace factors may be associated with alcohol-related morbidity, but previous studies have had limited opportunities to take non-occupational explanatory factors into account. The aim of this study is to investigate associations between job control, job demands and their combination (job strain) and diagnosed alcohol-related morbidity while accounting for several potentially confounding factors measured across the life-course, including education. Methods Job control, job demands and job strain were measured using the Swedish job exposure matrix measuring psychosocial workload on the occupational level linked to over 3 million individuals based on their occupational titles in 2005 and followed up until 2016. Cox regression models were built to estimate associations with alcohol-related diagnoses recorded in patient registers. Results Low job control was associated with an increased risk of alcohol-related morbidity, while high job demands tended to be associated with a decreased risk. Passive and high-strain jobs among men and passive jobs among women were also associated with an increased risk of alcohol diagnoses. However, all associations were found to be weakened in models adjusted for other factors measured prospectively over the life-course, especially in models that included level of education. Conclusion The associations between low job control and high job demands, and the risk of alcohol-related morbidity reflect underlying socioeconomic differences to some extent. Lower job control, however, remained associated with a higher risk of alcohol-related morbidity.

ObjectiveTo investigate the association between job control, job demands and their combination (job strain) and suicide attempts and deaths among male and female workers in Sweden.MethodsJob control and demands were measured separately for men and women using a job exposure matrix, which was linked to around three million individuals based on their occupational title in 2005. Suicide attempts and deaths were measured in the hospital and cause of death registers from 2006 to 2016. HRs were estimated using discrete proportional hazards models with annually updated age as the time axis. Models were adjusted for sociodemographic, family, health, labour market and childhood factors, as well as the time-varying effects of unemployment, sick leave and family factors during follow-up.ResultsLow job control was associated with an increased risk of suicide attempts and deaths among both men and women while high job demands tended to be associated with a decreased risk. The combination of job control and job demands (job strain) reflected the increased risk of low control jobs and the decreased risk of high demand jobs. Associations were attenuated but still present after adjustments.ConclusionsLow job control is related to suicide attempts and deaths, and this is only partially explained by important covariates measured both prebaseline and during follow-up. Attempts to increase job control among workers may be beneficial in preventing suicide.

BackgroundBoth low intelligence and low emotional control have previously been linked to a higher risk of suicide, but it is unknown whether the associations apply consistently over the life course.MethodsThe study was based on data on intelligence and emotional control, collected from 48 738 Swedish men conscripted in 1969–1970, at ages 18–20 years. The data were linked to national registers giving information on subsequent suicidal behavior (completed and attempted suicide) up to the age of 59 years. The associations were investigated using logistic regression and Cox proportional hazards regression models, with adjustment for childhood socioeconomic status.ResultsIntelligence and emotional control assessed in late adolescence both showed robust inverse associations with suicidal behavior over the 38-year follow-up. However, while the association between lower intelligence and higher rate of suicidal behavior remained the same throughout (~40% increased hazard per unit on a five-level scale), the association between lower emotional control and suicidal behavior was substantially stronger in early adulthood (~100% increased hazard per unit) than in late middle age (~30% increased hazard per unit).ConclusionsThe study adds to previous research by showing that the association between poor emotional control and subsequent suicide risk in men becomes weaker over the life course, while the association between low intelligence and suicide risk seems to be constant. The particularly high suicide risk of young men with poor emotional control may motivate targeted prevention efforts.

Earlier research has identified personality traits × intelligence interaction effects on academic performance. The present study, employing data from the 1997 National Longitudinal Survey of Youth (NLSY97, N = 8984), identified some interaction effects, mainly involving indicators of dependability, on high school grades. The interaction effects tended to be synergistic, meaning that the association between the trait and grades tended to strengthen with increased intelligence. This could be due to a sufficient level of intelligence being necessary for higher grades, and that lack thereof cannot be compensated for by a high degree of some advantageous personality trait. However, a positive association between intelligence and reliability in the measurement of personality, as well as a reversed causal effect of grades on self-rated personality moderated by intelligence, could also be contributing causes to the tendency for synergistic interaction effects.

Background Throughout the industrialized world, demand for low skilled labour is falling. The length of schooling is increasing in response, but so is the proportion of individuals not finishing upper secondary school. The objective of this study was to evaluate the associations between labour market positions at age 18 and all-cause and suicide- and accident-specific mortality in later adulthood. Methods Labour market positions at age 18 were categorized for all Swedes born 1972-77 (n=630 959) into four main groups: employed, successful students, students not about to qualify (SNAQs), and individuals not in employment, education or training (NEETs). Cox proportional hazard models were fitted to assess all-cause, suicide and accident mortality up to 2016 (ages 39-44), adjusting for high school grades, parental and own prior psychiatric diagnoses, and childhood socioeconomic status. Findings SNAQs had substantially increased all-cause (men: HR=2.10; 95% CI 1.92-2.28, women: HR=1.64; 95% CI: 1.44-1.86), suicide (men: HR=2.16; CI: 1.86-2.51, women: HR=2.10; 95% CI 1.64-2.69), and accident specific (men: HR=2.08; 95% CI 1.77-2.44, women: 1.87; 95% CI 1.33;2.62) mortality risks compared to successful students. The risks were similar for NEETs. There was no increased risk among full-time employed compared to successful students. Interpretation Expanding the educational system may be a natural response to falling demand for low skilled labour but not by far one that corrects the major societal challenge of it. Unless educational systems adequately respond to this challenge, only more inequality is to be expected ahead. Funding This work was supported by a grant to FR and AL from the Swedish Research Council for Health, Working Life, and Welfare with contract number (2014-2009).

BackgroundHigh job demands, low job control, and their combination (job strain) may increase workers' risk of depression. Previous research is limited by small populations, not controlling for previous depression, and relying on the same informant for reporting exposure and outcome. This study aims to examine the relationship between objectively measured workplace factors and the risk of developing clinical depression among the Swedish working population while controlling for previous psychiatric diagnoses and sociodemographic factors.MethodsControl, demands, and job strain were measured using the Swedish Job Exposure Matrix (JEM) measuring psychosocial workload linked to around 3 million individuals based on their occupational titles in 2005. Cox regression models were built to estimate associations between these factors and diagnoses of depression recorded in patient registers.ResultsLower job control was associated with an increased risk of developing depression (HR 1.43, 95% CI 1.39–1.48 and HR 1.27, 95% CI 1.24–1.30 for men and women with the lowest control, respectively), and this showed a dose–response relationship among men. Having high job demands was associated with a slight decrease in depression risk for men and women. High strain and passive jobs (both low control jobs) were associated with an increased risk of depression among men, and passive jobs were associated with an increased risk among women.ConclusionHigh job control appears important for reducing the risk of developing depression even when accounting for previous psychiatric diagnoses and sociodemographic factors. This is an important finding concerning strategies to improve occupational and in turn mental health.

BackgroundCharacteristics of the neighbourhood environment, including population density, social fragmentation, and trust, have been linked to mental health outcomes. Using a longitudinal population-based cohort, we explored the relationship between objective and subjective neighbourhood characteristics and the odds of suicidal thoughts and attempts.MethodsWe conducted a longitudinal study of 20764 participants living in Stockholm County who participated in the Stockholm Public Health Survey. We used multilevel modelling to examine if suicidal thoughts and attempts were associated with neighbourhood characteristics, independent of individual associations. We included objective and subjective measures to explore if there was a different relationship between these measures of the neighbourhood environment and suicidality.ResultsAssociations between neighbourhood factors and suicidality were predominantly explained by individual characteristics, with the exception of neighbourhood-level deprivation and average residential trust. Each unit increase of deprivation was linked to increased odds of suicidal thoughts [Odds ratio (OR) 1.04, 95% confidence interval (CI) 1.00–1.07] and attempts (OR 1.11, 95% CI 1.06–1.17). Decreasing residential trust was associated with increased odds of suicide attempts (OR 1.09, 95% CI 1.02–1.17). There was no evidence that neighbourhood-level fragmentation or average trust in public and political institutions had an independent effect on suicidality once individual and sociodemographic factors were accounted for.ConclusionsThis study showed that much of the neighbourhood-level variation in suicidal thoughts and attempts could be explained by compositional factors, including sociodemographic clustering within neighbourhoods. The independent effect of neighbourhood-level deprivation and average residential trust provide evidence that the neighbourhood context may exert an independent effect on suicidality beyond the impact of individual characteristics.

Poor academic performance in childhood is associated with suicide attempt in adulthood, but the mechanisms are not known. We investigated educational attainment as a possible pathway.We followed two sets of cohorts, born around 1950/1970, respectively, in the Swedish population-representative 'Evaluation Through Follow-up' study for a first suicide attempt in national records up to 2013. Data on grade point average (GPA) at age 13/16 and educational attainment (years of schooling) in adulthood were used. The path models included linear and Cox proportional hazards regressions. A model with matched age range during follow-up was used to compare the cohorts.In the 1970 cohort, the association between GPA and suicide attempt between age 26 and 46 was partly mediated by attained education (total association, β=-0.82; via education: -0.29, per SD increase in GPA), but GPA also had a direct path to suicide attempt (β=-0.53). There was no evidence of such a pathway in the 1950 cohort between age 41 and 65. In the age-matched analysis, at age 26-46, the association between GPA and suicide attempt was stronger in the 1970 cohort compared to the 1950 cohort (β=-0.72 and -0.24, respectively).Differences in attained education seem to partly explain the associations of academic performance with suicide attempt up to middle age. Furthermore, there is some indication that academic performance may have become more important for young people's mental health than it was in previous generations.

Background An association between higher intelligence and lower probability of serious depression has previously been established. Yet, to our knowledge, no large prospective study has examined the relationship across the lifespan. Methods A cohort of 49,321 Swedish men was followed from conscription in 1969–70 (age 18–20) through to 2008. Odds ratios (OR) for first time hospitalisation for depression (FTHD) were calculated in relation to intelligence for distinct time periods across the lifespan, while controlling for established risk factors for depression. Results There was a linear association between higher intelligence in youth and lower odds for FTHD during the entire follow-up period, 1973–2008. The association got progressively weaker across the lifespan. During 1973–80, one step down on the stanine scale was associated with an unadjusted increase in OR of 1.34 [95% confidence interval (CI) 1.26–1.42], adjusted OR 1.23 [1.15–1.32]; while, during 2001–2008, the ORs were less than half of the magnitude of the first period, unadjusted 1.14 [1.07–1.21], and adjusted 1.09 [1.01–1.17]. Limitations The study includes men only, and the number of available places for in-patient care decreased during the follow-up period. Conclusion For the first time, we have shown that the association between lower intelligence and depression decreases over time. The attenuation of the association in the adjusted models suggests a slower accumulation of depressogenic stressors among people with a higher IQ-score. Further exploration of intelligence's role in the etiology of depression across the lifespan is required in order to facilitate adequate diagnoses and ameliorating interventions.

Background Both low intelligence and low emotional control have previously been linked to a higher risk of suicide, but it is unknown whether the associations apply consistently over the life course. Methods The study was based on data on intelligence and emotional control, collected from 48 738 Swedish men conscripted in 1969–1970, at ages 18–20 years. The data were linked to national registers giving information on subsequent suicidal behavior (completed and attempted suicide) up to the age of 59 years. The associations were investigated using logistic regression and Cox proportional hazards regression models, with adjustment for childhood socioeconomic status. Results Intelligence and emotional control assessed in late adolescence both showed robust inverse associations with suicidal behavior over the 38-year follow-up. However, while the association between lower intelligence and higher rate of suicidal behavior remained the same throughout (~40% increased hazard per unit on a five-level scale), the association between lower emotional control and suicidal behavior was substantially stronger in early adulthood (~100% increased hazard per unit) than in late middle age (~30% increased hazard per unit). Conclusions The study adds to previous research by showing that the association between poor emotional control and subsequent suicide risk in men becomes weaker over the life course, while the association between low intelligence and suicide risk seems to be constant. The particularly high suicide risk of young men with poor emotional control may motivate targeted prevention efforts.

Background\ud \ud The incidence of major depression among adults has been shown to be socially differentiated, and there are reasons to seek explanations for this before adulthood. In this cohort study, we examined whether academic performance in adolescence predicts depression in adulthood, and the extent to which externalizing disorders explain this association.\ud \ud \ud Methods\ud \ud We followed 26,766 Swedish women and men born 1967–1982 from the last year of compulsory school, at age about 16, up to 48 years of age. We investigated the association between grade point average (GPA, standardized by gender) and first diagnosis of depression in national registers of in- or out-patient psychiatric care. We used Cox proportional hazards models, adjusting for lifetime externalizing diagnoses and potential confounders including childhood socioeconomic position and IQ.\ud \ud \ud Results\ud \ud During follow-up, 7.0% of the women and 4.4% of the men were diagnosed with depression. A GPA in the lowest quartile, compared with the highest, was associated with an increased risk in both women (hazard ratio 95% confidence interval 1.7, 1.3–2.1) and men (2.9, 2.2–3.9) in models controlling for potential confounders. Additional control for externalizing disorders attenuated the associations, particularly in women.\ud \ud \ud Conclusions\ud \ud The findings suggest that poor academic performance is associated with depression in young adulthood and that the association is partly explained by externalizing disorders. Our results indicate the importance of early detection and management of externalizing disorders among children and adolescents.

BackgroundThe association between childhood cognitive ability measured with IQ tests and mortality is well documented. However, studies on the association in women are few and conflicting, and the mechanisms underlying the association are unclear.MethodsData on IQ were collected at school at age 13 among 19 919 men and women born in 1948 and 1953. Information on childhood socioeconomic position, the participants’ socioeconomic and social circumstances in middle age and mortality up to 2013 was collected through national registers.ResultsLower IQ was associated with an increased risk of all-cause mortality among men (1070 cases, HR 1.31, 95% CI 1.23 to 1.39 for one SD decrease in IQ) and among women (703 cases, HR 1.16, 95% CI 1.08 to 1.25). IQ was associated with mortality from several causes of death in men, and cancer and cardiovascular disorder mortality in women. Adjustment for socioeconomic factors in childhood and, in particular, in adulthood attenuated the associations considerably in men and near completely in women.ConclusionLower IQ was associated with an increased risk of mortality in men and women. The explanatory effects of socioeconomic factors in adulthood suggest that they constitute an important pathway in the association between IQ and mortality, especially in women.

Background An association between lower IQ of parents, measured early in life, and smoking among their offspring has been reported. The extent to which other background factors account for this association is unknown. Methods Data on IQ, smoking, mental health, social class, parental divorce and social problems in a cohort of men born during 1949–1951 and conscripted for military service in 1969 were linked to smoking data on 682 offspring interviewed in the Swedish Surveys of Living Conditions 1984–2009. Results In an age-adjusted model, a one-step decrease on a stanine scale was associated with an OR of 1.19 (95% CI 04 to 1.35) for offspring smoking. Adjusting for father9s socioeconomic background and smoking, mental illness and social problems in youth only marginally lowered the OR9s. Conclusions Lower IQ among fathers measured at ages 18–20 years was associated with smoking in their offspring. The association was not explained by father9s social class in childhood or a higher prevalence of mental illness, social problems or smoking measured among the fathers in their late adolescence.

Background Lower intelligence early in life is associated with increased risks for coronary heart disease (CHD) and mortality. Intelligence level might affect compliance to treatment but its prognostic importance in patients with CHD is unknown. Methods A cohort of 1923 Swedish men with a measure of intelligence from mandatory military conscription in 1969–1970 at age 18–20, who were diagnosed with CHD 1991–2007, were followed to the end of 2008. Primary outcome: recurrent CHD event. Secondary outcome: case fatality from the first event, cardiovascular and all-cause mortality. National registers provided information on CHD events, comorbidity, mortality and socioeconomic factors. Results The fully adjusted HRs for recurrent CHD for medium and low intelligence, compared with high intelligence, were 0.98, (95% CIs 0.83 to 1.16) and 1.09 (0.89 to 1.34), respectively. The risks were increased for cardiovascular and all-cause mortality with lower intelligence, but were attenuated in the fully adjusted models (fully adjusted HRs for cardiovascular mortality 1.92 (0.94 to 3.94) and 1.98 (0.89 to 4.37), respectively; for all-cause mortality 1.63 (1.00 to 2.65) and 1.62 (0.94 to 2.78), respectively). There was no increased risk for case-fatality at the first event (fully adjusted ORs 1.06 (0.73 to 1.55) and 0.97 (0.62 to 1.50), respectively). Conclusions Although we found lower intelligence to be associated with increased mortality in middle-aged men with CHD, there was no evidence for its possible effect on recurrence in CHD.

Intelligence quotient (IQ) is associated with mental health in youth onwards, as well as somatic health and longevity later in life. However, little is known about the association with somatic health in youth. We aimed to investigate the cross-sectional association between IQ and a range of somatic diagnoses and health indicators in late adolescence. In a cohort comprising 49 321 Swedish men, IQ test performance and health status were recorded at conscription in 1969–70, at ages 18–20. Information on socioeconomic factors in childhood was obtained from the national census. Odds ratios (ORs) were estimated by logistic regression. With adjustment for socioeconomic background, each step decrease in IQ test performance on a nine-point scale was associated with an increased OR for the following somatic diagnoses: impaired hearing (1.14, 1. 1.12–1.16), endocrine disorders (1.13, 1.10–1.17), symptoms and ill-defined conditions (1.11, 1.08–1.14), back pain (1.10, 1.08–1.12), digestive system diseases (1.08, 1.05–1.10) and injuries (1.02, 1.00–1.05); and a decreased OR for hayfever (0.87, 0.85–0.90) and refractive errors (0.87, 0.86–0.88). IQ was also associated with increased ORs for low physical capacity (1.12, 1.10–1.14), signs of inflammation (1.07, 1.06–1.09) and low self-rated health (1.03, 1.02–1.05). Several diagnoses were not associated with IQ. In conclusion, lower IQ at conscription was associated with a higher risk for several diagnoses and indicators of poor health, but the risk was decreased for a few of the diagnoses. The mechanisms underlying the associations presumably differ. However, socioeconomic factors in childhood could not explain the associations.

BackgroundCardiovascular fitness influences many aspects of brain function. However, the relationship between cardiovascular fitness and suicidal behaviour is unknown. Therefore, we aimed to determine whether cardiovascular fitness at age 18 years is associated with future risk of suicide attempt/death.MethodWe performed a population-based Swedish longitudinal cohort study of male conscripts with no previous or ongoing mental illness (n = 1 136 527). The conscription examination, which took place during 1968–2005, included the cycle ergonometric test and tests of cognitive performance. Future risk of suicide attempt/death over a 5- to 42-year follow-up period was calculated with Cox proportional hazards models controlling for several confounders including familial factors.ResultsAt least one suicide attempt was recorded for 12 563 men. Death by suicide without a prior attempt was recorded in 4814 additional individuals. In fully adjusted models low cardiovascular fitness was associated with increased risk for future attempt/death by suicide [hazard ratio (HR) 1.79, 95% confidence interval (CI) 1.64–1.94]. The HR changed only marginally after exclusion of persons who received in-patient care for depression (HR 1.76, 95% CI 1.61–1.94). Poor performance on both the cardiovascular fitness and cognitive tests was associated with a fivefold increased risk of suicide attempt or suicide death (HR 5.46, 95% CI 4.78–6.24).ConclusionsLower cardiovascular fitness at age 18 years was, after adjustment for a number of potential confounders, associated with an increased risk of attempt/death by suicide in adulthood. It remains to be clarified whether interventions designed to improve fitness in teens can influence the risk of suicidal behaviour later in life.

ObjectiveTo investigate the association between intelligence and disability pension due to mental, musculoskeletal, cardiovascular, and substance-use disorders among men and women, and to assess the role of childhood social factors and adulthood work characteristics.MethodsTwo random samples of men and women born 1948 and 1953 (n = 10 563 and 9 434), and tested for general intelligence at age 13, were followed in registers for disability pension until 2009. Physical and psychological strains in adulthood were assessed using job exposure matrices. Associations were examined using Cox proportional hazard regression models, with increases in rates reported as hazard ratios (HRs) with 95% confidence intervals (95%CI) per decrease in stanine intelligence.ResultsIn both men and women increased risks were found for disability pension due to all causes, musculoskeletal disorder, mental disorder other than substance use, and cardiovascular disease as intelligence decreased. Increased risk was also found for substance use disorder in men. In multivariate models, HRs were attenuated after controlling for pre-school plans in adolescence, and low job control and high physical strain in adulthood. In the fully adjusted model, increased HRs remained for all causes (male HR 1.11, 95%CI 1.07-1.15, female HR 1.06, 95%CI 1.02-1.09) and musculoskeletal disorder (male HR 1.16, 95%CI 1.09-1.24, female HR 1.08, 95%CI 1.03-1.14) during 1986 to 2009.ConclusionRelatively low childhood intelligence is associated with increased risk of disability pension due to musculoskeletal disorder in both men and women, even after adjustment for risk factors for disability pension measured over the life course.

Background Intelligence quotient (IQ) is associated with mental health from youth onwards, as well as somatic health and longevity later in life. However, little is known about the association with somatic health in youth. We aimed to investigate the cross-sectional association between IQ and a range of somatic diagnoses and health indicators in early adulthood. Methods In a cohort comprising …

BackgroundCognitive ability/intelligence quotient (IQ) in youth has previously been associated with subsequent completed and attempted suicide, but little is known about the mechanisms underlying the associations. This study aims to assess the roles of various risk factors over the life course in explaining the observed relationships.MethodThe present investigation is a cohort study based on data on IQ test performance and covariates, recorded on 49 321 Swedish men conscripted in 1969–1970, at ages 18–20 years. Information on suicides and hospital admissions for suicide attempt up to the age of 57 years, childhood and adult socio-economic position, and adult family formation, was obtained from linkage to national registers.ResultsLower IQ was associated with increased risks of both suicide and suicide attempt during the 36 years of follow-up. The associations followed a dose–response pattern. They were attenuated by approximately 45% in models controlling for social background, mental ill-health, aspects of personality and behavior, adult socio-economic position and family formation. Based on one-unit decreases in IQ test performance on a nine-point scale, the hazard ratios between ages 35 and 57 years were: for suicide 1.19 [95% confidence interval (CI) 1.13–1.25], fully adjusted 1.10 (95% CI 1.04–1.18); and for suicide attempt 1.25 (95% CI 1.20–1.31), fully adjusted 1.14 (95% CI 1.09–1.20).ConclusionsCognitive ability was found to be associated with subsequent completed and attempted suicide. The associations were attenuated by 45% after controlling for risk factors measured over the life course. Psychiatric diagnosis, maladjustment and aspects of personality in young adulthood, and social circumstances in later adulthood, contributed in attenuating the associations.