Exploring the genetic etiology across the continuum of the general psychopathology factor: a Swedish population-based family and twin study.

Psychiatric comorbidity can be accounted for by a latent general psychopathology factor (p factor), which quantifies the variance that is shared to varying degrees by every dimension of psychopathology. It is unclear whether the entire continuum of the p factor shares the same genetic origin. We investigated whether mild, moderate, and extreme elevations on the p factor shared the same genetic etiology by, first, examining the linearity of the association between p factors across siblings (N = 580,891 pairs). Second, we estimated the group heritability in a twin sample (N = 17,170 pairs), which involves testing whether the same genetic variants influence both extreme and normal variations in the p factor. In both samples, the p factor was based on 10 register-based psychiatric diagnoses. Results showed that the association between siblings' p factors appeared linear, even into the extreme range. Likewise, the twin group heritabilities ranged from 0.42 to 0.45 (95% CI: 0.33-0.57) depending on the thresholds defining the probands (2-3.33 SD beyond the mean; >2 SD beyond the mean; >4.33 SD beyond the mean; and >5.33 SD beyond the mean), and these estimates were highly similar to the estimated individual differences heritability (0.41, 95% CI: 0.39-0.43), indicating that scores above and below these thresholds shared a common genetic origin. Together, these results suggest that the entire continuum of the p factor shares the same genetic origin, with common genetic variants likely playing an important role. This implies, first, genetic risk factors for the aspect that is shared between all forms of psychopathology (i.e., genetic risk factors for the p factor) might be generalizable between population-based cohorts with a higher prevalence of milder cases, and clinical samples with a preponderance of more severe cases. Second, prioritizing low-cost genome-wide association studies capable of identifying common genetic variants, rather than expensive whole genome sequencing that can identify rare variants, may increase the efficiency when studying the genetic architecture of the p factor.

Bidirectional association between autoimmune disease and perinatal depression: a nationwide study with sibling comparison.

Although major depression, characterized by a pro-inflammatory profile, genetically overlap with autoimmune disease (AD) and the perinatal period involve immune system adaptations and AD symptom alterations, the bidirectional link between perinatal depression (PND) and AD is largely unexplored. Hence, the objective of this study was to investigate the bidirectional association between PND and AD. Using nationwide Swedish population and health registers, we conducted a nested case-control study and a matched cohort study. From 1,347,901 pregnancies during 2001-2013, we included 55,299 incident PND, their unaffected full sisters, and 10 unaffected matched women per PND case. We identified 41 subtypes of AD diagnoses recorded in the registers and compared PND with unaffected population-matched women and full sisters, using multivariable regressions. Women with an AD had a 30% higher risk of subsequent PND (95% CI 1.2-1.5) and women exposed to PND had a 30% higher risk of a subsequent AD (95% CI 1.3-1.4). Comparable associations were found when comparing exposed women with their unaffected sisters (nested case-control OR: 1.3, 95% CI 1.2-1.5, matched cohort HR: 1.3, 95% CI 1.1-1.6), and when studying antepartum and postpartum depression. The bidirectional association was more pronounced among women without psychiatric comorbidities (nested case-control OR: 1.5, 95% CI 1.4-1.6, matched cohort HR: 1.4, 95% CI 1.4-1.5) and strongest for multiple sclerosis (nested case-control OR: 2.0, 95% CI 1.6-2.3, matched cohort HR: 1.8, 95% CI 1.0-3.1). These findings demonstrate a bidirectional association between AD and PND independent of psychiatric comorbidities, suggesting possibly shared biological mechanisms. If future translational science confirms the underlying mechanisms, healthcare providers need to be aware of the increased risk of PND among women with ADs and vice versa.

Health, behavior, and social outcomes among offspring of parents with criminal convictions: a register-based study from Sweden.

BACKGROUND: There is currently insufficient understanding of the health and behavior of children whose parents engage in criminal behavior. We examined associations between parental criminal convictions and wide range of offspring health, behavioral, and social outcomes by age 18 in a large, national sample, aiming to get a comprehensive picture of the risks among children of offending parents. METHODS: We studied 1,013,385 individuals born in Sweden between 1987 and 1995, and their parents. Using data from several longitudinal nationwide registers, we investigated parental convictions and 85 offspring outcomes until the end of 2013, grouped into birth-related conditions, psychiatric and somatic disorders, accidents and injuries, mortality, school achievement, violent victimization, and criminality. Cox proportional hazards regression and logistic regression models were used to examine the associations. The role of genetic factors in intergenerational associations was studied in children-of-siblings analyses. We also examined the co-occurrence of multiple outcomes using Poisson regression. RESULTS: A total of 223,319 (22.0%) individuals had one parent convicted and 31,241 (3.1%) had both parents convicted during the first 18 years of their life. The strongest associations were found between parental convictions and offspring behavioral problems, substance use disorders, poor school achievement, violent victimization, and criminality, with an approximately 2 to 2.5-fold increased risk in children with one convicted parent and 3- to 4-fold increased risk in children with two convicted parents. The risks were particularly elevated among children of incarcerated parents with a history of violent convictions. The associations appeared to be at least partly explained by genetic influences. Parental convictions were also associated with an increased likelihood of experiencing multiple outcomes. CONCLUSIONS: Our findings help to calibrate the risks of a wide range of adverse outcomes associated with parental convictions and may be used to guide prevention efforts and identify key areas for future research.

Childhood and adolescence outcomes in offspring to parents with bipolar disorder: the impact of lifetime parental comorbidity, parental sex, and bipolar subtype.

BACKGROUND: Offspring of parents with bipolar disorder have increased risks of their own psychopathology. However, a large-scale survey of psychiatric, somatic, and adverse social outcomes up to adulthood, which could aid in prioritizing and tailoring prevention, is lacking. It also remains to clarify how risks are modified by other parental factors. METHODS: Swedish population registers were linked to compare offspring having (N = 24,788) and not having (N = 247,880) a parent with bipolar disorder with respect to psychiatric diagnoses and psychotropic medication, birth-related and somatic conditions, social outcomes, accidents, suicide attempts, and mortality. Individuals were followed until age 18. We estimated the influence of lifetime parental psychiatric comorbidity, bipolar disorder subtype, and sex on outcomes. RESULTS: Children of parents with bipolar disorder had 2-3 times higher risks of all psychiatric diagnoses, except for bipolar disorder, for which the risk was 11-fold. Significantly increased risks were also found for several somatic conditions, low school grades, criminal behavior, victimization, accidents, and suicidal behavior. Adjusting for lifetime parental psychiatric comorbidity attenuated most associations. Offspring of a parent with bipolar disorder type 2 had statistically significantly higher risks of attention deficit hyperactivity disorder, respiratory tract conditions, and accidents compared with offspring of a parent with bipolar disorder type 1. Offspring of mothers with bipolar disorder had higher risks of several psychiatric diagnoses, respiratory tract conditions, low school grades, and accidents compared with offspring of fathers with bipolar disorder. Having two parents with bipolar disorder entailed the highest risks of psychiatric outcomes in offspring. CONCLUSIONS: Early intervention and family support are particularly warranted for the offspring of a parent with bipolar disorder in the presence of lifetime parental psychiatric comorbidity, when the parent has bipolar disorder type 2, or when the mother or both parents have bipolar disorder.

ADHD Pharmacotherapy and Mortality in Individuals With ADHD.

Importance: Attention-deficit/hyperactivity disorder (ADHD) is associated with increased risks of adverse health outcomes including premature death, but it is unclear whether ADHD pharmacotherapy influences the mortality risk. Objective: To investigate whether initiation of ADHD pharmacotherapy was associated with reduced mortality risk in individuals with ADHD. Design, Setting, and Participants: In an observational nationwide cohort study in Sweden applying the target trial emulation framework, we identified individuals aged 6 through 64 years with an incident diagnosis of ADHD from 2007 through 2018 and no ADHD medication dispensation prior to diagnosis. Follow-up started from ADHD diagnosis until death, emigration, 2 years after ADHD diagnosis, or December 31, 2020, whichever came first. Exposures: ADHD medication initiation was defined as dispensing of medication within 3 months of diagnosis. Main Outcomes and Measures: We assessed all-cause mortality within 2 years of ADHD diagnosis, as well as natural-cause (eg, physical conditions) and unnatural-cause mortality (eg, unintentional injuries, suicide, and accidental poisonings). Results: Of 148 578 individuals with ADHD (61 356 females [41.3%]), 84 204 (56.7%) initiated ADHD medication. The median age at diagnosis was 17.4 years (IQR, 11.6-29.1 years). The 2-year mortality risk was lower in the initiation treatment strategy group (39.1 per 10 000 individuals) than in the noninitiation treatment strategy group (48.1 per 10 000 individuals), with a risk difference of -8.9 per 10 000 individuals (95% CI, -17.3 to -0.6). ADHD medication initiation was associated with significantly lower rate of all-cause mortality (hazard ratio [HR], 0.79; 95% CI, 0.70 to 0.88) and unnatural-cause mortality (2-year mortality risk, 25.9 per 10 000 individuals vs 33.3 per 10 000 individuals; risk difference, -7.4 per 10 000 individuals; 95% CI, -14.2 to -0.5; HR, 0.75; 95% CI, 0.66 to 0.86), but not natural-cause mortality (2-year mortality risk, 13.1 per 10 000 individuals vs 14.7 per 10 000 individuals; risk difference, -1.6 per 10 000 individuals; 95% CI, -6.4 to 3.2; HR, 0.86; 95% CI, 0.71 to 1.05). Conclusions and Relevance: Among individuals diagnosed with ADHD, medication initiation was associated with significantly lower all-cause mortality, particularly for death due to unnatural causes.

Associations between ß-blockers and psychiatric and behavioural outcomes: A population-based cohort study of 1.4 million individuals in Sweden.

BACKGROUND: ß-blockers are widely used for treating cardiac conditions and are suggested for the treatment of anxiety and aggression, although research is conflicting and limited by methodological problems. In addition, ß-blockers have been associated with precipitating other psychiatric disorders and suicidal behaviour, but findings are mixed. We aimed to examine associations between ß-blockers and psychiatric and behavioural outcomes in a large population-based cohort in Sweden. METHODS AND FINDINGS: We conducted a population-based longitudinal cohort study using Swedish nationwide high-quality healthcare, mortality, and crime registers. We included 1,400,766 individuals aged 15 years or older who had collected ß-blocker prescriptions and followed them for 8 years between 2006 and 2013. We linked register data on dispensed ß-blocker prescriptions with main outcomes, hospitalisations for psychiatric disorders (not including self-injurious behaviour or suicide attempts), suicidal behaviour (including deaths from suicide), and charges of violent crime. We applied within-individual Cox proportional hazards regression to compare periods on treatment with periods off treatment within each individual in order to reduce possible confounding by indication, as this model inherently adjusts for all stable confounders (e.g., genetics and health history). We also adjusted for age as a time-varying covariate. In further analyses, we adjusted by stated indications, prevalent users, cardiac severity, psychiatric and crime history, individual ß-blockers, ß-blocker selectivity and solubility, and use of other medications. In the cohort, 86.8% (n = 1,215,247) were 50 years and over, and 52.2% (n = 731,322) were women. During the study period, 6.9% (n = 96,801) of the ß-blocker users were hospitalised for a psychiatric disorder, 0.7% (n = 9,960) presented with suicidal behaviour, and 0.7% (n = 9,405) were charged with a violent crime. There was heterogeneity in the direction of results; within-individual analyses showed that periods of ß-blocker treatment were associated with reduced hazards of psychiatric hospitalisations (hazard ratio [HR]: 0.92, 95% confidence interval [CI]: 0.91 to 0.93, p < 0.001), charges of violent crime (HR: 0.87, 95% CI: 0.81 to 0.93, p < 0.001), and increased hazards of suicidal behaviour (HR: 1.08, 95% CI: 1.02 to 1.15, p = 0.012). After stratifying by diagnosis, reduced associations with psychiatric hospitalisations during ß-blocker treatment were mainly driven by lower hospitalisation rates due to depressive (HR: 0.92, 95% CI: 0.89 to 0.96, p < 0.001) and psychotic disorders (HR: 0.89, 95% CI: 0.85 to 0.93, p < 0.001). Reduced associations with violent charges remained in most sensitivity analyses, while associations with psychiatric hospitalisations and suicidal behaviour were inconsistent. Limitations include that the within-individual model does not account for confounders that could change during treatment, unless measured and adjusted for in the model. CONCLUSIONS: In this population-wide study, we found no consistent links between ß-blockers and psychiatric outcomes. However, ß-blockers were associated with reductions in violence, which remained in sensitivity analyses. The use of ß-blockers to manage aggression and violence could be investigated further.

Neurodevelopmental disorders and subsequent risk of violent victimization: exploring sex differences and mechanisms.

BACKGROUND: Neurodevelopmental disorders (NDs) are associated with experiences of victimization, but mechanisms remain unclear. We explored sex differences and the role of familial factors and externalizing problems in the association between several NDs and violent victimization in adolescence and young adulthood. METHODS: Individuals born in Sweden 1985-1997, residing in Sweden at their 15th birthday, were followed until date of violent victimization causing a hospital visit or death, death due to other causes, emigration, or December 31, 2013, whichever came first. The exposures were diagnoses of attention-deficit/hyperactivity disorder (ADHD), autism spectrum disorder (ASD), intellectual disability (ID) and other NDs. We used three different Cox regression models: a crude model, a model adjusted for familial confounding using sibling-comparisons, and a model additionally adjusted for externalizing problems. RESULTS: Among 1 344 944 individuals followed, on average, for 5 years, 74 487 were diagnosed with NDs and 37 765 had a hospital visit or died due to violence. ADHD was associated with an increased risk of violent victimization in males [hazard ratio (HR) 2.56; 95% confidence interval (CI) 2.43-2.70) and females (HR 5.39; 95% CI 4.97-5.85). ASD and ID were associated with an increased risk of violent victimization in females only. After adjusting for familial factors and externalizing problems, only ADHD was associated with violent victimization among males (HR 1.27; 95% CI 1.06-1.51) and females (HR 1.69; 95% CI 1.21-2.36). CONCLUSIONS: Females with NDs and males with ADHD are at greater risk of being victim of severe violence during adolescence and young adulthood. Relevant mechanisms include shared familial liability and externalizing problems. ADHD may be independently associated with violent victimization.

Associations of parental and perinatal factors with subsequent risk of stress-related disorders: a nationwide cohort study with sibling comparison.

Little is known about the contribution of pregnancy-related parental and perinatal factors to the development of stress-related disorders. We aimed to investigate whether parental/perinatal adversities entail higher risks of stress-related disorders in the offspring, later in life, by accounting for genetic and early environmental factors. Based on the nationwide Swedish registers, we conducted a population-based cohort study of 3,435,747 singleton births (of which 2,554,235 were full siblings), born 1973-2008 and survived through the age of 5 years. Using both population- and sibling designs, we employed Cox regression to assess the association between parental and perinatal factors with subsequent risk of stress-related disorders. We identified 55,511 individuals diagnosed with stress-related disorders in the population analysis and 37,433 in the sibling analysis. In the population-based analysis we observed increased risks of stress-related disorders among offspring of maternal/paternal age <25, single mothers, parity ≥4, mothers with BMI ≥ 25 or maternal smoking in early pregnancy, gestational diabetes, and offspring born moderately preterm (GA 32-36 weeks), or small-for-gestational-age. These associations were significantly attenuated toward null in the sibling analysis. Cesarean-section was weakly associated with offspring stress-related disorders in population [hazard ratio (HR) 1.09, 95% confidence interval (CI) 1.06-1.12] and sibling analyses (HR 1.10, 95% CI 1.02-1.20). Our findings suggest that most of the observed associations between parental and perinatal factors and risk of stress-related disorders in the population analysis are driven by shared familial environment or genetics, and underscore the importance of family designs in epidemiological studies on the etiology of psychiatric disorders.

Labor epidural analgesia and subsequent risk of offspring autism spectrum disorder and attention-deficit/hyperactivity disorder: a cross-national cohort study of 4.5 million individuals and their siblings.

BACKGROUND: A recent study has suggested that labor epidural analgesia may be associated with increased rates of offspring autism spectrum disorder. Subsequent replication attempts have lacked sufficient power to confidently exclude the possibility of a small effect, and the causal nature of this association remains unknown. OBJECTIVE: This study aimed to investigate the extent to which exposure to labor epidural analgesia is associated with offspring autism spectrum disorder and attention-deficit/hyperactivity disorder following adjustments for unmeasured familial confounding. STUDY DESIGN: We identified 4,498,462 singletons and their parents using the Medical Birth Registers in Finland (cohorts born from 1987-2005), Norway (1999-2015), and Sweden (1987-2011) linked with population and patient registries. These cohorts were followed from birth until they either had the outcomes of interest, emigrated, died, or reached the end of the follow-up (at mean ages 13.6-16.8 years), whichever occurred first. Cox regression models were used to estimate country-specific associations between labor epidural analgesia recorded at birth and outcomes (eg, at least 1 secondary care diagnosis of autism spectrum disorder and attention-deficit/hyperactivity disorder or at least 1 dispensed prescription of medication used for the treatment of attention-deficit/hyperactivity disorder). The models were adjusted for sex, birth year, birth order, and unmeasured familial confounders via sibling comparisons. Pooled estimates across all the 3 countries were estimated using inverse variance weighted fixed-effects meta-analysis models. RESULTS: A total of 4,498,462 individuals (48.7% female) were included, 1,091,846 (24.3%) of which were exposed to labor epidural analgesia. Of these, 1.2% were diagnosed with autism spectrum disorder and 4.0% with attention-deficit/hyperactivity disorder. On the population level, pooled estimates showed that labor epidural analgesia was associated with increased risk of offspring autism spectrum disorder (adjusted hazard ratio, 1.12; 95% confidence interval, 1.10-1.14, absolute risks, 1.20% vs 1.07%) and attention-deficit/hyperactivity disorder (adjusted hazard ratio, 1.20; 95% confidence interval, 1.19-1.21; absolute risks, 3.95% vs 3.32%). However, when comparing full siblings who were differentially exposed to labor epidural analgesia, the associations were fully attenuated for both conditions with narrow confidence intervals (adjusted hazard ratio [autism spectrum disorder], 0.98; 95% confidence interval, 0.93-1.03; adjusted hazard ratio attention-deficit/hyperactivity disorder, 0.99; 95% confidence interval, 0.96-1.02). CONCLUSION: In this large cross-national study, we found no support for the hypothesis that exposure to labor epidural analgesia causes either offspring autism spectrum disorder or attention-deficit/hyperactivity disorder.

Association of maternal snuff use and smoking with Sudden Infant Death Syndrome: a national register study.

BACKGROUND: The aim was to study whether non-combustible nicotine (Swedish snuff) use in pregnancy is associated with elevated risk of post neonatal mortality, Sudden Infant Death Syndrome (SIDS), and Sudden Unexpected Infant Death (SUID) and to study how cessation before the antenatal booking influenced these risks. METHODS: This was a population-based register study of all infants with information on tobacco exposure in early pregnancy born in Sweden 1999-2019, n = 2,061,514. Self-reported tobacco use in early pregnancy was categorized as nonuse, snuff use, and moderate and heavy smoking. Multiple logistic regression models were used to estimate crude and adjusted odds ratios (aORs) with 95% confidence intervals (CIs). RESULTS: Maternal snuff use was associated with increased risks of post neonatal mortality, SIDS, and SUID. The risks of snuff use and moderate smoking were of similar magnitude. Heavy smoking was associated with the highest risks. Cessation of smoking and snuff use before the antenatal booking was associated with lower risks of SIDS and SUID compared to that of continuous usage. CONCLUSIONS: Maternal snuff use was associated with increased risks of post neonatal mortality, SIDS, and SUID. Nicotine is the common substance in cigarette smoke and snuff. These findings support the hypothesis that nicotine contributes to an elevated risk of SIDS. IMPACT: Maternal snuff use and smoking in early pregnancy were associated with increased risks of post neonatal mortality, SIDS, and SUID. Cessation of smoking and snuff use before the first antenatal visit was associated with reduced risks of SIDS and SUID. The common substance in cigarette smoke and snuff is nicotine. Our findings suggest that nicotine contributes to an elevated risk of SIDS and SUID. The implication of our findings is that all forms of nicotine should be avoided in pregnancy.

Melatonin use and the risk of self-harm and unintentional injuries in youths with and without psychiatric disorders.

BACKGROUND: Sleep disorders in youth have been associated with increased risks of injury, including suicidal behavior. This study investigated whether melatonin, which is the most common medication for sleep disturbances in youth in Sweden, is associated with a decreased risk of injury. METHODS: This population-based cohort study included 25,575 youths who initiated melatonin treatment between ages 6 and 18. Poisson regression was used to estimate rate of injuries in the year prior to and following melatonin treatment initiation. A within-individual design was used to estimate relative risks by comparing injury risk in the last unmedicated month with injury risks in the 12 months after medication initiation. Analyses were stratified by sex, injury type, psychiatric comorbidities and age at melatonin-treatment initiation. RESULTS: While body injuries, falls and transport accident rates were comparable in the year before and after melatonin-treatment initiation, the risk of self-harm was highest in the months immediately prior to medication, and decreased thereafter. This was particularly prominent among adolescents with depression and/or anxiety, with females displaying greater absolute risks than males. Compared to the last unmedicated month, the 12 months post medication initiation had decreased relative risks for self-harm, with an IRR [95% CI] in the month following melatonin-treatment initiation of 0.46 [0.27-0.76] among adolescent females with psychiatric disorders, after excluding antidepressant users. CONCLUSIONS: Decreased risk of intentional self-harm was observed following melatonin-treatment initiation among females with depression and anxiety, suggesting that sleep interventions could be considered in an effort to reduce risk of self-harm in this population.

Factors associated with long-term benzodiazepine and Z-drug use across the lifespan and 5-year temporal trajectories among incident users: a Swedish nationwide register-based study.

PURPOSE: Despite being discouraged by guidelines, long-term use of benzodiazepines and related Z-drugs (BZDR) remains frequent in the real-world. An improved understanding of factors associated with the transition from new to long-term BZDR use and of temporal BZDR use trajectories is needed. We aimed to assess the proportion of long-term BZDR use (> 6 months) in incident BZDR-recipients across the lifespan; identify 5-year BZDR use trajectories; and explore individual characteristics (demographic, socioeconomic and clinical) and prescribing-related factors (pharmacological properties of the initial BZDR, prescriber's healthcare level, and concurrent dispensing of other medications) associated with long-term BZDR use and distinct trajectories. METHODS: Our nationwide register-based cohort included all BZDR-recipients in Sweden with first dispensation in 2007-2013. Trajectories of BZDR use days per year were built using group-based trajectory modelling. Cox regression and multinomial logistic regression were fitted to assess the predictors of long-term BZDR use and trajectories' membership. RESULTS: In 930,465 incident BZDR-recipients, long-term use increased with age (20.7%, 41.0%, and 57.4% in 0-17, 18-64, and ≥ 65-year-olds, respectively). Four BZDR use trajectories emerged, labelled 'discontinued', 'decreasing', 'slow decreasing' and 'maintained'. The proportion of the 'discontinued' trajectory members was the largest in all ages, but reduced from 75.0% in the youths to 39.3% in the elderly, whereas the 'maintained' increased with age from 4.6% to 36.7%. Prescribing-related factors, in particular multiple BZDRs at initiation and concurrent dispensing of other medications, were associated with increased risks of long-term (vs short-term) BZDR use and developing other trajectories (vs 'discontinued') in all age groups. CONCLUSIONS: The findings highlight the importance of raising awareness and providing support to prescribers to make evidence-based decisions on initiating and monitoring BZDR treatment across the lifespan.

Association of parental substance misuse with offspring substance misuse and criminality: a genetically informed register-based study.

BACKGROUND: Genetically informed studies have provided mixed findings as to what extent parental substance misuse is associated with offspring substance misuse and antisocial behavior due to shared environmental and genetic factors. METHODS: We linked data from nationwide registries for a cohort of 2 476 198 offspring born in Sweden 1958-1995 and their parents. Substance misuse was defined as International Classification of Diseases diagnoses of alcohol/drug use disorders or alcohol/drug-related criminal convictions. Quantitative genetic offspring-of-siblings analyses in offspring of monozygotic and dizygotic twin, full-sibling, and half-sibling parents were conducted. RESULTS: Both maternal and paternal substance misuse were robustly associated with offspring substance misuse [maternal adjusted hazard ratio (aHR) = 1.83 (95% confidence interval (CI) 1.80-1.87); paternal aHR = 1.96 (1.94-1.98)] and criminal convictions [maternal aHR = 1.56 (1.54-1.58); paternal aHR = 1.66 (1.64-1.67)]. Additive genetic effects explained 42% (95% CI 25-56%) and 46% (36-55%) of the variance in maternal and paternal substance misuse, respectively, and between 36 and 44% of the variance in substance misuse and criminality in offspring. The associations between parental substance misuse and offspring outcomes were mostly due to additive genetic effects, which explained 54-85% of the parent-offspring covariance. However, both nuclear and extended family environmental factors also contributed to the associations, especially with offspring substance misuse. CONCLUSIONS: Our findings from a large offspring-of-siblings study indicate that shared genetic influences mostly explain the associations between parental substance misuse and both offspring substance misuse and criminality, but we also found evidence for the contribution of environmental factors shared by members of nuclear and extended families.

Association of severe childhood infections with depression and intentional self-harm in adolescents and young adults.

Early-life infections have been linked with subsequent depression and self-harm. Examination of specific groups of infections and the role of familial factors may elucidate this observed relationship. We addressed these considerations in our investigations of the association of severe childhood infections with the risks of depression and self-harm in adolescence and early-adulthood. This population-based cohort study included all individuals born in Sweden between 1982 and 1996, with follow-up through 2013 (N = 1,506,070). Severe childhood infections were identified using inpatient and outpatient diagnoses from birth through age 12. Any infection as well as specific groups of infections were investigated. We examined diagnoses of depression and self-harm within inpatient and outpatient care and death by self-harm between ages 13 and 31. Cox proportional hazards regression models were used to estimate absolute risks, hazard ratios (HRs), and 95% CIs. When adjusting for sex and birth year, individuals exposed to any childhood infection demonstrated increased absolute risk differences for both outcomes (2.42% [95% CI, 0.41-4.43%] of being diagnosed with depression up until age 31, and 0.73% [-2.05% to 3.51%] of self-harm up until age 31) and increased relative risks (HR, 1.22 [1.20-1.24] for depression and HR, 1.29 [1.25-1.32] for self-harm). When controlling for unmeasured factors shared between family members by comparing discordant siblings, no strong association persisted. Our findings show that childhood infections may not be involved in the etiology of later depression and self-harm, and highlight the importance of identifying these genetic and environmental familial risk factors, which may serve as targets for interventions.

A Nation-Wide Swedish Cohort Study on Early Maternal Age at First Childbirth and Risk for Offspring Deaths, Accidents, and Suicide Attempts.

In a sample of over one million Swedish first-born offspring, we examined associations between early maternal age at first childbirth (MAFC; i.e., < 20 and 20-24 vs 25-29 years) and offspring non-accidental deaths, accidental deaths, deaths by suicide, non-fatal accidents, and suicide attempts. We included year of birth and several maternal and paternal characteristics as covariates and conducted maternal cousin comparisons to adjust for unmeasured confounding. Early MAFC (e.g., teenage childbearing) was associated with all outcomes, with the most pronounced risk elevation for accidental deaths [Hazard Ratio (HR) < 20 2.50, 95% confidence interval (CI) 2.23, 2.80], suicides (HR < 20 2.08, 95% CI 1.79, 2.41), and suicide attempts (HR < 20 2.85, 95% CI 2.71, 3.00). Adjusting for covariates and comparing cousins greatly attenuated associations (e.g., accidental deaths HR < 20 1.61, 95% CI 1.22, 2.11; suicides HR < 20 1.01, 95% CI 0.69, 1.47; and suicide attempts HR < 20 1.35, 95% CI 1.19, 1.52). A similar pattern emerged for non-accidental deaths and non-fatal accidents. Therefore, results indicated maternal background factors may be largely responsible for observed associations.

Genetic and environmental sources of familial coaggregation of obsessive-compulsive disorder and suicidal behavior: a population-based birth cohort and family study.

Obsessive-compulsive disorder (OCD) is associated with high risk of suicide. It is yet unknown whether OCD and suicidal behaviors coaggregate in families and, if so, what are the mechanisms underlying this coaggregation. In a population-based birth cohort and family study, we linked individuals born in Sweden in 1967-2003 (n = 3,594,181) to their parents, siblings, and cousins, and collected register-based diagnoses of OCD, suicide attempts, and deaths by suicide and followed them until December 31, 2013. We also applied quantitative genetic modeling to estimate the contribution of genetic and environmental factors to the familial coaggregation of OCD and suicidal behavior. An elevated risk of suicide attempts was observed across all relatives of individuals with OCD, increasing proportionally to the degree of genetic relatedness, with odds ratios (OR) ranging from 1.56 (95% confidence interval (CI) 1.49-1.63) in parents to 1.11 (95% CI 1.07-1.16) in cousins. The risk of death by suicide also increased alongside narrowing genetic distance, but was only significant in parents (OR 1.55; 95% CI 1.40-1.72) and full siblings (OR 1.80; 95% CI 1.43-2.26) of individuals with OCD. Familial coaggregation of OCD and suicide attempts was explained by additive genetic factors (60.7%) and non-shared environment (40.4%), with negligible contribution of shared environment. Similarly, familial coaggregation with death by suicide was attributed to additive genetics (65.8%) and nonshared environment (34.2%). Collectively, these observations indicate that OCD and suicidal behaviors coaggregate in families largely due to genetic factors. The contribution of unique environment is also considerable, providing opportunities to target high-risk groups for prevention and treatment.

Adverse clinical outcomes among youths with nonsuicidal self-injury and suicide attempts: a longitudinal cohort study.

BACKGROUND: More knowledge about risks of clinical outcomes associated with nonsuicidal self-injury (NSSI) and suicide attempts (SAs) is needed to inform risk assessment and intervention. METHODS: Longitudinal cohort study based on 1,855 youths was clinically assessed for NSSI and SA, and followed up (from December, 2011 to December 2013) for the outcomes; diagnosed self-injury, alcohol/substance use disorder, and psychiatric inpatient care data derived from Swedish registers. Hazard ratios (HRs) and 95% confidence intervals (CIs) of the outcomes were estimated with Cox regressions, and additionally adjusted for the potential effect of sex and the number of clinical assessments. NSSI and SA were treated as time-varying covariates. RESULTS: Youths with NSSI had elevated risks of all outcomes, compared with youths without NSSI or SA; the HR was 2.3, 95% confidence interval [1.6, 3.4] for self-injury, 1.4 [0.9, 2.1] for alcohol/substance use disorder, and 1.3 [1.0, 1.7] for psychiatric inpatient care. Youths with SA displayed higher risks for the outcomes than the NSSI group; the HR was 5.5 [2.4, 12.6] for self-injury, 2.0 [0.9, 4.4] for alcohol/substance use disorder, and 2.6 [1.5, 4.5] for psychiatric inpatient care. Youths with both NSSI and SA showed similar risks as youths with SA; HR 4.1 [2.0, 8.3] for self-injury, 2.0 [1.1, 4.1] for alcohol/substance use disorder, but a higher risk of psychiatric inpatient care; HR 5.0 [3.1, 7.9]. All results remained virtually unchanged in the adjusted analyses. CONCLUSIONS: Youths with NSSI and/or SA had higher risks for subsequent adverse clinical outcomes. These excess risks were more pronounced among youths with SA and youths with both NSSI and SA, and the risk for psychiatric inpatient care was particularly high in youths with both NSSI and SA. Our findings suggest that early interventions for youths with NSSI or SA should not exclusively focus on suicide prevention, but also consider the risk of subsequent alcohol/substance use disorder.

Hit-and-run: a Swedish nationwide cohort study of serious transport accidents and convictions due to traffic offenses in obsessive-compulsive disorder.

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.

Mental Disorders in Peyronie's Disease: A Swedish Cohort Study of 3.5 Million Men.

PURPOSE: Studies have shown that men with Peyronie's disease often suffer from psychological problems, but the psychiatric burden of this disorder remains largely unknown. We assessed risks of a range of psychiatric outcomes in a population based Swedish cohort comprising 3.5 million men. MATERIALS AND METHODS: We conducted a longitudinal cohort study based on Swedish national registers. A total of 8,105 men diagnosed with Peyronie's disease and 3.5 million comparison subjects from the general Swedish population were selected, and followed up with for diagnosed psychiatric outcomes including substance use disorder, alcohol misuse, anxiety disorder, depression, and self-injurious behaviors. Risks of psychiatric outcomes were estimated with Cox regressions and additionally adjusted for birth year. RESULTS: Men with Peyronie's disease had increased risks of being diagnosed with substance use disorder (HR 1.4, 95% CI 1.1-1.9), no excess risk of alcohol misuse (HR 0.9, CI 0.8-1.1), but elevated risks of anxiety disorder (HR 1.9, CI 1.6-2.2), depression (HR 1.7, CI 1.5-2.0), self-injurious behaviors (HR 2.0, 95% CI 1.7-2.3) as well as any psychiatric outcomes (HR 1.4, 95% CI 1.2-1.5). The risk estimates were slightly decreased when adjusted for birth year. A limitation of the study was that we had no information about Peyronie's disease diagnoses assigned before year 1997. CONCLUSIONS: Men with Peyronie's disease are at increased risk of being diagnosed with adverse psychiatric outcomes. Health care providers should ensure that men with Peyronie's disease have a documented mental health status assessment.

Serious Transport Accidents in Tourette Syndrome or Chronic Tic Disorder.

BACKGROUND: It is unknown whether individuals with tic disorders are at increased risk for serious transport accidents. OBJECTIVES: The aim of this study was to investigate the risk for injuries or death caused by transport and motor vehicle accidents in individuals with Tourette syndrome or chronic tic disorder. METHODS: This population-based, sibling-controlled cohort study included all individuals aged ≥18 years living in Sweden between 1997 and 2013 (N = 6,127,290). A total of 3449 individuals had a registered diagnosis of Tourette syndrome or chronic tic disorder in the Swedish National Patient Register. We also identified 2191 families with full siblings discordant for tic disorders. Cox proportional hazards regression modeling was used to estimate the risk for injuries or deaths as a result of transport accidents in individuals with a lifetime diagnosis of Tourette syndrome or chronic tic disorder compared with unexposed individuals and siblings. RESULTS: Individuals with tic disorders had a higher risk for transport injuries or death compared with the general population (adjusted hazard ratio, 1.50 [95% confidence interval: 1.33-1.69]) and their unaffected siblings (adjusted hazard ratio, 1.41 [95% confidence interval: 1.18-1.68]). The risks were similar across sexes. The exclusion of most psychiatric comorbidities did not alter the magnitude of the estimates. However, the risks were no longer significant after exclusion of individuals with comorbid attention deficit hyperactivity disorder. CONCLUSIONS: The marginally increased risk for serious transport accidents in tic disorders is mainly driven by attention deficit hyperactivity disorder comorbidity. Improved detection and management of attention deficit hyperactivity disorder symptoms in this patient group are warranted. © 2020 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.