Familial aggregation of schizophrenia: the moderating effect of age at onset, parental immigration, paternal age and season of birth

Selective mutism and the risk of mental and neurodevelopmental disorders among siblings

The siblings of children with mental disorders are more likely to experience mental health issues themselves, but there has been a lack of sibling studies on selective mutism (SM). The aim of this population-based study was to use national registers to examine associations between children with SM and diagnoses of various mental disorder in their siblings. All singleton children born in Finland from 1987 to 2009, and diagnosed with SM from 1998 to 2012, were identified from national health registers and matched with four controls by age and sex. Their biological siblings and parents were identified using national registries and the diagnostic information on the siblings of the subjects and controls was obtained. The final analyses comprised 658 children with SM and their 1661 siblings and 2092 controls with 4120 siblings. The analyses were conducted using generalized estimating equations. Mental disorders were more common among the siblings of the children with SM than among the siblings of the controls. The strongest associations were observed for childhood emotional disorders and autism spectrum disorders after the data were adjusted for covariates and comorbid diagnoses among SM subjects. The final model showed associations between SM and a wide range of disorders in siblings, with strongest associations with disorders that usually have their onset during childhood. Our finding showed that SM clustered with other mental disorders in siblings and this requires further research, especially the association between SM and autism spectrum disorders. Strong associations with childhood onset disorders may indicate shared etiologies.

Common Genetic Variation and Age of Onset of Anorexia Nervosa

Background

Genetics and biology may influence the age of onset of anorexia nervosa (AN). The aims of this study were to determine whether common genetic variation contributes to age of onset of AN and to investigate the genetic associations between age of onset of AN and age at menarche.

Methods

A secondary analysis of the Psychiatric Genomics Consortium genome-wide association study (GWAS) of AN was performed, which included 9335 cases and 31,981 screened controls, all from European ancestries. We conducted GWASs of age of onset, early-onset AN (<13 years), and typical-onset AN, and genetic correlation, genetic risk score, and Mendelian randomization analyses.

Results

Two loci were genome-wide significant in the typical-onset AN GWAS. Heritability estimates (single nucleotide polymorphism-h 2) were 0.01-0.04 for age of onset, 0.16-0.25 for early-onset AN, and 0.17-0.25 for typical-onset AN. Early- and typical-onset AN showed distinct genetic correlation patterns with putative risk factors for AN. Specifically, early-onset AN was significantly genetically correlated with younger age at menarche, and typical-onset AN was significantly negatively genetically correlated with anthropometric traits. Genetic risk scores for age of onset and early-onset AN estimated from independent GWASs significantly predicted age of onset. Mendelian randomization analysis suggested a causal link between younger age at menarche and early-onset AN.

Conclusions

Our results provide evidence consistent with a common variant genetic basis for age of onset and implicate biological pathways regulating menarche and reproduction.

Familial risk and heritability of intellectual disability: a population-based cohort study in Sweden

BACKGROUND

Intellectual disability (ID) aggregates in families, but factors affecting individual risk and heritability estimates remain unknown.

METHODS

A population-based family cohort study of 4,165,785 individuals born 1973-2013 in Sweden, including 37,787 ID individuals and their relatives. The relative risks (RR) of ID with 95% confidence intervals (95% CI) were obtained from stratified Cox proportional-hazards models. Relatives of ID individuals were compared to relatives of unaffected individuals. Structural equation modeling was used to estimate heritability.

RESULTS

Relatives of ID individuals were at increased risk of ID compared to individuals with unaffected relatives. The RR of ID among relatives increased proportionally to the degree of genetic relatedness with ID probands; 256.70(95% CI 161.30-408.53) for monozygotic twins, 16.47(13.32-20.38) for parents, 14.88(12.19-18.16) for children, 7.04(4.67-10.61) for dizygotic twins, 8.38(7.97-8.83) for full siblings, 4.56(4.02-5.16) for maternal, 2.90(2.49-3.37) for paternal half-siblings, 3.03(2.61-3.50) for nephews/nieces, 2.84(2.45-3.29) for uncles/aunts, and 2.04(1.91-2.20) for cousins. Lower RRs were observed for siblings of probands with chromosomal abnormalities (RR 5.53, 4.74-6.46) and more severe ID (mild RR 9.15, 8.55-9.78, moderate RR 8.13, 7.28-9.08, severe RR 6.80, 5.74-8.07, and profound RR 5.88, 4.52-7.65). Male sex of relative and maternal line of relationship with proband was related to higher risk (RR 1.33, 1.25-1.41 for brothers vs. sisters and RR 1.49, 1.34-1.68 for maternal vs. paternal half-siblings). ID was substantially heritable with 0.95(95% CI 0.93-0.98) of the variance in liability attributed to genetic influences.

CONCLUSIONS

The risk estimates will benefit researchers, clinicians, families in understanding the risk of ID in the family and the whole population. The higher risk of ID related to male sex and maternal linage will be of value for planning and interpreting etiological studies in ID.

Discovery of an unusually high number of de novo mutations in sperm of older men using duplex sequencing

De novo mutations (DNMs) are important players in heritable diseases and evolution. Of particular interest are highly recurrent DNMs associated with congenital disorders that have been described as selfish mutations expanding in the male germline, thus becoming more frequent with age. Here, we have adapted duplex sequencing (DS), an ultradeep sequencing method that renders sequence information on both DNA strands; thus, one mutation can be reliably called in millions of sequenced bases. With DS, we examined ∼4.5 kb of the FGFR3 coding region in sperm DNA from older and younger donors. We identified sites with variant allele frequencies (VAFs) of 10-4 to 10-5, with an overall mutation frequency of the region of ∼6 × 10-7 Some of the substitutions are recurrent and are found at a higher VAF in older donors than in younger ones or are found exclusively in older donors. Also, older donors harbor more mutations associated with congenital disorders. Other mutations are present in both age groups, suggesting that these might result from a different mechanism (e.g., postzygotic mosaicism). We also observe that independent of age, the frequency and deleteriousness of the mutational spectra are more similar to COSMIC than to gnomAD variants. Our approach is an important strategy to identify mutations that could be associated with a gain of function of the receptor tyrosine kinase activity, with unexplored consequences in a society with delayed fatherhood.

Detection of Morphological Abnormalities in Schizophrenia: An Important Step to Identify Associated Genetic Disorders or Etiologic Subtypes

Current research suggests that alterations in neurodevelopmental processes, involving gene X environment interactions during key stages of brain development (prenatal period and adolescence), are a major risk for schizophrenia. First, epidemiological studies supporting a genetic contribution to schizophrenia are presented in this article, including family, twin, and adoption studies. Then, an extensive literature review on genetic disorders associated with schizophrenia is reviewed. These epidemiological findings and clinical observations led researchers to conduct studies on genetic associations in schizophrenia, and more specifically on genomics (CNV: copy-number variant, and SNP: single nucleotide polymorphism). The main structural (CNV) and sequence (SNP) variants found in individuals with schizophrenia are reported here. Evidence of genetic contributions to schizophrenia and current knowledge on genetic syndromes associated with this psychiatric disorder highlight the importance of a clinical genetic examination to detect minor physical anomalies in individuals with ultra-high risk of schizophrenia. Several dysmorphic features have been described in schizophrenia, especially in early onset schizophrenia, and can be viewed as neurodevelopmental markers of vulnerability. Early detection of individuals with neurodevelopmental abnormalities is a fundamental issue to develop prevention and diagnostic strategies, therapeutic intervention and follow-up, and to ascertain better the underlying mechanisms involved in the pathophysiology of schizophrenia.

The other face of advanced paternal age: a scoping review of its terminological, social, public health, psychological, ethical and regulatory aspects

BACKGROUND

There is a global tendency for parents to conceive children later in life. The maternal dimension of the postponement transition has been thoroughly studied, but interest in the paternal side is more recent. For the moment, most literature reviews on the topic have focused on the consequences of advanced paternal age (APA) on fertility, pregnancy and the health of the child.

OBJECTIVE AND RATIONALE

The present review seeks to move the focus away from the biological and medical dimensions of APA and synthesise the knowledge of the other face of APA.

SEARCH METHODS

We used the scoping review methodology. Searches of interdisciplinary articles databases were performed with keywords pertaining to APA and its dimensions outside of biology and medicine. We included scientific articles, original research, essays, commentaries and editorials in the sample. The final sample of 177 documents was analysed with qualitative thematic analysis.

OUTCOMES

We identified six themes highlighting the interdisciplinary nature of APA research. The 'terminological aspects' highlight the lack of consensus on the definition of APA and the strategies developed to offer alternatives. The 'social aspects' focus on the postponement transition towards reproducing later in life and its cultural dimensions. The 'public health aspects' refer to attempts to analyse APA as a problem with wider health and economic implications. The 'psychological aspects' focus on the consequences of APA and older fatherhood on psychological characteristics of the child. The 'ethical aspects' reflect on issues of APA emerging at the intersection of parental autonomy, children's welfare and social responsibility. The 'regulatory aspects' group different suggestions to collectively approach the implications of APA. Our results show that the field of APA is still in the making and that evidence is lacking to fully address the issues of APA. The review suggests promising avenues of research such as introducing the voice of fathers of advanced age into the research agenda.

WIDER IMPLICATIONS

The results of this review will be useful for developing policies and preconception health interventions that consider and include prospective fathers of advanced age.

Polygenic risk for schizophrenia and season of birth within the UK Biobank cohort

BACKGROUND

There is strong evidence that people born in winter and in spring have a small increased risk of schizophrenia. As this 'season of birth' effect underpins some of the most influential hypotheses concerning potentially modifiable risk exposures, it is important to exclude other possible explanations for the phenomenon.

METHODS

Here we sought to determine whether the season of birth effect reflects gene-environment confounding rather than a pathogenic process indexing environmental exposure. We directly measured, in 136 538 participants from the UK Biobank (UKBB), the burdens of common schizophrenia risk alleles and of copy number variants known to increase the risk for the disorder, and tested whether these were correlated with a season of birth.

RESULTS

Neither genetic measure was associated with season or month of birth within the UKBB sample.

CONCLUSIONS

As our study was highly powered to detect small effects, we conclude that the season of birth effect in schizophrenia reflects a true pathogenic effect of environmental exposure.

Birth month and later diagnosis of schizophrenia. A population-based cohort study in Sweden

The objective of the present study was to examine if the monthly variation in births of individuals diagnosed with schizophrenia currently differs from that of unaffected individuals in Sweden. In an extensive linkage of Swedish national and regional population registers we here investigate the birth pattern of the population born 1940-97 (5,995,499 individuals) which included 30,684 individuals diagnosed with schizophrenia in the National Patient Register by December 31, 2016. Among 2,409,862 individuals born since 1973 we investigated potential confounding by co-variates associated with pregnancy and birth. We also compared the monthly birth pattern of 22,570 affected individuals to that of their 41,528 unaffected full siblings. We observe a significant birth excess of individuals with schizophrenia in December, HR 1.07 95%CI (1.01-1.13). Patients born in December received a registered diagnosis of schizophrenia at a slightly younger age than those born during other months. A number of co-variates were associated not only with schizophrenia but also varied across birth months. Inclusion of these in the models however had virtually no influence on the risk for schizophrenia associated with December birth. In comparisons between full siblings, the association between December birth and later diagnosis of schizophrenia remained, albeit slightly attenuated, HR 1.06 (0.99-1.12). Risk for schizophrenia associated with birth in December in Sweden during the study period does not appear to be fully explained by our investigated co-variates or factors shared between family members and may thus represent monthly/seasonal variation in environmental factors involved in the etiology of schizophrenia.

Parental characteristics and the risk of schizophrenia in a Chinese population: a case-control study

BACKGROUND

Genetic studies have provided convergent results indicating that schizophrenia is a polygenic disorder with a heritability estimate of ∼60-80%. The propensity for schizophrenia is ∼10 times higher in individuals with first-degree relatives with schizophrenia when compared to the general population.

AIM

To identify associations between parental characteristics and the risk of schizophrenia in a Chinese population.

METHODS

Participants with a diagnosis of schizophrenia were recruited along with healthy controls (HCs) matched for age and gender from Weifang, China. Logistic regression models and generalized linear models were used to explore the associations between parental characteristics with the risk and age at onset of schizophrenia. In total, 414 cases and 639 HCs were recruited for the study.

RESULTS

We observed an inverse association between levels of paternal and maternal education and risk of schizophrenia after controlling for potential confounders (Paternal: OR = 1.525, 95% CI: 1.080-2.153, p = .017; Maternal: OR = 1.984, 95% CI: 1.346-2.924, p = .001). Younger paternal and maternal childbearing age were associated with a higher risk of diagnosis of schizophrenia. We furtherly observed that individuals with earlier age at onset of schizophrenia had fewer siblings (p = .007) and had higher rates of parental marital disharmony (p = .033).

CONCLUSION

Our results indicate that parental years of education and age of childbearing are associated with an increased risk of schizophrenia in a Chinese population. Age of onset of schizophrenia was positively associated with a greater number of siblings and negatively associated with parental marital disharmony.

Associations between risk factors for schizophrenia and concordance in four monozygotic twin samples

Concordance for schizophrenia is high in monozygotic twins but the extent to which concordance varies according to the presence of other schizophrenia risk factors is not well established. We aimed to investigate this in systematically ascertained twin samples. DSM-III-R/DSM-IV diagnoses were made from original data or published case histories from four systematically ascertained monozygotic twin samples. Probandwise concordance for schizophrenia was calculated according to the presence of psychotic disorder in first-degree relatives, birth order, gender, and age-at-onset. Logistic regression analysis was also performed to adjust for potential confounders. Psychotic disorder in parents and earlier age-at-onset were significantly associated with higher probandwise concordance for schizophrenia, including after adjustment for potential confounders. For example, when no parents had a psychotic disorder concordance was 34/88 (38.6%) versus 10/16 (62.5%) when one parent was affected; and for age-at-onset <23 years concordance was 25/46 (54.3%), declining to 13/44 (29.5%) for age-at-onset >30 years. These results are consistent with psychotic disorder in parents and age-at-onset being markers of the level of familial liability to schizophrenia and these factors may be useful in genetic counseling of monozygotic twins and in identifying and managing those at particularly high risk, if these findings are further replicated.

Quantifying the treatment goals of people recently diagnosed with schizophrenia using best-worst scaling

OBJECTIVE

This study seeks to quantify the treatment goals of people recently diagnosed with schizophrenia and explore their impact on treatment plan.

METHODS

People aged 18-35 years with a confirmed diagnosis of schizophrenia within the past 5 years were surveyed in the UK, Germany, and Italy. Treatment goals were assessed via a validated best-worst scaling instrument, where participants evaluated subsets of 13 possible treatment goals identified using a balanced incomplete block design. Participants identified the most and least important goals within each task. Data were also collected on current treatment and preference for daily oral versus long-acting injectable (LAI) treatment. Hierarchical Bayes was used to identify preference weights for the goals, and latent class analysis was used to identify segments of people with similar goals. The segments were compared with the current treatment and preference for oral versus LAI treatment.

RESULTS

Across 100 participants, the average age was 26 years, 75% were male and 50% were diagnosed within 2 years ago. Overall, preferences were most favorable for reduced disease symptoms, think clearly, reduced hospitalizations, reduced anxiety, and take care of self. A total of 61% preferred oral medication and 39% LAI. Two groups were identified with different treatment goals; 50% of participants emphasized clinical goals, including reduced disease symptoms (preference weight =19.7%), reduced hospitalizations (15.5%), and reduced anxiety (10.5%). The other 50% emphasized functional goals, including improved relationships with family/friends (11.4%), increased interest in work (10.6%), experiencing a fuller range of emotions (8.4%), and ability to socialize (7.5%). Those emphasizing functional goals were more likely to be on LAI (44% versus 26%; p=0.059) and preferred LAI (46% versus 32%; p=0.151).

CONCLUSIONS

People with recent-onset schizophrenia may focus more on clinical goals or functional goals, a discussion of which may help facilitate patient engagement.

What do register-based studies tell us about migrant mental health? A scoping review

BACKGROUND

Previous studies investigating the mental health of migrants have shown mixed results. The increased availability of register data has led to a growing number of register-based studies in this research area. This is the first scoping review on the use of registry and record-linkage data to examine the mental health of migrant populations. The aim of this scoping review is to investigate the topics covered and to assess the results yielded from these studies.

METHODS

We used a scoping review methodology to search MedLine, PubMed, PsychINFO, Web of Science, and SCOPUS for all register-based studies on the mental health of migrants. Two reviewers screened all papers, independently, using iteratively applied inclusion and exclusion criteria. Using gradually broadening inclusion and exclusion criteria for maximum "scope," newly published criteria developed to appraise the methodological quality of record-linkage studies were applied to eligible papers and data were extracted in a charting exercise.

RESULTS

A total of 1309 papers were screened and appraised, 51 of which met the eligibility and quality criteria and were included in the review. This review identified four major domains of register-based research within the topic of migrant mental health: rates and risks of psychiatric disorders, rates and risks of suicide mortality, the use of psychotropic drugs, and health service utilisation and mental health-related hospitalisation rates. We found that whilst migrants can be at an increased risk of developing psychotic disorders and suicide mortality, they are less likely to use psychotropic medication and mental health-related services.

CONCLUSIONS

This review systematically charts the register-based studies on migrants' mental health for the first time. It shows the main topics and gaps in knowledge in this research domain, discusses the disadvantages of register-based studies, and suggests new directions for forthcoming studies.

Is an Early Age at Illness Onset in Schizophrenia Associated With Increased Genetic Susceptibility? Analysis of Data From the Nationwide Danish Twin Register

Background

Early age at illness onset has been viewed as an important liability marker for schizophrenia, which may be associated with an increased genetic vulnerability. A twin approach can be valuable, because it allows for the investigation of specific illness markers in individuals with a shared genetic background.

Methods

We linked nationwide registers to identify a cohort of twin pairs born in Denmark from 1951 to 2000 (N = 31,524 pairs), where one or both twins had a diagnosis in the schizophrenia spectrum. We defined two groups consisting of; N = 788 twin pairs (affected with schizophrenia spectrum) and a subsample of N = 448 (affected with schizophrenia). Survival analysis was applied to investigate the effect of age at illness onset.

Findings

We found that early age at illness onset compared to later onset in the first diagnosed twin can be considered a major risk factor for developing schizophrenia in the second twin. Additionally, we found that the stronger genetic component in MZ twins compared to DZ twins is manifested in the proximity of assigned diagnosis within pairs.

Discussion

Early onset schizophrenia could be linked to a more severe genetic predisposition, indicating that age might be perceived as a clinical marker for genetic vulnerability for the illness.

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Early age at schizophrenia onset in one twin increases risk of illness in the second twin 4.7 times compared to a later onset.

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A stronger genetic predisposition may be needed to affect early schizophrenia onset in females compared to males.

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Genetic factors seem to play an important role in the proximity of assigned diagnosis within twin pairs.

The main aim of this study is to examine if early age at schizophrenia onset can be viewed as a clinical marker for increased genetic vulnerability in the illness. By linking the Danish Twin Register to other nationwide health registers we obtain accurate data regarding psychiatric diagnostic outcome in a complete twin population (> 31,000 twin pairs). Our study shows how an early age at illness onset in the first diagnosed twin in a pair is a major risk factor for developing schizophrenia in the second twin, underlining the importance of genetic factors in illness vulnerability.

The aetiology of schizophrenia: what have the Swedish Medical Registers taught us?

OBJECTIVE

To review the last thirty years of studies that, using Swedish population registers, have added to our understanding of the aetiology of schizophrenia SAMPLE INCLUDED/METHODS: A literature search was performed to systematically review all studies that using Swedish Population based registers have investigated the aetiology of schizophrenia. Key authors in the field, predominately from Swedish institutions, were additionally contacted and key journals hand searched, for missing references. A quality assessment methodological review was then conducted on each study. Data was extracted and tabulated on identified aetiological themes

RESULTS

61 articles were included corresponding to 10 identified aetiological themes. Although the majority of included studies were retrospective cohort studies, case control studies were also included where they used population based registers. Confirming previous research, schizophrenia was found to have a multi-factorial aetiological basis with pregnancy and birth factors, parental age, social adversity, genetics, substance misuse, migration and ethnicity, personality, non-psychiatric co-morbidity, psychiatric history and poor cognitive performance all found to be significantly associated with an increased risk of later schizophrenia.

CONCLUSIONS

Although some difficulties exist in analysing the interplay between each of these factors, the Swedish population registers have added considerably to our understanding of each of the presented individual aetiological themes. The ability to study the whole population over several decades has been particularly useful in determining the timing of exposures.

Association of older paternal age with earlier onset among co-affected schizophrenia sib-pairs

BACKGROUND

Advanced paternal age is associated with increased risk of schizophrenia. This study aimed to explore whether older paternal age is associated with earlier onset among co-affected schizophrenia sib-pairs with the same familial predisposition.

METHOD

A total of 1297 patients with schizophrenia from 630 families, which were ascertained to have at least two siblings affected, throughout Taiwan were interviewed using the Diagnostic Interview for Genetic Studies. Both inter-family comparisons, a hierarchical regression model allowing for familial dependence and adjusting for confounders, and within-family comparisons, examining the consistency between onset order and birth order, were performed.

RESULTS

An inverted U shape was observed between paternal age and onset of schizophrenia. Affected offspring with paternal age of 20-24 years had the oldest onset. As paternal age increased over 25 years, older paternal age exhibited a linear decrease in the onset of schizophrenia. On average, the onset was lowered by 1.5 years for paternal age of 25-29 years and by 5.5 years for paternal age ⩾50 years (p = 0.04; trend test). The proportion of younger siblings with earlier onset (58%) was larger than that of older siblings with earlier onset (42%) (p = 0.0002).

CONCLUSIONS

These findings indicate that paternal age older than 25 years and younger than 20 years were both associated with earlier onset among familial schizophrenia cases. The associations of advanced paternal age with both increased susceptibility to schizophrenia and earlier onset of schizophrenia are consistent with the rate of increases in spontaneous mutations in sperm as men age.

Recent research on the mental health of immigrants to Sweden: a literature review

The arrival of large numbers of economic migrants and refugees has seen the Swedish immigrant population increase rapidly. Research has shown that immigrants may be more susceptible to mental disorders because of traumatic events prior to immigration and adverse circumstances in their new country. The aim of this literature review is to summarize and interpret recent research on the mental health of immigrants to Sweden.

METHODS

A systematic search for relevant literature in PubMed was performed on 13 February 2014. Relevant literature was limited to original research articles published between 1 January 1994 and 13 February 2014. Content relating to mental disorders and suicide was reviewed and summarized.

RESULTS

Nationwide studies showed increased risks of common mental disorders such as depression, as well as psychotic disorders, in immigrants to Sweden compared to native Swedes. However, the results are complex, with notable differences between different immigrant groups and between males and females. Risk of suicide was increased in some immigrant groups, but decreased in others. There has been little qualitative research on the mental health of immigrants and few intervention studies have targeted immigrants.

CONCLUSION

Immigrants to Sweden are a mixed group with differing, but often increased, risks of mental disorders. Targeted qualitative and intervention studies may facilitate efforts to develop and implement preventive methods for immigrants at high risk of mental ill health, and to tailor treatment to the specific needs of different immigrant groups.

Age at onset mixture analysis and systematic comparison in schizophrenia spectrum disorders: Is the onset heterogeneity dependent on heterogeneous diagnosis?

A major obstacle to the identification of the neurobiological correlates of schizophrenia is the substantial diagnostic heterogeneity of this disorder. Dividing schizophrenia into "early" and "late" subtypes may reduce heterogeneity and facilitate identification of biomarkers related to this disease. Our objective was to assess the presence of different sub-groups in schizophrenia by age at onset analysis. The participants in this study were 612 unrelated patients with schizophrenia. Admixture analysis was applied in order to identify a model of separate normal distributions of age at onset characterized by different means, variances and population proportions to evaluate the effect of winter birth and ethnicity on early onset schizophrenia. The best-fitting model suggested three subgroups with means and standard deviations of 17.11 ± 2.09, 21.96 ± 3.43 and 30.02 ± 7.1 years, comprising 34.6%, 42.6% and 22.8% of the sample respectively. We considered as predictors of early onset schizophrenia: male gender, winter birth, white ethnicity and positive family history for psychiatric disorders. Earlier onset was significantly associated with male gender. We also compared our age at onset distribution with those published in other studies and we found significant differences with several studies suggesting heterogeneity in age at onset that is likely influenced by diagnostic heterogeneity in applying the DSM-IV criteria. Overall, our study showed that a typical early onset schizophrenia patient is more likely to be a white male with cannabis abuse and positive family history of psychiatric disorders. The heterogeneity in reporting age at onset across different studies suggests the application of more stringent criteria in diagnosing schizophrenia.

Schizophrenia susceptibility and age of diagnosis--a frailty approach

BACKGROUND

Using a frailty model approach, we aim to evaluate the effect of early-life risk factors on susceptibility and age at diagnosis of schizophrenia. We assume paternal age and familial schizophrenia influence the susceptibility, while these and several early risk factors influence the age of diagnosis.

METHOD

Schizophrenia incidence data were derived from the population-based Swedish Patient Registry; including individuals aged 18 to 45 years, diagnosed between 1974 and 2008. Data were analyzed by a frailty model, a random effects model in survival analysis, using a compound Poisson model.

RESULTS

15,340 incident schizophrenia cases were included. For individuals without familial schizophrenia, a protective effect was seen across most ages of diagnosis for females, low paternal age, born in rural areas, and being born in later cohorts. For individuals with familial schizophrenia, a protective effect is found for females diagnosed between ages 18 and 30 years, corresponding values were 18-25 years for low paternal age. Being born in rural areas and in the last birth cohort was protective for all. The estimated proportion of susceptible was 5% for those without familial schizophrenia and 18% for individuals with familial schizophrenia. There was no statistically significant effect of paternal age on the proportion of susceptible.

DISCUSSION

To our knowledge, this is the first regression modeling of time to schizophrenia diagnosis allowing for a non-susceptible fraction of the population, including age dependent modeling of covariate effects and an interaction. Applying frailty model to schizophrenia provide etiological clues, elucidating patterns of susceptibility and age-at-diagnosis for which early-life factors are of importance.

Family history of schizophrenia and bipolar disorder as risk factors for autism

CONTEXT

The clinical and etiologic relation between autism spectrum disorders (ASDs) and schizophrenia is unclear. The degree to which these disorders share a basis in etiology has important implications for clinicians, researchers, and those affected by the disorders.

OBJECTIVE

To determine whether a family history of schizophrenia and/or bipolar disorder is a risk factor for ASD.

DESIGN, SETTING, AND PARTICIPANTS

We conducted a case-control evaluation of histories of schizophrenia or bipolar disorder in first-degree relatives of probands in 3 samples—population registers in Sweden, Stockholm County (in Sweden), and Israel. Probands met criteria for ASD, and affection status of parents and siblings for schizophrenia and bipolar disorder were established.

RESULTS

The presence of schizophrenia in parents was associated with an increased risk for ASD in a Swedish national cohort (odds ratio [OR], 2.9; 95% CI, 2.5-3.4) and a Stockholm County cohort (OR, 2.9; 95% CI, 2.0-4.1). Similarly, schizophrenia in a sibling was associated with an increased risk for ASD in a Swedish national cohort (OR, 2.6; 95% CI, 2.0-3.2) and an Israeli conscription cohort (OR, 12.1; 95% CI, 4.5-32.0). Bipolar disorder showed a similar pattern of associations but of lesser magnitude.

CONCLUSIONS

Findings from these 3 registers along with consistent findings from a similar study in Denmark suggest that ASD, schizophrenia, and bipolar disorder share common etiologic factors.

Adoptive paternal age and risk of psychosis in adoptees: a register based cohort study

The association between advancing paternal age and increased risk of schizophrenia in the off-spring is well established. The underlying mechanisms are unknown. In order to investigate whether the psychosocial environment associated with growing up with an aged father explains the increased risk we conducted a study of all adoptive children in Sweden from 1955-1985 (n =31 188). Their risk of developing schizophrenia or non-affective psychosis in relation to advancing age of their adoptive fathers' was examined. We found no association between risk of psychoses and advancing adoptive paternal age. There was no support of psychosocial environmental factors explaining the "paternal age effect".