Familial-genetic and reproductive epidemiology of schizophrenia in rural Ireland: age at onset, familial morbid risk and parental fertility

The cliff edge model of the evolution of schizophrenia: Mathematical, epidemiological, and genetic evidence

How has schizophrenia, a condition that significantly reduces an individual's evolutionary fitness, remained common across generations and cultures? Numerous theories about the evolution of schizophrenia have been proposed, most of which are not consistent with modern epidemiological and genetic evidence. Here, we briefly review this evidence and explore the cliff edge model of schizophrenia. It suggests that schizophrenia is the extreme manifestation of a polygenic trait or a combination of traits that, within a normal range of variation, confer cognitive, linguistic, and/or social advantages. Only beyond a certain threshold, these traits precipitate the onset of schizophrenia and reduce fitness. We provide the first mathematical model of this qualitative concept and show that it requires only very weak positive selection of the underlying trait(s) to explain today's schizophrenia prevalence. This prediction, along with expectations about the effect size of schizophrenia risk alleles, are surprisingly well matched by empirical evidence. The cliff edge model predicts a dynamic change of selection of risk alleles, which explains the contradictory findings of evolutionary genetic studies.

Risk of schizophrenia in relatives of individuals affected by schizophrenia: A meta-analysis

A meta-analysis was conducted to estimate schizophrenia incidence in first-degree relatives (FDRs) of probands diagnosed with schizophrenia. The aim was to inform future schizophrenia research and improve accuracy of risk communication to patients. Schizophrenia risk in FDRs with 1 or 2 probands with schizophrenia was investigated by conducting a systematic review of cohort and case-control studies with the following criteria: published between 1977 and 2018; reported odds ratios (OR), relative risk (RR) or sufficient raw data to calculate OR or RR; used appropriate diagnostic criteria; and reported systematic proband recruitment and ascertainment of relatives. Studies were obtained via EMBASE and MEDLINE electronic database searches. From an initial 5755 articles, 19 met the inclusion criteria. Mean effect sizes across studies were estimated using random effects methods. Estimates for schizophrenia risk were OR = 7.69 (95% CI 5.11-11.56) for FDRs of one proband with schizophrenia compared to healthy control probands, increasing to OR = 11.11 (95% CI = 1.45-85.02) for FDRs with two probands with schizophrenia. These findings support the existing literature suggesting significant genetic liability for schizophrenia. The results can be used to educate individuals with a family history of schizophrenia about their risk.

First-episode schizophrenia, bipolar disorder and other psychoses in a rural Irish catchment area: Incidence and gender in the Cavan–Monaghan study at 5 years

Background

The potential of first-episode studies in schizophrenia is maximised through systematic epidemiological, clinical and biological comparisons between homogeneous populations of the psychoses.

Aims

To conduct prolonged accrual of ‘all’ cases of non-affective and affective psychotic illness on an epidemiologically complete basis.

Method

Within the region covered by Cavan–Monaghan psychiatric service (population 102 810), all putative cases of first-episode psychosis were diagnosed using DSM–IV.

Results

From 1995 to 2000, 69 cases of psychosis were ascertained, the incidence being 2.3-fold lower in females than in males. On resolving the ‘core’ diagnoses of schizophrenia and bipolar disorder, incidence of schizophrenia among women was 7.5-fold lower than among men whereas incidence of bipolar disorder among women was 6.6-fold lower than among men.

Conclusions

This homogeneous population, which eliminates factors associated with urbanicity and minimises confounding factors such as socioeconomic, ethnic and geographical diversity, shows a markedly reduced incidence among females both of schizophrenia and of bipolar disorder.

Common variants of HTR1A and SLC6A4 confer the increasing risk of Schizophrenia susceptibility: A population-based association and epistasis analysis

Schizophrenia (SZ) is a complex psychiatric disorder strongly influenced by genetic variants, some of which are associated with mood disorders. The neurotransmitter 5-hydoxytryptamine (5-HT) and its related biochemical factors have been shown to play a significant role in maintaining mood balance. Recent studies evaluating the association between SZ and genetic polymorphisms in a serotonin transporter (encoded by SLC6A4) and serotonin receptor 1A (encoded by HTR1A) show conflicting results. In this study, we performed a case-control association analysis using 4,000 individuals with Chinese-Han ancestry. Of these participants, 1,000 were SZ cases and 3,000 were healthy controls. Thirty-six single nucleotide polymorphisms (SNPs) located in SLC6A4 and HTR1A were genotyped in our 4,000 study samples. Of those, 33 polymorphic SNPs with a minor allele frequency >0.05 were used for further analysis. We found that rs878567 in HTR1A (asymptotic P-value = 3.89×10(-4) , corrected P-value = 0.0106) was significantly associated with SZ. Further haplotype-based analyses revealed that a two-SNP haplotype, rs2054847-rs140701 (TG) in gene SLC6A4, was significantly associated with SZ (P-value = 1.63×10(-4) and corrected P-value = 0.002799). We did not identify any significant epistatic interactions between the two genes. Our findings provide supportive evidence that genetic polymorphisms in SLC6A4 and HTR1A may influence the risk of SZ in Han Chinese individuals. © 2015 Wiley Periodicals, Inc.

The Concept of Schizophrenia: From Unity to Diversity

After over 100 years of research without clarifying the aetiology of schizophrenia, a look at the current state of knowledge in epidemiology, genetics, precursors, psychopathology, and outcome seems worthwhile. The disease concept, created by Kraepelin and modified by Bleuler, has a varied history. Today, schizophrenia is considered a polygenic disorder with onset in early adulthood, characterized by irregular psychotic episodes and functional impairment, but incident cases occur at all ages with marked differences in symptoms and social outcome. Men’s and women’s lifetime risk is nearly the same. At young age, women fall ill a few years later and less severely than men, men more rarely and less severely later in life. The underlying protective effect of oestrogen is antagonized by genetic load. The illness course is heterogeneous and depressive mood the most frequent symptom. Depression and schizophrenia are functionally associated, and affective and nonaffective psychoses do not split neatly. Most social consequences occur at the prodromal stage. Neither schizophrenia as such nor its main symptom dimensions regularly show pronounced deterioration over time. Schizophrenia is neither a residual state of a neurodevelopmental disorder nor a progressing neurodegenerative process. It reflects multifactorial CNS instability, which leads to cognitive deficits and symptom exacerbations.

Gender difference in age at onset of schizophrenia: a meta-analysis

BACKGROUND

Most studies reporting the gender difference in age at onset of schizophrenia show an earlier onset in males, but vary considerably in their estimates of the difference. This may be due to variations in study design, setting and diagnostic criteria. In particular, several studies conducted in developing countries have found no difference or a reversed effect whereby females have an earlier onset. The aim of the study was to investigate gender differences in age of onset, and the impact of study design and setting on estimates thereof.

METHOD

Study methods were a systematic literature search, meta-analysis and meta-regression.

RESULTS

A total of 46 studies with 29,218 males and 19,402 females fulfilled the inclusion criteria and were entered into a meta-analysis. A random-effects model gave a pooled estimate of the gender difference of 1.07 years (95% confidence interval 0.21-1.93) for age at first admission of schizophrenia, with males having earlier onset. The gender difference in age at onset was not significantly different between developed and developing countries. Studies using diagnostic and statistical manual of mental disorders (DSM) criteria showed a significantly greater gender difference in age at onset than studies using International Classification Of Diseases (ICD) criteria, the latter showing no difference.

CONCLUSIONS

The gender difference in age of onset in schizophrenia is smaller than previously thought, and appears absent in studies using ICD. There is no evidence that the gender difference differs between developed and developing countries.

Genetics of the schizophrenias: a model accounting for their persistence and myriad phenotypes

This article addresses the classic enigma about schizophrenia (SZ). The disease occurs with a lifetime prevalence of 1%, 80% of which is attributable to genetic factors. Females with SZ produce 50% as many children as normals, and males with SZ produce 25%. Genetic factors responsible for SZ should behave like lethal genes. Yet the prevalence of SZ remains around 1% throughout the world. How can that be? Additionally, CATIE concluded that the response of each individual with SZ to treatment with antipsychotic agents (effectiveness, side-effect profile, or long-term prognosis) cannot be predicted. Every case seems to be unique. Several recent publications have reported increased frequencies of single-nucleotide polymorphisms (SNPs) and of copy-number variants (CNVs) containing large regions of DNA in patients with SZ. These genetic perturbations often include neurodevelopmental genes. The overwhelming majority of SNPs and CNVs are post-fertilization mutations, occurring in somatic tissue, not germinal tissue. These mutations are a normal aspect of somatic cell division but occur more frequently in patients with SZ. Somatic mutations are not passed on to subsequent generations and therefore cannot account for the inheritance of SZ. Our speculation is that the genetic platform for SZ is the gene or genes that increase the number of de novo mutations in patients with SZ. We argue that balanced polymorphism is the most plausible hypothesis to account for the preservation of non-adaptive genes in nature-and, in particular, in SZ. Maladaptive genes in different combinations can confer increased fitness to the entire population, thus insuring their preservation in the gene pool. Somatic mutations explain both the sporadic occurrence of SZ within families and the wide variations in phenotypic expression of SZ. Increased frequency of somatic mutations may confirm greater overall fitness via balanced polymorphism to explain the maintenance of the SZ gene or genes within the human population.

Reduced Fertility and Fecundity among Patients with Bipolar I Disorder and Schizophrenia in Egypt

OBJECTIVE

To evaluate reproduction among patients with bipolar I disorder (BP1) or schizophrenia (SZ) in Egypt.

METHODS

BP1 patients (n=113) were compared with community based, demographically balanced controls (n=124) and SZ patients (n=79, DSM-IV). All participants were evaluated using structured interviews and corroborative data were obtained from relatives. Standard indices of procreation were included in multivariate analyses that incorporated key demographic variables.

RESULTS

Control individuals were significantly more likely to have children than BP1 or SZ patients (controls 46.8%, BP1 15.9%, SZ 17.7%), but the BP1-SZ differences were non-significant. The average number of children for BP1 patients (0.37±0.9) and SZ patients (0.38±0.9) was significantly lower than for controls (1.04±1.48) (BP1 vs controls, p<0.001; SZ vs controls, p<0.001). The frequency of marriages among BP1 patients was nominally higher than the SZ group, but was significantly lower than controls (BP1: 31.9% SZ: 27.8% control: 57.3%). Even among married individuals, BP1 (but not SZ) patients were childless more often than controls (p=0.001). The marital fertility, i.e., the average number of children among patients with conjugal relationships for controls (1.8±1.57) was significantly higher than BP1 patients (1.14±1.31, p=0.02), but not significantly different from SZ patients (1.36±1.32, p=0.2).

CONCLUSION

Selected reproductive measures are significantly and substantially reduced among Egyptian BP1 patients. The reproductive indices are similar among BP1 and SZ patients, suggesting a role for general illness related variables. Regardless of the cause/s, the impairment constitutes important, under-investigated disability.

Time-to-pregnancy and risk of schizophrenia

Schizophrenia has been linked to advanced paternal age, but the explanation is unknown. We questioned whether the incidence of schizophrenia would be related to male reproductive capacity, as reflected in the time taken to conceive. We measured the incidence of schizophrenia in relation to time to conception in a sub-group of 12,269 in the Jerusalem cohort whose mothers, interviewed post-partum, reported that the pregnancy had been intended. Compared with those conceived in less than 3 months, the unadjusted relative risks (RR) of schizophrenia associated with conception-waits of 3-5, 6-11 and 12+ months were 1.10 (95% confidence interval, 0.62-1.94), 1.41 (0.79-2.52) and 1.88 (1.05-3.37) with p for trend=0.035. This trend was attenuated somewhat by adjusting for paternal age, and was observed more strongly in offspring of fathers aged 30+ (p=.010). These findings suggest that factors associated with fecundability, either male or female, may contribute to the risk of schizophrenia.

Increased number of offspring in first degree relatives of psychotic individuals: a partial explanation for the persistence of psychotic illnesses

OBJECTIVE

As patients with psychotic illness have fewer offspring than controls, the persistence of psychotic illness is puzzling. We hypothesized that unaffected first-degree relatives of patients have more offspring than controls.

METHOD

Probands were 4904, individuals with non-affective psychotic disorders identified from a hospitalization registry. Unaffected first degree relatives and matched controls were identified from the Israeli Population Registry. The number of offspring of unaffected parents, biological siblings and controls was ascertained.

RESULTS

Unaffected parents of psychotic patients had more offspring/person than controls; 4.5 +/- 2.7 vs. 3.4 +/- 2.2, P = 0.000. Unaffected parents from familial psychosis families (more than one affected family member) had 1.83 more offspring than controls; unaffected parents from non-familial psychosis families had 0.97 more offspring than controls (both P < 0.001).

CONCLUSION

These findings might imply that genes which increase susceptibility for schizophrenia may be associated with increased number of offspring, perhaps supplying a partial explanation for the persistence of psychosis.

Familial risks of psychotic disorders and schizophrenia among siblings based on hospitalizations in Sweden

Familial risks of psychotic disorders and schizophrenia have been assessed in previous studies. However, the degree of familial clustering in large population datasets remains to be established. We conducted a study on familial risks of psychotic disorders and schizophrenia by linking the Multigeneration Register to the nationwide Swedish Hospital Discharge Register. All patients younger than 72 years hospitalized for psychotic disorders or schizophrenia between 1987 and 2004 were included. Standardized incidence ratios (SIRs) were calculated for individuals with affected singleton siblings, twins or spouses compared with individuals whose siblings or spouses had no hospitalization for psychotic disorders or schizophrenia. A total of 40,228 hospitalized cases were identified of which 3006 were affected sibling pairs. The overall significant familial SIRs were 4.82 for psychotic disorders and 7.34 for schizophrenia. The highest SIRs were found in the younger ages. There were no significant gender differences. The significant SIR for psychotic disorders among twin pairs was 6.40 and the significant SIRs for psychotic disorders among spouses varied between 3.17 and 3.29. Age difference between siblings had no effect on the magnitude of the SIRs. The findings of the present large-scale study suggest that heritable factors have a stronger effect on psychotic disorders and schizophrenia than environmental factors. Future studies could coordinate epidemiological studies of large populations with molecular biology resources.

Problems with the imprinting hypothesis of schizophrenia and autism

Crespi & Badcock (C&B) convincingly argue that autism and schizophrenia are diametric malfunctions of the social brain, but their core imprinting hypothesis is less persuasive. Much of the evidence they cite is unrelated to their hypothesis, is selective, or is overstated; their hypothesis lacks a clearly explained mechanism; and it is unclear how their explanation fits in with known aspects of the disorders.

Psychosis and autism as diametrical disorders of the social brain

Autistic-spectrum conditions and psychotic-spectrum conditions (mainly schizophrenia, bipolar disorder, and major depression) represent two major suites of disorders of human cognition, affect, and behavior that involve altered development and function of the social brain. We describe evidence that a large set of phenotypic traits exhibit diametrically opposite phenotypes in autistic-spectrum versus psychotic-spectrum conditions, with a focus on schizophrenia. This suite of traits is inter-correlated, in that autism involves a general pattern of constrained overgrowth, whereas schizophrenia involves undergrowth. These disorders also exhibit diametric patterns for traits related to social brain development, including aspects of gaze, agency, social cognition, local versus global processing, language, and behavior. Social cognition is thus underdeveloped in autistic-spectrum conditions and hyper-developed on the psychotic spectrum.;>We propose and evaluate a novel hypothesis that may help to explain these diametric phenotypes: that the development of these two sets of conditions is mediated in part by alterations of genomic imprinting. Evidence regarding the genetic, physiological, neurological, and psychological underpinnings of psychotic-spectrum conditions supports the hypothesis that the etiologies of these conditions involve biases towards increased relative effects from imprinted genes with maternal expression, which engender a general pattern of undergrowth. By contrast, autistic-spectrum conditions appear to involve increased relative bias towards effects of paternally expressed genes, which mediate overgrowth. This hypothesis provides a simple yet comprehensive theory, grounded in evolutionary biology and genetics, for understanding the causes and phenotypes of autistic-spectrum and psychotic-spectrum conditions.

Age-specific familial risks of psychotic disorders and schizophrenia: a nation-wide epidemiological study from Sweden

OBJECTIVE

This study analyzed men and women separately by age at hospital diagnosis of psychotic disorder or schizophrenia and by maternal or paternal disease after taking several possible confounders into account.

METHODS

The Multigeneration Register, in which all men and women born in Sweden from 1932 onwards are registered together with their parents, was linked to hospital data. This yielded 21,199 male and 19,029 female cases of psychotic disorders in addition to 12,799 paternal and 23,021 maternal cases of psychotic disorders (including schizophrenia). Standardized incidence ratios (SIRs) were calculated as the ratio of observed and expected number of cases among men and women with mothers and/or fathers affected by psychotic disorders or schizophrenia, compared with men and women whose mothers and/or fathers were not affected by psychotic disorders or schizophrenia.

RESULTS

The overall significant SIRs among men and women with a mother, father or both parents hospitalized for psychotic disorder varied between 2.86 and 20.30. Maternal transmission of psychotic disorder was stronger than paternal, and the highest SIRs were found in the youngest age groups. Similar results were found when the subgroup schizophrenia was analyzed separately. Maternal or paternal schizophrenia implied higher risks for the offspring than maternal or paternal psychotic disorders.

CONCLUSIONS

Hereditary factors have a strong influence on the onset of psychotic disorders and schizophrenia. Young people and individuals with both parents affected by these diseases need special attention as their SIRs were particularly increased.

Fertility of first-degree relatives of patients with schizophrenia: a three generation perspective

We explored the fertility in three generations; fertility of parents, siblings and offspring to patients with schizophrenia, to test the hypothesis that the decreased reproductive rate in the patients is compensated by an increased rate in their first-degree relatives. A population-based national database was created by linking the Swedish Multi-Generation and Hospital Discharge Registers. To maximize follow-up time for schizophrenia and reproductive history, three birth cohorts were selected: parental generation, born 1918-1927 (n=274464); affected generation, born 1932-1941 (n=108502) and offspring to affected generation, born 1951-1960 (n=103105). Ratios of estimated mean number of offspring were measured (fertility ratios), comparing the study subjects to the general population. The fertility among males with schizophrenia was decreased by over 70% (fertility ratio(patients/population)=0.29, 95% CI 0.25-0.35), whereas female patients had less than half as many offspring as the general female population (fertility ratio(patients/population)=0.48, 95% CI 0.42-0.55). When accounting for selection bias of larger families, no statistically significant difference was found among parents of patients with and without a diagnosis of schizophrenia. Further, the fertility among siblings of schizophrenic patients did not differ from the general population. A reduction in fertility was found among offspring to patients with schizophrenia, male offspring had 12% fewer offspring (fertility ratio(offspring/population)=0.88, 95%CI 0.77-1.01), while female offspring had 6% fewer offspring (fertility ratio(offspring/population)=0.94, 95% CI 0.84-1.05). In conclusion, we found reduced fertility in patients with schizophrenia and among their offspring that was not compensated by higher parental or sibling fertility.

Applications and limitations of empiric data in provision of recurrence risks for schizophrenia: a practical review for healthcare professionals providing clinical psychiatric genetics consultations

Schizophrenia is a common disorder that may frequently be encountered when taking family histories in the genetics clinic, whether or not the referral is for a psychiatric indication. Like in other common disorders, the provision of recurrence risks for schizophrenia is a complex clinical issue because empiric recurrence risks (while reasonably well established) can rarely be used without individual tailoring. This review seeks to identify and detail some pertinent issues surrounding the clinical utility of empiric recurrence risks for schizophrenia, and to provide an overview of important factors to consider when tailoring empiric risks for individual patients.

Genetic counselling for psychiatric disorders

Family, adoption and twin studies demonstrate that many adult psychiatric disorders, including schizophrenia, major depression and bipolar disorder, have a clear genetic component. The aetiology of psychiatric disorders is a complex combination of both genetic and environmental components. While potential susceptibility genes for psychiatric disorders have been identified, interaction with the environment is a crucial component in disease development. Pharmacogenetics and genetic testing have the potential to play key roles in the future of clinical psychiatry. At present, an increased risk of psychiatric disorders can be identified through a detailed family history. The empirical risk of developing a disorder has been determined for many psychiatric disorders and can be used as a general guide. Genetic counselling can extend and enhance patient care by providing information to patients about the complexities of inheriting psychiatric disorders and the associated risks of recurrence. The genetic counselling process can facilitate informed decision making, alleviate misconceptions and reduce stigma through an improved understanding of the genetic cause of psychiatric disorders, and offer support to patients and their families.

Heritability of schizophrenia and major affective disorder as a function of age, in the presence of strong cohort effects

It remains unclear whether age at onset for major psychiatric disorders is a useful marker of etiologic and genetic heterogeneity. The authors examined how heritability of schizophrenia and major affective disorders varied with age at onset. The sample was drawn from a large archival data set collected by Lionel Penrose, comprising 3,109 families with two or more members first hospitalized in Ontario between 1874 and 1944. The authors studied 1,295 sibships with schizophrenia (n = 487), major affective disorder (n = 378), both (n = 234) or neither (n = 196) of these disorders. Proportional hazards models were used to estimate how the hazard of hospitalization for each disorder (schizophrenia or major affective disorder) varied with proband age at onset, adjusted for changes in age at onset distribution between 1874 and 1944. A sibling's risk of hospitalization for the same illness significantly increased for each 10-year decrease in age at onset of the proband both for schizophrenia (hazard ratio = 1.21, 95 % confidence interval: 1.06, 1.39), and for affective disorder (hazard ratio = 1.29,95 % CI: 1.14, 1.45). Gender of proband was unrelated to sibling risk of the same illness, and tests of interaction effects between proband age at onset and gender on sibling risk were nonsignificant.

Could obsessive–compulsive disorder have originated as a group-selected adaptive trait in traditional societies?

Obsessive-compulsive disorder (OCD) possesses distinctive characteristics inviting evolutionary and anthropological explanations. A genetically based condition with low fecundity persisting through generations is paradoxical. The concept of group selection is an evolutionary principle capable of clarifying the perplexing epidemiology of OCD. Using a group-selection paradigm, the authors propose that OCD reflects an ancient form of behavioural specialization. The majority of compulsions such as checking, washing, counting, needing to confess, hoarding and requiring precision, all carry the potential to benefit society. Focussing primarily on hunting and gathering cultures, the potential evolutionary advantages of OCD are explored.

A review of the evidence from family, twin and adoption studies for a genetic contribution to adult psychiatric disorders

Family, twin and adoption studies have provided major evidence for the role of genetics in numerous psychiatric disorders including obsessive-compulsive disorder, panic disorder, major depressive disorder, bipolar disorder, schizophrenia and Alzheimer's disease. As the search for patterns of inheritance and candidate genes of these complex disorders continues, we review relevant findings from quantitative genetic studies and outline the main challenges for the field of psychiatric genetics to focus on in order to more definitively establish the underpinnings of genetic and environmental influences of adult psychopathology.

Genetic epidemiology and schizophrenia: a study of reproductive fitness

Genetic epidemiological studies have demonstrated markedly reduced rates in reproduction among schizophrenic patients. According to evolutionary theory, behavioral and psychological phenotypes are selected based on ecological "fit". Where differential survival or reproductive success exists, genotype frequencies are altered in subsequent generations. In the case of schizophrenia, lower rates of reproduction constitute a negative selection factor that should reduce genes in the population associated with the expression of the disease--ultimately leading to decreases in prevalence. However, studies reveal a stable prevalence of about 1% over time. Attempts to explain the apparent contradiction between negative selection and stable prevalence have taken several forms. One explanation suggests that reproductive rates in relatives of schizophrenic patients are increased--compensating for reproductive loss in affected family members. Family data from schizophrenic patients at the Maryland Psychiatric Research Center were compared with those of healthy volunteers and volunteers with schizophrenia spectrum personality (SSP) disorders. Controlling for important socio-cultural and demographic variables, a multiple regression model revealed a significant increase in the number of siblings associated with schizophrenia. No differences in reproductive fitness were found among normal and SSP volunteers. This observed pattern in reproductive fitness provides one mechanism by which prevalence rates can remain stable despite lower reproductive rates among individuals with schizophrenia. Evidence of increased reproductive fitness in relatives suggests the need to consider the complex interactions of proximate and ultimate (evolutionary) mechanisms in the expression of schizophrenia.

Gender and schizophrenia: association of age at onset with antecedent, clinical and outcome features

OBJECTIVE

There is evidence that gender and age at onset may have a bearing on schizophrenia. The extent to which this differential age at onset influences the clinical features of schizophrenia and its outcome in males and females is not clear.

METHOD

One hundred and twenty outpatients with DSM-III-R schizophrenia were studied to determine the association of antecedent, historical, clinical and 13-year outcome features with age at onset in females (n = 64) and in males (n = 56).

RESULTS

Males were significantly younger at illness onset but were not otherwise different from females in antecedent features of illness. For males, age at onset bore little relationship to outcome after 13 years. Females with early onset of illness were more likely to have experienced obstetric complications, to evidence poorer premorbid functioning, and to have a worse clinical, social and functional outcome than females with late onset.

CONCLUSIONS

Even though females may have a more benign illness than males, among females, those with early age at onset may be characterised by neurodevelopmental deviance and worse illness outcome.

Fertility and schizophrenia: evidence for increased fertility in the relatives of schizophrenic patients

Fertility has been observed to be reduced in patients with schizophrenia, although the disorder was seen to occur at a steady rate in the general population. The hypothesis of increased fertility in the healthy relatives of the patients, which maintained the genetic contribution to the disorder has been proposed but has not received much support. The present study reports the fertility rate in 100 schizophrenic patients and their relatives (grandparents, parents, uncles, aunts and siblings). The fertility of the different family members was compared, taking into account the completion of age of maximum reproductivity, i.e. up to 50 years of age. The trends in fertility rates over three generations of patients' families were compared with those in the general population of India over a corresponding period from 1950 to 2000 AD. The patients were observed to be hypofertile, but their parents showed a higher fertility than all other relatives, as well as the general population. The siblings of the patients also tended to have higher fertility rates than the general population. This increased fertility in parents and sibs, who are the probable carriers of the abnormal gene, could compensate for the reduction in genetic contribution to morbid risk for schizophrenia due to reduced reproductivity of the patients themselves.