Schizophrenia: age at onset, gender and familial risk

Comparison of clinical symptoms and symptom structure across different onset ages in schizophrenia inpatients

OBJECTIVE

This study aimed to explore differences in clinical symptom profiles and symptom network structures of inpatients with schizophrenia among early-onset schizophrenia (EOS), typical-onset schizophrenia (TOS), and late-onset schizophrenia (LOS) patients.

METHODS

Symptom severity was assessed using the Positive and Negative Syndrome Scale (PANSS) in 654 EOS, 1664 TOS, and 369 LOS inpatients with schizophrenia from an open dataset. Symptom severity comparisons were conducted among the three age of onset groups. Symptom networks were constructed, and measurements such as betweenness and closeness centrality were employed to investigate the interconnectivity between symptoms.

RESULTS

EOS inpatients exhibited significantly more severe symptoms compared to TOS and LOS, primarily attributable to more severe negative symptoms and general psychopathology. Analysis of the symptom networks revealed that uncontrolled hostility emerged as a core feature across EOS, TOS, and LOS. In the EOS network, anxiety domain served as bridge symptoms, while positive and disorganized thought were strongly associated with disease manifestations. TOS inpatients exhibited a similar pattern to EOS, but TOS showed higher betweenness and lower closeness in positive and negative symptoms, indicating that these domains play a crucial role in the overall network connectivity. In LOS, positive symptoms showed high betweenness centrality, suggesting their pivotal role in network connectivity.

CONCLUSIONS

These findings suggest that the symptom severity and symptoms network structure differ across different age of onset groups in schizophrenia inpatients. A deeper understanding of these network-level differences could shed light on the distinct pathogenesis mechanisms and guide the development of personalized treatment strategies for schizophrenia.

HYPOTHESIS

It has been consistently observed that inpatients with early-onset schizophrenia (EOS) have poorer treatment outcomes compared to typical-onset schizophrenia patients (TOS), while those with late-onset schizophrenia (LOS) tend to have better outcomes than typical-onset inpatients. The reasons behind these phenomena remain unclear. In this work, we aim to utilize network analysis to uncover potential symptom interactions that may contribute to the different treatment outcomes observed across different ages of onset schizophrenia inpatient groups.

Multiple rare inherited variants in a four generation schizophrenia family offer leads for complex mode of disease inheritance

Schizophrenia is a clinically and genetically heterogeneous neuropsychiatric disorder, with a polygenic basis but identification of the specific determinants is a continuing challenge. In this study, we analyzed a multigenerational family, with all healthy individuals in the first two generations, and four progeny affected with schizophrenia in the subsequent two generations, using whole exome sequencing. We identified five rare protein sequence altering heterozygous variants, in five different genes namely SMARCA5, PDE1B, TNIK, SMARCA2 and FLRT shared among all affected members and predicted to be damaging. Variants in SMARCA5 and PDE1B were inherited from the unaffected father whereas variants in TNIK, SMARCA2 and FLRT1 were inherited from the unaffected mother in all the three affected individuals in the third generation; and notably all these five variants were transmitted by an affected mother to her affected son. Microsatellite based analysis lent a modest linkage support (LOD score of 1.2; θ=0.0 at each variant). Of note, analysis of exome data of an ancestry matched unrelated schizophrenia cohort (n = 350), revealed a total of 16 rare variants (MAF < 0.01) in these five genes. Interestingly, these five genes involved in neurodevelopmental and/or neurotransmitter signaling processes are implicated in the etiology of schizophrenia previously. This study provides good evidence for a likely cumulative contribution of multiple rare variants from disease relevant genes with a threshold effect in disease development and seems to explain the unusual disease transmission pattern generally witnessed in such conditions, but warrants extensive replication efforts in families with similar complex disease inheritance profiles.

A comparative study of childhood/adolescent and adult onset schizophrenia: does the neurocognitive and psychosocial outcome differ?

AIMS & OBJECTIVES

The present study aimed to evaluate the neurocognitive functioning and psychosocial outcome (in terms of social functioning, disability and internalized stigma) in patients with schizophrenia with childhood/adolescent onset (age of onset ≤18 years) and adult onset (>18years) schizophrenia and to evaluate the effect of neurocognitive impairment on the outcome variables in patients with youth and adult onset schizophrenia.

METHODOLOGY

34 patients with youth onset schizophrenia (Group-I) and 56 patients with adult onset schizophrenia (Group-II), who were currently in clinical remission were assessed on a comprehensive neurocognitive battery,Positive and Negative syndrome Scale (PANSS), Global Assessment of Functioning Scale (GAF), Indian Disability Evaluation and Assessment Scale (IDEAS),Social and Occupational Functioning Assessment Scale (SOFS) and Internalised Stigma of Mental Illness Scale (ISMIS).

RESULTS

On neurocognitive domains (after adjusting for co-variates) significant differences were noted between the two groups in terms of processing speed (TMT-A; I > II; p-value -0.009), verbal fluency (COWA;I < II;p-value-0.001) and cognitive flexibility (TMT-B; I > II; p -0.031). Compared to patients with adult onset schizophrenia, patients with childhood & adolescent onset schizophrenia had significantly higher PANSS negative score, higher disability in all domains of IDEAS, poorer socio-occupational functioning, low global functioning and reported more stigma in the domains of alienation and discrimination.In patients with childhood & adolescent onset schizophrenia, higher deficits in the processing speed and verbal fluency were associated with significantly lower socio-occupational functioning and higher disability; higher executive dysfunction was associated with higher internalized stigma. Among patients with adult onset schizophrenia, higher disability was related to executive dysfunction only and higher stigma was associated with poor cognitive processing, selective attention and poor executive functioning.

CONCLUSIONS

The present study suggests that compared to adult onset schizophrenia, patients with childhood & adolescent onset schizophrenia have more deficits in neurocognition, have higher level of disability, poorer socio-occupational functioning and have higher level of self-stigma.

Family history of psychiatric disorders and age at first contact in schizophrenia: An epidemiological study

Background

The risk for schizophrenia has been associated with a family history of this and other psychiatric disorders. The relationship between age at first contact and family history of psychiatric illness is not certain.

Aims

To estimate the risks for schizophrenia associated with a range of psychiatric diagnoses in family members and to investigate the relationship between these risks and age at first contact for schizophrenia.

Method

A nested case–control study design was employed. Psychiatric admission data and socio-economic data were available for 7704 cases admitted between 1981 and 1998 in Denmark, 192 590 gender- and age-matched controls, and for the parents and siblings of all subjects.

Results

Controlling for socio-economic factors, risk for schizophrenia was associated with a family history of all psychiatric disorders except substance misuse and independently with a family history of suicide. The risk for schizophrenia associated with a family history of psychiatric disorders decreased as age at first contact increased.

Conclusions

Risk for schizophrenia is associated with a range of psychiatric disorders in family members and these risks are not constant across the risk period.

The clinical impact of a positive family history of psychosis or mental illness in psychotic and non-psychotic mentally ill adolescents

BACKGROUND

A family history of psychosis is associated with negative clinical characteristics of psychosis.

AIM

We aimed to determine the relationship between a family history (in first-degree relatives) of psychosis (FHP) or of any mental illness (FHM), and the clinical features (including cannabis use) of first episode early onset psychosis (EOP).

METHOD

Forty-five adolescents with first episode EOP presenting to psychiatric services were assessed by clinical interview with the following tools: socio-demographic questionnaire, Positive and Negative Syndrome Scale (PANSS), Symptom Onset in Schizophrenia (SOS) inventory, and the World Health Organisation's (WHO) Alcohol, Smoking, and Substance Involvement Screening Test (ASSIST) for cannabis misuse. Forty-five gender and age matched controls with incident non-psychotic mental illness were recruited from the same clinical sites.

RESULTS

While there was evidence of trend associations, EOP adolescents and controls did not differ in terms of either FHP or FHM. However, adolescents with a non-psychotic mental illness (controls) were significantly more likely to have a family history of non-psychotic mental illness (EOP = 13%; controls = 47%, p = 0.001). In EOP adolescents, a positive FHP was associated with a significantly lower mean PANSS positive score (p = 0.009), but not with other clinical features.

CONCLUSION

FHP may be a diagnostic clue in adolescents and is not necessarily associated with negative clinical characteristics at disease onset in EOP. However, this requires further research.

Sex-Dependent Association of Perigenual Anterior Cingulate Cortex Volume and Migration Background, an Environmental Risk Factor for Schizophrenia

Migration status is one of the best-established risk factors for schizophrenia. An increase in risk is observed in both first- and second-generation immigrants, with a varying magnitude depending on the ethnic background of the individuals. The underlying mechanisms for the increased risk are only recently coming into focus. A causal role for social stress has been widely proposed, and recent work indicated altered neural stress processing in the perigenual anterior cingulate cortex (pACC) in migrants. Since previous work shows that social stress may lead to enduring changes in the gray matter volume of vulnerable brain regions, we investigated the impact of migration background on brain structure. We studied healthy young adults (N = 124), native Germans and second-generation migrants, using whole-brain structural magnetic resonance imaging. Groups were matched for a broad range of sociodemographic characteristics including age, gender, urban exposure, and education. We found a significant group by sex interaction effect in pACC gray matter volume, which was reduced in males with migration background only. This mirrors previous findings in urban upbringing, another risk factor for schizophrenia. Our results provide convergent evidence for an impact of environmental risk factors linked to schizophrenia on gray matter volume and extend prior data by highlighting the possibility that the pACC structure may be particularly sensitive to the convergent risk factors linked to schizophrenia.

Neuropsychiatric Features in Primary Mitochondrial Disease

Mitochondrial diseases are a clinically heterogeneous group of disorders that ultimately result from dysfunction of the mitochondrial respiratory chain. There is some evidence to suggest that mitochondrial dysfunction plays a role in neuropsychiatric illness; however, the data are inconclusive. This article summarizes the available literature published in the area of neuropsychiatric manifestations in both children and adults with primary mitochondrial disease, with a focus on autism spectrum disorder in children and mood disorders and schizophrenia in adults.

Sex differences in the genetic risk for schizophrenia: history of the evidence for sex-specific and sex-dependent effects

Although there is a long history to examinations of sex differences in the familial (and specifically, genetic) transmission of schizophrenia, there have been few investigators who have systematically and rigorously studied this issue. This is true even in light of population and clinical studies identifying significant sex differences in incidence, expression, neuroanatomic and functional brain abnormalities, and course of schizophrenia. This review highlights the history of work in this arena from studies of family transmission patterns, linkage and twin studies to the current molecular genetic strategies of large genome-wide association studies. Taken as a whole, the evidence supports the presence of genetic risks of which some are sex-specific (i.e., presence in one sex and not the other) or sex-dependent (i.e., quantitative differences in risk between the sexes). Thus, a concerted effort to systematically investigate these questions is warranted and, as we argue here, necessary in order to fully understand the etiology of schizophrenia.

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.

ANK3 as a risk gene for schizophrenia: new data in Han Chinese and meta analysis

Histological and neuroimaging evidence supports the hypothesis that neuronal disconnectivity may be involved in the pathogenesis of schizophrenia. A genome-wide association study (GWAS) showed a single nucleotide polymorphism (SNP), rs10761482 in ankyrin 3 (ANK3), a major neuron-enriched gene, was associated with schizophrenia although inconsistent results had been reported. Two meta analyses reported another SNP rs10994336 in ANK3 gene confers risk to bipolar disorder (BD). Due to evidence of genetic overlap between schizophrenia and BD, we investigated common findings by analyzing the association of ANK3 polymorphisms (rs10761482, rs10994336, and two missenses, rs3808942 and rs3808943) with schizophrenia, using the Han Chinese population. A total of 516 schizophrenia cases, 400 controls, and 81 trios of early onset schizophrenia were recruited for association studies. Furthermore, the published datasets were combined with our results to determine the effect of the loci on schizophrenia. Our association study showed the frequencies of C allele of rs10761482 and T allele of rs10994336 were higher in patients than in controls. Furthermore, allele condition analyses indicated the association signal observed at rs10761482 and rs10994336 was independent. A haplotype analysis revealed the rs10761482-rs3808942-rs3808943 haplotype was associated with schizophrenia. The frequency of the T-T-T haplotype was higher in patients than in controls. In the transmission disequilibrium test analysis, the C allele of rs10761482 and the rs10761482-rs3808942-rs3808943 haplotype were preferentially transmitted in the trios. Meta analysis incorporating previous and current studies also showed rs10761482 and rs10994336 were associated with schizophrenia. We conclude that ANK3 gene has a major influence on susceptibility to schizophrenia across populations.

Effect of SOX10 gene polymorphism on early onset schizophrenia in Chinese Han population

Schizophrenia is one of highly heritable psychiatric disorders. Patients with early onset schizophrenia tend to have a greater genetic loading and may be an attractive subpopulation for genetics studies. A single nucleotide polymorphism (SNP) rs139887 in sex-determining region Y-box 10 (SOX10), a candidate gene for schizophrenia, was suggested to be associated with schizophrenia although inconsistent results had been reported. The aim of this study was to evaluate the association between SOX10 rs139887 polymorphism and schizophrenia using an early onset sample in the Chinese Han population. A total of 321 schizophrenic patients with onset before age 18 and 400 healthy controls were recruited for association study. In addition, two populations involved in three studies were selected for meta-analysis to determine the effect of rs139887 on schizophrenia. Our association study results showed that the allele and genotype frequencies were significantly different between schizophrenic patients and controls (P=0.013 and P=0.034, respectively). Interestingly, a significant association in allele and genotype frequencies were found in male patients (P=0.017 and P=0.045, respectively), but not female patients. Moreover, the C/C genotype had a significant association with an earlier age of onset in male schizophrenic patients (Kaplan-Meier log-rank test P=0.029), but not in female patients (Kaplan-Meier log-rank test P=0.876). The meta-analysis result showed the same C allele was significantly associated with schizophrenia (P=0.007). In conclusion, the SOX10 rs139887 polymorphism was related to the development of schizophrenia in a gender-specific manner, and may be a significant genetic marker for managing subgroups and etiological clues in schizophrenia.

Family history of psychosis negatively impacts age at onset, negative symptoms, and duration of untreated illness and psychosis in first-episode psychosis patients

Family history (FH) of psychosis has been a focus of investigations attempting to explain the heterogeneity in schizophrenia. Previous studies have demonstrated that FH is associated with earlier age at onset, severity of positive and negative symptoms, and the duration of untreated illness (DUI). The current study examined the impact of FH on the clinical presentation and help-seeking behaviors of a well-characterized, first-episode sample. The present study utilized the Symptom Onset in Schizophrenia (SOS) Inventory, the Positive and Negative Syndrome Scale (PANSS), and structured interviews on FH to examine these relationships in a large (n=152) sample of predominantly African American patients. Results showed that patients with a first-degree FH of psychosis had a younger age at onset of both the prodrome and psychosis, but did not differ in duration of prodromal period. Furthermore, FH and sex interacted to influence severity of negative, but not positive symptoms. Finally, FH interacted with sex to influence both the DUI and DUP in that only males with FH had longer DUI and DUP. The findings have implications for understanding the impact of specific family-related mechanisms on both clinical and help-seeking factors, as well as for informing future family-based intervention efforts.

Sex-specific rates of transmission of psychosis in the New England high-risk family study

Recent molecular genetic studies have demonstrated X-chromosome abnormalities in the transmission of psychosis, a finding that may contribute to understanding sex differences in the disorder. Using our family high risk paradigm, we tested the hypothesis that there are sex-specific patterns of transmission of psychosis and whether there is specificity comparing nonaffective- with affective-type psychoses. We identified 159 parents with psychoses (schizophrenia psychosis spectrum disorders (SPS, n=59) and affective (AP, n=100)) and 114 comparable, healthy control parents. 203 high risk (HR) and 147 control offspring were diagnostically assessed (185 females; 165 males). We compared the proportion of male:female offspring with psychoses by affected parent sex and the consistency for SPS compared to AP parents, and tested (using exact logistic regression) whether the male:female ratio for affected offspring differed significantly between affected mothers and affected fathers. Risk of psychosis in offspring was a function of the sex of the parent and offspring. Among ill mothers, 18.8% of their male offspring developed psychosis compared with 9.5% of their daughters. In contrast, among ill fathers, 3.1% of their male offspring developed psychosis compared with 15.2% of their daughters. The male:female ratio for affected offspring differed significantly (p < 0.05) between affected mothers and fathers. Similar patterns held for SPS and AP. Results demonstrated sex-specific transmission of psychosis regardless of psychosis-type and suggest X-linked inheritance. This has important implications for molecular genetic studies of psychoses underscoring the impact of one's gender on gene-brain-behavior phenotypes of SCZ.

Gender differences in Singaporean Chinese patients with schizophrenia

The purpose of this study was to compare gender differences in age of onset of illness, clinical features and prescription patterns in Chinese schizophrenia patients in Singapore. A cross-sectional study was conducted which recruited 903 subjects diagnosed with schizophrenia from the Institute of Mental Health between 2005 and 2008. Information on age of onset of schizophrenia, body mass index (BMI), psychiatric family history and current medication was collected via a standardised collection form. Symptom severity was assessed with Positive and Negative Syndrome Scale (PANSS). Differences in age of onset of schizophrenia illness, clinical features and prescription patterns were compared between gender groups. Among sporadic schizophrenia cases, female subjects demonstrated a bimodal distribution in age of onset of illness, and had a significantly later age of illness onset compared with male subjects. For subjects with family history of psychiatric disorder, no significant gender differences were found in age of onset of illness. Female subjects had significantly higher BMI, higher proportion of diabetes mellitus, lower negative symptom scores and were prescribed more atypical antipsychotics and antidepressants compared with male subjects. Male subjects after age 50 were prescribed a lower antipsychotic dose, but this difference was not observed in female subjects. In conclusion, we found differences in age of onset of schizophrenia, severity of negative symptoms and prescription patterns between the male and female gender groups in Chinese schizophrenia patients in Singapore. These differences were consistent with findings from Caucasian population, and could possibly be explained by influences of oestrogen.

Service utilization in a tertiary psychiatric care setting in South India

OBJECTIVE

To carry out an audit reviewing the utilization of psychiatric services and types of disorders presenting to a tertiary care psychiatry hospital in a developing Asian country.

METHOD

Consecutive adult patients who came for detailed consultation in 1 year were included in this study. A senior consultant psychiatrist reconfirmed the diagnosis in each patient who underwent detailed psychiatric evaluation. Psychiatric evaluation consists of clinical history from the patients and the relatives and a mental state examination. Data was obtained from the detailed work up evaluation psychiatry records of these patients.

RESULTS

Mood disorder was the most common diagnosis followed by substance use disorders and psychotic disorders (ICD 10). There is a substantial delay of more than 2-5 years for seeking treatment in most disorders including schizophrenia. More than 80% of the population directly seeks treatment at this tertiary hospital. Sixty-four percent of the patients came for at least one follow up.

CONCLUSION

The result suggests the urgent need for strengthening community care in India and similar low and middle-income countries for early and optimal treatment.

Dissection of phenotype reveals possible association between schizophrenia and Glutamate Receptor Delta 1 (GRID1) gene promoter

Recent linkage and association data have implicated the Glutamate Receptor Delta 1 (GRID1) locus in the etiology of schizophrenia. In this study, we sought to test whether variants in the promoter region are associated with this disorder. The distribution of CpG islands, which are known to be relevant for transcriptional regulation, was computationally determined at the GRID1 locus, and the putative transcriptional regulatory region at the 5'-terminus was systematically tagged using HapMap data. Genotype analyses were performed with 22 haplotype-tagging single nucleotide polymorphisms (htSNPs) in a German sample of 919 schizophrenia patients and 773 controls. The study also included two SNPs in intron 2 and one in intron 3 which have been found to be significantly associated with schizophrenia in previous studies. For the transcriptional regulatory region, association was obtained with rs3814614 (p=0.0193), rs10749535 (p=0.0245), and rs11201985 (p=0.0222). For all further analyses, the patient samples were divided into more homogeneous subgroups according to sex, age at onset, positive family history of schizophrenia and lifetime history of major depression. The p-value of the schizophrenia association finding for the three markers decreased by approximately one order of magnitude, despite the reduction in the total sample size. Marker rs3814614 (unadjusted p=0.0005), located approximately 2.0 kb from the transcriptional start point, also withstood a two-step correction for multiple testing (p=0.030). No support was obtained for previously reported associations with the intronic markers. Our results suggest that genetic variants in the GRID1 transcriptional regulatory region may play a role in the etiology of schizophrenia, and that future association studies of schizophrenia may require stratification to ensure more homogeneous patient subgroups.

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.

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.

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.

Patterns of axis II comorbidity in early-onset versus late-onset panic disorder in Japan

Early onset of psychiatric disorders has been reported to be associated with increased familial risk or more severe clinical symptoms. In this study, we specifically examine the association between clinical severity and early versus late onset in panic disorder. We hypothesize the existence of differences in rates of axis II disorders in these two groups that will relate to clinical severity. Subjects were a consecutive clinical case series of 105 panic disorder patients (age, 18.3 to 70.9 years). Thirty-one panic disorder patients were classified as early onset (age of onset < or = 25 years) and 74 as late onset (age of onset >25). We compared symptomatology and rates of comorbid axis II disorders (diagnosed by structured clinical interview) between the early- and the late-onset groups. We found a statistically significant increase in the number of suicide attempts and likelihood of comorbid axis II disorders in the early-onset group compared to the late-onset group. In logistic regression analyses, cluster B personality disorders (PDs), especially borderline and histrionic, were statistically significantly associated with the presence of suicide attempts. The following limitations are present: first, we have not taken into consideration comorbidity of other axis I disorders, especially major depression. Second, there is imprecision associated with efforts to date the onset of panic disorder retrospectively. We conclude that comorbid axis II disorders are more likely to occur in early-onset panic disorder patients. Cluster B PDs, especially borderline or histrionic, may be associated with a high frequency of suicide attempts in this group. In clinical practice, efforts to aggressively detect and treat axis II disorders in early-onset panic disorder patients are warranted.

Genome-wide linkage analysis of families with obsessive-compulsive disorder ascertained through pediatric probands

The goal of this study was to identify chromosomal regions likely to contain susceptibility alleles for early-onset obsessive-compulsive disorder (OCD). A genome scan was done in 56 individuals from seven families ascertained through pediatric OCD probands; 27 of the 56 subjects had a lifetime diagnosis of definite OCD. Denser mapping of regions on chromosomes 2, 9, and 16 was subsequently done with those subjects and ten additional subjects from the largest family in the study. Direct interviews were completed with 65 of the 66 genotyped individuals. Relatives were interviewed blind to proband status. Of the 65 interviewed individuals, 32 had a lifetime diagnosis of definite OCD. Three of the seven probands had a history of Tourette disorder. Two of the 25 relatives with OCD had a tic history, whereas none of the 33 relatives without OCD had tics. The genome scan consisted of 349 microsatellite markers with an average between-marker distance of 11.3 centiMorgan (cM). Fine mapping was done with 24 additional markers at an average spacing of 1.6 cM. Parametric and nonparametric linkage analyses were conducted using GENEHUNTER(+). The maximum multipoint LOD score with a dominant model was 2.25 on 9p. However, with fine mapping and additional subjects, that LOD score decreased to 1.97. The maximum multipoint nonparametric LOD* score was 1.73 on 19q. The maximum multipoint LOD score with a recessive model was 1.40 on 6p. The results provide suggestive evidence for linkage on 9p and identify regions requiring further study with much larger samples.

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.

Sex difference in age at onset of schizophrenia: discrepant findings from India

Consecutive male (n=100) and female (n=100) DSM-IV schizophrenics newly registered for treatment in a large psychiatric hospital were examined with regard to age at onset of the first psychotic symptom. Age at onset of the first psychotic symptom did not differ between the sexes regardless of whether schizophrenia was diagnosed by DSM-IV or by several alternative systems. Age at onset defined by other criteria, namely age at first contact with a physician, and age at first admission for psychiatric care, also did not show any differences between the sexes. Survival analysis of subjects having a documented date of birth revealed a female preponderance at younger ages. A higher positive symptom score predicted older age at onset of the first psychotic symptom in the total sample. These findings call into question the universality of the traditional view of a younger age at onset of schizophrenia among males. Tentative neurodevelopmental and cultural explanations are presented to explain why there is no sex difference in age at onset of schizophrenia in India.

Sex differences in neuropsychological function in non-psychotic relatives of schizophrenic probands

Some recent studies suggest that men with schizophrenia may have greater neuropsychological deficits than women. It is not known, however, whether similar sex differences may be present in biological relatives of schizophrenic patients. We evaluated neuropsychological functioning of 54 relatives of schizophrenic patients and 72 normal volunteers. It was hypothesized that, if sex differences were present, they would be accounted for largely by deficits in male relatives. We were particularly interested in three neuropsychological functions that we previously identified as putative neuropsychological vulnerability indicators for schizophrenia: (1) abstraction/executive function; (2) verbal memory; and (3) auditory attention. There were significant group x sex interactions for verbal memory and motor function, and trends toward significant interactions for auditory attention and mental control/encoding. However, with the exception of motor function, it was the female relatives who accounted for most of the impairment. A speculative explanation for the findings is that women may have a higher threshold than men for developing schizophrenia. If so, female relatives might be able to withstand greater impairments than men before developing psychotic symptoms. Consequently, in a sample that was limited to non-psychotic relatives--as in the present study--there could be over-representation of both less impaired men and more impaired women. Alternative explanations and limitations of the study are also discussed.

Schizophrenia and neurological soft signs: gender differences in clinical correlates and antecedent factors

Although it is recognized that patients with schizophrenia demonstrate more neurological soft signs (NSS) than control subjects, the significance and clinical correlates of these signs remain poorly defined. The present study examined 48 patients with DSM-III-R schizophrenia for evidence of NSS. The majority (98%) of patients demonstrated at least one NSS, although the range of scores was wide. There was no relationship between current dosage of neuroleptic medication and NSS score. Among males, there was a significant relationship between NSS and duration of illness. Males whose mothers experienced obstetric complications had higher NSS scores, while females with a family history of schizophrenia exhibited higher scores. These relationships in schizophrenia between NSS and factors of etiological importance wuch as obstetric complications and family history require further evaluation. The present findings are in accord with a body of evidence which suggests that gender may influence the impact of genetic and environmental factors on the neurology of the disorder.

Age at onset in schizophrenia and risk of illness in relatives. Results from the Roscommon Family Study

BACKGROUND

For many common medical and neuropsychiatric disorders, early age at onset reflects high familial liability to illness. However, for schizophrenia, most studies do not find such a relationship.

METHOD

Using Cox proportional hazard modes, we investigate this question in the epidemiologically-based Roscommon family study.

RESULTS

No relationship was found between age at onset in schizophrenic probands and the hazard rate for schizophrenia in their relatives. Similar results were obtained when the definition of illness was expanded to include schizoaffective disorder and other non-affective psychoses.

CONCLUSIONS

For schizophrenia, a 'common-sense' model for age of onset (i.e. those with highest familial liability to illness succumb first while those with lower liability survive longer before falling ill) does not seem to apply. Our results are more consistent with a model in which variation in age at onset of schizophrenia is due to random developmental effects or to environmental experiences unique to the individual.

Age of onset in familial and sporadic schizophrenia

We have studied the gender and family history differences with regard to age of onset of schizophrenia. These differences have often been viewed as an important clue to the aetiology of the illness. Patients from three centres in Europe and Canada were included in the study. A sample of 1089 subjects was categorized according to the subject's sex, family history of schizophrenia, and the centre. The principal statistical method was analysis of variance. Patients with no family history of schizophrenia had a consistently higher average age of onset. This effect was seen in both male and female subjects across all three groups. These results support the relationship between familial risk and early onset, but no interaction of gender and family history was found.

Incorporating lag effects in register-based age-of-onset distributions in schizophrenia

Epidemiological studies often use age-of-first-admission from psychiatric case registers to estimate age-of-onset in schizophrenia. Retrospective, interview-based methods have shown that there is a delay between onset of symptoms and eventual contact with psychiatric services, and that this delay can vary both among individuals and at different ages. This delay or lag can confound the interpretation of first admission data such as age-of-onset. To evaluate the potential impact of this factor, we constructed a flexible mathematical model which integrates age-at-first-admission with estimates of this lag, which were derived from interview-based studies and clinical judgement. We applied this model to age-of-first-admission data for 4218 patients with ICD8/9 schizophrenia drawn from a state-wide psychiatric register. Both the raw age-of-first-admission distribution curve and the transformed data ('estimated age-of-onset') reinforce previous findings that (a) there is a wide range of age-of-onset and (b) the shapes of the curves differ between the sexes. Inspection of the mathematically derived distribution supports the proposition that (a) transformation for a lag effect produces a lower onset age and (b) including a variable length of lag produces a change in shape of the distribution. We propose that the mathematical transformation of age-of-first-admission data may have heuristic value, but requires further empirical data on which to base the assumptions of the model.

Irish study on high-density schizophrenia families: field methods and power to detect linkage

Large samples of multiplex pedigrees will probably be needed to detect susceptibility loci for schizophrenia by linkage analysis. Standardized ascertainment of such pedigrees from culturally and ethnically homogeneous populations may improve the probability of detection and replication of linkage. The Irish Study of High-Density Schizophrenia Families (ISHDSF) was formed from standardized ascertainment of multiplex schizophrenia families in 39 psychiatric facilities covering over 90% of the population in Ireland and Northern Ireland. We here describe a phenotypic sample and a subset thereof, the linkage sample. Individuals were included in the phenotypic sample if adequate diagnostic information, based on personal interview and/or hospital record, was available. Only individuals with available DNA were included in the linkage sample. Inclusion of a pedigree into the phenotypic sample required at least two first, second, or third degree relatives with non-affective psychosis (NAP), one whom had schizophrenia (S) or poor-outcome schizo-affective disorder (PO-SAD). Entry into the linkage sample required DNA samples on at least two individuals with NAP, of whom at least one had S or PO-SAD. Affection was defined by narrow, intermediate, and broad criteria. The phenotypic sample contained 277 pedigrees and 1,770 individuals and the linkage sample 265 pedigrees and 1,408 individuals. Using the intermediate definition of affection, the phenotypic sample contained 837 affected individuals and 526 affected sibling pairs. Parallel figures for the linkage sample were 700 and 420. Individuals with schizophrenia from these multiplex pedigrees resembled epidemiologically sampled cases with respect to age at onset, gender distribution, and most clinical symptoms, although they were more thought-disordered and had a poorer outcome. Power analyses based on the model of linkage heterogeneity indicated that the ISHDSF should be able to detect a major locus that influences susceptibility to schizophrenia in as few as 20% of families. Compared to first-degree relatives of epidemiologically sampled schizophrenic probands, first-degree relatives of schizophrenic members from the ISHDSF had a similar risk for schizotypal personality disorder, affective illness, alcoholism, and anxiety disorder. With sufficient resources, large-scale ascertainment of multiplex schizophrenia pedigrees is feasible, especially in countries with catchmented psychiatric care and stable populations. Although somewhat more severely ill, schizophrenic members of such pedigrees appear to clinically resemble typical schizophrenic patients. Our ascertainment process for multiplex schizophrenia families did not select for excess familial risk for affective illness or alcoholism. With its large sample ascertained in a standardized manner from a relatively homogeneous population, the ISHDSF provides considerable power to detect susceptibility loci for schizophrenia.

Analysis of case-control/family sampling design

A commonly adopted design in genetic epidemiologic studies is the so-called case-control/family sampling design. Here, cases and controls are sampled and response variables, either quantitative or qualitative, for relatives of cases are contrasted with those of control relatives. This design can be used to examine familial aggregation, contribute to identification of genetic subtypes, and test the discrete versus continuous spectrum hypothesis for disorders of unknown etiology. However, the statistical independence assumption required by conventional case-control studies is violated for observations from related individuals who share the same genetic/environmental conditions. Consequently, ignoring dependence among related subjects will lead to incorrect sample size calculations and potentially erratic scientific conclusions. In this paper, we discuss several statistical issues that are relevant to the case-control/family sampling design with a focus on the use of this design in psychiatric research. Specifically, we 1) discuss the relative merit of matched versus unmatched designs; 2) present statistical methods that are useful for analyzing family data and 3) present sample size formulas for studies of quantitative and qualitative traits. A genetic epidemiologic study of schizophrenia is used for illustrative purposes.

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

Among all ascertainable cases of DSM IIIR schizophrenia within an unusually homogeneous region of rural Ireland, family history information was sought from multiple sources. Morbid risk for schizophrenia among probands' first degree relatives was 6.1% and did not differ between male (6.5%) and female (5.5%) probands; risk among probands' siblings (8.3%) exceeded that among their parents (1.4%), with only 2% of male and 31% of female probands being themselves married. Both age at onset <25 and having >7 siblings were associated with elevated morbid risk, particularly among relatives of male probands (11.9% vs. 2.2% and 11.8% vs. 3.7%, respectively). Increased fertility particularly among parents of male patients with high familial-genetic loading may contribute to perpetuation of the disorder in the face of those patients' own extremely low fecundity.

Genetic heterogeneity may in part explain sex differences in the familial risk for schizophrenia

The purpose of this study was to attempt, in part, to explain significant sex differences in the familial risk (FMR) for schizophrenia found in previous studies. We hypothesized that, like probands, relatives of male vs. female probands may express different forms or subsyndromal symptoms of schizophrenia, i.e., differential expression of flat affect. Studied were 332 schizophrenic probands defined by Diagnostic and Statistical Manual of Mental Disorders, 3rd ed. (DSM-III), criteria and 725 first-degree relatives from well-known retrospective cohort family studies. Results showed that relatives of male probands were at significantly higher risk for expressing flat affect than relatives of female probands, which did not hold for relatives of normal controls. Logistic regression was used to show that when flat affect was incorporated into the definition of affected among relatives, sex differences in FMR disappeared.

Age at onset, sex, and familial psychiatric morbidity in schizophrenia. Camberwell Collaborative Psychosis Study

BACKGROUND

Although a genetic component in schizophrenia is well established, it is likely that the contribution of genetic factors is not constant for all cases. Several recent studies have found that the relatives of female or early onset schizophrenic patients have an increased risk of schizophrenia, compared to relatives of male or late onset cases. These hypotheses are tested in the current study.

METHOD

A family study design was employed; the probands were 195 patients with functional psychosis admitted to three south London hospitals, diagnosed using Research Diagnostic Criteria (RDC), and assessed using the Present State Examination (PSE). Information on their relatives was obtained by personal interview of the mother of the proband, and from medical records. Psychiatric diagnoses were made using Family History-Research Diagnostic Criteria (FH-RDC), blind to proband information.

RESULTS

There was a tendency for homotypia in the form of psychosis within families. The lifetime risk of schizophrenia in the first degree relatives of schizophrenic probands, and the risk of bipolar disorder in the first degree relatives of bipolar probands, were 5-10 times higher than reported population risks. Relatives of female and early onset (< 22 years) schizophrenic probands had higher risk of schizophrenia than relatives of male and late onset schizophrenic probands. However, this effect was compensated in part by an excess of non-schizophrenic psychoses in the relatives of male probands.

CONCLUSIONS

These results suggest a high familial, possibly genetic, loading in female and early onset schizophrenia, but do not resolve the question of heterogeneity within schizophrenia.

Childhood-onset schizophrenia: timely neurobiological research

OBJECTIVE

To review timely research on childhood-onset schizophrenia in view of advances in biological research on, and neurodevelopmental theories of, the later-onset disorder.

METHOD

Research issues are outlined including further clarification of ICD- and DSM-defined childhood schizophrenia, and differentiation from autism "spectrum" and other subtle, chronic developmental disorders. Key neurobiological advances are reviewed for which child studies are relevant and feasible.

CONCLUSION

It is anticipated that narrowly defined childhood-onset schizophrenics will constitute a predominantly male population. A high rate of family illness or chromosomal and/or brain developmental abnormalities, which will be instructive regarding the pathophysiology of later-onset schizophrenia, is expected.

Schizophrenia: sex and familial morbidity

Several recent studies have found a greater risk of schizophrenia among the relatives of female schizophrenic probands than the relatives of male schizophrenic probands. These results are contradictory to those of earlier studies. The current investigation, using family data collected in the 1950's and 1960's in Sweden, did not find a difference in the risk of schizophrenia among the relatives of male and female schizophrenic probands. However, significantly more relatives of female probands than relatives of male probands had manic-depressive psychosis. These findings suggest that the earlier studies may have included some female schizophrenic probands who would be classified as having manic-depression by modern criteria.

Symptoms in schizophrenic syndromes in relation to age, sex, duration of illness and number of previous hospitalizations

In studies by means of the Swedish version of the Positive and Negative Syndrome Scale, we have demonstrated a 5-factor model of schizophrenia, including positive, negative, excited, anxious/depressive and cognitive factors. In this study, the 5 factors were correlated with background factors in a series comprising 140 patients with schizophrenic syndromes. None of the 5 factors revealed any significant age or sex differences. The positive factor correlated positively with the number of previous hospitalizations and the negative factor correlated negatively. The excited factor correlated negatively with age at onset, age at first hospitalization and positively with the duration of the illness and the number of previous hospitalizations. The cognitive factor correlated negatively with age at onset and age at first hospitalization and positively with the duration of the illness. Age at onset was positively correlated with delusions, excitement, unusual thought content and poor impulse control and negatively with lack of spontaneity. The duration of illness correlated positively with excitement, difficulty in abstract thinking and mannerisms. The number of previous hospitalizations correlated positively with delusions, excitement, unusual thought content and poor impulse control and significant negative correlations were demonstrated as concerns blunted affect and lack of spontaneity.

A typological model of schizophrenia based on age at onset, sex and familial morbidity

We investigated the age at onset distributions of schizophrenia in men and women and the relationship of age at onset and sex to the familial rates of schizophrenia and manic-depression in data from a Swedish family study of 270 schizophrenic probands. On the logarithmic scale, the age at onset distribution of schizophrenia in both male and female relatives was bimodal, suggesting that broadly defined schizophrenia may be a mixture of 2 (probably related) disorders. The risk of schizophrenia in relatives decreased as a function of the age at onset of the proband, irrespective of the sex of the proband or relative. In contrast, the risk of manic-depression was significantly higher in relatives of female probands with an age at onset in the twenties than in relatives of female probands with earlier or later onset, or in relatives of male probands. This suggests a third disorder related to affective psychosis, with an intermediate age at onset and female preponderance.

Extended latent class approach to the study of familial/sporadic forms of a disease: its application to the study of the heterogeneity of schizophrenia

When no method exists for detecting genetic forms of a disorder, epidemiologists classify probands according to the presence or absence of an affected relative (familial or sporadic). Not only is this a surrogate measure but if the risk for the disorder is associated with characteristics such as age and gender, then probands with varied distributions of these characteristics among their relatives are subject to misclassification. A latent class approach is presented which explicitly models the relationship between the affected status of the relatives and the unobservable familial/sporadic status of the proband in order to adjust for these characteristics. Lastly, an approach is introduced to correct for attenuation in measures of association between familial/sporadic status and other variables that could result if probands are misclassified. This approach incorporates the latent class probabilities directly into the regression model without classifying probands. These methods are applied to a study of the heterogeneity of schizophrenia.

The role of gender in understanding the familial transmission of schizoaffective disorder

The purpose of this study was to test the effect of gender on the familial risk for schizophrenia and affective disorders in probands with schizoaffective disorder. The sample consisted of 42 DSM-III schizoaffective probands and 149 first-degree relatives from the retrospective cohort family studies, the Iowa 500 and non-500. Survival analysis estimated differences in morbidity risks, analysed by sex of proband and of relative. Findings showed that, among probands, relatives of females had significantly higher rates of schizophrenia and unipolar disorder than relatives of males. Further, among relatives, males were at significantly higher risk for schizophrenia spectrum disorders than females. Results were similar when probands were subdivided into their primary symptom patterns, that is 'mainly schizophrenic' or 'mainly affective', as well as by 'schizoaffective, depressed' or 'schizoaffective, manic'. Implications for the taxonomy of schizoaffective disorder suggest a stronger relationship with schizophrenia, although the relationship with affective disorder remains unclear.

Sex differences in schizophrenia: a demographic, symptomatic, life history and genetic study

Twenty-one male and 32 female inpatients who met the criteria of schizophrenia according to the Research Diagnostic Criteria were compared for demographic, symptomatic, life history, and genetic variables. Female schizophrenics were marginally less likely to have auditory hallucinations; They were more likely to have early loss experiences (either bereavement or separation from a parent) before the age of 16. No other differences were found between the men and women.

Work environment and schizophrenia: an extension of the arousal hypothesis to occupational self-selection

The present study investigated a possible mechanism underlying the occupational self-selection of future schizophrenic patients prior to their first admission. More precisely, we explored whether schizophrenic patients are more likely than other psychotic patients to work in environments with a low potential for arousal (low complexity environments) in the last full-time job that preceded their hospitalization. All first admissions with psychotic symptoms to 15 hospitals providing inpatient psychiatric services in the Baltimore-Washington area were surveyed during a 6-year period. Patients diagnosed with schizophrenia were compared to patients diagnosed with bipolar disorder and other psychotic disorders to evaluate the suspected association. Study participants were assessed with a modified version of the Diagnostic Interview Schedule. Standard survey questions were used to assess occupational background. A measure based on the dictionary of occupational titles (DOT) was used to estimate the degree of complexity to which patients had been exposed in their last full-time occupation. Data were analyzed using multinomial logistic regression. After adjustment for age, gender, marital status, unemployment, socioeconomic status, hospital type, and physical demands and hazards on the job, patients with schizophrenia were more likely to have been working in low complexity environments in their last full-time jobs (e.g., janitors, gardeners, guards) than patients with bipolar disorder or with other psychotic disorders. Alternative explanations and potential implications regarding which work environments might be best suited to the social behavior of patients with schizophrenia are examined.

The impact of gender and age at onset on the familial aggregation of schizophrenia

Some recent family studies have shown that the familial risk for schizophrenia is higher in female than in male schizophrenics. It is debated whether the risks for the other disorders, such as schizotypal personality disorder or affective disorders in families of schizophrenics are similarly influenced by the proband's gender. Also, the reason for the effect of proband's gender on the recurrence risk for schizophrenia has not been clarified. This family study (159 probands, 589 first degree relatives) confirms that schizophrenia, but also schizophrenia spectrum disorders were more frequent in families of female compared with male schizophrenics. Neither age at onset in probands nor the interaction between gender and age at onset in probands had a relevant impact on the risk figures in relatives. Affective disorders occurred in families independently of the probands' gender. Aetiological heterogeneity or ascertainment bias may account for the modifying effect of proband's gender in schizophrenia.

Genes, viruses and neurodevelopmental schizophrenia

Recent neuroimaging and neuropathological studies suggest a developmental origin for schizophrenia. Some cases may, therefore, be caused by a genetic defect in the specification of brain development. Early environmental hazards such as obstetric complications, and maternal exposure during pregnancy to influenza epidemics, have also been found to increase the risk of later schizophrenia. The relationship between the prevalence of influenza and birth date has been found more consistently for female than male schizophrenics. Female schizophrenia is also associated with a higher risk of schizophrenia in first degree relatives. This raises the question of whether part of the genetic predisposition to schizophrenia may comprise an abnormal reaction to maternal influenza.

Gender and the familial risk for schizophrenia. Disentangling confounding factors

Recent studies of the effect of gender on the familial risk for schizophrenia have shown that relatives of females have a higher risk for schizophrenia than relatives of males. This study attempts to explain the effect by examining factors found to differentiate schizophrenic men and women and found to be related to the familial risk for schizophrenia. Cox proportional hazard regression model was used to examine the simultaneous effects of age at onset, season of birth, and premorbid history, controlled for symptoms that have been found to differ by gender (dysphoria, paranoia, and flat affect). Results showed that the effect of gender on the transmission of schizophrenia could not be explained by gender differences in age at onset, symptom expression, premorbid history, and winter birth. However, premorbid history had an effect on familial risk independent of gender, indicating that probands with a poor premorbid history had a lower familial risk for schizophrenia than those with a good premorbid history. Implications of the findings are discussed.

Season of birth of siblings of schizophrenic patients

The hypothesis that mothers of winter-spring-born schizophrenics have an unusual pattern of conception which results in an excess of winter-spring births was tested by studying the distribution of birth-dates of 401 siblings of 120 winter-spring-born schizophrenics and 157 siblings of 59 winter-spring-born controls. All analyses were gender-specific. The results suggest there is no association between the probability of a winter-spring date of birth and being a sibling of a winter-spring-born schizophrenic or control.

Schizophrenia: gender and familial risk

The morbid risks for schizophrenia and any nonaffective psychosis in the first degree relatives of male and female schizophrenic probands were compared utilizing Cox proportional hazards models. The schizophrenic probands (275 male; 106 female) were drawn from a larger sample of hospitalized patients obtained by systematically screening all psychiatric admissions to 15 facilities over a six-year period. Proband diagnoses (DSM-III) were based on a direct assessment of the patient and a review of medical records. The family history method was used to obtain information about the first degree relatives of the probands. Cox proportional hazards models were adjusted for duration of illness of the proband and gender of the relatives. First degree relatives of female probands had significantly higher morbid risks for schizophrenia and nonaffective psychosis than relatives of male probands. The differential risk for schizophrenia in the relatives of male and female probands demonstrated in this study, as well as others, suggests that males and females may be at different risk for subtypes of the disorder.

Estimating effects of probands' characteristics on familial risk: I. Adjustment for censoring and correlated ages at onset

Family studies with age at onset of the disease as the endpoint face two important problems: censoring and correlation of age at onset among relatives. We present a multivariate survival model for ages at onset of relatives which incorporates the problems cited above. The interpretations of regression coefficients and association parameter in the context of family studies are emphasized. The present paper describes a statistical method for estimating these parameters. In a companion paper [Pulver and Liang, Genet Epidemiol 8:339-350, 1991] this model is applied to a genetic epidemiologic study of schizophrenia.

Estimating effects of proband characteristics on familial risk: II. The association between age at onset and familial risk in the Maryland schizophrenia sample

In this report we apply methods outlined in the companion paper [Liang, Genet Epidemiol 8:329-338, 1991] to study the association between proband age at onset and familial risk among first-degree relatives of 374 schizophrenic probands. The analyses take into consideration the potential problems of censoring and correlation of age at onset within families. All analyses were done by gender of the proband; age at onset was dichotomized. The results of the analyses of the male probands suggest that there is an increased risk of schizophrenia among the relatives of male probands who have an onset prior to age 17 when compared to relatives of male probands who have an onset later than 16. We did not find an association between age at onset and familial risk among the female probands, but this may be due to the smaller number of female probands and the lower power associated with the analyses.