The clinical characteristics of major depression as indices of the familial risk to illness

The genetic basis of major depressive disorder

The genetic dissection of major depressive disorder (MDD) ranks as one of the success stories of psychiatric genetics, with genome-wide association studies (GWAS) identifying 178 genetic risk loci and proposing more than 200 candidate genes. However, the GWAS results derive from the analysis of cohorts in which most cases are diagnosed by minimal phenotyping, a method that has low specificity. I review data indicating that there is a large genetic component unique to MDD that remains inaccessible to minimal phenotyping strategies and that the majority of genetic risk loci identified with minimal phenotyping approaches are unlikely to be MDD risk loci. I show that inventive uses of biobank data, novel imputation methods, combined with more interviewer diagnosed cases, can identify loci that contribute to the episodic severe shifts of mood, and neurovegetative and cognitive changes that are central to MDD. Furthermore, new theories about the nature and causes of MDD, drawing upon advances in neuroscience and psychology, can provide handles on how best to interpret and exploit genetic mapping results.

Associations of Brain-Derived Neurotropic Factor rs6265 Gene Polymorphism with Personality Dimensions among Athletes

Brain-Derived Neurotropic Factor (BDNF) is one of the essential mediating factors of exercise-induced neuroplasticity, but the underlying molecular mechanisms of exercise-induced neuroplasticity are still largely unknown. Personality dimensions differentiate individuals and depend on genes and environmental factors. The dimensions of openness to experience, emotional stability, extraversion and conscientiousness have been reported to be positively related to performance; considering agreeableness, a negative relation with sports performance was emphasized. However, not enough effort has been put into investigating the relationship between genetic polymorphisms affecting psychological abilities and competitive power sports. The aim of this study was to investigate the association of the rs6265 polymorphism of BDNF with personality dimensions in martial arts athletes. The study was conducted among martial arts athletes. The study group included 258 volunteers (martial arts athletes (n = 106) and controls (n = 152). BDNF polymorphism testing was performed using the real-time PCR method; personality dimensions were assessed using standardized NEO-FFI questionnaires. All analyses were performed using STATISTICA 13. We observed that martial arts athletes’ G/G genotypes compared to the control group G/G genotypes presented significantly higher severity of personality dimension “conscientiousness”. In comparison with the controls, the case group subjects had significantly higher scores in the dimension extraversion (M 6.89 vs. M 6.43, p = 0.0405) and conscientiousness/scale (M 7.23 vs. M 5.89, p < 0.0001). The results of 2 × 3 factorial ANOVA noticed a statistically significant effect of combined factor BDNF rs6265 genotype of martial arts/control (F2,252 = 3.11, p = 0.0465, η2 = 0.024). Additionally, we observed that the results of 2 × 3 factorial ANOVA showed a statistically significant influence of combined factor BDNF rs6265 of genotype martial arts/ control (F2,252 = 6.16, p = 0.0024, η2 = 0.047). The combination of the analysis of personality dimensions with genetics—as in the case of the polymorphism of the BDNF gene related to neuroplasticity—indicates that neurobiology cannot be ignored in educating sports champions. We already know that this is related to genetics. However, little is still known about the influence of personality traits on sports performance. We observed that martial arts athletes’ G/G genotypes, in comparison to the control group’s G/G genotypes, presented significantly higher severity of personality dimension “conscientiousness”. This is worthy of further analysis and probably longitudinal studies on a more numerous group of athletes.

Clinical utility of family history of depression for prognosis of adolescent depression severity and duration assessed with predictive modeling

BACKGROUND

Family history of depression (FHD) is a known risk factor for the new onset of depression. However, it is unclear if FHD is clinically useful for prognosis in adolescents with current, ongoing, or past depression. This preregistered study uses a longitudinal, multi-informant design to examine whether a child's FHD adds information about future depressive episodes and depression severity applying state-of-the-art predictive out-of-sample methodology.

METHODS

We examined data in adolescents with current or past depression (age 11-17 years) from the National Institute of Mental Health Characterization and Treatment of Adolescent Depression (CAT-D) study. We asked whether a history of depression in a first-degree relative was predictive of depressive episode duration (72 participants) and future depressive symptom severity in probands (129 participants, 1,439 total assessments).

RESULTS

Family history of depression, while statistically associated with time spent depressed, did not improve predictions of time spent depressed, nor did it improve models of change in depression severity measured by self- or parent-report.

CONCLUSIONS

Family history of depression does not improve the prediction of the course of depression in adolescents already diagnosed with depression. The difference between statistical association and predictive models highlights the importance of assessing predictive performance when evaluating questions of clinical utility.

[Family history of affective disorders, the gender factor and clinical characteristics of depression]

OBJECTIVE

Analysis of clinical features of development and course of depression in patients with FH of mood disorders taking into account sex differences.

MATERIAL AND METHODS

This multicenter cross-sectional study included patients over 18 years of age with depressive episode/recurrent depressive disorder. Clinical characteristics of depression, presence of comorbid mental illness and family history (FH) information were obtained in a structured clinical interview.

RESULTS

One hundred and seventy-one patients (mean age (M (SD)) 40.87 (15.86) y.o.), including 64.5% of women, were enrolled in the study. FH was revealed in 30.2% of patients. The proportion of FH did not differ in men and women (p=0.375). Generalized anxiety disorder (GAD) was more frequent in FH positive patients (p=0.016). Logistic regression also revealed that FH is a risk factor for concomitant GAD (p=0.019, OR=2.4). The GLM demonstrated a significant joint effect of FH and sex on the maximum duration of a depressive episode (p=0.044), as well on the number of suicide attempts (p=0.055) and the number of depressive episodes as a trend (p=0.072).

CONCLUSION

We have demonstrated the specific interaction of FH of mood disorders with sex on clinical course of depression. Thus, the manifestation of a genetic influence on the clinical phenotype of depression can be significantly moderated by sex.

Familial aggregation of depression, but no familial aggregation of individual depressive symptoms

Background

Familial aggregation of major depression might indicate a genetic liability for the disorder. The complete disorder or, alternatively, only some individual symptoms might be inherited. Under the latter condition, an increased frequency of inherited symptoms might consecutively increase the likelihood to reach the threshold for depression in relatives and, thus, might cause the familial aggregation of depression. Up to now, no study investigated the possibility of a relationship between individual depressive symptoms and the familial aggregation of depression.

Methods

The familial aggregation of early-onset depression (age-at-onset < 60 years, EOD) but less so of late-onset depression (LOD) has been shown in this sample. To assess the hypothesis of an inheritance of individual depressive symptoms as a possible cause of the familial aggregation of depression, frequencies of symptoms were compared in relatives of depressed patients and of controls using forward logistic regression analyses.

Results

Some individual depressive symptoms showed clustering in relatives of patients with depression, but the pattern of inheritance was inconsistent, i.e. the clustering of symptoms was different between non-depressed and depressed relatives of patients with EOD and LOD, respectively. No intra-familial clustering of specific depressive symptoms within families of depressed subjects could be observed.

Conclusions

Due to the inconsistencies in the clustering of individual symptoms in non-depressed and depressed relatives and the lack of intra-familial clustering, the familial aggregation of depression is unlikely to be caused by the aggregation of individual depressive symptoms. An inheritance of the vulnerability for complete depressive disorders influenced by environmental factors is more likely.

Age of onset and family history as indicators of polygenic risk for major depression

BACKGROUND

The extent to which earlier age of onset (AO) is a reflection of increased genetic risk for major depression (MD) is still unknown. Previous biometrical research has provided mixed empirical evidence for the genetic overlap of AO with MD. If AO is demonstrated to be relevant to molecular polygenic risk for MD, incorporation of AO as a phenotype could enhance future genetic studies.

METHODS

This research estimated the SNP-based heritability of AO in the China, Oxford and VCU Experimental Research on Genetic Epidemiology (CONVERGE) case-control sample (N = 9,854; MD case, n = 4,927). Common single nucleotide polymorphism heritability of MD was also examined across both high and low median-split AO groups, and best linear unbiased predictor (BLUP) scores of polygenic risk, in split-halves, were used to predict AO. Distributions of genetic risk across early and late AO were compared, and presence of self-reported family history (FH) of MD was also examined as a predictor of AO.

RESULTS

AO was not significantly heritable and polygenic risk derived from the aggregated effects of common genetic variants did not significantly predict AO in any analysis. AO was modestly but significantly lower in cases with a first-degree genetic FH of MD.

CONCLUSIONS

Findings indicate that AO is associated with greater self-reported genetic risk for MD in cases, yet not associated with common variant polygenic risk for MD. Future studies of early MD may benefit more from the examination of important moderating variables such as early life events.

The genetics of major depression

Major depression is the commonest psychiatric disorder and in the U.S. has the greatest impact of all biomedical diseases on disability. Here we review evidence of the genetic contribution to disease susceptibility and the current state of molecular approaches. Genome-wide association and linkage results provide constraints on the allele frequencies and effect sizes of susceptibility loci, which we use to interpret the voluminous candidate gene literature. We consider evidence for the genetic heterogeneity of the disorder and the likelihood that subtypes exist that represent more genetically homogenous conditions than have hitherto been analyzed.

Investigating the genetic variation underlying episodicity in major depressive disorder: suggestive evidence for a bipolar contribution

BACKGROUND

Highly recurrent major depressive disorder (MDD) has reportedly increased risk of shifting to bipolar disorder; high recurrence frequency has, therefore, featured as evidence of 'soft bipolarity'. We aimed to investigate the genetic underpinnings of total depressive episode count in recurrent MDD.

METHODS

Our primary sample included 1966 MDD cases with negative family history of bipolar disorder from the RADIANT studies. Total episode count was adjusted for gender, age, MDD duration, study and center before being tested for association with genotype in two separate genome-wide analyses (GWAS), in the full set and in a subset of 1364 cases with positive family history of MDD (FH+). We also calculated polygenic scores from the Psychiatric Genomics Consortium MDD and bipolar disorder studies.

RESULTS

Episodicity (especially intermediate episode counts) was an independent index of MDD familial aggregation, replicating previous reports. The GWAS produced no genome-wide significant findings. The strongest signals were detected in the full set at MAGI1 (p=5.1×10(-7)), previously associated with bipolar disorder, and in the FH+ subset at STIM1 (p=3.9×10(-6) after imputation), a calcium channel signaling gene. However, these findings failed to replicate in an independent Munich cohort. In the full set polygenic profile analyses, MDD polygenes predicted episodicity better than bipolar polygenes; however, in the FH+ subset, both polygenic scores performed similarly.

LIMITATIONS

Episode count was self-reported and, therefore, subject to recall bias.

CONCLUSIONS

Our findings lend preliminary support to the hypothesis that highly recurrent MDD with FH+ is part of a 'soft bipolar spectrum' but await replication in larger cohorts.

Neuroticism, depressive symptoms and white-matter integrity in the Lothian Birth Cohort 1936

BACKGROUND

Clinical depression is associated with reductions in white-matter integrity in several long tracts of the brain. The extent to which these findings are localized or related to depressive symptoms or personality traits linked to disease risk remains unclear. Method Members of the Lothian Birth Cohort 1936 (LBC936) were assessed in two waves at mean ages of 70 and 73 years. At wave 1, they underwent assessments of depressive symptoms and the personality traits of neuroticism and extraversion. Brain diffusion magnetic resonance imaging (MRI) data were obtained at the second wave and mood assessments were repeated. We tested whether depressive symptoms were related to reduced white-matter tract fractional anisotropy (FA), a measure of integrity, and then examined whether high neuroticism or low extraversion mediated this relationship.

RESULTS

Six hundred and sixty-eight participants provided useable data. Bilateral uncinate fasciculus FA was significantly negatively associated with depressive symptoms at both waves (standardized β=0.12-0.16). Higher neuroticism and lower extraversion were also significantly associated with lower uncinate FA bilaterally (standardized β=0.09-0.15) and significantly mediated the relationship between FA and depressive symptoms.

CONCLUSIONS

Trait liability to depression and depressive symptoms are associated with reduced structural connectivity in tracts connecting the prefrontal cortex with the amygdala and anterior temporal cortex. These effects suggest that frontotemporal disconnection is linked to the etiology of depression, in part through personality trait differences.

Genetic association between helpless trait and depression-related phenotypes: evidence from crossbreeding studies with H/Rouen and NH/Rouen mice

Genetic factors are believed to be involved in the aetiology of unipolar depressive disorders. We have previously described a model built up by selective breeding of mice with different responses in the tail suspension test, a screening test for potential antidepressants. In this model, helpless H/Rouen mice are essentially immobile in this test, as well as in the Porsolt forced-swim test, whereas non-helpless NH/Rouen mice show the opposite behaviour, i.e. very low immobility. However, it is unclear whether or not the other phenotypic differences (forced swim test, locomotor activity, sucrose test, sleep patterns, effect of fluoxetine) observed between H/Rouen and the NH/Rouen mice may be attributed to a genetic drift phenomenon during the selection step, rather than being related to the trait of selection. In this study we used reciprocal crossbreeding between H/Rouen and NH/Rouen mice and obtained a segregating F2 population in order to determine whether phenotypic differences between the two lines co-segregate with the trait of selection. In the segregating F2 population, we found significant and strong genetic correlations between helplessness in the tail suspension test and some phenotypical features associated with depressive disorders such as 'alterations of sleep patterns', behavioural response to fluoxetine, immobility duration in the forced swim test, and anhedonia. Our results converge with clinical observations in depressed humans. These results strengthen the validity of the H/Rouen mouse as a model of depression, notably for preclinical studies with antidepressants. In addition, this model should open the way to identifying genes related to depression-like behaviours.

Clinical predictors of familial depression in Han Chinese women

BACKGROUND

A number of clinical features potentially reflect an individual's familial vulnerability to major depression (MD), including early age at onset, recurrence, impairment, episode duration, and the number and pattern of depressive symptoms. However, these results are drawn from studies that have exclusively examined individuals from a European ethnic background. We investigated which clinical features of depressive illness index familial vulnerability in Han Chinese females with MD.

METHODS

We used lifetime MD and associated clinical features assessed at personal interview in 1,970 Han Chinese women with DSM-IV MD between 30-60 years of age. Odds Ratios were calculated by logistic regression.

RESULTS

Individuals with a high familial risk for MD are characterized by severe episodes of MD without known precipitants (such as stress life events) and are less likely to feel irritable/angry or anxious/nervous.

CONCLUSIONS

The association between family history of MD and the lack of a precipitating stressor, traditionally a characteristic of endogenous or biological depression, may reflect the association seen in other samples between recurrent MD and a positive family history. The symptomatic associations we have seen may reflect a familial predisposition to other dimensions of psychopathology, such as externalizing disorders or anxiety states.

Stressful life events and depression among adolescent twin pairs

Using the twin pairs sample from the National Longitudinal Study ofAdolescent Health, we estimate bivariate Cholesky models for the influence of stressful life events (SLEs) on depressive symptoms. We show that depressive symptoms (h2Depression = .28) and dependent SLEs (events influenced by an individual's behavior) are both moderately heritable (h2SLE Dependent = .43). We find no evidence for the heritability of independent SLEs. Results from the bivariate Cholesky model suggest that roughly one-half of the correlation between depression and dependent SLEs is due to common genetic factors. Our findings suggest that attempts to characterize the causal effect of SLEs on mental health should limit their list of SLEs to those that are outside of the control of the individual.

Psychiatric 'diseases' versus behavioral disorders and degree of genetic influence

BACKGROUND

Psychiatric conditions in which symptoms arise involuntarily ('diseases') might be assumed to be more heritable than those in which choices are essential (behavioral disorders). We sought to determine whether psychiatric 'diseases' (Alzheimer's disease, schizophrenia, and mood and anxiety disorders) are more heritable than behavioral disorders (substance use disorders and anorexia nervosa).

METHOD

We reviewed the literature for recent quantitative summaries of heritabilities. When these were unavailable, we calculated weighted mean heritabilities from twin studies meeting modern methological standards.

RESULTS

Heritability summary estimates were as follows: bipolar disorder (85%), schizophrenia (81%), Alzheimer's disease (75%), cocaine use disorder (72%), anorexia nervosa (60%), alcohol dependence (56%), sedative use disorder (51%), cannabis use disorder (48%), panic disorder (43%), stimulant use disorder (40%), major depressive disorder (37%), and generalized anxiety disorder (28%).

CONCLUSIONS

No systematic relationship exists between the disease-like character of a psychiatric disorder and its heritability; many behavioral disorders seem to be more heritable than conditions commonly construed as diseases. These results suggest an error in 'common-sense' assumptions about the etiology of psychiatric disorders. That is, among psychiatric disorders, there is no close relationship between the strength of genetic influences and the etiologic importance of volitional processes.

Predictive value of family history on severity of illness: the case for depression, anxiety, alcohol dependence, and drug dependence

CONTEXT

If family history is associated with clinical features that are thought to index seriousness of disorder, this could inform clinicians predicting patients' prognosis and researchers selecting cases for genetic studies. Although tests of associations between family history and clinical features are numerous for depression, such tests are relatively lacking for other disorders.

OBJECTIVE

To test the hypothesis that family history is associated with 4 clinical indexes of disorder (recurrence, impairment, service use, and age at onset) in relation to 4 psychiatric disorders (major depressive episode, anxiety disorder, alcohol dependence, and drug dependence).

DESIGN

Prospective longitudinal cohort study.

SETTING

New Zealand.

PARTICIPANTS

A total of 981 members of the 1972 to 1973 Dunedin Study birth cohort (96% retention).

MAIN OUTCOME MEASURES

For each disorder, family history scores were calculated as the proportion of affected family members from data on 3 generations of the participants' families. Data collected prospectively at the study's repeated assessments (ages 11-32 years) were used to assess recurrence, impairment, and age at onset; data collected by means of a life history calendar at age 32 years were used to assess service use.

RESULTS

Family history was associated with the presence of all 4 disorder types. In addition, family history was associated with a more recurrent course for all 4 disorders (but not significantly for women with depression), worse impairment, and greater service use. Family history was not associated with younger age at onset for any disorder.

CONCLUSIONS

Associations between family history of a disorder and clinical features of that disorder in probands showed consistent direction of effects across depression, anxiety disorder, alcohol dependence, and drug dependence. For these disorder types, family history is useful for determining patients' clinical prognosis and for selecting cases for genetic studies.

Brain derived neurotrophic factor Val66Met polymorphism, the five factor model of personality and hippocampal volume: Implications for depressive illness

Altered hippocampal volume, the brain-derived neurotrophic factor (BDNF) Val66Met polymorphism, and neuroticism have each been implicated in the etiology of psychiatric disorders, especially depression. However, the relationship between these variables is not well understood. Here, we determined the effects of the BDNF Val66met polymorphism on the five-factor personality dimensions (assessed using the NEO-FFI), trait depression (assessed with the DASS-21) in a cross-sectional cohort of 467 healthy volunteers. A large matched subset of this cohort was also assessed for grey matter volume of the hippocampus and contiguous temporal cortical regions using magnetic resonance imaging. In Met carriers, elevations in neuroticism and trait depression and stress were associated with lower mean hippocampal volume, but there were no such associations in Val homozygotes. Trait depression, in particular, was found to moderate the effects of BDNF genotypes on hippocampal volume. Met carriers with high trait depression showed a reduction in grey matter volume of the mean hippocampus compared with Val homozygotes. These findings suggest that even in otherwise healthy subjects, trait depression may contribute to the susceptibility of Met carriers to hippocampal grey matter loss.

Familiality of depression in the community; associations with gender and phenotype of major depressive disorder

INTRODUCTION

Although associations between family history and depression have been shown in clinical patients, it is unknown if they also apply to subjects living in the community. The present study considers the relationship between family loading and depression phenotype characteristics in a large community-based sample.

METHOD

In a Dutch representative population sample of 7,076 individuals, lifetime diagnosis of depression was classified according to severity, course and age of onset. A family loading score of depression (FLSD) was computed by taking the proportion of the first-degree relatives for whom a history of depression was reported.

RESULTS

There was a strong association between FLSD and lifetime diagnosis of MDD. Severity, recurrence and early onset of depression were the specific phenotypic characteristics associated with familiality. The effects of FLSD and gender were independent.

CONCLUSION

Associations between family history and risk for depression in the community confirm those reported from clinical-based studies using direct interviewing of relatives. A stronger degree of familiality is associated with specific phenotypic characteristics of depression.

Familiality of major depressive disorder and patterns of lifetime comorbidity. The NEMESIS and GenMood studies. A comparison of three samples

BACKGROUND

Major depressive disorder (MDD) aggregates in families and is associated with high rates of lifetime axis-I comorbidity. This study examined whether familiality of MDD is associated with the presence of specific comorbid disorders, which might be an important factor to be taken into account in MDD treatment and research into MDD etiology.

METHODS

A population sample was divided into subjects with familial (f-MDD; n=432) and nonfamilial MDD (nf-MDD; n=454). Since, more comorbidity was expected in clinical cases, a clinical sample with f-MDD (n=120) was also studied. Subjects were assessed with the Composite International Diagnostic Interview and family history methods. Binary logistic regression analyses were carried out to examine the influence of familiality of MDD on comorbidity. Analyses were adjusted for potential confounders, including MDD characteristics such as severity and age of onset.

RESULTS

Dysthymia, anxiety disorders, and alcohol use disorders were significantly more prevalent in subjects with f-MDD than in subjects with nf-MDD. Clinical f-MDD was associated with more anxiety disorders and fewer alcohol use disorders than population f-MDD. After adjustment for MDD characteristics including age at onset, severity, and disease course, comorbid disorders remained more prevalent in f-MDD than in nf-MDD.

LIMITATIONS

The instruments used in the population and the clinical samples were not identical, however, they were comparable to a substantial degree.

CONCLUSIONS

F-MDD, especially in clinical cases, appears to increase the risk of development of comorbid disorders, regardless of MDD characteristics. The link between familiality and comorbidity is important because it will aid a better understanding of the MDD phenotype, and it contributes to planning of effective treatment and to molecular genetic studies.

Familiality of major depressive disorder and gender differences in comorbidity

OBJECTIVE

Gender differences exist in the prevalence and psychiatric comorbidity of major depressive disorder (MDD). This study investigates whether familiality of MDD contributes to observed gender differences in comorbidity.

METHOD

Familial (f-MDD) and non-familial (nf-MDD) MDD cases from a population sample were assessed for comorbid dysthymia, anxiety disorders and alcohol-related disorders using the Composite International Diagnostic Interview (CIDI). Logistic regression analyses were performed to examine the effect of f-MDD on gender differences in comorbidity, adjusted for confounders.

RESULTS

Women with f-MDD reported significantly more comorbid dysthymia and generalized anxiety disorder (GAD) than their male counterparts; women with nf-MDD reported significantly more comorbid simple phobias and agoraphobia than their male counterparts. Gender differences in comorbid panic disorder and alcohol-related disorders occurred independently of the familial load. Adjustment for age of onset, severity and recurrence of MDD did not change these results.

CONCLUSION

Models to explain comorbidity patterns of MDD differ by gender. Familiality of MDD should be taken into account.

Family history of depression is associated with younger age of onset in patients with recurrent depression

BACKGROUND

Genetic epidemiology data suggest that younger age of onset is associated with family history (FH) of depression. The present study tested whether the presence of FH for depression or anxiety in first-degree relatives determines younger age of onset for depression.

METHOD

A sample of 1022 cases with recurrent major depressive disorder (MDD) was recruited at the Max Planck Institute and at two affiliated hospitals. Patients were assessed using the Schedules for Clinical Assessment in Neuropsychiatry and questionnaires including demographics, medical history, questions on the use of alcohol and tobacco, personality traits and life events. Survival analysis and the Cox proportional hazard model were used to determine whether FH of depression signals earlier age of onset of depression.

RESULTS

Patients who reported positive FH had a significantly earlier age of onset than patients who did not report FH of depression (log-rank=48, df=1, p<0.0001). The magnitude of association of FH varies by age of onset, with the largest estimate for MDD onset before age 20 years (hazard ratio=2.2, p=0.0009), whereas FH is not associated with MDD for onset after age 50 years (hazard ratio=0.89, p=0.5). The presence of feelings of guilt, anxiety symptoms and functional impairment due to depressive symptoms appear to characterize individuals with positive FH of depression.

CONCLUSIONS

FH of depression contributes to the onset of depression at a younger age and may affect the clinical features of the illness.

The genetics of depression: a review

Major depressive disorder (MDD) is common and moderately heritable. Recurrence and early age at onset characterize cases with the greatest familial risk. Major depressive disorder and the neuroticism personality trait have overlapping genetic susceptibilities. Most genetic studies of MDD have considered a small set of functional polymorphisms relevant to monoaminergic neurotransmission. Meta-analyses suggest small positive associations between the polymorphism in the serotonin transporter promoter region (5-HTTLPR) and bipolar disorder, suicidal behavior, and depression-related personality traits but not yet to MDD itself. This polymorphism might also influence traits related to stress vulnerability. Newer hypotheses of depression neurobiology suggest closer study of genes related to neurotoxic and neuroprotective (neurotrophic) processes and to overactivation of the hypothalamic-pituitary axis, with mixed evidence regarding association of MDD with polymorphisms in one such gene (brain-derived neurotrophic factor [BDNF]). Several genome-wide linkage studies of MDD and related traits have been reported or are near completion. There is some evidence for convergence of linkage findings across studies, but more data are needed to permit meta-analysis. Future directions will include more intensive, systematic study of linkage candidate regions and of the whole genome for genetic association; gene expression array studies; and larger-scale studies of gene-environment interactions and of depression-related endophenotypes.

[Comorbidity between eating disorders and mood disorders: review]

OBJECTIVE

Comorbidity between eating disorders (ED) and mood disorders is a major issue when evaluating and treating patients with anorexia nervosa (AN) or bulimia nervosa (BN). In the literature, estimated comorbidity rates of mood disorders in subjects with ED differ widely across studies. Obviously, it is difficult to compare results from various sources because of differences in methods of assessment of depressive symptoms and in diagnostic criteria for both ED and mood disorders. Furthermore, few studies have included control groups, and, since mood disorders are among the most frequent psychiatric disorders in women--with an average estimated lifetime prevalence of 23.9 % (Kessleret al., 1994)--, it is not clear, yet, whether mood disorders are more common among women with an ED (AN or BN) than among women from the community. The only review articles we found on the relationships between ED and mood disorders survey different types of arguments in favour of a link between both categories of disorders, including symptoms, personal and family comorbidity, overlap in biological findings, and treatment results, but do not review in detail available comorbidity data. The aim of this paper is to conduct a critical literature review on studies assessing the prevalence of mood disorders in subjects with an ED (AN or BN). In the first part, we will discuss methodological issues relevant to comorbidity studies between ED and mood disorders, and select the most reliable studies. In the second part, taking into account these methodological considerations raised, we summarize the findings of these studies.

METHOD

We performed a manual and computerized search (Medline) for all published studies on comorbidity between ED and AD, limiting our search to the 1985-2002 period, in order to get sufficiently homogeneous diagnostic criteria for both categories of disorders.

RESULTS

Too few studies include control groups and few studies have compared diagnostic subgroups of ED subjects, with scarce or conflicting results.

DISCUSSION

We reviewed numerous studies here and conclude simply that there are many arguments in favor of elevated rates of MD in ED subjects, but there is no convincing evidence yet. Many questions are left unanswered or have conflicting responses. Our review highlights the need for further studies, which should address several requisites: comorbidity studies should be designed with this as a specific goal, rather than as a secondary aim within other types of studies (such as treatment studies, follow-up studies, etc.). Kendler et al. (1991) state that individuals with two disorders are more likely to present for treatment than individuals with one, therefore, comorbidity rates (which are not in agreement with a special etiologic relationship between BN and depression) may be exaggerated in clinical population results. New studies should include control subjects, matched (at least) for sex and age with ED subjects. Studies should evaluate prevalence of all types of MD in order to yield comparable estimates of MD in general. Comorbidity studies should be conducted on both current and recovered patients, compared to subjects from the community. It is still necessary to demonstrate specificity of findings, i.e. that early onset MD are of specific etiological importance to ED and do not simply increase the risk of later psychopathology in general. Studies should be conducted on larger samples, and all diagnostic subgroups should be considered (restrictive and bulimic anorexics, bulimics with and without history of AN, with or without purging). Multivariate comparisons should be performed, taking into account subject age, sex (if men are included), in- and outpatient status, course of illness, and other possibly relevant variables. Thus, more reliable estimates of the frequency of MD in subjects with ED could provide us with valuable etiologic, therapeutic and prognostic information.

Dissecting the genetic etiology of major depressive disorder using linkage analysis

Major depressive disorder (MDD) is clinically and genetically heterogeneous. Studies suggest that recurrence, early onset and comorbid phenotypes define more genetically homogeneous sub-samples. The concordance of linkage findings in recent studies using such approaches is encouraging. Sex-specific analyses and broader phenotypes have also yielded interesting results. These findings indicate that future research should consider comorbid disorders and sex-specific analyses. However, this direction must be approached with caution, owing to the complex multiple-testing issues that arise when considering numerous related phenotypes. With appropriate interpretation, these findings indicate a new potential for positional cloning efforts to locate genes in consensus regions. Genes found might influence specific subtypes of MDD or broader phenotypes, leading to enhanced clinical characterization and management of MDD.

Genome-wide linkage analyses of extended Utah pedigrees identifies loci that influence recurrent, early-onset major depression and anxiety disorders

Major depressive disorder (MDD) is a common, clinically heterogeneous disorder often found comorbid with other disorders. We studied recurrent, early-onset MDD (MDD-RE) and anxiety disorders in combination to define powerful phenotypes for genetic study. We used 87 large, extended Utah pedigrees to investigate linkage to 3 phenotypes: "MDD-RE;" "MDD-RE or anxiety;" and "MDD-RE and anxiety;" where in the latter definition the disorders must appear comorbid within an individual. Pedigrees ranged in size from 2 to 6 generations and contained 3 to 42 individuals affected with MDD or anxiety (718 total). In primary analyses, we identified three regions with at least suggestive genome-wide evidence for linkage on chromosomes 3centr, 7p, and 18q. Both 7p and 18q are replication findings for related phenotypes. The best linkage evidence was for a novel locus at 3p12.3-q12.3 (LOD = 3.88, "MDD-RE or anxiety") and 18q21.33-q22.2 (LOD = 3.75, "MDD-RE and anxiety"), a well-established susceptibility locus for bipolar disorder. In our secondary sex-specific analyses, we identified two further regions of interest on chromosomes 4q and 15q. Using linked pedigrees, we localized 3centr and 18q to 9.8 and 12.2 cM, respectively, with potential for further localization with the addition of markers in specific pedigrees. Our success in replication and novel locus identification illustrates the utility of large extended pedigrees for common disorders, such as MDD. Further, it supports the hypothesis that MDD and anxiety disorders have over-lapping genetic etiologies and suggests that comorbid diagnoses may be useful in defining more genetically homogeneous forms of MDD for linkage mapping.

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.

JR, Scheftner WA, Weissman MM, Zubenko WN, Boutelle S, Murphy-Eberenz K, MacKinnon D, McInnis MG, Marta DH, Adams P, Knowles JA, Gladis M, Thomas J, Chellis J, Miller E, Levinson DF. Genomewide significant linkage to recurrent, early-onset major depressive disorder on chromosome 15q

A genome scan was performed on the first phase sample of the Genetics of Recurrent Early-Onset Depression (GenRED) project. The sample consisted of 297 informative families containing 415 independent affected sibling pairs (ASPs), or, counting all possible pairs, 685 informative affected relative pairs (555 ASPs and 130 other pair types). Affected cases had recurrent major depressive disorder (MDD) with onset before age 31 years for probands or age 41 years for other affected relatives; the mean age at onset was 18.5 years, and the mean number of depressive episodes was 7.3. The Center for Inherited Disease Research genotyped 389 microsatellite markers (mean spacing of 9.3 cM). The primary linkage analysis considered allele sharing in all possible affected relative pairs with the use of the Z(lr) statistic computed by the ALLEGRO program. A secondary logistic regression analysis considered the effect of the sex of the pair as a covariate. Genomewide significant linkage was observed on chromosome 15q25.3-26.2 (Zlr=4.14, equivalent LOD = 3.73, empirical genomewide P=.023). The linkage was not sex specific. No other suggestive or significant results were observed in the primary analysis. The secondary analysis produced three regions of suggestive linkage, but these results should be interpreted cautiously because they depended primarily on the small subsample of 42 male-male pairs. Chromosome 15q25.3-26.2 deserves further study as a candidate region for susceptibility to MDD.

Genetics of recurrent early-onset depression (GenRED): design and preliminary clinical characteristics of a repository sample for genetic linkage studies

This is an initial report on a six-site collaborative project, Genetics of Recurrent Early-Onset Depression (GenRED). This is a study of a large sample of families with recurrent major depressive disorder (DSM-IV) beginning by the age 30 in probands or 40 in relatives. Evidence suggests that early onset and recurrence of depressive episodes predict substantially increased risk of depression in first-degree relatives compared with the general population, suggesting that susceptibility genes might be mapped with this phenotype. The projected sample of 800-1,000 affected sibling pairs (ASPs) and other relatives will be studied using genome scan methods. Biological materials and blinded clinical data will be made available through the NIMH cell repository program. The sample should have good-to-excellent power to detect a locus associated with a 24% or greater population-wide increase in risk to siblings. We describe 838 affected individuals from the first 305 families containing 434 independent ASPs, or 613 ASPs counting all possible pairs. The mean age at the onset was 18.5 years, with a mean of 7.3 episodes and longest episode of 655 days. Almost all subjects had experienced at least 4 weeks of depression with five or more additional symptom criteria. Frequencies of symptoms and psychiatric and medical comorbid are provided. Substance use was more common in males, and panic disorder in females. Within pairs of affected siblings, correlations were significant for age at onset, substance abuse/dependence, panic disorder, obsessive-compulsive disorder and nicotine initiation and persistence. We replicated previously reported associations among comorbid panic disorder and social phobia, chronicity of depression and suicidal behavior. This suggests comparability of our cases to those in earlier large family studies. This dataset should prove useful for genetic studies of a highly familial form of major depressive disorder.

D2S2944 identifies a likely susceptibility locus for recurrent, early-onset, major depression in women

Recurrent, early-onset, major depressive disorder (RE-MDD) is a strongly familial condition whose malignant effects have a significant negative impact on the health and longevity of patients and their family members. Sixteen of the 19 candidate susceptibility loci identified by a recent genome survey revealed allelic associations with RE-MDD in men or women, but not in both sexes. The association of D2S2944 alleles and genotypes with RE-MDD and related disorders was evaluated using a case-control study design employing 100 adults with RE-MDD and 100 adult controls who had no personal or family history of mental disorders. The results of the case-control study were subsequently evaluated in a sample of 81 families ascertained through probands with RE-MDD using the transmission/disequilibrium test. The frequency of the D2S2944 124-bp allele among women with RE-MDD was approximately three times that for female controls (P = 0.0003). Women who carried the D2S2944 124-bp allele revealed a significantly elevated risk of developing RE-MDD, as indicated by an odds ratio of 4.5 compared to female controls (P<0.001). In contrast, men with RE-MDD did not have an increased frequency of this allele compared to male controls, and men who were carriers did not exhibit an increased risk of developing RE-MDD or related disorders. Our findings also suggest that the D2S2944 124-bp allele increases the risk of alcohol and other substance use disorders among women with RE-MDD. The transmission/disequilibrium test provided confirmatory evidence of these sex-specific findings within families. The results of this study confirm the existence of sex-specific susceptibility loci for RE-MDD, and suggest that there may be important differences in the molecular pathophysiology of RE-MDD in men and women. Alternatively, our findings may reflect the existence of sex-specific differences in the molecular mechanisms that determine resilience to endogenous or environmental depressogenic stimuli. The identification and characterization of the D2S2944 susceptibility locus for RE-MDD and related substance use disorders is likely to provide important new insights into the clinical biology, treatment, and prevention of these disorders.

Genetic linkage of region containing the CREB1 gene to depressive disorders in women from families with recurrent, early-onset, major depression

This report describes the results of a model-free linkage analysis of six polymorphic markers, located in a 15 cM region of chromosome 2q33-35, and unipolar Mood Disorders in 81 families identified by probands with Recurrent, Early-Onset Major Depressive Disorder (RE-MDD), a severe and familial form of clinical depression. Our findings reveal significant evidence of linkage of unipolar Mood Disorders to a 451 Kb region of 2q33-34 flanked by D2S2321 and D2S2208 in these families. Increasing peak LOD scores were observed in both the single point and multipoint analyses for Mood Disorder phenotypes whose definitions embodied progressively less stringent severity criteria for inclusion in the affected group. The sex-dependent multipoint linkage analysis of any Major or Minor Mood Disorders produced LOD scores that reached 6.331 and 6.866 at D2S2321 and D2S2208, respectively. Linkage of Mood Disorders to this region was observed exclusively among female affected relative pairs; no suggestion of linkage was observed when male affected relative pairs were analyzed. These observations imply that a sex-specific susceptibility gene in this region contributes to the vulnerability of women in these families to the development of unipolar Mood Disorders that ranged in severity from minor to severe at the time of clinical assessment. The region between the markers that yielded the peak LOD score includes the CREB1 gene, which encodes a cAMP-responsive element-binding protein (CREB) that is a member of the bZIP family of transcription factors. Based on considerable clinical and preclinical evidence, CREB1 is an attractive candidate for a susceptibility gene for unipolar Mood Disorders. The sex-specificity of the susceptibility locus identified by our study may result from reported synergistic interactions of CREB with nuclear estrogen receptors.

Parental depression and depression in offspring: evidence for familial characteristics and subtypes?

The objectives of this paper were twofold. First, to evaluate in a community sample the age of onset of major depression in adolescents and young adults with and without parental major depression. Second, to examine whether specific clinical characteristics of major depression in adolescents and young adults are associated with elevated rates of major depression among parents. Baseline and 4-year follow-up data were used from the Early Developmental Stages of Psychopathology Study (EDSP), a prospective-longitudinal community study of adolescents and young adults. Results are based on 470 subjects who completed the follow-up, for whom diagnostic information for both parents was available, and who reported at least one episode of major depression according to DSM-IV-criteria through second follow-up. Diagnostic assessment in respondents was accomplished by using the standardized Munich-Composite International Diagnostic Interview (M-CIDI). Information on major depression in parents was collected as family history information from the respondents, and additionally from M-CIDI diagnostic interviews with parents of the younger cohort. Both recurrence and impairment as clinical characteristics of major depression in adolescents and young adults were associated with elevated rates of major depression among parents. Age of onset as well as overall higher impairment as clinical characteristics of major depression in youth were associated with elevated rates of parental major depression in the univariate, but not in the multiple, analyses. Our findings suggest that clinical features of major depression may indicate familial subtypes of the disorder, most evident for recurrence and impairment.

Genome survey for susceptibility loci for recurrent, early-onset major depression: results at 10cM resolution

Recurrent (two or more episodes), early-onset (first episode at < or = 25 years) major depressive disorder (RE-MDD) is a strongly familial condition (lambda(first-degree relatives) = 8) whose malignant effects have a significant negative impact on the health and longevity of patients and their family members. The goal of this study was to identify candidate susceptibility loci that influence the development of RE-MDD. We completed a systematic survey of the human genome, conducted at an average resolution of 10 cM, for the identification of simple sequence tandem repeat polymorphisms (SSTRPs) that target susceptibility genes for RE-MDD by virtue of linkage disequilibrium. The efficiency of our association study was enhanced by genotyping pools of DNA from 100 adults with RE-MDD and 100 adult controls who had no personal or family history of mental disorders. Both groups included equal numbers of Caucasian men and women and were matched as closely as possible for age and ethnicity. Allelic associations with RE-MDD were observed for 19 of the 387 SSTRPs in the CHLC Human Screening Set/Weber Version 9. Sixteen of the 19 candidate susceptibility loci revealed significant allelic associations with RE-MDD in men (n = 7) or women (n = 9), but not in both sexes. Evidence for both risk and protective alleles was detected. Two of the candidate susceptibility loci reside within several Mb of loci previously reported-megabases to be linked to "comorbid alcoholism and depression" in families of individuals with alcoholism and to a broadly defined affected phenotype that included recurrent major depression in the families of patients with bipolar disorder. Although it has been suggested that the genes that influence risk for MDD in the two sexes may not be entirely the same, the results of our study suggest that sex specificity of susceptibility loci for RE-MDD may be the rule rather than the exception. The observed preponderance of sex-specific susceptibility loci for RE-MDD suggests that there may be important differences in the molecular pathophysiology of RE-MDD in men and women. Alternatively, our findings may reflect the existence of sex-specific differences in the molecular mechanisms that determine resilience to endogenous or environmental depressogenic stimuli.

Genetic segregation analysis of recurrent, early-onset major depression: evidence for single major locus transmission

Coordinated efforts are now underway to identify susceptibility genes for unipolar major depressive disorder (MDD) and related disorders. These studies have focused on recurrent, early-onset MDD (RE-MDD), thought to be the most familial form of this disorder. The goal of this study was to conduct a complex segregation analysis of recurrent MDD and other major mood disorders aggregating in families identified by probands with RE-MDD. Eighty-one families were identified through probands over the age of 18 who met criteria for recurrent (> or =2 episodes), early-onset (< or =25 years), nonpsychotic, unipolar MDD (RE-MDD) and included 407 first-degree relatives and 835 extended relatives. Psychiatric diagnoses for probands and their family members who provided blood samples were formulated from structured personal interviews, structured family history assessments, and available medical records. The remaining family members who participated and those who were deceased were evaluated through the family history method augmented by available medical records. Best-estimate diagnoses were made during a consensus conference according to established diagnostic criteria. Segregation analyses were performed using the REGD routine in S.A.G.E. release 4.0. The segregation analysis of recurrent MDD supported a sex-independent Mendelian codominant model. Analysis of major mood disorders supported a sex-independent Mendelian dominant model. Interestingly, inclusion of spousal residual correlations provided better fitting models for recurrent MDD but not the broader phenotype of major mood disorders. Unlike unipolar MDD, the lifetime prevalence of bipolar I disorder in this sample of families did not exceed the reported population prevalence [Zubenko et al., 2001]. Our results suggest that a major locus contributes to the expression of recurrent MDD and possibly other major mood disorders within families identified by probands with RE-MDD. Due to the limitations of the segregation analysis model, our results cannot address whether the same major locus is segregating across families in our sample or whether multiple major loci are involved (genetic heterogeneity). The absence of aggregation of bipolar I disorder in these families strongly suggests that while the genetic determinants of unipolar and bipolar disorders may overlap, they are not identical. Our findings illustrate the advantage of employing families identified by probands with RE-MDD in studies designed to detect susceptibility loci for unipolar MDD and related disorders.

Malignancy of recurrent, early-onset major depression: a family study

Coordinated efforts to identify susceptibility genes for unipolar major depressive disorder (MDD) and related disorders are now underway. These studies have focused on recurrent, early-onset MDD (RE-MDD), the most heritable form of this disorder. The goal of this study was to characterize the burden of MDD and other mood disorders, comorbid mental disorders, and excess mortality in RE-MDD families. A total of 81 families were identified through probands over the age of 18, who met criteria for recurrent (> or = 2 episodes), early-onset (< or = 25 years), nonpsychotic, unipolar MDD (RE-MDD), and included 407 first-degree relatives and 835 extended relatives. Psychiatric diagnoses for probands and their family members who provided blood samples were formulated from structured personal interviews, structured family history assessments, and available medical records. The remaining family members who participated and those who were deceased were evaluated through the family history method augmented by available medical records. Best estimate diagnoses were made during a consensus conference according to established diagnostic criteria. Approximately half of the first-degree relatives and a quarter of extended relatives of RE-MDD probands suffered from at least one mood disorder, typically MDD. As commonly observed for other oligogenic, multifactorial disorders, the severity of MDD reflected by age at onset and number of episodes attenuated with increasing familial/genetic distance from the proband. A substantial fraction of RE-MDD probands and their first-degree relatives met diagnostic criteria for additional psychiatric disorders that include prominent disturbances of mood. The deceased relatives of RE-MDD probands died at a median age that was 8 years earlier than for the local population; over 40% died before reaching age 65. These differences in mortality statistics resulted from a shift toward younger ages at death across the lifespan, including a fivefold increase in the proportion of individuals who died in the first year of life. Several-fold increases in the proportion of deaths by suicide, homicide, and liver disease were observed among the relatives of RE-MDD probands. However, the rank order of the three most common causes of death-heart disease, cancer, and stroke-remained unchanged and differences in the proportions of deaths from the remaining causes were small. RE-MDD is a strongly familial condition with a high rate of psychiatric comorbidity, whose malignant effects have a significant negative impact on the health and longevity of patients and their family members.

Family history of depression in clinic and community samples

Because most published family studies of depression ascertained subjects from treatment settings, the reported familial aggregation of depression could be an artifact if a family history of depression increased the likelihood of seeking treatment. To investigate this possibility, we compared the family history of depression in three groups of probands aged 18-44; 54 women randomly selected from the community with depression in the prior year, 41 women who entered a clinical trial for depression and 37 women randomly selected from the community who had not been depressed in the prior year. The presence of depression in the parents and siblings of the probands was assessed by the family history method and quantified via family history scores which took the age, gender and number of relatives into account. Depressed probands ascertained from clinical sources had markedly higher family history scores of depression than other two groups (P < 0.00005 in each instance). In the absence of direct interviews with relatives, we cannot exclude the impact of differential reporting. A family history of depression might be associated with an increased probability of treatment or the differential reporting of family history. It is thus possible that the familial aggregation of depression observed in probands from treatment settings is an artifact.

Unipolar relatives in bipolar pedigrees: a search for elusive indicators of underlying bipolarity

In an effort to identify features indicative of underlying bipolarity within the unipolar relatives of bipolar probands, we compared unipolar relatives of bipolars with unipolar relatives of controls. Using data from the Yale-NIMH Collaborative Study of Depression, we compared a number of demographic and clinical features individually, and then developed a logistic regression model for the differences found. Unipolar relatives of bipolars were generally similar to relatives of controls, but they were older and more likely to suffer from more severe, even psychotic, depression, and somewhat less likely to report a brief transition into their illness. A multiple logistic regression model for observed differences was highly statistically significant, but had limited ability to discriminate effectively between the two groups. These findings suggest that more stringent diagnostic criteria might be beneficial if unipolar relatives are counted as affected in linkage studies of bipolar disorder. The ability of this strategy to improve the "clinical phenotype" is limited, however, and other approaches may be needed to identify features of underlying bipolarity and thus to define "caseness" for unipolar relatives in linkage analyses of bipolar disorder.

The validity and reliability of the fatigue syndrome that follows glandular fever

The validity and reliability of an empirically defined fatigue syndrome were tested in a prospective cohort study of 245 primary care patients, with glandular fever or an upper respiratory tract infection. Subjects were interviewed three times in the 6 months after onset. Subjects with the empirically defined fatigue syndrome were compared with those who were well and those who had a psychiatric disorder. The validity of the fatigue syndrome was supported, separate from psychiatric disorders in general and depressive disorders in particular. Only 16% of subjects with the principal component derived fatigue factor also met criteria for a psychiatric disorder (excluding pre-morbid phobias). Compared with subjects with psychiatric disorders, subjects with the operationally defined fatigue syndrome reported more severe physical fatigue, especially after exertion, were just as socially incapacitated, had fewer mental state abnormalities, and showed little overlap on independent questionnaires. A more mild fatigue state also existed. Both fatigue syndrome and state were more reliable diagnoses over time than depressive disorders. The empirically defined syndrome probably is a valid and reliable condition in the six months following glandular fever.

Familial depression versus depression identified in a control group: are they the same?

Subjects who meet the criteria for an affective syndrome possibly are aetiologically heterogeneous. An approach to this possibility involves examining affectively ill subjects obtained by different methods of ascertainment. This study compares depressed and manic subjects who are related to affectively ill probands with affectively ill subjects who were obtained from a study of a control population, and, therefore, were less likely to be familial. The subjects were identified in a large collaborative study of depression where both family members as well as controls were personally interviewed and followed up for 6 years after admission to the study. Data were obtained on subtypes of affective disorder using the Research Diagnostic Criteria and information was gathered about psychiatric hospitalizations, suicide attempts, alcoholism and psychological functioning prior to admission. Similar assessments were made for the comparison groups for the 6 year period between intake and follow-up. Relatives of bipolar I/schizoaffective manic probands were more likely to show mania than affectively ill controls or relatives of unipolar/schizoaffective depressed probands. Affectively ill controls were less likely to be hospitalized and less likely to suffer from an incapacitating depression. They were also likely to have functioned in a more healthy fashion than the affectively ill relatives of the bipolars and unipolars, in the 5 years before admission to the study. In the 6 year follow-up, both the subjects themselves and raters assessed the depressed controls as functioning better than the affectively ill relatives of the probands. Further, assessment of global adjustment during the 6 year period was worse for the relatives of affectively ill probands than for the depressed controls. Length of major depression was longer in relatives of bipolar and unipolar probands than in controls. Though all of the subjects in this study met research criteria for an affective illness, there were marked differences in the qualitative aspects of these illnesses with the relatives of affectively ill probands, who functioned less well and had longer and more severe episodes and more hospitalizations.

Clinical characteristics of familial generalized anxiety disorder

The authors seek to determine whether the clinical characteristics of generalized anxiety disorder (GAD) differ in individuals with a high vs. low familial vulnerability to illness. We identified 486 personally interviewed female twins from a population-based register who had both an interviewed co-twin and a lifetime history of GAD using modified DSM-III-R criteria which required a one-month minimum duration of illness. We attempted to predict risk for GAD in the co-twin from the clinical features of the GAD in the proband twin using the Cox proportional hazard model, controlling for year of birth and zygosity. Only two variables uniquely predicted an increased risk for GAD in the co-twin: number of GAD symptoms endorsed and comorbidity with bulimia. Variables that did not uniquely predict risk of illness in the co-twin included age at onset, duration of the longest episode and number of episodes. The familial vulnerability to GAD can be meaningfully indexed by clinical features of the syndrome. These results suggest that if the syndrome of GAD is to be narrowed, it would, from a familial perspective, be more valid to increase the minimum number of required symptoms rather than to increase the minimum duration of illness.