Characterisation of age and polarity at onset in bipolar disorder

BACKGROUND

Studying phenotypic and genetic characteristics of age at onset (AAO) and polarity at onset (PAO) in bipolar disorder can provide new insights into disease pathology and facilitate the development of screening tools.

AIMS

To examine the genetic architecture of AAO and PAO and their association with bipolar disorder disease characteristics.

METHOD

Genome-wide association studies (GWASs) and polygenic score (PGS) analyses of AAO (n = 12 977) and PAO (n = 6773) were conducted in patients with bipolar disorder from 34 cohorts and a replication sample (n = 2237). The association of onset with disease characteristics was investigated in two of these cohorts.

RESULTS

Earlier AAO was associated with a higher probability of psychotic symptoms, suicidality, lower educational attainment, not living together and fewer episodes. Depressive onset correlated with suicidality and manic onset correlated with delusions and manic episodes. Systematic differences in AAO between cohorts and continents of origin were observed. This was also reflected in single-nucleotide variant-based heritability estimates, with higher heritabilities for stricter onset definitions. Increased PGS for autism spectrum disorder (β = -0.34 years, s.e. = 0.08), major depression (β = -0.34 years, s.e. = 0.08), schizophrenia (β = -0.39 years, s.e. = 0.08), and educational attainment (β = -0.31 years, s.e. = 0.08) were associated with an earlier AAO. The AAO GWAS identified one significant locus, but this finding did not replicate. Neither GWAS nor PGS analyses yielded significant associations with PAO.

CONCLUSIONS

AAO and PAO are associated with indicators of bipolar disorder severity. Individuals with an earlier onset show an increased polygenic liability for a broad spectrum of psychiatric traits. Systematic differences in AAO across cohorts, continents and phenotype definitions introduce significant heterogeneity, affecting analyses.

Genome-wide association study identifies 30 loci associated with bipolar disorder

Bipolar disorder is a highly heritable psychiatric disorder. We performed a genome-wide association study (GWAS) including 20,352 cases and 31,358 controls of European descent, with follow-up analysis of 822 variants with P < 1 × 10-4 in an additional 9,412 cases and 137,760 controls. Eight of the 19 variants that were genome-wide significant (P < 5 × 10-8) in the discovery GWAS were not genome-wide significant in the combined analysis, consistent with small effect sizes and limited power but also with genetic heterogeneity. In the combined analysis, 30 loci were genome-wide significant, including 20 newly identified loci. The significant loci contain genes encoding ion channels, neurotransmitter transporters and synaptic components. Pathway analysis revealed nine significantly enriched gene sets, including regulation of insulin secretion and endocannabinoid signaling. Bipolar I disorder is strongly genetically correlated with schizophrenia, driven by psychosis, whereas bipolar II disorder is more strongly correlated with major depressive disorder. These findings address key clinical questions and provide potential biological mechanisms for bipolar disorder.

Efficient region-based test strategy uncovers genetic risk factors for functional outcome in bipolar disorder

Genome-wide association studies of case-control status have advanced the understanding of the genetic basis of psychiatric disorders. Further progress may be gained by increasing sample size but also by new analysis strategies that advance the exploitation of existing data, especially for clinically important quantitative phenotypes. The functionally-informed efficient region-based test strategy (FIERS) introduced herein uses prior knowledge on biological function and dependence of genotypes within a powerful statistical framework with improved sensitivity and specificity for detecting consistent genetic effects across studies. As proof of concept, FIERS was used for the first genome-wide single nucleotide polymorphism (SNP)-based investigation on bipolar disorder (BD) that focuses on an important aspect of disease course, the functional outcome. FIERS identified a significantly associated locus on chromosome 15 (hg38: chr15:48965004 - 49464789 bp) with consistent effect strength between two independent studies (GAIN/TGen: European Americans, BOMA: Germans; n = 1592 BD patients in total). Protective and risk haplotypes were found on the most strongly associated SNPs. They contain a CTCF binding site (rs586758); CTCF sites are known to regulate sets of genes within a chromatin domain. The rs586758 - rs2086256 - rs1904317 haplotype is located in the promoter flanking region of the COPS2 gene, close to microRNA4716, and the EID1, SHC4, DTWD1 genes as plausible biological candidates. While implication with BD is novel, COPS2, EID1, and SHC4 are known to be relevant for neuronal differentiation and function and DTWD1 for psychopharmacological side effects. The test strategy FIERS that enabled this discovery is equally applicable for tag SNPs and sequence data.

Genome-wide association study of 40,000 individuals identifies two novel loci associated with bipolar disorder

Bipolar disorder (BD) is a genetically complex mental illness characterized by severe oscillations of mood and behaviour. Genome-wide association studies (GWAS) have identified several risk loci that together account for a small portion of the heritability. To identify additional risk loci, we performed a two-stage meta-analysis of >9 million genetic variants in 9,784 bipolar disorder patients and 30,471 controls, the largest GWAS of BD to date. In this study, to increase power we used ∼2,000 lithium-treated cases with a long-term diagnosis of BD from the Consortium on Lithium Genetics, excess controls, and analytic methods optimized for markers on the X-chromosome. In addition to four known loci, results revealed genome-wide significant associations at two novel loci: an intergenic region on 9p21.3 (rs12553324, P =  5.87 × 10 ^{-  9}; odds ratio (OR) = 1.12) and markers within ERBB2 (rs2517959, P =  4.53 × 10 ^{-  9}; OR = 1.13). No significant X-chromosome associations were detected and X-linked markers explained very little BD heritability. The results add to a growing list of common autosomal variants involved in BD and illustrate the power of comparing well-characterized cases to an excess of controls in GWAS.

Joint analysis of psychiatric disorders increases accuracy of risk prediction for schizophrenia, bipolar disorder, and major depressive disorder

Genetic risk prediction has several potential applications in medical research and clinical practice and could be used, for example, to stratify a heterogeneous population of patients by their predicted genetic risk. However, for polygenic traits, such as psychiatric disorders, the accuracy of risk prediction is low. Here we use a multivariate linear mixed model and apply multi-trait genomic best linear unbiased prediction for genetic risk prediction. This method exploits correlations between disorders and simultaneously evaluates individual risk for each disorder. We show that the multivariate approach significantly increases the prediction accuracy for schizophrenia, bipolar disorder, and major depressive disorder in the discovery as well as in independent validation datasets. By grouping SNPs based on genome annotation and fitting multiple random effects, we show that the prediction accuracy could be further improved. The gain in prediction accuracy of the multivariate approach is equivalent to an increase in sample size of 34% for schizophrenia, 68% for bipolar disorder, and 76% for major depressive disorders using single trait models. Because our approach can be readily applied to any number of GWAS datasets of correlated traits, it is a flexible and powerful tool to maximize prediction accuracy. With current sample size, risk predictors are not useful in a clinical setting but already are a valuable research tool, for example in experimental designs comparing cases with high and low polygenic risk.

Enrichment of cis-regulatory gene expression SNPs and methylation quantitative trait loci among bipolar disorder susceptibility variants

We conducted a systematic study of top susceptibility variants from a genome-wide association (GWA) study of bipolar disorder to gain insight into the functional consequences of genetic variation influencing disease risk. We report here the results of experiments to explore the effects of these susceptibility variants on DNA methylation and mRNA expression in human cerebellum samples. Among the top susceptibility variants, we identified an enrichment of cis regulatory loci on mRNA expression (eQTLs), and a significant excess of quantitative trait loci for DNA CpG methylation, hereafter referred to as methylation quantitative trait loci (mQTLs). Bipolar disorder susceptibility variants that cis regulate both cerebellar expression and methylation of the same gene are a very small proportion of bipolar disorder susceptibility variants. This finding suggests that mQTLs and eQTLs provide orthogonal ways of functionally annotating genetic variation within the context of studies of pathophysiology in brain. No lymphocyte mQTL enrichment was found, suggesting that mQTL enrichment was specific to the cerebellum, in contrast to eQTLs. Separately, we found that using mQTL information to restrict the number of single-nucleotide polymorphisms studied enhances our ability to detect a significant association. With this restriction a priori informed by the observed functional enrichment, we identified a significant association (rs12618769, P(bonferroni)<0.05) from two other GWA studies (TGen+GAIN; 2191 cases and 1434 controls) of bipolar disorder, which we replicated in an independent GWA study (WTCCC). Collectively, our findings highlight the importance of integrating functional annotation of genetic variants for gene expression and DNA methylation to advance the biological understanding of bipolar disorder.

Evidence for association of bipolar disorder to haplotypes in the 22q12.3 region near the genes stargazin, IFT27 and parvalbumin

We have previously reported genome-wide significant linkage of bipolar disorder to a region on 22q12.3 near the marker D22S278. Towards identifying the susceptibility gene, we have conducted a fine-mapping association study of the region in two independent family samples, an independent case-control sample and a genome-wide association dataset. Two hundred SNPs were first examined in a 5 Mb region surrounding the D22S278 marker in a sample of 169 families and analyzed using PLINK. The peak of association was a haplotype near the genes stargazin (CACNG2), intraflagellar transport protein homolog 27 (IFT27) and parvalbumin (PVALB; P = 4.69 × 10(-4)). This peak overlapped a significant haplotype in a family based association study of a second independent sample of 294 families (P = 1.42 × 10(-5)). Analysis of the combined family sample yielded statistically significant evidence of association to a rare three SNP haplotype in the gene IFT27 (P = 8.89 × 10(-6)). Twelve SNPs comprising these haplotypes were genotyped in an independent sample of 574 bipolar I cases and 550 controls. Statistically significant association was found for a haplotype window that overlapped the region from the first two family samples (P = 3.43 × 10(-4)). However, analyses of the two family samples using the program LAMP, found no evidence for association in this region, but did yield significant evidence for association to a haplotype 3' of CACNG2 (P = 1.76 × 10(-6)). Furthermore, no evidence for association was found in a large genome-wide association dataset. The replication of association to overlapping haplotypes in three independent datasets suggests the presence of a bipolar disorder susceptibility gene in this region.

Novel loci for major depression identified by genome-wide association study of Sequenced Treatment Alternatives to Relieve Depression and meta-analysis of three studies

We report a genome-wide association study (GWAS) of major depressive disorder (MDD) in 1221 cases from the Sequenced Treatment Alternatives to Relieve Depression (STAR*D) study and 1636 screened controls. No genome-wide evidence for association was detected. We also carried out a meta-analysis of three European-ancestry MDD GWAS data sets: STAR*D, Genetics of Recurrent Early-onset Depression and the publicly available Genetic Association Information Network-MDD data set. These data sets, totaling 3957 cases and 3428 controls, were genotyped using four different platforms (Affymetrix 6.0, 5.0 and 500 K, and Perlegen). For each of 2.4 million HapMap II single-nucleotide polymorphisms (SNPs), using genotyped data where available and imputed data otherwise, single-SNP association tests were carried out in each sample with correction for ancestry-informative principal components. The strongest evidence for association in the meta-analysis was observed for intronic SNPs in ATP6V1B2 (P=6.78 x 10⁻⁷), SP4 (P=7.68 x 10⁻⁷) and GRM7 (P=1.11 x 10⁻⁶). Additional exploratory analyses were carried out for a narrower phenotype (recurrent MDD with onset before age 31, N=2191 cases), and separately for males and females. Several of the best findings were supported primarily by evidence from narrow cases or from either males or females. On the basis of previous biological evidence, we consider GRM7 a strong MDD candidate gene. Larger samples will be required to determine whether any common SNPs are significantly associated with MDD.

Genome-wide linkage and follow-up association study of postpartum mood symptoms

OBJECTIVE

Family studies have suggested that postpartum mood symptoms might have a partly genetic etiology. The authors used a genome-wide linkage analysis to search for chromosomal regions that harbor genetic variants conferring susceptibility for such symptoms. The authors then fine-mapped their best linkage regions, assessing single nucleotide polymorphisms (SNPs) for genetic association with postpartum symptoms.

METHOD

Subjects were ascertained from two studies: the NIMH Genetics Initiative Bipolar Disorder project and the Genetics of Recurrent Early-Onset Depression. Subjects included women with a history of pregnancy, any mood disorder, and information about postpartum symptoms. In the linkage study, 1,210 women met criteria (23% with postpartum symptoms), and 417 microsatellite markers were analyzed in multipoint allele sharing analyses. For the association study, 759 women met criteria (25% with postpartum symptoms), and 16,916 SNPs in the regions of the best linkage peaks were assessed for association with postpartum symptoms.

RESULTS

The maximum linkage peak for postpartum symptoms occurred on chromosome 1q21.3-q32.1, with a chromosome-wide significant likelihood ratio Z score (Z(LR)) of 2.93 (permutation p=0.02). This was a significant increase over the baseline Z(LR) of 0.32 observed at this locus among all women with a mood disorder (permutation p=0.004). Suggestive linkage was also found on 9p24.3-p22.3 (Z(LR)=2.91). In the fine-mapping study, the strongest implicated gene was HMCN1 (nominal p=0.00017), containing four estrogen receptor binding sites, although this was not region-wide significant.

CONCLUSIONS

This is the first study to examine the genetic etiology of postpartum mood symptoms using genome-wide data. The results suggest that genetic variations on chromosomes 1q21.3-q32.1 and 9p24.3-p22.3 may increase susceptibility to postpartum mood symptoms.

Investigating the role of p11 (S100A10) sequence variation in susceptibility to major depression

Recent evidence suggests a potential role for the p11 gene in conferring risk to depressive disorders. p11 has been shown to influence serotonergic transmission, and its expression was found to be reduced in a mouse model of depression, as well as in post-mortem brain tissue from major depressive disorder (MDD) cases. In the present study, we tested for rare variants in p11 by resequencing promoter, exonic and flanking intronic regions in 176 MDD cases and 176 matched controls. We also assessed common variation by genotyping eight single nucleotide polymorphisms (SNPs), seven tag SNPs and one found through resequencing, in 641 cases and 650 controls. Resequencing revealed nine novel rare variants, including a missense mutation (Asp60Glu) observed in one case and one control, and four variants that occurred only in cases and not controls. The number of rare variants in cases did not exceed that expected by chance for the length of sequence analyzed, and also was not significantly greater than that observed in controls. Resequencing also identified two known SNPs, one (rs4845720) of which was significantly more frequent in cases than controls in the resequenced sample (3.1% vs. 0.9%, P = 0.03), though not in the larger sample (3% vs. 2%, P = 0.15). None of the tag SNPs showed any evidence of association. Our results do not support a major role for either common or rare p11 SNPs with MDD. Several limitations of the study are discussed.

A comparison of the familiality of chronic depression in recurrent early-onset depression pedigrees using different definitions of chronicity

BACKGROUND

The study of chronicity in the course of major depression has been complicated by varying definitions of this illness feature. Because familial clustering is one component of diagnostic validity we compared family clustering of chronicity as defined in the DSM-IV to that of chronicity determined by an assessment of lifetime course of depressive illness.

METHODS

In 1750 affected subjects from 652 families recruited for a genetic study of recurrent, early-onset depression, we applied several definitions of chronicity. Odds ratios were determined for the likelihood of chronicity in a proband predicting chronicity in an affected relative.

RESULTS

There was greater family clustering of chronicity as determined by assessment of lifetime course (OR=2.54) than by DSM-IV defined chronic major depressive episode (MDE) (OR=1.93) or dysthymic disorder (OR=1.76). In families with probands who had preadolescent onset of MDD, familiality was increased by all definitions, with a much larger increase observed for chronicity by lifetime course (ORs were 6.14 for lifetime chronicity, 2.43 for chronic MDE, and 3.42 for comorbid dysthymic disorder). Agreement between these definitions of chronicity was only fair.

LIMITATIONS

The data used to determine chronicity were collected retrospectively and not blindly to relatives' status, and assessment of lifetime course was based on global clinical impressions gathered during a semi-structured diagnostic interview. Also, it can be difficult to determine whether individuals with recurrent major depressive episodes who frequently experience long periods of low grade depressive symptoms meet the strict timing requirements of DSM-IV dysthymic disorder.

CONCLUSIONS

An assessment of lifetime symptom course identifies a more familial, and thus possibly a more valid, type of chronic depression than the current DSM-IV categories which are defined in terms of particular cross-sectional features of illness.

Genetics of recurrent early-onset major depression (GenRED): final genome scan report

OBJECTIVE

The authors carried out a genomewide linkage scan to identify chromosomal regions likely to contain genes that contribute to susceptibility to recurrent early-onset major depressive disorder, the form of the disorder with the greatest reported risk to relatives of index cases.

METHOD

Microsatellite DNA markers were studied in 656 families with two or more such cases (onset before age 31 in probands and age 41 in other relatives), including 1,494 informative "all possible" affected relative pairs (there were 894 independent affected sibling pairs). Analyses included a primary multipoint allele-sharing analysis (with ALLEGRO) and a secondary logistic regression analysis taking the sex of each relative pair into account (male-male, male-female, female-female).

RESULTS

Genomewide suggestive evidence for linkage was observed on chromosome 15q25-q26 (at 105.4 centimorgans [cM]). The authors previously reported genomewide significant linkage in this region in the first 297 families. In the secondary analysis, after empirical genomewide correction for multiple testing, suggestive linkage results were observed on chromosome 17p12 (28.0 cM, excess sharing in male-male and male-female pairs) and on chromosome 8p22-p21.3 (25.1 cM, excess sharing in male-male pairs).

CONCLUSIONS

These regions of chromosomes 15q, 17p, and 8p might contain genes that contribute to susceptibility to major depression and related disorders. Evidence for linkage has been reported independently in the same regions of chromosome 15q for major depression and of chromosome 8p for related personality traits.

Genetics of recurrent early-onset major depression (GenRED): significant linkage on chromosome 15q25-q26 after fine mapping with single nucleotide polymorphism markers

OBJECTIVE

The authors studied a dense map of single nucleotide polymorphism (SNP) DNA markers on chromosome 15q25-q26 to maximize the informativeness of genetic linkage analyses in a region where they previously reported suggestive evidence for linkage of recurrent early-onset major depressive disorder.

METHOD

In 631 European-ancestry families with multiple cases of recurrent early-onset major depressive disorder, 88 SNPs were genotyped, and multipoint allele-sharing linkage analyses were carried out. Marker-marker linkage disequilibrium was minimized, and a simulation study with founder haplotypes from these families suggested that linkage scores were not inflated by linkage disequilibrium.

RESULTS

The dense SNP map increased the information content of the analysis from around 0.7 to over 0.9. The maximum evidence for linkage was the Z likelihood ratio score statistic of Kong and Cox (Z(LR))=4.69 at 109.8 cM. The exact p value was below the genomewide significance threshold. By contrast, in the genome scan with microsatellite markers at 9 cM spacing, the maximum Z(LR) for European-ancestry families was 3.43 (106.53 cM). It was estimated that the linked locus or loci in this region might account for a 20% or less populationwide increase in risk to siblings of cases.

CONCLUSIONS

This region has produced modestly positive evidence for linkage to depression and related traits in other studies. These results suggest that DNA sequence variations in one or more genes in the 15q25-q26 region can increase susceptibility to major depression and that efforts are warranted to identify these genes.

Familial aggregation of illness chronicity in recurrent, early-onset major depression pedigrees

OBJECTIVE

The authors used a large sample collected for genetic studies to determine whether a chronic course of illness defines a familial clinical subtype in major depressive disorder.

METHOD

A measure of lifetime chronicity of depressive symptoms (substantial mood symptoms most or all of the time) was tested for familial aggregation in 638 pedigrees from the Genetics of Recurrent Early-Onset Depression (GenRED) project.

RESULTS

In subjects with chronic depression, the mean age at illness onset was lower and rates of attempted suicide, panic disorder, and substance abuse were higher than among those with nonchronic depression. Chronicity was assessed in 37.8% of affected first-degree relatives of probands with chronic depression and in 20.2% of relatives of probands with nonchronic depression. Analysis using the generalized estimating equation model yielded an odds ratio of 2.52 (SE=0.39, z=6.02, p<0.0001) for the likelihood of chronicity in a proband predicting chronicity in an affected relative. With stratification by proband age at illness onset, the odds ratio for chronicity in relatives by proband chronicity status was 6.17 (SE=2.09, z=5.35, p<0.0001) in families of probands whose illness onset was before age 13 and 1.92 (SE=0.34, z=3.72, p<0.0001) in families of probands whose illness started at age 13 or later.

CONCLUSIONS

These findings suggest that chronicity of depressive symptoms is familial, especially in preadolescent-onset illness. Chronicity is also associated with other indicators of illness severity in recurrent, early-onset major depression. Further study using chronicity as a subtype in the genetic analysis of depressive illness is warranted. Refinement of the definition of chronicity in depressive illness may increase the power of such studies.

Is perinatal depression familial?

BACKGROUND

While major depressive disorder (MDD) is familial, it is not clear whether distinct familial-genetic factors influence vulnerability to depression during or after pregnancy. Here we examine familial aggregation of perinatal major depression (PND, any episode during pregnancy or the month after childbirth) and the subset of post-partum depression (PPD) in families with multiple cases of recurrent, early-onset MDD from the Genetics of Recurrent Early-Onset Depression dataset.

METHODS

The dataset included 691 childbearing women who could be classified as PND (27.6%) or non-PND (NPND), of whom 328 were members of 148 sibships with two or more PND or NPND women. PND and NPND subjects were compared for differences in putative predictors. Prediction of sibling PND or PPD by the proband's history was examined using logistic regression and general estimating equation methods.

RESULTS

PND was associated with fewer episodes and younger current age. Odds ratios for prediction of sibling status were significant for PND (2.28) and PPD (3.96), particularly when current age was under 46 (2.87 and 4.39, respectively). ORs for PPD were not significantly different from those for PND. The OR for PPD (3.52), but not for PND, remained significant after current age was introduced as a covariate, but not when both current age and number of episodes were included in the model.

LIMITATIONS

Because detailed data were not collected for all pregnancies, we cannot determine whether current age and number of episodes mediated the observed effects due to recall bias or other factors (cohort effect, number of episodes).

CONCLUSIONS

A familial component to PND, and particularly PPD, is suggested by the results. However more systematic study is needed to confirm this result. A greater understanding of both genetic and non-genetic familial factors could lead to improved prevention and clinical management.

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.

Treatment Choice in Neuroleptic Malignant Syndrome

A literature review of patients with symptomatic neuroleptic malignant syndrome (NMS) treated with electroconvulsive therapy (ECT) yielded 26 cases, to which we add five cases. ECT was associated with a positive outcome in 26 of 31 cases with one unclear outcome and a poor outcome in four cases, including two deaths. ECT appeared to be effective in eight of nine patients previously treated with dantrolene and/or bromocriptine; no difference in time to apparent response was seen between those treated with medication first and those undergoing ECT first. The mean time to clinical response after the first ECT was 1.46 +/- 2.38 days, with 19 of 20 having a clinical response by 72 h. The possible relationship of ECT to the two deaths is discussed. Given this experience, the suggested treatment sequence is medication (dantrolene or bromocriptine) for 48 h; if no clinical response is seen, ECT should be initiated. ECT may be used earlier in response to specific clinical situations.

Lithium discontinuation and subsequent effectiveness

OBJECTIVE

Several reports have raised concern that the discontinuation of lithium may result in treatment resistance following recurrence of affective disorder. This report explores this possibility.

METHOD

The data derive from a large, naturalistic follow-up of patients with major depressive disorder or mania. Twenty-eight of the patients in the study were free of lithium and experiencing an episode of mania or schizoaffective mania diagnosed according to Research Diagnostic Criteria when they entered the study, recovered while taking lithium, later experienced a recurrence while not taking lithium, and then resumed lithium treatment. Survival analyses of time to recovery and, subsequently, time to recurrence, used continued lithium treatment as an additional censoring variable.

RESULTS

Patients given lithium recovered no more quickly from their index episode than they did from their first prospectively observed episode. Moreover, lithium prophylaxis appeared no less effective after the first prospectively observed episode than after the index episode.

CONCLUSIONS

These findings provide no evidence that lithium discontinuation results in treatment resistance when lithium is resumed.

Interactions of risk factors in predicting suicide

The authors examined interactions among risk factors for suicide, a strategy not typically followed in suicide research. Their results suggest an explanation for gender differences in suicide rates and qualifications in the relationship between hopelessness and suicide based on history of drug and alcohol abuse.

Association between major depressive disorder and physical illness

The association between major depressive disorder (MDD) and self-reported histories of specific physical illnesses was investigated in 320 controls and 1968 first-degree relatives and 254 spouses of probands in the NIMH Collaborative Depression study. The Schedule for Affective Disorders and Schizophrenia-Lifetime Version was used to assign Research Diagnostic Criteria (RDC) diagnoses and a structured self-report instrument was used to assess lifetime medical history. Lifetime MDD was diagnosed in 914 subjects, 402 of whom had been hospitalized or received somatic treatment ('treated' MDD). Strong associations were observed between MDD (either treated or untreated) and both frequent/severe headaches and migraine headaches. There was a marked gender effect such that the relative odds for a woman with treated MDD to report migraine were over 5:1. Other associations were found between MDD and skin infections, respiratory illness, ulcer, hypotension, and diabetes. This is the largest non-patient sample using standardized assessment of mental disorders by direct interview in which associations between specific physical illnesses and MDD have been demonstrated. Implications for clinical practice and neurobiological research in depression are discussed.

Concordance of symptoms in recurrent depressive episodes

The presence or absence of 12 depressive symptoms was examined in 93 bipolar and 108 unipolar patients who had two discrete episodes of major depression over a 5-year period. For each symptom the concordance of its presence or absence across episodes was low. The agreement observed was largely that to be expected by chance. A substantial amount of concordance was obtained if differences in episode intensity (propensity to have symptoms) were taken into account. This suggests that although there may be factors related to depression which remain stable across episodes, symptom presentation is moderated by other factors, such as intensity, which vary from episode to episode.

Time-related predictors of suicide in major affective disorder

The authors studied 954 psychiatric patients with major affective disorders and found that nine clinical features were associated with suicide. Six of these--panic attacks, severe psychic anxiety, diminished concentration, global insomnia, moderate alcohol abuse, and severe loss of interest or pleasure (anhedonia)--were associated with suicide within 1 year, and three others--severe hopelessness, suicidal ideation, and history of previous suicide attempts--were associated with suicide occurring after 1 year. These findings draw attention to the importance of 1) standardized prospective data for studies of suicide, 2) assessment of short-term suicide risk factors, and 3) anxiety symptoms as modifiable suicide risk factors within a clinically relevant period.

Sex differences in the lifetime prevalence of depression: does varying the diagnostic criteria reduce the female/male ratio?

Most studies report the lifetime prevalence of major depressive disorder to be higher among women than men. One possible explanation is that this finding is the result of the diagnostic criteria used, in particular the inclusion of criterion symptoms associated with depressed mood. The number of criterion symptoms required for a diagnosis were varied and applied to 2163 first-degree relatives of affectively disordered probands of the NIMH Collaborative Study of the Psychobiology of Depression. Results indicated that differences between men and women in number of symptoms reported could not account for the difference in rates of depression. Women had a greater number of associated symptoms only at higher symptom levels, suggesting an excess of women only above a diagnostic threshold. Thus, findings supported a true difference in rates of major depressive disorder rather than a general trend for women to remember or report more criterion symptoms.

Gender differences in the clinical features of unipolar major depressive disorder

Gender differences in the presence or absence and the severity of forty-seven clinician-rated features of depression were examined, controlling for the sex of the rater. Subjects consisted of 498 moderately to severely depressed patients coming for treatment and diagnosed as suffering from nonpsychotic, unipolar major depressive disorder. Significant differences were found only for increased appetite and weight. No differences were observed in endogenous symptoms, global severity of depression, or impairment in functioning. The results indicate that, although the rate of major depressive disorder is greater in women, its symptomatology is relatively homogeneous with regard to gender.

Relationship of electroconvulsive therapy to course in affective illness: a collaborative study

Bipolars treated with electroconvulsive therapy (ECT) during the index episode were matched on the variables of age, sex, previous admissions and previous hospitalizations with 23 bipolars who did not receive ECT. A similar match was made for 42 unipolars who were under the age of 40 at time of admission. All patients were followed for 5 years. Those patients treated with ECT, both bipolars and unipolars, had the same numbers of episodes in follow-up as their matched groups. However, in both bipolar and unipolar ECT-treated patients, there were more follow-up rehospitalizations. The reason for this is not known but three possibilities exist. Successful treatment with ECT may make the family and patient more prone to consider rehospitalization. Secondly, the originally treated ECT patients may have had more aggressive doctors who were more likely to rehospitalize. Finally, ECT may change the course of an individual's illness in such a way that more severe episodes occur and rehospitalizations are necessary. The findings suggest the need for long-term studies following ECT on clinical and biological variables.

What is the mechanism by which suicide attempts predispose to later suicide attempts? A mathematical model

A state dependence model of serial behavior suggests that each occurrence increases the subsequent likelihood of that behavior being repeated. A heterogeneity model, by contrast, suggests that the likelihood of a behavior occurring is predetermined, and uninfluenced by intervening occurrences. We have applied the random-effects probit model of Gibbons and Bock (1987) to examine the fit of the state dependence and heterogeneity models to longitudinal data on suicide attempts by 928 patients with affective disorder. Heterogeneity but not state dependence was required to model these data. The findings suggest that when considering patients with moderate to severe major affective disorder, the clinician should not interpret the absence of any recent suicide attempts to mean that the patient is at relatively low risk for attempting suicide in the future. An implication of the heterogeneity model is that suicide attempts made many years ago may have equal value to recent attempts when estimating an individual's "predisposition" to nonlethal attempts in the future.

Family history and five-year suicide risk

Family history was examined to determine whether suicide in index patients is associated with suicidal behaviour or mental disorder in their first-degree relatives. Twenty-seven suicides occurred within 5 1/2 years among 955 affectively disordered probands. Among 5042 proband relatives aged 18 years and older, 44 had committed suicide prior to proband entry to the study; however, only one was the relative of a proband suicide. Only two of the relatives who committed suicide were themselves related. As to attempted suicide of relatives, neither the number of attempts nor the severity of attempt was predictive of suicide in probands. Comparison of diagnosis between groups of relatives showed more drug abuse among relatives of proband suicides; this appears to be related to drug abuse among the proband suicides themselves. In contrast to the clustering of suicides within biological families found in other research, these data do not support the use of family history as a clinically useful indicator of suicidal potential in affectively disordered probands.

Depression and panic attacks: the significance of overlap as reflected in follow-up and family study data

Ninety-one patients with panic attacks limited historically to depressive episodes had more severe depressive symptoms and were less likely to recover during a 2-year follow-up than 417 depressed patients who did not have panic attacks. Family study data clearly distinguished another 15 patients with panic disorder and secondary depression; interviewed relatives of panic disorder patients were significantly less likely to have primary depression and significantly more likely to have various anxiety disorders. These data support the hierarchical system by which many of the contemporary diagnostic systems separate panic disorder and major depression.

A field test of Motto's risk estimator for suicide

The authors undertook a field test of Motto and colleagues' Risk Estimator for Suicide by selecting a subset (N = 593) of psychiatric patients with major or chronic affective disorder that corresponded to Motto's sample. They rated each subject on Motto's scale, using standardized data collected at hospital admission. Fourteen patients (2.4%) in their sample and 136 (4.9%) in Motto's sample died by suicide within 2 years. The authors tested the null hypothesis of a uniform suicide risk across all 10 deciles of risk scores by comparing observed and expected frequencies of suicide using the variance test for homogeneity of the binomial distribution. Their findings raise questions about Motto's risk scale but do not definitively invalidate it.

Lack of stability of the RDC endogenous subtype in consecutive episodes of major depression

The stability of the endogenous subtype of major depressive disorder was examined within individuals across consecutive episodes. The subjects were 119 probands from the NIMH Collaborative Depression Study who experienced at least two episodes of unipolar major depressive disorder within a two-year period of biannual evaluations. Structured data collection methods and Research Diagnostic Criteria were employed. The inter-episode stability of subtype diagnosis was low, never producing a kappa of greater than 0.25. This result was not attributable to threshold for diagnosis, time between episodes, differences in severity, or changes in raters.

The endogenous sub-type of depression: a study of its internal construct validity

The internal construct validity of the endogenous sub-type of major depression was investigated by statistically modelling the RDC endogenous and DSM-III melancholia diagnostic criteria. Data consisted of symptom ratings on 788 patients with major depression from NIMH Collaborative Depression Study. Results indicated that the symptoms in the criteria do not specify a dichotomous classification, melancholic-non-melancholic or endogenous-nonendogenous. Results did support the existence of two sub-typings, one related to anhedonia, and one related to vegetative symptoms. The vegetative sub-type rarely occurred in non-anhedonic patients. Previous studies may have found support for a simple endogenous sub-type because of this hierarchical relationship and as a result of methodological differences.

Differences between anhedonic and normally hedonic depressive states

In this study of 101 patients who met DSM-III criteria for major depression, those with extreme anhedonia (N = 23) were younger, more depressed, and less neurotic than the patients with a normal-range capacity for pleasurable experiences (N = 78). The anhedonic depressed patients recovered more rapidly; at discharge they consequently had levels of symptom severity equal to those of the hedonic patients, yet they remained significantly more anhedonic. The anhedonic patients exhibited loss of pleasure in appetite, sex, social contacts, and work, which suggests a global dulling of the capacity for pleasure.

Assessing anhedonia in psychiatric patients

In two studies of depressed, manic, schizophrenic, and normal subjects, a scale for measuring the intensity of subjects' pleasureable responses to normally emjoyable situations (the Pleasure Scale) evidenced good internal reliability and moderate agreement with the Chapman Anhedonia Scale and Indexes of depressive symptom severity. Only the depressed patients showed extremely anhedonic responses. Although more than half the depressed patients evidenced pleasure scores in the normal range, about 185 of them seemed more anhedonic than any norma subject. A mixture analysis resolved depressed patient scores into two distinct distributions: a normal-range distribution (88% of depressives) and an extremely anhedonic distribution (12%). The findings provide some support for the existence of a qualitatively distinct subtype of major depression that has been variously defined an "endogenomorphic" or "melancholic."

Reliability of lifetime diagnoses and symptoms in patients with a current psychiatric disorder

In this study we assess the reliability of rating past psychiatric symptoms and lifetime diagnoses in a currently ill population using the SADS and RDC. Five raters from different centers interviewed 25 subjects in a short-interval test-retest design. Subjects had a wide diversity of affective and non-affective diagnoses and high levels of manifest psychopathology. Our results demonstrate that it is possible for raters from different research centers to reliably rate lifetime diagnoses and previous symptoms. Two important exceptions to the high reliability are the lifetime diagnoses of hypomania and the recurrent unipolar subtype of major depressive disorder, and we alert clinicians and researchers to be cautious when diagnosing these conditions. We conclude that the next step in measuring reliability should be a long-interval test-retest design with separate interviews conducted at the later assessment, one by the original rater and the other by a blind rater.