Investigating polygenic burden in age at disease onset in bipolar disorder: Findings from an international multicentric study

OBJECTIVES

Bipolar disorder (BD) with early disease onset is associated with an unfavorable clinical outcome and constitutes a clinically and biologically homogenous subgroup within the heterogeneous BD spectrum. Previous studies have found an accumulation of early age at onset (AAO) in BD families and have therefore hypothesized that there is a larger genetic contribution to the early-onset cases than to late onset BD. To investigate the genetic background of this subphenotype, we evaluated whether an increased polygenic burden of BD- and schizophrenia (SCZ)-associated risk variants is associated with an earlier AAO in BD patients.

METHODS

A total of 1995 BD type 1 patients from the Consortium of Lithium Genetics (ConLiGen), PsyCourse and Bonn-Mannheim samples were genotyped and their BD and SCZ polygenic risk scores (PRSs) were calculated using the summary statistics of the Psychiatric Genomics Consortium as a training data set. AAO was either separated into onset groups of clinical interest (childhood and adolescence [≤18 years] vs adulthood [>18 years]) or considered as a continuous measure. The associations between BD- and SCZ-PRSs and AAO were evaluated with regression models.

RESULTS

BD- and SCZ-PRSs were not significantly associated with age at disease onset. Results remained the same when analyses were stratified by site of recruitment.

CONCLUSIONS

The current study is the largest conducted so far to investigate the association between the cumulative BD and SCZ polygenic risk and AAO in BD patients. The reported negative results suggest that such a polygenic influence, if there is any, is not large, and highlight the importance of conducting further, larger scale studies to obtain more information on the genetic architecture of this clinically relevant phenotype.

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.

Genome-wide linkage scan of 98 bipolar pedigrees and analysis of clinical covariates

Despite compelling evidence that genetic factors contribute to bipolar disorder (BP), attempts to identify susceptibility genes have met with limited success. This may be due to the genetic heterogeneity of the disorder. We sought to identify susceptibility loci for BP in a genome-wide linkage scan with and without clinical covariates that might reflect the underlying heterogeneity of the disorder. We genotyped 428 subjects in 98 BP families at the Center for Inherited Disease Research with 402 microsatellite markers. We first carried out a non-parametric linkage analysis with MERLIN, and then reanalyzed the data with LODPAL to incorporate clinical covariates for age at onset (AAO), psychosis and comorbid anxiety. We sought to further examine the top findings in the covariate analysis in an independent sample of 64 previously collected BP families. In the non-parametric linkage analysis, three loci were nominally significant under a narrow diagnostic model and seven other loci were nominally significant under a broader model. The top findings were on chromosomes 2q24 and 3q28. The covariate analyses yielded additional evidence for linkage on 3q28 with AAO in the primary and independent samples. Although none of the linked loci were genome-wide significant, their congruence with prior results and, for the covariate analyses, their identification in two separate samples increases the likelihood that they are true positives and deserve further investigation. These findings further demonstrate the value of considering clinical features that may reflect the underlying heterogeneity of disease in order to facilitate gene mapping.

A tree-based model for allele-sharing-based linkage analysis in human complex diseases

By adapting a well-known affected-relative-pair linkage model that can incorporate covariate or sub-phenotype information [Olson, 1999: Am J Hum Genet 65:1760-1769], we have developed a recursive-partitioning (RP) algorithm (tree-based model) for identifying phenotype and covariate groupings that interact with the evidence for linkage. This strategy is designed to identify subgroups of affected relative pairs demonstrating increased evidence for linkage, where subgroups are defined by pair-level or family-level covariates. After growing a full tree, we identified optimal tree size through a form of tree pruning and chose the best covariate at each split by using bootstrap algorithms. Simulation studies showed that power to detect linkage can increase in the presence of gene-environment interactions, depending on the magnitude of the interaction. As expected, however, power can decrease by examining more covariates, despite the pruning to optimize tree size. The RP model correctly identifies tree structure in a large proportion of simulations. We applied the RP model to a dataset of families with bipolar affective disorder (BPAD) where linkage regions on chromosome 18 have been previously identified. Using the all-pairs score in Genehunter, the NPL tests showed no regions with strong linkage evidence on chromosome 18. However, using the RP model, several suggestive regions were found on chromosome 18. Two covariates appeared to influence the degree of linkage: the type II BPAD subtype and a pattern of displaying mania before or after a depressive episode. The RP model has the potential to identify previously unknown gene-environmental interactions; here we have demonstrated the practical utility and potential this new methodology holds.

Linkage of bipolar affective disorder on chromosome 8q24: follow-up and parametric analysis

Our group first reported a linkage finding for bipolar (BP) disorder on chromosome 8q24 in a study of 50 multiplex pedigrees, with an HLOD score reaching 2.39. Recently, Cichon et al reported an LOD score of 3.62 in the same region using two-point parametric analysis. Subsequently, we published the results of a genome scan for linkage to BP disorder using a sample extended to 65 pedigrees in which chromosome 8q24 provided the best finding, an NPL score of 3.13, approaching the accepted score for suggestive linkage. We have now fine mapped this region of chromosome 8 in our 65 pedigrees by the addition of 19 microsatellite markers reaching a marker density of 0.8 cM and an information content of 0.84. After the addition of the new data, the original NPL score slightly increased to 3.25. Two-point parametric analysis using the model employed by Cichon et al obtained an LOD score of 3.32 for marker D8S256 at theta=0.14 exceeding the proposed threshold for genomewide significance. After adjusting the parameters in accordance with the 'common disease-common variant' hypothesis, multipoint parametric analysis resulted in an HLOD of 2.49 (alpha=0.78) between D8S529 and D8S256, and defined a 1-LOD interval corresponding to a 2.3 Mb region. No allelic association with the disease was observed for our set of microsatellite markers. Biologically, plausible candidate genes in this region include thyroglobulin, KCNQ3 coding for a voltage-gated potassium channel and the gene for brain adenyl-cyclase (ADCY8).

Findings in an independent sample support an association between bipolar affective disorder and the G72/G30 locus on chromosome 13q33

Markers near the nested genes G72 and G30 on chromosome 13q33 have been implicated in the etiology of schizophrenia and, recently, bipolar affective disorder (BPAD). Hattori et al (2003) reported that single-nucleotide polymorphisms (SNPs) near the G72/G30 locus were associated with BPAD in a sample of 22 pedigrees, and that SNP haplotypes were associated in a second, larger sample of triads. The present study attempts to replicate this finding in an independent case-control sample. Six SNPs near the G72/G30 locus, including the most strongly associated markers in the previous study, were tested in 139 cases and 113 ethnically matched controls. Significant association was detected between BPAD and two adjacent SNPs (smallest P=0.007; global P=0.024). Haplotype analysis produced additional support for association (smallest P=0.004; global P=0.004). Analysis of 31 unlinked microsatellite markers detected no population stratification in the cases or controls studied. Although the associated alleles and haplotypes differ from those previously reported, these new results provide further evidence, in an independent sample, for an association between BPAD and genetic variation in the vicinity of the genes G72 and G30.

Novel CAG/CTG repeat expansion mutations do not contribute to the genetic risk for most cases of bipolar disorder or schizophrenia

The possible presence of anticipation in bipolar affective disorder and schizophrenia has led to the hypothesis that repeat expansion mutations could contribute to the genetic etiology of these diseases. Using the repeat expansion detection (RED) assay, we have systematically examined genomic DNA from 100 unrelated probands with schizophrenia and 68 unrelated probands with bipolar affective disorder for the presence of CAG/CTG repeat expansions. Our results show that 28% of the probands with schizophrenia and 30% of probands with bipolar disorder have a CAG/CTG repeat in the expanded range, but that each expansion could be explained by one of three nonpathogenic repeat expansions known to exist in the general population. We conclude that novel CAG/CTG repeat expansions are not a common genetic risk factor for bipolar disorder or schizophrenia.

Family-based association study of 76 candidate genes in bipolar disorder: BDNF is a potential risk locus. Brain-derived neutrophic factor

Identification of the genetic bases for bipolar disorder remains a challenge for the understanding of this disease. Association between 76 candidate genes and bipolar disorder was tested by genotyping 90 single-nucleotide polymorphisms (SNPs) in these genes in 136 parent-proband trios. In this preliminary analysis, SNPs in two genes, brain-derived neurotrophic factor (BDNF) and the alpha subunit of the voltage-dependent calcium channel were associated with bipolar disorder at the P<0.05 level. In view of the large number of hypotheses tested, the two nominally positive associations were then tested in independent populations of bipolar patients and only BDNF remains a potential risk gene. In the replication samples, excess transmission of the valine allele of amino acid 66 of BDNF was observed in the direction of the original result in an additional sample of 334 parent-proband trios (T/U=108/87, P=0.066). Resequencing of 29 kb surrounding the BDNF gene identified 44 additional SNPs. Genotyping eight common SNPs identified three additional markers transmitted to bipolar probands at the P < 0.05 level. Strong LD was observed across this region and all adjacent pairwise haplotypes showed excess transmission to the bipolar proband. Analysis of these haplotypes using TRANSMIT revealed a global P value of 0.03. A single haplotype was identified that is shared by both the original dataset and the replication sample that is uniquely marked by both the rare A allele of the original SNP and a novel allele 11.5 kb 3'. Therefore, this study of 76 candidate genes has identified BDNF as a potential risk allele that will require additional study to confirm.

Genetic analysis of the (CTG)n NOTCH4 polymorphism in 65 multiplex bipolar pedigrees

A strong genetic association between the NOTCH4 locus on chromosome 6 and schizophrenia was recently reported. Based on the data suggesting overlapping susceptibility for schizophrenia and bipolar disorder, we genotyped the polymorphic (CTG)n encoding polyleucine repeat in exon 1 of NOTCH4 in 65 pedigrees ascertained for a genetic linkage study of bipolar disorder. In addition, we analyzed a subset of our pedigrees with psychotic features at this locus. We failed to find any association between the (CTG)n NOTCH4 polymorphism and either the bipolar or the psychotic bipolar phenotype in our 65 pedigrees.

NEDD4L on human chromosome 18q21 has multiple forms of transcripts and is a homologue of the mouse Nedd4-2 gene

The validation of full-length cDNA represents a crucial step in gene identification and subsequent functional analysis. In searching for candidate genes for bipolar disorder on chromosome 18q21, a novel gene homologous to NEDD4 (Neural precursor cells expressed developmentally down-regulated) was identified using exon trapping and cDNA cloning. This novel gene is termed NEDD4L (Human Gene Nomenclature Committee symbol). Typical NEDD4 orthologues that contain a C2 (Ca(2+)/lipid-binding) and a HECT (Homologous to the E6-AP Carboxyl Terminus) ubiquitin-protein ligase domain, and multiple WW domains have been shown to regulate the epithelial sodium channel (ENaC). In mice, Nedd4 has two distinct isoforms termed Nedd4-1 that belongs to the typical NEDD4 class, and Nedd4-2 that is homologous to Nedd4-1 but lacks the C2 domain. NEDD4L contains the WW and HECT domains seen in the NEDD4 gene family, but lacks the C2 domain in the N-terminus. BLAST database search showed that the deduced polypeptide of NEDD4L has 97 and 62% sequence identity to mouse Nedd4-2 and human NEDD4, respectively. Multiple forms of transcripts of NEDD4L have been isolated, which differ in transcription start and termination sites together with the presence or absence of an alternative spliced exon. Northern blot analysis showed a 3.4 kb mRNA species was specifically expressed in heart and skeletal muscle, while a 3.2 kb band and/or an additional 3.6 kb band is seen in other tissues tested. Striking homology of NEDD4L to mouse Nedd4-2 suggests it is the human homologue of mouse Nedd4-2. Its position in a region of linkage for autosomal dominant orthostatic hypotensive disorder and its potential role in regulating ENaC make NEDD4L a candidate gene for this disorder.

Linkage of bipolar disorder to chromosome 18q and the validity of bipolar II disorder

BACKGROUND

An analysis of the relationship between clinical features and allele sharing could clarify the issue of genetic linkage between bipolar affective disorder (BPAD) and chromosome 18q, contributing to the definition of genetically valid clinical subtypes.

METHODS

Relatives ascertained through a proband who had bipolar I disorder (BPI) were interviewed by a psychiatrist, assigned an all-sources diagnosis, and genotyped with 32 markers on 18q21-23. Exploratory findings from the first 28 families (n = 247) were tested prospectively in an additional 30 families (n = 259), and the effect of confirmed findings on the linkage evidence was assessed.

RESULTS

In exploratory analyses, paternal allele sharing on 18q21 was significantly (P =.03) associated with a diagnostic subtype, and was greatest in pairs where both siblings had bipolar II disorder (BPII). Prospective analysis confirmed the finding that BPII-BPII sibling pairs showed significantly (P =.016) greater paternal allele sharing. Paternal allele sharing across 18q21-23 was also significantly greater in families with at least one BPII-BPII sibling pair. In these families, multipoint affected sibling-pair linkage analysis produced a peak paternal lod score of 4.67 (1-lod confidence interval, 12 centimorgans [cM]) vs 1.53 (1-lod confidence interval, 44 cM) in all families.

CONCLUSIONS

Affected sibling pairs with BPII discriminated between families who showed evidence of linkage to 18q, and families who did not. Families with a BPII sibling pair produced an increased lod score and improved linkage resolution. These findings, limited by the small number of BPII-BPII sibling pairs, strengthen the evidence of genetic linkage between BPAD and chromosome 18q, and provide preliminary support for BPII as a genetically valid subtype of BPAD.

The familial aggregation of psychotic symptoms in bipolar disorder pedigrees

OBJECTIVE

Symptomatic overlap between affective disorders and schizophrenia has long been noted. More recently, family and linkage studies have provided some evidence for overlapping genetic susceptibility between bipolar disorder and schizophrenia. If shared genes are responsible for the psychotic manifestations of both disorders, these genes may result in clustering of psychotic symptoms in some bipolar disorder pedigrees. The authors tested this hypothesis in families ascertained for a genetic study of bipolar disorder.

METHOD

Rates of psychotic symptoms-defined as hallucinations or delusions-during affective episodes were compared in families of 47 psychotic and 18 nonpsychotic probands with bipolar I disorder. The analysis included 202 first-degree relatives with major affective disorder.

RESULTS

Significantly more families of psychotic probands than families of nonpsychotic probands (64% versus 28%) contained at least one relative who had affective disorder with psychotic symptoms. Significantly more affectively ill relatives of psychotic probands than of nonpsychotic probands (34% versus 11%) had psychotic symptoms. An analysis of clustering of psychotic subjects across all families revealed significant familial aggregation. Clustering of psychosis was also apparent when only bipolar I disorder was considered the affected phenotype.

CONCLUSIONS

Psychotic bipolar disorder may delineate a subtype of value for genetic and biological investigations. Families with this subtype should be used to search for linkage in chromosomal regions 10p12-13, 13q32, 18p11.2, and 22q11-13, where susceptibility genes common to bipolar disorder and schizophrenia may reside. Putative schizophrenia-associated biological markers, such as abnormal evoked response, oculomotor, and neuroimaging measures, could similarly be explored in such families.

Women with bipolar disorder: findings from the NIMH Genetics Initiative sample

Bipolar I (BPI) mood disorder is a severe recurrent mental Illness with a population prevalence of 1 percent. Evidence is strong for genetic risk factors in onset. However, unlike unipolar mood disorders, in which women outnumber men by 2 to 1, for BPI disorder, the male:female ratio is equal. Perhaps for this reason, relatively little research has examined gender-related risks in BPI course. This article presents data from 186 BPI women and 141 BPI men ascertained as part of the NIMH Genetics Initiative, a multisite collaborative molecular genetic study. Subjects were interviewed using the Diagnostic Interview for Genetic Studies (DIGS). DIGS items included a medical history, and for women, questions concerning psychiatric disorders in relation to childbearing, the menstrual cycle, and menopause. Almost half of BPI women who had been pregnant reported having experienced severe emotional disturbances in relation to childbearing, with close to one-third reporting episode onset during pregnancy. Two-thirds of BPI women reported frequent premenstrual mood disturbances and almost 20 percent of postmenopausal BPI women reported severe emotional disturbances during the menopausal transition. More BPI women than men reported thyroid disorder and migraine headaches. Findings are discussed in relation to gender differences in population and other clinical samples, and in terms of their implications for the development of new treatments and preventive interventions.

Attempted suicide and alcoholism in bipolar disorder: clinical and familial relationships

OBJECTIVE

This study examined the clinical and familial relationships between comorbid alcoholism and attempted suicide in affectively ill relatives of probands with bipolar I disorder.

METHOD

In 71 families ascertained for a genetic linkage study, 337 subjects with major affective disorder were assessed by using the Schedule for Affective Disorders and Schizophrenia-Lifetime Version.

RESULTS

Subjects with bipolar disorder and alcoholism had a 38.4% lifetime rate of attempted suicide, whereas those without alcoholism had a 21.7% rate. Attempted suicide among subjects with bipolar disorder and alcoholism clustered in a subset of seven families. Families with alcoholic and suicidal probands had a 40.7% rate of attempted suicide in first-degree relatives with bipolar disorder, whereas other families had a 19.0% rate.

CONCLUSIONS

Comorbid alcoholism was associated with a higher rate of attempted suicide among family members with bipolar disorder. Attempted suicide and alcoholism clustered in a subset of families. These relationships may have a genetic origin and may be mediated by intoxication, mixed states, and/or temperamental instability.

Mitochondrial DNA sequence diversity in bipolar affective disorder

OBJECTIVE

Point mutations in mitochondrial DNA (mtDNA) are one mechanism that could explain the apparent excess maternal transmission of bipolar affective disorder observed in some families. The authors sequenced the mtDNA from probands with bipolar disorder and tested nucleotide variants for association with the disorder.

METHOD

The entire 16.5 kilobase mitochondrial genome was sequenced in nine unrelated probands selected from large pedigrees with exclusively maternal transmission of bipolar affective disorder. Compared to a reference sequence, variants were detected at 107 nucleotide positions. Fifteen variants of possible pathogenic significance were selected for further study. These variants were assayed in 93 unrelated probands with bipolar I, bipolar II, or schizoaffective-manic disorder and 63 comparison subjects, all of whom were classified into the major groups comprising the European mtDNA haplotype structure (haplogroups).

RESULTS

The major European haplogroups were represented at the expected frequencies among both probands and comparison subjects. There was no significant difference between probands and comparison subjects in the frequency of any variant, although odds ratios >2 or <0.5 were observed for four variants. Frequencies of these four variants were similar in probands and haplogroup-matched comparison subjects. The results of all comparisons were essentially unchanged when probands from families with an apparently paternal transmission pattern were excluded.

CONCLUSIONS

The results demonstrate that bipolar affective disorder occurs across all of the major European mtDNA haplogroups but do not reveal any point mutations that explain excess maternal transmission of the disorder.

Allelic distribution of CTG18.1 in Caucasian populations: association studies in bipolar disorder, schizophrenia, and ataxia

CTG18.1 is a highly polymorphic and unstable CTG repeat within an intron of the SEF2-1 gene. We tested the CTG18.1 repeat length in affective disorder, schizophrenia, and nonspecific ataxia; these diseases all have shown clinical evidence for anticipation. There was no difference in the allele frequencies comparing the controls and disease groups. The most common allele contains 11 CAGs (35%) followed by alleles with 14-17 CAGs (35%). There was no difference in the distribution of the alleles in the cases vs controls for ataxia (P = 0.11), affective disorders (P = 0.21), or schizophrenia (P = 0.26). The frequency of unstable CTG18.1 alleles was approximately 3% in a population of N. European descent and is not related to the phenotypes tested.

Searching high and low: a review of the genetics of bipolar disorder

OBJECTIVES

To review the methodologies and findings in the genetics of bipolar disorder (BPD), and to suggest future directions for research.

METHODS

Reports of family, twin, adoption, linkage, association, cytogenetic, and animal model studies, and segregation analyses in English, were identified from multiple MEDLINE searches. Hand searches were carried out in bibliographies from review articles.

RESULTS

Family, twin, and adoption studies have provided strong evidence for a genetic etiology in BPD. Early reports of linkage of BPD to DNA markers at several chromosomal sites have not proven robust, perhaps because of the complex nature of BPD inheritance. However, linkage findings in the 1990s, on chromosomes 18, 21q, 12q, and 4p, have provided leads that are being pursued through both genetic and physical mapping. No gene has yet been definitively implicated in BPD.

CONCLUSIONS

Strategies for increasing the power to detect BPD genes include: (1) dividing the phenotype into genetically meaningful subtypes to decrease heterogeneity: and (2) ascertaining a very large family sample--a multicenter study now in progress will collect 700 bipolar I sibling pairs. BPD may result from several genes acting in concert so that new multilocus statistical methods could enhance the capacity to detect loci involved. Family-based association studies using a very large number of newly identified single nucleotide polymorphisms (SNPs) may allow for more efficient screening of the genome. As the Human Genome Project approaches its goal of isolating all genes by 2003, the data generated is likely to speed identification of candidate BPD genes.

Suggestive evidence of a locus on chromosome 10p using the NIMH genetics initiative bipolar affective disorder pedigrees

As part of a four-center NIMH Genetics Initiative on Bipolar Disorder, a genome screen using 365 markers was performed on 540 DNAs from 97 families, enriched for affected relative pairs. This is the largest uniformly ascertained and assessed linkage sample for this disease, and includes 232 subjects diagnosed with bipolar I (BPI), 32 with schizo-affective, bipolar type (SABP), 72 with bipolar II (BPII), and 88 with unipolar recurrent depression (UPR). A hierarchical set of definitions of affected status was examined. Under Model I, affected individuals were those with a diagnosis of BPI or SABP, Model II included as affected those fitting Model I plus BPII, and Model III included those fitting Model II plus UPR. This data set was previously analyzed using primarily affected sib pair methods. We report the results of nonparametric linkage analyses of the extended pedigree structure using the program Genehunter Plus. The strongest finding was a lod score of 2.5 obtained on chromosome 10 near the marker D10S1423 with diagnosis as defined under Model II. This region has been previously implicated in genome-wide studies of schizophrenia and bipolar disorder. Other chromosomal regions with lod scores over 1.50 for at least one Model Included chromosomes 8 (Model III), 16 (Model III), and 20 (Model I). Am. J. Med. Genet. (Neuropsychiatr. Genet.) 96:18-23, 2000

Pilot study on patients' and spouses' attitudes toward potential genetic testing for bipolar disorder

OBJECTIVE

The purpose of this pilot study was to gain information about attitudes of individuals with bipolar disorder and their spouses toward some of the ethical and social issues arising from rapidly advancing genetic research on bipolar disorder.

METHOD

Patients with bipolar disorder and their unaffected spouses were asked to answer questionnaires assessing their knowledge and attitudes about treatment response rates for bipolar disorder, probability of inheritance, genetic testing, disclosure of genetic information, abortion, marriage, and child-bearing.

RESULTS

The overwhelming majority of the patients and spouses said that they would take advantage of genetic tests for bipolar disorder if such tests were to become available. Most patients and spouses agreed that the benefits of knowing whether one carries a gene for bipolar disorder would outweigh the risks. The decisive majority of respondents also felt that they would not abort a fetus that carried a gene for bipolar disorder. Furthermore, most patients and spouses agreed that the knowledge that one of them carried a gene for bipolar disorder would not have deterred them from marriage or childbearing.

CONCLUSIONS

The results of this study suggest that most individuals believe that they would benefit from the use of genetic testing for bipolar disorder if it were to become available. Follow-up studies using a broader patient sample and nonclinical control groups would be useful in further evaluating the issues addressed in this pilot study.

Bipolar disorder and panic disorder in families: an analysis of chromosome 18 data

OBJECTIVE

The authors performed an analysis of their published chromosome 18 linkage data on 28 families in which there was bipolar disorder to test the potential of comorbid panic disorder to define a genetic subtype of bipolar disorder.

METHOD

Families ascertained through probands with bipolar I disorder were stratified into three groups based on a history of panic disorder, panic attacks, or no panic attacks in the probands. Multipoint nonparametric linkage analysis was performed on data from bipolar I and II family members in each group.

RESULTS

Linkage scores for five consecutive 18q marker loci were highest in the families of the probands with panic disorder and lowest for the families of the probands without panic attacks.

CONCLUSIONS

This study supports the authors' previously reported clinical hypothesis of a genetic subtype of bipolar disorder identified by comorbid panic disorder. The hypothesis merits prospective testing.

Integrating clinical and laboratory data in genetic studies of complex phenotypes: a network-based data management system

The identification of genes underlying a complex phenotype can be a massive undertaking, and may require a much larger sample size than thought previously. The integration of such large volumes of clinical and laboratory data has become a major challenge. In this paper we describe a network-based data management system designed to address this challenge. Our system offers several advantages. Since the system uses commercial software, it obviates the acquisition, installation, and debugging of privately-available software, and is fully compatible with Windows and other commercial software. The system uses relational database architecture, which offers exceptional flexibility, facilitates complex data queries, and expedites extensive data quality control. The system is particularly designed to integrate clinical and laboratory data efficiently, producing summary reports, pedigrees, and exported files containing both phenotype and genotype data in a virtually unlimited range of formats. We describe a comprehensive system that manages clinical, DNA, cell line, and genotype data, but since the system is modular, researchers can set up only those elements which they need immediately, expanding later as needed.

Linkage of bipolar affective disorder to chromosome 18 markers in a new pedigree series

Several groups have reported evidence suggesting linkage of bipolar affective disorder (BPAD) to chromosome 18. We have reported data from 28 pedigrees that showed linkage to marker loci on 18p and to loci 40 cM distant on 18q. Most of the linkage evidence derived from families with affected phenotypes in only the paternal lineage and from marker alleles transmitted on the paternal chromosome. We now report results from a series of 30 new pedigrees (259 individuals) genotyped for 13 polymorphic markers spanning chromosome 18. Subjects were interviewed by a psychiatrist and were diagnosed by highly reliable methods. Genotypes were generated with automated technology and were scored blind to phenotype. Affected sib pairs showed excess allele sharing at the 18q markers D18S541 and D18S38. A parent-of-origin effect was observed, but it was not consistently paternal. No robust evidence of linkage was detected for markers elsewhere on chromosome 18. Multipoint nonparametric linkage analysis in the new sample combined with the original sample of families supports linkage on chromosome 18q, but the susceptibility gene is not well localized.

A novel, heritable, expanding CTG repeat in an intron of the SEF2-1 gene on chromosome 18q21.1

There are currently 13 diseases known to be caused by unstable triplet repeat mutations; however, there are some instances (as with FRAXF and FRA16) when these mutations appear to be asymptomatic. In a search for polymorphic CTG repeats as candidate genes for bipolar disorder, we screened a genomic human chromosome 18-specific library and identified a 1.6 kb clone (7,6A) with a CTG24 repeat that maps to 18q21.1. The CTG repeat locus, termed CTG18.1, is located within an intron of human SEF2-1, a gene encoding a basic hellx-loop-hellx DNA binding protein involved in transcriptional regulation. The CTGn repeat is highly polymorphic and very enlarged alleles, consistent with expansions of up to CTG2100, were identified. PCR and Southern blot analysis in pedigrees ascertained for a Johns Hopkins University bipolar disorder linkage study and in CEPH reference pedigrees revealed a tripartite distribution of CTG18.1 alleles with stable alleles (CTG10-CTG37), moderately enlarged and unstable alleles (CTG53-CTG250), and very enlarged, unstable alleles (CTG800-CTG2100). Moderately enlarged alleles were not associated with an abnormal phenotype and have a combined enlarged allele frequency of 3% in the CEPH and bipolar populations. Very enlarged alleles, detectable only by Southern blot analysis of genomic digests, have thus far been found in only three individuals from our bipolar pedigrees, and to date, have not been found in any of the CEPH reference pedigrees. These enlarged alleles may arise, at least in part, via somatic mutation.

Quantitative analysis of leukocyte mitochondrial DNA deletion in affective disorders

Mutations in mitochondrial DNA (mtDNA) are implicated in the pathophysiology of affective disorders. To determine whether the 4977-base-pair deletion in mtDNA is more frequent in affective disorders, we quantitated the concentration of this deletion in leukocyte mtDNA in 34 probands with affective disorders (20 bipolar and 14 unipolar) and 20 controls. We found no significant difference in the quantitative ratio of deletion to wild-type mtDNA between patients and controls. One patient with unipolar depression and 1 of 2 patients previously reported as having a large quantity of the deleted mtDNA did have a markedly high ratio; however, the deletion did not segregate with the disease in these two families. These results do not support a hypothesis that the 4977-base-pair deletion plays an important role in the pathophysiology of affective disorders.

Panic disorder with familial bipolar disorder

If bipolar disorder is genetically heterogeneous, it may be possible to discern clinically heterogeneous familial subtypes based on differential risk for psychiatric comorbidity, for example panic disorder. We evaluated 528 members of 57 families ascertained for a genetic linkage study of bipolar disorder. Families were assorted according to the panic disorder diagnosis of the bipolar proband; the rates of panic and other disorders in relatives were compared. Eighty-eight percent of the 41 subjects with panic disorder had bipolar disorder. Panic disorder was diagnosed in 18% of family members with bipolar disorder. Ten of 57 bipolar probands had panic disorder. Their bipolar first-degree relatives had a significantly higher prevalence of panic disorder, bipolar II, cyclothymia, and dysthymia, but had lower prevalence of substance abuse than the relatives of the bipolar probands without panic disorder. These findings suggest the testable hypothesis that comorbid panic disorder is a marker of genetic heterogeneity in bipolar disorder.

Initial genome screen for bipolar disorder in the NIMH genetics initiative pedigrees: chromosomes 2, 11, 13, 14, and X

We report on an initial genome screen of 540 individuals from 97 families collected as part of the NIMH Genetics Initiative Bipolar Group. Among the individuals studied, 232 were diagnosed with bipolar (BP) I, 72 with BPII, 88 with major depressive disorder-recurrent type (UPR), and 32 with schizoaffective disorder, bipolar type (SA/BP). A total of 53 markers on chromosomes 2, 11, 13, 14, and X (average spacing: 11.5 cM) were studied at Johns Hopkins University. Tests for linkage were performed using nonparametric affected sib-pair and whole pedigree methods with three definitions of affected status. Three regions of interest were identified (13q14-32, Xp22, and Xq26-28). On chromosomes 2, 11, and 14, a disease locus with relative risk lambda(i) = 1.5 could be excluded in <10% of the genetic distance studied, while a locus conferring lambda(i) = 3 or greater could be excluded across at least 96%. The autosomal region that could not be excluded even with lambda(i) = 5 was near 13q14-32. In this region, two-point affected sib-pair analyses revealed a pair of consecutive loci with excess sharing (P < 0.05) and a multipoint affected sib-pair LOD score of 1.12. On the X chromosome, nonparametric multipoint affected sib-pair analyses revealed peak total LOD scores of 0.94 on Xp22 and 1.34 on Xq26-28. A locus linked to the markers in Xp22 would have lambda(i) = 3.6 in affected brother-brother pairs, while a locus linked to the markers in Xq26-28 would have lambda(i) > 1.9 in affected sister-sister pairs. The results on 13q14-32, Xp22, and Xq26-28 suggest areas of interest for further studies.

Initial genomic scan of the NIMH genetics initiative bipolar pedigrees: chromosomes 3, 5, 15, 16, 17, and 22

As part of the four-center NIMH Genetics Initiative on Bipolar Disorder we carried out a genomic scan of chromosomes 3, 5, 15, 16,17, and 22. Genotyping was performed on a set of 540 DNAs from 97 families, enriched for affected relative pairs and parents where available. We report here the results of the initial 74 markers that have been typed on this set of DNAs. The average distance between markers (theta) was 12.3 cM. Nonparametric analysis of excess allele sharing among affected sibling pairs used the SIBPAL program of the S.A.G.E. package to test three hierarchical models of affected status. D16S2619 gave some evidence of linkage to bipolar disorder, with P = 0.006 for Model II (in which bipolar 1, bipolar 2 and schizoaffective-bipolar type individuals are considered affected). Nearby markers also showed increased allele sharing. A second interesting region was toward the telomere of chromosome 5q, where D5S1456 and nearby markers showed increased allele sharing; for D5S1456, P = 0.05, 0.015 and 0.008 as the models of affected status become more broad. MOD score analysis also supported the possible presence of a susceptibility locus in this region of chromosome 5. A pair of adjacent markers on chromosome 3, D3S2405 and D3S3038, showed a modest increased allele sharing in the broad model. Several isolated markers had excess allele sharing at the P < 0.05 level under a single model. D15S217 showed a MOD score of 2.37 (P < 0.025). Multipoint analysis flagged the region of chromosome 22 around D22S533 as the most interesting. Thus, several regions showed modest evidence for linkage to bipolar disorder in this initial genomic scan of these chromosomes, including broad regions near previous reports of possible linkage.

Initial genome scan of the NIMH genetics initiative bipolar pedigrees: chromosomes 1, 6, 8, 10, and 12

A report on an initial genome screen on 540 individuals in 97 families was collected as part of the NIMH Genetics Initiative on Bipolar Disorder. Families were ascertained to be informative for genetic linkage and underwent a common ascertainment and assessment protocol at four clinical sites. The sample was genotyped for 65 highly polymorphic markers from chromosomes 1, 6, 8, 10, and 12. The average intermarker interval was 16 cM. Genotypic data was analyzed using affected sib pair, multipoint affected sib pair, and pedigree analysis methods. Multipoint methods gave lod scores of approximately two on chromosomes 1, 6, and 10. The peak lod score on chromosome 6 occurred at the end of the q-arm, at some distance from the 6p24-22 area previously implicated for schizophrenia. We are currently genotyping additional markers to reduce the intermarker interval around the signals. The interpretation of results from a genome screen of a complex disorder and the problem of achieving a balance between detecting false positive results and the ability to detect genes of modest effect are discussed.

Initial genome scan of the NIMH genetics initiative bipolar pedigrees: chromosomes 4, 7, 9, 18, 19, 20, and 21q

An initial genome scan was performed on 540 individuals from 97 families segregating bipolar disorder, collected through the National Institutes of Mental Health Genetics Initiative. We report here affected-sib-pair (ASP) data on 126 marker loci (approximately 68,000 genotypes) mapping to chromosomes 4, 7, 9, 18, 19, 20, and 21q, under three affection status models. Modest increases in identical-by-descent (IBD) allele sharing were found at the following loci: D4S2397 and D4S391 (P < 0.05) on 4p, D4S1647 (P < 0.05) on 4q, D7S1802 and D7S1869 (low P = 0.01) on 7p, D9S302 (P = 0.004) on 9q, and D20S604 on 20p and D20S173 on 20q (P < 0.05). In addition, five markers on 7q displayed increased IBD sharing (P = 0.046-0.002). Additional ASP analyses on chromosomes 18 and 21q marker data were performed using disease phenotype models defined previously. On chromosome 18, only D18S40 on 18p and D18S70 on 18q yielded a slight elevation in allele sharing (P = 0.02), implying that the reported linkages in these regions were not confirmed. On chromosome 21q, a cluster of markers within an approximately 9 cM interval: D21S1254, D21S65, D21S1440, and D21S1255 exhibited excess allele sharing (P = 0.041-0.008). Multilocus data on overlapping marker quartets, from D21S1265 to D21S1255, which were consistent with increased IBD sharing (P < 0.01, with a low of 0.0009), overlapped a broad interval of excess allele sharing reported previously, increasing support for a susceptibility locus for bipolar disorder on 21q.

Genetics of manic depressive illness

Manic depressive illness is a common and frequently debilitating familial psychiatric disorder. Efforts to understand the mechanisms of inheritance have been hindered by the complexity of the phenotype, which may range from benign mood swings to chronic psychosis, and by apparently nonmendelian modes of transmission. Early reports of linkage to chromosomal loci have fallen into doubt; however they have helped encourage the development of more sophisticated methods for analyzing complex phenotypes. Using such methods, linkage of manic depressive illness to loci on chromosome 18 has been reported and apparently replicated, and work is proceeding to identify genes associated with what is probably a genetically heterogeneous set of disorders. As molecular mechanisms of inheritance are elucidated, it will be important to consider the ethical implications of genetic testing in a clinically and genetically complex disorder such as manic depressive illness.

Psychiatric diagnoses in the child and adolescent members of extended families identified through adult bipolar affective disorder probands

OBJECTIVE

To investigate the type and distribution of psychiatric disorders in the child and adolescent members of extended pedigrees identified through bipolar probands.

METHOD

The child and adolescent offspring (24 male, 26 female, aged 6 to 17 years) and the adult parents (60) of 14 bipolar pedigrees ascertained for the National Institutes of Mental Health Genetics Initiative Study of Bipolar Affective Disorder were personally assessed using structured psychiatric interviews. A parent was also interviewed about each child or adolescent offspring.

RESULTS

Twelve of the 50 interviewed offspring received a lifetime DSM-III-R diagnosis of an affective disorder. This included six cases of bipolar disorder, five cases of major depressive disorder, and one case of dysthymia. Eight of the offspring who received an affective disorder diagnosis also qualified for an anxiety disorder (four), a disruptive behavior disorder (two), or both (two). Offspring who had a parent with an affective disorder had a 5.1-fold higher risk for receiving an affective disorder diagnosis than did offspring with healthy parents.

CONCLUSIONS

In a consecutive series of families identified through a proband with bipolar disorder, there were significant increases in the prevalence of affective disorder diagnoses in the child and adolescent offspring. The distribution of illness in offspring was compatible with the presence of important genetic factors which contribute to early-onset affective illness.

cDNA cloning of a human homologue of the Caenorhabditis elegans cell fate-determining gene mab-21: expression, chromosomal localization and analysis of a highly polymorphic (CAG)n trinucleotide repeat

The two most consistent features of the diseases caused by trinucleotide repeat expansion-neuropsychiatric symptoms and the phenomenon of genetic anticipation-may be present in forms of dementia, hereditary ataxia, Parkinsonism, bipolar affective disorder, schizophrenia and autism. To identify candidate genes for these disorders, we have screened human brain cDNA libraries for the presence of gene fragments containing polymorphic trinucleotide repeats. Here we report the cDNA cloning of CAGR1, originally detected in a retinal cDNA library. The 2743 bp cDNA contains a 1077 bp open reading frame encoding 359 amino acids. This amino acid sequence is homologous (56% amino acid identify and 81% amino acid conservation) to the Caenorhabditis elegans cell fate-determining protein mab-21. CAGR1 is expressed in several human tissues, most prominently in the cerebellum, as a message of approximately 3.0 kb. The gene was mapped to 13q13, just telomeric to D13S220. A 5'-untranslated CAG trinucleotide repeat is highly polymorphic, with repeat length ranging from six to 31 triplets and a heterozygosity of 87-88% in 684 chromosomes from several human populations. One allele from an individual with an atypical movement disorder and bipolar affective disorder type II contains 46 triplets, 15 triplets longer than any other allele detected. Though insufficient data are available to link the long repeat to this clinical phenotype, an expansion mutation of the CAGR1 repeat can be considered a candidate for the etiology of disorders with anticipation or developmental abnormalities, and particularly any such disorders linked to chromosome 13.

Diagnostic accuracy and confusability analyses: an application to the Diagnostic Interview for Genetic Studies

The dominant, contemporary paradigm for developing and refining diagnoses relies heavily on assessing reliability with kappa coefficients and virtually ignores a core component of psychometric practice: the theory of latent structures. This article describes a psychometric approach to psychiatric nosology that emphasizes the diagnostic accuracy and confusability of diagnostic categories. We apply these methods to the Diagnostic Interview for Genetic Studies (DIGS), a structured psychiatric interview designed by the NIMH Genetics Initiative for genetic studies of schizophrenia and bipolar disorder. Our results show that sensitivity and specificity were excellent for both DSM-III-R and RDC diagnoses of major depression, bipolar disorder, and schizophrenia. In contrast, diagnostic accuracy was substantially lower for subtypes of schizoaffective disorder-especially for the DSM-III-R definitions. Both the bipolar and depressed subtypes of DSM-III-R schizoaffective disorder had excellent specificity but poor sensitivity. The RDC definitions also had excellent specificity but were more sensitive than the DSM-III-R schizoaffective diagnoses. The source of low sensitivity for schizoaffective subtypes differed for the two diagnostic systems. For RDC criteria, the schizoaffective subtypes were frequently confused with one another; they were less frequently confused with other diagnoses. In contrast, the DSM-III-R subtypes were often confused with schizophrenia, but not with each other.

Evidence for linkage of bipolar disorder to chromosome 18 with a parent-of-origin effect

A susceptibility gene on chromosome 18 and a parent-of-origin effect have been suggested for bipolar affective disorder (BPAD). We have studied 28 nuclear families selected for apparent unilineal transmission of the BPAD phenotype, by using 31 polymorphic markers spanning chromosome 18. Evidence for linkage was tested with affected-sib-pair and LOD score methods under two definitions of the affected phenotype. The affected-sibpair analyses indicated excess allele sharing for markers on 18p within the region reported previously. The greatest sharing was at D18S37: 64% in bipolar and recurrent unipolar (RUP) sib pairs (P = .0006). In addition, excess sharing of the paternally, but not maternally, transmitted alleles was observed at three markers on 18q: at D18S41, 51 bipolar and RUP sib pairs were concordant for paternally transmitted alleles, and 21 pairs were discordant (P = 0004). The evidence for linkage to loci on both 18p and 18q was strongest in the 11 paternal pedigrees, i.e., those in which the father or one of the father's sibs is affected. In these pedigrees, the greatest allele sharing (81%; P = .00002) and the highest LOD score (3.51; phi = 0.0) were observed at D18S41. Our results provide further support for linkage of BPAD to chromosome 18 and the first molecular evidence for a parent-of-origin effect operating in this disorder. The number of loci involved, and their precise location, require further study..

Patterns of maternal transmission in bipolar affective disorder

The mode of inheritance of bipolar affective disorder (BPAD) appears complex, and non-Mendelian models of inheritance have been postulated. Two non-Mendelian phenomena, genomic imprinting and mitochondrial inheritance, may contribute to the complex inheritance pattern seen in BPAD. Both imprinting and mitochondrial inheritance share the feature of differential expression of the phenotype, depending on the parent of origin. In this study we tested the hypothesis of a parent-of-origin effect on the transmission of BPAD. We examined the frequency and risk of affective disorder among relatives in a sample of 31 families ascertained through treated probands with BPAD and selected for the presence of affected phenotypes in only one parental lineage. Three specific comparisons were performed: (1) the observed frequency of transmitting mothers versus transmitting fathers; (2) the observed frequency and lifetime risk of BPAD among the maternal versus the paternal relatives of probands; and (3) the observed frequency and lifetime risk of BPAD for the offspring of affected mothers compared with the offspring of affected fathers. We observed a higher than expected frequency of affected mothers (P < .04), a 2.3-2.8-fold increased risk of illness for maternal relatives (P < .006), and a 1.3- 2.5-fold increased risk of illness for the offspring of affected mothers (P < .017). In seven enlarged pedigrees, fathers repeatedly failed to transmit the affected phenotype to daughters or sons. Taken together, these findings indicate a maternal effect in the transmission of BPAD susceptibility and suggest that molecular studies of mtDNA and imprinted DNA are warranted in patients with BPAD.

Influence of clinical subtype, sex, and lineality on age at onset of major affective disorder in a family sample

OBJECTIVE

The authors analyzed data from a family sample ascertained for a genetic linkage study of bipolar disorder to address the following questions: Do the major clinical subtypes of familial affective disorder have distinct distributions of age at onset? What factors other than clinical subtype affect these distributions? After controlling for these factors, do the differences in age at onset persist among the subtypes?

METHODS

Eighty-two families were ascertained through a treated proband with bipolar disorder who had a family history of two or more affected siblings or one affected sibling and one affected parent. After participating in an interview conducted by a psychiatrist using the Schedule for Affective Disorders and Schizophrenia--Lifetime Version, 274 probands and their first-degree relatives were diagnosed as having bipolar I, bipolar II, or recurrent unipolar disorder according to Research Diagnostic Criteria. Age at first major affective episode and other clinical data were collected.

RESULTS

Onset age distributions were similar for bipolar I and bipolar II disorder but significantly different for recurrent unipolar disorder. This finding persisted after adjustment for a significantly earlier onset among females. Subjects with affective disorder in both parental lines (bilineal) also experienced a significantly earlier onset. Substance abuse, physical illness, and sex of the affected parent had no significant impact on onset age.

CONCLUSIONS

Although differences in age at onset may reflect several factors, these results provide indirect support for the view that bipolar I and bipolar II disorders are genetically related phenotypes and suggest that bilineal families may be more complex than previously assumed.

Mood variability in normal subjects on lithium

To investigate the effect of lithium carbonate on normal volunteers' moods, we randomly assigned 30 subjects to 5 weeks each of placebo and lithium treatment with crossover at midstudy. Lithium levels were maintained during the treatment period at a mean serum level of 0.54 mEq/L. All subjects completed visual analogue mood scales (VAMS) daily throughout the study period; segmented visual analogue scales (SVAS) measuring mood, anxiety, and energy and the Profile of Mood States (POMS) were completed weekly at testing sessions. Neither mean mood nor mood variability as assessed by the delta square (mean square successive difference) differed between placebo and lithium conditions. Segmented visual analogue scale mood ratings were highly correlated with the VAMS and similarly showed no difference between conditions. The self-rated mood variability, however, declined significantly in both experimental conditions as a function of time on study. None of the POMS factors differed between placebo and lithium conditions. These data suggest that lithium, in modest doses administered over 5 weeks, does not have a substantial mood-stabilizing effect in normal subjects.

Are you recognizing depression in your patients?

Major depression is a prevalent condition that causes significant morbidity and mortality. Diagnosis may be complicated in depressed patients who offer a medical symptom as their chief complaint. Once the diagnosis is established, treatment is relatively straightforward. In prescribing an antidepressant, consideration should be given to the patient's previous response to medications, the documented efficacy of various agents, their side-effect profiles, and their potential for toxicity. Although the more severe and complicated cases should be referred to a psychiatrist, most depressed patients can be treated by their primary care physician.

Anticipation in bipolar affective disorder

Anticipation refers to the increase in disease severity or decrease in age at onset in succeeding generations. This phenomenon, formerly ascribed to observation biases, correlates with the expansion of trinucleotide repeat sequences (TNRs) in some disorders. If present in bipolar affective disorder (BPAD), anticipation could provide clues to its genetic etiology. We compared age at onset and disease severity between two generations of 34 unilineal families ascertained for a genetic linkage study of BPAD. Life-table analyses showed a significant decrease in survival to first mania or depression from the first to the second generation (P < .001). Intergenerational pairwise comparisons showed both a significantly earlier age at onset (P < .001) and a significantly increased disease severity (P < .001) in the second generation. This difference was significant under each of four data-sampling schemes which excluded probands in the second generation. The second generation experienced onset 8.9-13.5 years earlier and illness 1.8-3.4 times more severe than did the first generation. In additional analyses, drug abuse, deaths of affected individuals prior to interview, decreased fertility, censoring of age at onset, and the cohort effect did not affect our results. We conclude that genetic anticipation occurs in this sample of unilineal BPAD families. These findings may implicate genes with expanding TNRs in the genetic etiology of BPAD.

Bipolar II: the most common bipolar phenotype?

OBJECTIVE

The purpose of this study was to compare the pattern of affective psychopathology in families ascertained for genetic linkage studies through bipolar I probands to that in families ascertained through bipolar II probands.

METHOD

All available first-degree relatives (N = 266) of 48 bipolar I and eight bipolar II probands were interviewed with the Schedule for Affective Disorders and Schizophrenia--Lifetime Version by one of two psychiatrists who had attained high interrater reliability for bipolar II disorder and other diagnoses.

RESULTS

Bipolar II disorder was the most common affective disorder in both family sets. Forty percent of the 47 first-degree relatives of the bipolar II probands and 22% of the 219 first-degree relatives of the bipolar I probands were diagnosed with bipolar II disorder. On the other hand, only one bipolar I relative was found in the bipolar II families.

CONCLUSIONS

Bipolar II disorder was the most prevalent affected phenotype in both bipolar I and bipolar II families and was the only expressed phenotype in half of the bipolar II families. This suggests that bipolar II disorder is genetically related to but less complex than bipolar I disorder. Accurate diagnosis of bipolar II disorder may be crucial in finding the genetic loci underlying bipolar disorders generally.

Assessment of lineality in bipolar I linkage studies

OBJECTIVE

To assess lineality in families of bipolar I probands, the authors used direct interviews of family members to reclassify families initially categorized as unilineal by family history.

METHOD

The families of 1,800 treated bipolar I probands were screened by the family history method with multiple informants. If the proband had one or more affected sibs and one apparently unaffected parent, the parents (and then other available first- and second-degree relatives) were directly interviewed by psychiatrists.

RESULTS

Of the 1,800 families screened, 56 were apparently suitable unilineal families with multiple affected members; 46 families were interviewed directly. After interviews with the parents, 12 families (26.1%) were found to be bilineal. Direct interviews of all available relatives in the 34 remaining families revealed that only 22 (47.8% of the 46 interviewed families) were unilineal or probably unilineal and 12 were probably bilineal. The probably bilineal families had a significantly higher proportion of siblings with unipolar disorder. In addition, the affected sibs from the probably bilineal families tended to have earlier onsets but had significantly fewer symptoms in the most severe depressive episode.

CONCLUSIONS

Fewer than 50% of bipolar I families appearing unilineal according to family history were found to be unilineal by direct interviews. The phenotypic differences between the affected sibs from the probably bilineal families and those from the unilineal and probably unilineal families suggest differences in genetic mechanisms. These findings highlight the need to systematically assess lineality in all families considered for bipolar I linkage studies and support the preferential inclusion of unilineal families in linkage studies.

Bipolar II affective disorder in eating disorder inpatients

We examined the association between affective disorders and eating disorders in 22 eating disorder inpatients who were interviewed using the Schedule for Affective Disorders and Schizophrenia-Lifetime Version. The first series of 11 were interviewed as part of an interrater reliability study; the second series, done as follow-up to the first, consisted of 11 consecutive admissions. Overall, there were 15 bulimics and seven anorexics. Nineteen patients had a major affective disorder, and 13 (59%) had bipolar II affective disorder. Bipolar II affective disorder appears to be a common finding in hospitalized patients with severe persistent eating disorders.

Depression following myocardial infarction

OBJECTIVE

Although many investigators have studied mood disorders following myocardial infarction, the prevalence, severity, and persistence of depression have been disputed, and standard rating scales and criteria for depressive disorders have infrequently been utilized. The authors' goal was to determine how frequently depressive disorders occur after myocardial infarction, and to investigate predisposing factors for such disorders.

METHOD

Structured clinical interviews were administered to 129 inpatients within ten days of myocardial infarction. Patients were also evaluated using standardized rating scales for depression, social function, cognition, and physical impairment. DSM-III diagnoses were derived from the structured interview.

RESULTS

Major depressive syndromes were present in 19 percent (n = 25) of the patients and were associated with prior history of mood disorder, female sex, large infarcts, and functional physical impairment.

CONCLUSION

Major depression is common in the acute post-myocardial infarction period. Such disorders confer significant psychiatric morbidity and, if sustained, require psychiatric intervention.

Fluoxetine treatment of bipolar II depression

We have previously reported on the familial aggregation of bipolar II affective disorder and have speculated that new treatment approaches might be required for this difficult disorder. Based on Reimherr's report that fluoxetine responders were more likely to have poor prior responses to tricyclics and to have chronic depressions with "atypical" clinical features, we used fluoxetine to treat the chronic atypical depression in selected bipolar II outpatients. The 16 bipolar II patients in our series had been depressed for an average of 5.3 years prior to starting fluoxetine and had had poor responses to tricyclics, MAOIs, and lithium. All but one have had some response to fluoxetine. Ten of the 13 patients who have been taking fluoxetine for 10 or more months have had a good to very good response and the other 3 have had a fair response. Only one patient discontinued fluoxetine because of side effects. These findings should encourage further treatment research using fluoxetine and other serotonin reuptake blockers as well as research into the pathophysiologic identity of bipolar II as a possible distinct form of affective disorder.

Bipolar disorder and Crohn's disease

Despite an extensive literature examining the relationship between Crohn's disease and psychiatric illness, there is only one published report of mania in a patient with Crohn's disease. The authors describe seven patients, six men and one woman, with both bipolar disorder and Crohn's disease. The age at onset of Crohn's disease was highly correlated with the age at onset of affective disorder (r = .89, p = .016) and mania (r = .79, p = .06). Four patients received prednisone therapy for Crohn's disease from 3 to 52 weeks before their first manic episode. The authors discuss the relationship of the two illnesses, including possible common provoking factors, the possible role of steroids, and the genetics of the disorders.

Bipolar II disorder in six sisters

Several studies have suggested the utility of separating the type II (BPII) from type I bipolar affective disorder (BPI). The data supporting this suggestion include differences in the course of BPII illness, poorer response of BPII to medications, the higher frequency in BPII patients of non-affective co-morbidity and an increased risk of BPII disorder among relatives of BPII patients. This report of a family in which six sisters and several other family members share the disorder further supports the suggestion that BPII disorder 'breeds true', at least in some families. Since the diagnosis of the BPII disorder is relatively unstable, further study will be needed to establish BPII as distinct from BPI and unipolar disorders. Among others, molecular genetic methods will be useful in the resolution of this issue.

Genetic linkage studies of bipolar affective disorder

Underrecognition and undertreatment of affective disorders constitute a serious public health problem in this country. The recent availability of improved methods of genetic linkage analysis make the definition of the genetic basis of some types of bipolar affective disorders feasible within the foreseeable future.