Genetic factors in moderately severe and mild affective disorders

Review of dysthymia and persistent depressive disorder: history, correlates, and clinical implications

Persistent depressive disorder is a chronic mood disorder that is common and often more disabling than episodic major depression. In DSM-5, the term subsumes several chronic depressive presentations, including dysthymia with or without superimposed major depressive episodes, chronic major depression, and recurrent major depression without recovery between episodes. Dysthymia can be difficult to detect in psychiatric and primary care settings until it intensifies in the form of a superimposed major depressive episode. Although information is scarce concerning the cause of persistent depressive disorder including dysthymia, the causation is likely to be multifactorial. In this narrative Review, we discuss current knowledge about the nosology and neurobiological basis of dysthymia and persistent depressive disorder, emphasising a dimensional perspective based on course for further research. We also review new developments in psychotherapy and pharmacotherapy for persistent depressive disorder, and propose a tailored, modular approach to accommodate its multifaceted nature.

Epidémiologie de la dépression: données récentes. II — Epidémiologie analytique et épidémiologie d’évaluation

Les données provenant d’études récentes concernant l’épidémiologie analytique et l’épidémiologie d’évauation de la dépression sont examinées.

Au sujet de l’épidémiologie analytique, il peut être conclu de la littérature actuellement disponible que les principaux facteurs de risques pour la dépression majeure sont : a) Sociodémographiques, à savoir : être une femme, être jeune, séparé, divorcé, ou avoir des problèmes conjugaux (les auteurs soulignent en particulier que les différences entre les sexes, concernant la dépression, sont réelles et ne sont pas un artefact lié à la façon de relater les troubles ou au comportement vis-à-vis des soins), b) Environnementaux: facteurs prédisposants (les événements de vie qui surviennent durant l'enfance peuvent prédisposer un individu à la dépression à l’âge adulte) et facteurs précipitants (il y a relation entre la survenue d’événements de vie pendant la vie adulte et le début de la dépression), c) Familiaux: il y a une multiblication par 2 à 5 du taux de dépression majeure chez les parents de premier degré de sujets témoins par rapport à es témoins non malades. L’influence de l’hérédité génétique est supportée par des études de jumeaux et des études adoption, mais une large part de la variance ne peut être expliquée, d) Divers: qui concernent le cycle de reproduc- 10n de la femme (la période du post partum entraîne une augmentation du taux de dépression) et les variations saisonneres (pics au printemps et en automne).

En ce qui concerne l'épidémiologie d’évaluation, il est habituel de distinguer prévention primaire, secondaire et teriaie. Leur dessein est respectivement de diminuer l’incidence de la dépression, la prévalence de la dépression et les isques de chronicité et de la récurrence. Les efforts concernant la prévention primaire ne peuvent avoir qu’un effet imité. Dans le domaine de la prévention secondaire, il peut être conclu que beaucoup de dépressifs ne sont pas diaglostiqués ou ne sont pas traités. La prévention tertiaire a pour dessein de limiter deux risques: la chronicité et la récurence. Le premier pourrait être évalué à 15-20% à chaque épisode. Les facteurs de risques principaux seraient la présence un trouble psychiatrique non affectif ou d’une affection physique, une personnalité névrotique et un faible niveau le traitement. Pour le risque de récurrence, on peut considérer qu’entre 50 et 85% des patients ayant fait un épisode lépressif majeur feront au moins un autre épisode de dépression ultérieurement. Les facteurs de risques pourraient re un Stand nombre d’épisodes antérieurs, un antécédent d’épisode maniaque ou d’hypomanie, l’association à un ésordre psychiatrique non affectif ou à une affection physique, une histoire familiale de maladie affective ou un âge e début tardif.

Génétique épidémiologique des troubles de l’humeur: une nouvelle voie de recherches?

Les récents progrès de la biologie moléculaire offrent l’espoir d’une meilleure compréhension de la composante génétique des maladies mentales, la dépression en particulier. L’accès à un nombre quasiment illimité de marqueurs génétiques polymorphes et couvrant le génome, accroît l’efficacité des techniques de liaison génétique (linkage) qui permettent l’étude de la cotransmission des marqueurs génétiques et du trait clinique dans des familles dont plusieurs membres sont malades. D’ores et déjà, en ce qui concerne les troubles de l’humeur, 2 pistes ont été mises en évidence: celle d’une liaison à l’extrémité distale du bras long du chromosome X (Mendlewicz et al., 1987) et celle d’une liaison à l’extrémité du bras court du chromosome 11 (Egeland et al., 1987). Toutefois, ces résultats n’ont pas été constamment répliqués, ce qui soulève le problème de l’hétérogénéité étiologique des troubles dépressifs.

Resequencing three candidate genes discovers seven potentially deleterious variants susceptibility to major depressive disorder and suicide attempts in Chinese

BACKGROUND

To date almost 200 genes were found to be associated with major depressive disorder (MDD) or suicide attempts (SA), but very few genes were reported for their molecular mechanisms. This study aimed to find out whether there were common or rare variants in three candidate genes altering the risk for MDD and SA in Chinese.

METHODS

Three candidate genes (HOMER1, SLC6A4 and TEF) were chosen for resequencing analysis and association studies as they were reported to be involved in the etiology of MDD and SA. Following that, bioinformatics analyses were applied on those variants of interest.

RESULTS

After resequencing analysis and alignment for the amplicons, a total of 34 common or rare variants were found in the randomly selected 36 Hong Kong Chinese patients with both MDD and SA. Among those, seven variants show potentially deleterious features. Rs60029191 and a rare variant located in regulatory region of the HOMER1 gene may affect the promoter activities through interacting with predicted transcription factors. Two missense mutations existed in the SLC6A4 coding regions were firstly reported in Hong Kong Chinese MDD and SA patients, and both of them could affect the transport efficiency of SLC6A4 to serotonin. Moreover, a common variant rs6354 located in the untranslated region of this gene may affect the expression level or exonic splicing of serotonin transporter. In addition, both of a most studied polymorphism rs738499 and a low-frequency variant in the promoter region of the TEF gene were found to be located in potential transcription factor binding sites, which may let the two variants be able to influence the promoter activities of the gene.

CONCLUSIONS

This study elucidated the potentially molecular mechanisms of the three candidate genes altering the risk for MDD and SA. These findings implied that not only common variants but rare variants could make contributions to the genetic susceptibility to MDD and SA in Chinese.

Norwegian Twin Registers and Norwegian Twin Studies — An Overview

The Norwegian Twin Registers include several sets of population-based sub-registers, and covers twin pairs born between 1895 and today. Except for the missing birth years 1960 to 1967, the register is almost complete. Most of the register contains information about both same-sexed and opposite-sexed twin pairs, except for twin pairs born between 1946 and 1960, where only same-sexed twins are registered. In a substantial part of the register, information about zygosity is obtained, mainly by a mailed questionnaire and in some cases supported by DNA testing. These are the birth years 1915 to 1960 and the birth years 1967 to 1979. Zygosity information is further obtained in the different twin studies derived from the twin register. In 1990 the whole register was made available in a computerized form. Several twin studies have been derived from the different parts of the register. In this article, studies from the two earliest parts of the register are reviewed and grouped by recruitment specifics. Finally, future plans for the register and twin studies are discussed.

The spectrum of adjustment disorders: too broad to be clinically helpful

The clinical value of the current Diagnostic and Statistical Manual of Mental Disorders diagnosis of adjustment disorder is controversial. The aim of this article is to review the literature on adjustment disorder and to present suggestions for the improvement of this diagnostic category in future classification systems. The literature utilized for this review was retrieved by MEDLINE (1967 until May 2009) and was supplemented by a manual search of the literature. The analysis of the literature indicates that the diagnosis of adjustment disorder is not characterized by consistent clinical description and prognosis, adequate differentiation from other disorders, or specific psychometric and neurobiologic features. The spectrum of affective disturbances entailed by the diagnosis of adjustment disorder appears to be too broad. A major problem seems to lie in the fact that it is an exclusion diagnosis that overlaps with subthreshold manifestations of mood and anxiety disorders. More precise characterizations of stress-related disturbances are available.

Population-specific functional variant of the TPH2 gene 2755C>A polymorphism contributes risk association to major depression and anxiety in Chinese peripartum women

The rate-limiting enzyme of serotonin biosynthesis, tryptophan hydroxylase 2 (TPH2), is one of the most promising candidate genes for psychiatric disorders. Although evidence strongly suggests that the TPH2 is significant in the etiology of major depression and anxiety disorder, whether it also contributes to the etiology of peripartum major depression and anxiety disorder, a specific subtype influenced considerably by other environmental factors like hormones, is unclear. This study investigated the role of TPH2 in the etiology of peripartum major depression and anxiety disorder in a Han Chinese population in Taiwan. Six single nucleotide polymorphisms were selected from previously profiled genetic information of TPH2 in Han Chinese. A cohort of postpartum Chinese women that included 117 patients with major depression, anxiety disorder, or both and 83 healthy controls were genotyped with selected TPH2 markers. The TPH2 2755A allele was found only in women with peripartum major depression and anxiety disorder (p = 0.043) and exhibited a dominant gene action (p = 0.038) with an estimated disease risk of 1.73. Although the sample size is small, results from this study suggest that the TPH2 C2755A polymorphism may represent a population-specific risk factor for peripartum major depression and anxiety disorder, perhaps by interacting with hormones.

Unipolar depressive disorders have a common genotype

BACKGROUND

The purpose of this study was to estimate the contribution of genetic, common- and unique environmental factors in the aetiology of unipolar major depression (MD), and to investigate whether the unipolar depressive disorders; MD, atypical depression/depression NOS, dysthymia and depressive adjustment disorder can be viewed as various expressions of an underlying genetic commonality.

METHODS

A sample consisting of same-sexed mono- and dizygotic twins was drawn from in- and outpatient hospital registers (N=303). DSM-III-R criteria were assessed by personal interviews. One hundred and forty-three of the probands fulfilled the criteria for one or another unipolar depressive disorder. Cross-tabulations were used to compare concordance rates for MD and different combinations of MD and other unipolar depressive disorders. Correlations in liability and estimations of the heritability (h(2)) with biometrical model fitting were performed.

RESULTS

Concordance rates were higher among MZ- than among DZ pairs for both MD and all the different combinations of MD and other unipolar depressive disorders. Cross-concordance between MD and other unipolar disorders was observed. In all instances, except for the situation when MD was considered alone, the correlations in liability among MZ pairs were more than twice the correlations in liability among DZ pairs. The heritability of MD was 0.42, of MD+atypical depression 0.51, of MD+atypical depression+dysthymia 0.45 and of MD+atypical depression+dysthymia+depressive adjustment disorder 0.46.

LIMITATION

Probands were not sampled from the general population. Most often the same person interviewed both twins in a pair.

CONCLUSION

Unipolar MD is moderately heritable without significant shared family environmental effects. Unipolar depressive disorders taken together are moderately heritable without any detectable shared family environmental effects. The tendency is towards higher heritability estimates for the combined groups compared to MD alone. The study suggests that the disorders in the unipolar depressive spectrum may be different manifestations of the same genetic liability.

Molecular epidemiology of major depressive disorder

Major depressive disorder causes significant morbidity, affecting people's ability to work, function in relationships, and engage in social activities. Moreover, major depressive disorder increases the risk of suicidal ideation, attempted suicide and death by completed suicide. There is evidence that chronic stress can cause major depressive disorder. As for genetic factors, only minor susceptibility genes have been reliably identified. The serotonin system provides a logical source of susceptibility genes for depression, because this system is the target of selective serotonin reuptake-inhibitor drugs that are effective in treating depression. The 5-hydroxytryptamine (serotonin) transporter (5-HTT) has received particular attention because it is involved in the reuptake of serotonin at brain synapses. One common polymorphic variant of the 5-HTT-linked polymorphic region (5-HTTLPR), which affects the promoter of the 5-HTT gene, causes reduced uptake of the neurotransmitter serotonin into the presynaptic cells in the brain. The authors discussed the relationship between genetic polymorphisms and major depressive disorder, with special emphasis on the 5-HTTTLPR polymorphism. As the 5-HTTLPR polymorphism was significantly associated with an increased risk of major depressive disorder, the 5-HTT gene may be a candidate for a major depressive disorder susceptibility gene. As major depressive disorder is a multifactorial disease, an improved understanding of the interplay of environmental and genetic polymorphisms at multiple loci may help identify individuals who are at increased risk for major depressive disorder. Hopefully, in the future we will be able to screen for major depressive disorder susceptibility by using specific biomarkers.

Heritability of bipolar spectrum disorders. Unity or heterogeneity?

BACKGROUND

The purpose of this study was to investigate whether the three disorders in the bipolar spectrum, Bipolar I disorder, Bipolar II disorder and Cyclothymia, are various expressions of an underlying genetic commonality.

METHOD

A sample consisting of same-sexed mono (MZ)- and dizygotic (DZ) twins were identified using hospital and outpatient registers (N=303). DSM-III-R criteria were assessed by personal interviews. Cross tabulations were used to compare concordance rates for different definitions of the bipolar spectrum. Correlations in liability and estimation of the heritability (h) with biometrical model fitting were performed.

RESULTS

Concordance rates were higher among MZ- than DZ pairs for all the single diagnoses and main combinations of diagnoses. Cross-concordance between different diagnoses was observed. The heritability of Bipolar I was .73, of Bipolar I+II .77 and of Bipolar I+II+Cyclothymia .71.

LIMITATION

Probands were not sampled from the general population. Most often the same person interviewed both twins in a pair. The statistical power was restricted in some sub-analyses.

CONCLUSION

The 'Bipolar Spectrum' category consisting of Bipolar I disorder, Bipolar II disorder and Cyclothymia constitute one entity with high heritability without detectable shared family environmental effects. Future genetic and clinical work might consider that all variants of the bipolar spectrum are an expression of one underlying genetic liability.

Restoring melancholia in the classification of mood disorders

The present DSM criteria for major depression poorly identify samples for treatment selection, prognosis, and assessments of pathophysiology. Melancholia, in contrast, is a disorder with definable clinical signs that can be verified by laboratory tests and treatment response. It identifies more specific populations than the present system and deserves individual identification in psychiatric classification. Its re-introduction will refine diagnosis, prognosis, treatment selection, and studies of pathophysiology of a large segment of the psychiatrically ill.

Phosphodiesterase genes are associated with susceptibility to major depression and antidepressant treatment response

Cyclic nucleotide phosphodiesterases (PDEs) constitute a family of enzymes that degrade cAMP and cGMP. Intracellular cyclic nucleotide levels increase in response to extracellular stimulation by hormones, neurotransmitters, or growth factors and are down-regulated through hydrolysis catalyzed by PDEs, which are therefore candidate therapeutic targets. cAMP is a second messenger implicated in learning, memory, and mood, and cGMP modulates nervous system processes that are controlled by the nitric oxide (NO)/cGMP pathway. To investigate an association between genes encoding PDEs and susceptibility to major depressive disorder (MDD), we genotyped SNPs in 21 genes of this superfamily in 284 depressed Mexican Americans who participated in a prospective, double-blind, pharmacogenetic study of antidepressant response, and 331 matched controls. Polymorphisms in PDE9A and PDE11A were found to be associated with the diagnosis of MDD. Our data are also suggestive of the association between SNPs in other PDE genes and MDD. Remission on antidepressants was significantly associated with polymorphisms in PDE1A and PDE11A. Thus, we found significant associations with both the diagnosis of MDD and remission in response to antidepressants with SNPs in the PDE11A gene. We show here that PDE11A haplotype GAACC is significantly associated with MDD. We conclude that PDE11A has a role in the pathophysiology of MDD. This study identifies a potential CNS role for the PDE11 family. The hypothesis that drugs affecting PDE function, particularly cGMP-related PDEs, represent a treatment strategy for major depression should therefore be tested.

The genetics of depression: a review

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

Association of a D2S2944 allele with depression specifically among those with substance abuse or antisocial personality

Associations have previously been reported between a 124-bp allele at D2S2944 and recurrent, early-onset depression in women. These earlier reports also noted but did not emphasize a possible association between this allele and alcohol-specific depression. We have analyzed the Iowa Adoption Study data to test this association. D2S2944 allele typing was available for 247 subjects from the Iowa Adoption Studies. Information on lifetime affective, alcohol, drug, and antisocial personality (ASPD) disorders was available from a structured interview. We used logistic regression to analyze adjusted and interactive D2S2944 associations with depression. Controlling other risk factors, the 124-bp allele had a strong association with DSM-IV major depression specific to those with histories of alcohol abuse/dependence and/or ASPD. (Overlap between the two prevented further specification of the interaction.) The association was not gender-specific and was not limited to alcohol-related depressive episodes. This relationship appears stronger than the D2S2944 association previously reported for early-onset depression in women. We note that, in combination with additional liabilities towards depression in women and alcoholism/sociopathy in men, the 124-bp allele may provide a basis for the phenomenon of depressive spectrum illness proposed by Winokur.

Bipolar affective disorder: advances in genetics and mood-stabilising medication

The lifetime prevalence of bipolar affective disorder is between 1 % and 2%. This educational review paper focuses on two areas of interest and relevance to trainees preparing for the membership examination of the Royal College of Psychiatrists: (a) advances in the genetics of bipolar affective disorder; and (b) mood-stabilising medication in bipolar affective disorder.

Changes in children's behavior and costs for service use associated with parents' response to treatment for dysthymia

OBJECTIVE

This study examined differences in children's behavior and expenditures for health and social services used when their parents with dysthymia did or did not respond to antidepressant therapy.

METHOD

Children ages 4 to 16 years of consenting parents enrolled in a treatment trial for dysthymia who did and did not respond to treatment were compared at baseline and 24 months. The responder was a parent with at least a 40% reduction in his or her baseline depressive symptoms using the Montgomery Asberg Depression Rating Scale. Children's behavior was measured using the Child Behavior Checklist, and expenditures for health and social services use was measured in Canadian dollars using the Health and Social Service Utilization Questionnaire.

RESULTS

Children of parents with dysthymia who responded to treatment had significantly greater reductions in emotional symptoms at 2-year follow-up than children of nonresponders, along with an economically important (not statistically significant) reduction in expenditures for health and social services use.

CONCLUSIONS

Reductions in parental symptoms of dysthymia may be associated with reductions in childhood behavioral problems and in expenditures for the child's use of services.

Children of a cohort of depressed patients 25 years on: identifying those at risk

OBJECTIVE

Factors associated with psychological outcome in children of patients with depression have been examined piecemeal, with emphasis on young rather than adult children. We hypothesized that psychological morbidity in adult children of patients with depression would be associated with characteristics of the children, their parents and their family relationships.

METHOD

Factors predicting psychopathology in children (n = 94) of a cohort of patients with depression, admitted to a teaching hospital 25 years earlier, were examined using logistic regression.

RESULTS

Psychological morbidity in children was predicted by their being younger at parent's admission, their perception of the depressed parent as more controlling and chronicity of the parent's depression. Correlations between child characteristics, parent illness and family relationship variables showed systemic interactions between parental illness, child psychopathology and family relationships.

CONCLUSION

Chronicity (though neither recurrence nor severity) of parent depression and younger children's age at the time of parental admission for depression were associated with psychological morbidity in the children in adulthood. The interaction between child psychopathology, parental illness and family relationships emphasizes the need for a systemic, family focus in the treatment of depression.

Association of tryptophan hydroxylase gene polymorphism with depression, anxiety and comorbid depression and anxiety in a population-based sample of postpartum Taiwanese women

Depression and anxiety disorders often coexist clinically and both are known to have a genetic basis, but the mode of inheritance is too complicated to be determined so far. Serotonin is the biogenic amine neurotransmitter most commonly associated with depression and anxiety. Since tryptophan hydroxylase (TPH1) is the rate-limiting enzyme in serotonin biosynthesis, its role in the pathophysiology of these psychiatric diseases has been intensively studied. In this study, we examined whether polymorphism of the TPH1 gene is related to the etiology of major depression, anxiety and comorbid depression and anxiety. Five single nucleoside polymorphisms of the TPH1 gene were studied in a population-based sample of postpartum Taiwanese women consisting of 120 subjects with depression or/and anxiety and 86 matched normal controls. A significant difference (P = 0.0107) in genotype frequency for the T27224C polymorphism was found between the comorbid and normal groups, and risk analysis showed that the C allele conferred a strong protective effect (odds ratio = 0.27; 95% confident interval = 0.11-0.7). Three-allele haplotypes involving T27224C polymorphism were constructed and haplotype associations between particular haplotype combinations and various diseases identified. However, the associations were weak and the overall haplotype frequency profiles in all groups were similar. The results suggest that depression, anxiety, and comorbid depression and anxiety disorders may have related etiologies. In addition, this study suggests that the TPH1 gene might play a role in the pathogenesis of these closely related disorders.

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

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

A genome-wide scan of symptom dimensions in bipolar disorder pedigrees of adult probands

Although twin and adoption show bipolar disorder (BP) has a strong genetic component, few chromosomal regions have been consistently implicated by molecular genetic studies. To address this issue, we sought to determine if quantitative dimensions of bipolar disorder symptoms would be useful for detecting genes that underlie the susceptibility to bipolar disorder. Subjects were 520 individuals diagnosed with bipolar I, bipolar II or schizoaffective disorder, bipolar type who had participated in the NIMH genetics initiative for bipolar disorder. We constructed symptom scores from 29 psychiatric symptoms recorded in the Diagnostic Interview for Genetic Studies (DIGS). Principal components factor analysis followed by a varimax rotation was used to extract symptom dimensions. Factor scores were calculated for all genotyped individuals in the sample, regardless of affection status. Heritable factors were used in a variance-components linkage analysis, which utilized the exact likelihoods of allele-sharing identical-by-descent for each pair of relatives within each pedigree. The principal components factor analysis resulted in five independent dimensions: depressed state, psychosis, sleep disturbances, psychomotor acceleration, and irritability. Two factors were significantly heritable: depression (h2=0.53, p<0.001) and irritable vs. euphoric mania (h2=0.35, p=0.03). These were subsequently used in a linkage analysis that resulted in LOD scores of <2.0, which are not statistically significant. The five constructs developed through factor analysis appear to be consistent with previous factor analyses. Notably, only the dimensions associated with the type of mood disturbance showed high heritability, which suggests that careful measurements of depression, euphoria and irritability may be particularly useful in clarifying the genetic etiology of bipolar disorder in future studies.

X-box binding protein 1 (XBP1) C−116G polymorphisms in bipolar disorders and age of onset

X-box binding protein 1 (XBP1), a critical gene in the endoplasmic reticulum stress response, is located on chromosome 22q12, which has been linked with bipolar disorders in several studies. Recently, associations have been reported between a polymorphism (-116C --> G) in the promoter region of XBP1, and bipolar disorders in both case-control study and family-based association study, however, this finding is not yet confirmed by other research using independent sample populations. To replicate this finding and determine the association between onset age of bipolar disorders and the XBP1 C--116G polymorphism, we investigated the prevalence of this polymorphism in a Chinese population (153 bipolar disorder patients and 174 controls). We were unable, however, to demonstrate a significant association between the C--116G polymorphism and bipolar disorders (P = 0.674 for genotype and P = 0.436 for allele frequency) or age at onset (P = 0.563). Further, no association was demonstrated between this polymorphism and family history in bipolar disorder patients. These negative findings suggest that the XBP1 C--116G polymorphism does not play a major role in the pathogenesis of bipolar disorders in Chinese populations.

The impact of high neuroticism in parents on children's psychosocial functioning in a population at high risk for major affective disorder: a family-environmental pathway of intergenerational risk

Behavioral genetic studies indicate that nongenetic factors play a role in the development of bipolar and major depressive disorders. The trait of neuroticism is common among individuals with major affective disorders. We hypothesized that high neuroticism among parents affects the family environment and parenting practices and thereby increases the risk of psychosocial problems among offspring. This hypothesis is tested in a sample of participants at high and low risk for major affective disorders, which contained parents with bipolar disorder (55), major depression (21), or no mental disorder (148) and their 146 children between 4 and 14 years of age. Parents with high neuroticism scores were characterized by low psychosocial functioning, poor parenting, more dependent stressful life events, and the use of more emotion-focused and less task-oriented coping skills. High neuroticism in parents was associated with internalizing and externalizing problems among the children, as assessed by parent and teacher ratings on the Child Behavior Checklist and clinician ratings. The results suggest that high neuroticism in parents with major affective disorders is associated with inadequate parenting practices and the creation of a stressful family environment, which are subsequently related to psychosocial problems among the offspring.

Family, twin, and adoption studies of bipolar disorder

Family, twin, and adoption studies have been essential in defining the genetic epidemiology of bipolar disorder over the past several decades. Family studies have documented that first-degree relatives of affected individuals have an excess risk of the disorder, while twin studies (and to a lesser extent, adoption studies) suggest that genes are largely responsible for this familial aggregation. We review these studies, including the magnitude of familial risk and heritability estimates, efforts to identify familial subtypes of bipolar disorder, and the implications of family/genetic data for validating nosologic boundaries. Taken together, these studies indicate that bipolar disorder is phenotypically and genetically complex.

Predisposition locus for major depression at chromosome 12q22-12q23.2

Major depression disorder is a common psychiatric disease with a major economic impact on society. In many cases, no effective treatment is available. The etiology of major depression is complex, but it is clear that the disease is, to a large extent, determined genetically, especially among individuals with a familial history of major depression, presumably through the involvement of multiple predisposition genes in addition to an environmental component. As a first step toward identification of chromosomal loci contributing to genetic predisposition to major depression, we have conducted a genomewide scan by using 628 microsatellite markers on 1,890 individuals from 110 Utah pedigrees with a strong family history of major depression. We identified significant linkage to major depression in males at marker D12S1300 (multipoint heterogeneity LOD score 4.6; P=.00003 after adjustment for multiple testing). With additional markers, the linkage evidence became highly significant, with the multipoint heterogeneity LOD score at marker D12S1706 increasing to 6.1 (P=.0000007 after adjustment for multiple testing). This study confirms the presence of one or more genes involved in psychiatric diseases on the q arm of chromosome 12 and provides strong evidence for the existence of a sex-specific predisposition gene to major depression at 12q22-q23.2.

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

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

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

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

Linkage analysis in psychiatric disorders: the emerging picture

Gene finding in genetically complex diseases has been difficult as a result of many factors that have diagnostic and methodologic considerations. For bipolar disorder and schizophrenia, numerous family, twin, and adoption studies have identified a strong genetic component to these behavioral psychiatric disorders. Despite difficulties that include diagnostic differences between sample populations and the lack of statistical significance in many individual studies, several promising patterns have emerged, suggesting that true susceptibility loci for schizophrenia and bipolar disorder may have been identified. In this review, the genetic epidemiology of these disorders is covered as well as linkage findings on chromosomes 4, 12, 13, 18, 21, and 22 in bipolar disorder and on chromosomes 1, 6, 8, 10, 13, 15, and 22 in schizophrenia. The sequencing of the human genome and identification of numerous single nucleotide polymorphisms (SNP) should substantially enhance the ability of investigators to identify disease-causing genes in these areas of the genome.

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

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

Depression and chronic diabetic foot disability. A case report of suicide

Evidence at the scene of death and the postmortem examination led the pathologist to conclude suicide by intentional insulin overdose. The examination was conducted one day after the patient's death. The amount of insulin injected is not known, but levels of insulin in the vitreous gel were extremely high. While glucose and insulin are more stable in vitreous than in postmortem blood, the longer the delay between death and sample collection, the greater the uncertainty of the exact concentrations of substances at the time of death [42]. Patients with diabetes may have at their disposal the resources to end their lives; misuse of insulin and suicide by insulin overdose are presumably underreported events. Not only do diabetics have insulin available, but they may also have narcotics, tricyclic antidepressants or other drugs that are toxic at high doses. Even in the absence of depression, all patients with diabetes face multiple emotional issues related to the diagnosis and course of the disease. Diabetes often requires significant lifestyle changes, such as diet and physical activity, upon its diagnosis. Patients face the possibility of long-term, possibly debilitating, complications: vision loss, sexual dysfunction, and amputation. Any podiatrist who treats a large number of diabetic patients will encounter the situation of a patient at risk of losing a limb. A patient may consciously or unconsciously view amputation as punishment; limb loss interferes physically with bodily function and has extensive emotional consequences as well. It is important for patients to be involved with a healthcare team (including primary care physician, nurse educator, ophthalmologist, and podiatrist) that provides support throughout their lives [3]. As learned early on in podiatry school, podiatric physicians don't treat feet; they treat patients who have foot problems. It is as important to know when to refer a patient to the primary care physician or a psychiatrist for mental health complaints as it is to know when to refer a patient to an orthopedic surgeon for hip pain or to an ophthalmologist for vision problems. We do not propose that this patient's diabetic foot disease was the direct cause of his depression and suicide; however, the prevalence of depression in the general population and its even higher rates in patients with chronic medical illness require awareness of these problems by all members of the medical profession.

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

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

Family, twin, and adoption studies of bipolar disease

Bipolar disease features states of severe depression that usually fluctuate with at least one episode of intense elation or mania. It is a disorder that has been thought for some time to have a heritable component. The lifetime prevalence of bipolar disease in the general population is approximately 1%. In contrast, family studies have shown the approximate lifetime risk of a first-degree relative of a bipolar proband to be 5% to 10%. Moreover, studies of monozygotic twins show that their risk of contracting the disease is as much as 75 times greater than that for the general population. In addition, adoption studies have demonstrated that biological relatives of bipolar patients are substantially more likely to have the disorder than are adoptive relatives.

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

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

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

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

Polymorphism of CTLA-4 gene for major depression in the Korean population

This study was carried out to verify the relationship between major depression and cytotoxic T lymphocyte antigen-4 (CTLA-4), which is related to immunological function such as T-cell regulation. Among the Korean patients diagnosed with major depression according to DSM-IV, 77 patients without neurological illness, hormonal disorder, or comorbid mental illness were selected. The stored data on 149 normal Koreans from the Catholic Hemopoietic Stem Cell Bank of Korea, were used as a control group. The data of the Korean control group were compared with those of the studies of different ethnic groups. DNA was extracted from whole blood using proteinase K and the exon 1 region of CTLA-4 gene was amplified by polymerase chain reaction. Gene typing was performed using single strand conformation polymorphism. The results were assessed. There were significant differences in frequencies of CTLA-4 allele (chi2 = 56.472, d.f. = 1, P = 0.001) and genotype (chi2 = 46.132, d.f. = 2, P = 0.001) between the Korean population and the Caucasian population. However, we could not find any differences between the Korean and the Japanese population. There were no significant differences in genotype frequencies of CTLA-4*G/G, CTLA-4*G/A, and CTLA-4*A/A between the patients with major depression and the control group in the Korean population (48.1% vs. 46.3%, 41.6% vs 39.6%, 10.3% vs. 14.1%, respectively). There were no significant differences in allelic frequencies of CTLA-4*G and CTLA-4*A between the patients with major depression and the control group in the Korean population (68.8% vs. 66.1%, 31.2% vs. 33.9%, respectively). Although the present study produced negative results for the association of exon 1 polymorphism of CTLA-4 gene with major depression in the Korean population, further systematic research, including diverse clinical variables, would be necessary.

Assessing the heritability of attentional networks

BACKGROUND

Current efforts to study the genetics of higher functions have been lacking appropriate phenotypes to describe cognition. One of the problems is that many cognitive concepts for which there is a single word (e.g. attention) have been shown to be related to several anatomical networks. Recently we have developed an Attention Network Test (ANT) that provides a separate measure for each of three anatomically defined attention networks. In this small scale study, we ran 26 pairs of MZ and DZ twins in an effort to determine if any of these networks show sufficient evidence of heritability to warrant further exploration of their genetic basis.

RESULTS

The efficiency of the executive attention network, that mediates stimulus and response conflict, shows sufficient heritability to warrant further study. Alerting and overall reaction time show some evidence for heritability and in our study the orienting network shows no evidence of heritability.

CONCLUSIONS

These results suggest that genetic variation contributes to normal individual differences in higher order executive attention involving dopamine rich frontal areas including the anterior cingulate. At least the executive portion of the ANT may serve as a valid endophenotype for larger twin studies and subsequent molecular genetic analysis in normal subject populations.

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.

Genetics of bipolar disorder

Bipolar disorder (also known as manic depressive illness) is a complex genetic disorder in which the core feature is pathological disturbance in mood (affect) ranging from extreme elation, or mania, to severe depression usually accompanied by disturbances in thinking and behaviour. The lifetime prevalence of 1% is similar in males and females and family, twin, and adoption studies provide robust evidence for a major genetic contribution to risk. There are methodological impediments to precise quantification, but the approximate lifetime risk of bipolar disorder in relatives of a bipolar proband are: monozygotic co-twin 40-70%; first degree relative 5-10%; unrelated person 0.5-1.5%. Occasional families may exist in which a single gene plays the major role in determining susceptibility, but the majority of bipolar disorder involves the interaction of multiple genes (epistasis) or more complex genetic mechanisms (such as dynamic mutation or imprinting). Molecular genetic positional and candidate gene approaches are being used for the genetic dissection of bipolar disorder. No gene has yet been identified but promising findings are emerging. Regions of interest identified in linkage studies include 4p16, 12q23-q24, 16p13, 21q22, and Xq24-q26. Chromosome 18 is also of interest but the findings are confusing with up to three possible regions implicated. To date most candidate gene studies have focused on neurotransmitter systems influenced by medication used in clinical management of the disorder but no robust positive findings have yet emerged. It is, however, almost certain that over the next few years bipolar susceptibility genes will be identified. This will have a major impact on our understanding of disease pathophysiology and will provide important opportunities to investigate the interaction between genetic and environmental factors involved in pathogenesis. This is likely to lead to major improvements in treatment and patient care but will also raise important ethical issues that will need to be addressed.

Genética e fisiopatologia dos transtornos depressivos

Fatores genéticos, neurobiológicos e ambientais participam da gênese das depressões. Esta breve revisão visa enfatizar os estudos sobre os aspectos genéticos, neuroquímicos e neuroanatômicos na etiologia e fisiopatologia das depressões e suas implicações no desenvolvimento de novos tratamentos. Procura-se enfatizar as limitações encontradas até o momento na tentativa do estabelecimento de uma etiopatogenia comum às depressões, principalmente em função da dificuldade no diagnóstico e da heterogeneidade na fenomenologia do episódio agudo e no curso longitudinal. Perspectivas para futuras pesquisas também são apresentadas.

"Mother's child" and "father's child" among twins. A longitudinal twin study from pregnancy to 21 years age, with special reference to development and psychiatric disorders

234 pairs of twins were studied from pregnancy up to 21 years of age on the basis of records from maternity hospitals, neonatal wards and children's health centres and questionnaires filled in by the parents when the twins were aged 2-10 and 12-21 years, and by the twins themselves at age 12-21. 74 twins were personally interviewed about human relationships in their families and with the Present State Examination (PSE) at age 15-21. When the evaluation of parental preference was made by the parents, the mother's favourites had learned to speak earlier and were more often the psychic leader of the pair, but they more often had sleeping difficulties and other psychosomatic symptoms in adolescence. They were most often scored in class 2-3, non-specific neurotic symptoms in the PSE, but none of them was placed in the higher classes of possible or probable psychiatric disorder. Mothers seem to develop a tighter affectionate bond towards their favourites than do fathers, thus inducing a good basic trust and faster language acquisition in childhood, but probably also transient non-specific neurotic symptoms in adolescence in face of the developmental task of entering autonomous adulthood. The father's favorites were more often the physical leaders of the pair, showed less accident proneness and most often reported tendencies towards autonomy from their co-twins, thus indicating that the fathers' attitudes may be more encouraging towards independence. As the least psychosomatic symptoms were seen in twins in the intermediate position regarding parental preference, it seems reasonable that the division of twins between parents on the grounds of favouritism should not be strict.

Inherited Hypohedonia Leads to Learned Helplessness: A Conjecture Updated

The reformulated learned helplessness theory posits depressogenic explanatory style (DES) as a vulnerability factor in depression. Early-life adversity has been suggested as the source of DES, but this is contradicted by empirically established features of the learned helplessness phenomenon itself and by the evidence for human resilience in the face of adversity. This article extends a conjecture first advanced by P. E. Meehl (1975) and argues that an inherited defect in hedonic capacity would be sufficient to produce DES by causing intermittent schedules of reinforcement to be experienced as extinction schedules, resulting in a pervasive and unremitting sense of helplessness. This proposed hedonic defect also provides a means for integrating the original and reformulated versions of learned helplessness theory and for integrating learned helplessness with emerging research and theory on the biology of vulnerability to depression.

Genetic and non-genetic subtypes of major depressive disorder

BACKGROUND

We aimed to examine the hypotheses that major depression is aetiologically heterogeneous consisting of a mixture of 'genetic' and 'non-genetic' forms or, alternatively, a mixture of one form that is 'pure' depression and another that has a familial relationship with alcohol dependency or other disorders.

METHOD

One hundred and eleven twin pairs (44 monozygotic, 67 dizygotic) where the proband had received treatment for DSM-IV major depression were ascertained via a hospital register. Family history information on parents and siblings was obtained from the proband, co-twin or both. Diagnoses on parents and siblings were made blind to twin zygosity or concordance and compared in the relatives of concordant versus discordant twins.

RESULTS

The lifetime prevalence and age-corrected risk of depression were no different in the relatives of concordant and discordant twin pairs. There was a marginally significant increase in the rate of alcohol abuse or dependence among the relatives of concordant twins but no difference between concordant and discordant pairs in respect of other axis I diagnosis among family members.

CONCLUSIONS

The results argue against genetic heterogeneity and suggest that major depression cannot usefully be divided into genetic and non-genetic forms or into 'pure' depression and depression associated with other disorders such as alcohol dependency.

Generalized anxiety disorder and its comorbidities: disputes at the boundaries

This theoretical paper reviews the status of generalized anxiety disorder (GAD) and the Axis I and Axis II disorders with which it is often comorbid. Differences in comorbidity between the epidemiological and clinical literatures are discussed. Special attention is given to panic disorder, the symptoms of which are similar to those of GAD. The boundaries of GAD and its relationship to other Axis I disorders and to Axis II disorders raise important implications for its classification.

Genetic segregation analysis of early-onset recurrent unipolar depression

Major depression is a relatively common psychiatric disorder that can be quite debilitating. Family, twin, and adoption studies indicate that unipolar depression has both genetic and environmental components. Early age at onset and recurrent episodes in the proband each increase the familiarity of the illness. To investigate the potential genetic underpinnings of the disease, we have performed a complex segregation analysis on 832 individuals from 50 multigenerational families ascertained through a proband with early-onset recurrent unipolar major depression. The analysis was conducted by use of regressive models, to test a variety of hypotheses to explain the familial aggregation of recurrent unipolar depression. Analyses were conducted under two alternative definitions of affection status for the relatives of probands: (1) "narrow," in which relatives were assumed to be affected only if they were diagnosed with recurrent unipolar depression; and (2) "broad," in which relatives were assumed to be affected if diagnosed with any major affective illness. Under the narrow-definition assumption, the model that best explains these family data is a transmitted (although non-Mendelian) recessive major effect with significant residual parental effects on affection status. Under the broad-definition assumption, the best-fitting model is a Mendelian codominant major locus with significant residual parental and spousal effects.

Do psychotic, minor and intermittent depressive disorders exist on a continuum?

The following paper uses information from a family study and 10-year follow-up of probands with unipolar depression to describe relationships between psychotic and non-psychotic major depressive disorder (MDD) and, in turn, between psychotic MDD and minor or intermittent depressive disorders. Probands began follow-up as they sought treatment for MDD at any of five participating academic centers. Follow-up evaluations then occurred at 6-month intervals for 5 years and then annually for an additional 5 years. Two-thirds of the probands also entered a family study in which raters attempted direct interviews of all available adult first-degree relatives. Findings that individual symptoms comprising the endogenous MDD subtype had higher severity ratings, that the full MDD syndrome was present for a greater number of weeks in each year of follow-up, and that time to new episodes of MDD were shorter, all indicated that patients with psychotic features had a severe variant of MDD. An increased familial risk for psychotic MDD per se, and a sustained tendency for psychotic features to recur, indicated an important discontinuity, however. The increase in morbidity over time which characterized psychotic patients manifested in the full MDD syndrome, but not in mild MDD, minor or intermittent depressive syndromes. These milder syndromes tended to be more prominent over time among patients who began with non-psychotic MDD. This fails to support a continuum spanning both psychotic MDD and the mild, subsyndromal forms of unipolar depression.