Adoption study supporting genetic transmission in manic--depressive illness

The Nature of the Familial Risk for Psychosis in Bipolar Disorder

BACKGROUND AND HYPOTHESIS

To clarify whether the familial liability to psychosis associated with bipolar disorder (BD) is nonspecific or has a greater effect on risk for psychosis in cases with prominent mood symptoms and/or a remitting course.

STUDY DESIGN

We examined, in 984 809 offspring raised in intact families in Sweden, born 1980-1996 and followed-up through 2018, by multivariable Cox proportional hazards regression, risk in offspring of parents with BD for 7 psychotic disorders: Psychotic MD (PMD), psychotic BD (PBD), schizoaffective disorder (SAD), acute psychoses, psychosis NOS, delusional disorder (DD) and schizophrenia (SZ). Diagnoses were obtained from national registers.

STUDY RESULTS

In the offspring of BD parents, the hazard ratios (HR) for these 7 disorders formed an inverted U-shaped curve, rising from 2.98 for PMD, to peak at 4.49 for PBD and 5.25 for SAD, and then declining to a HR of 3.48 for acute psychoses and 3.22 for psychosis NOS, to a low of 2.19 for DD and 2.33 for SZ. A similar pattern of risks was seen in offspring of mothers and fathers affected with BD and in offspring predicted from age at onset in their BD parent.

CONCLUSIONS

The BD-associated risk for psychosis impacts most strongly on mood disorders, moderately on episodic psychotic syndromes, and least on chronic psychotic disorders. These results support prior clinical studies suggesting a qualitative difference in the familial substrate for psychosis occurring in BD and SZ.

Functional genomic analysis delineates regulatory mechanisms of GWAS-identified bipolar disorder risk variants

BACKGROUND

Genome-wide association studies (GWASs) have identified multiple risk loci for bipolar disorder (BD). However, pinpointing functional (or causal) variants in the reported risk loci and elucidating their regulatory mechanisms remain challenging.

METHODS

We first integrated chromatin immunoprecipitation sequencing (ChIP-Seq) data from human brain tissues (or neuronal cell lines) and position weight matrix (PWM) data to identify functional single-nucleotide polymorphisms (SNPs). Then, we verified the regulatory effects of these transcription factor (TF) binding-disrupting SNPs (hereafter referred to as "functional SNPs") through a series of experiments, including reporter gene assays, allele-specific expression (ASE) analysis, TF knockdown, CRISPR/Cas9-mediated genome editing, and expression quantitative trait loci (eQTL) analysis. Finally, we overexpressed PACS1 (whose expression was most significantly associated with the identified functional SNPs rs10896081 and rs3862386) in mouse primary cortical neurons to investigate if PACS1 affects dendritic spine density.

RESULTS

We identified 16 functional SNPs (in 9 risk loci); these functional SNPs disrupted the binding of 7 TFs, for example, CTCF and REST binding was frequently disrupted. We then identified the potential target genes whose expression in the human brain was regulated by these functional SNPs through eQTL analysis. Of note, we showed dysregulation of some target genes of the identified TF binding-disrupting SNPs in BD patients compared with controls, and overexpression of PACS1 reduced the density of dendritic spines, revealing the possible biological mechanisms of these functional SNPs in BD.

CONCLUSIONS

Our study identifies functional SNPs in some reported risk loci and sheds light on the regulatory mechanisms of BD risk variants. Further functional characterization and mechanistic studies of these functional SNPs and candidate genes will help to elucidate BD pathogenesis and develop new therapeutic approaches and drugs.

Shared postulations between bipolar disorder and polycystic ovary syndrome pathologies

INTRODUCTION

Women with bipolar disorder (BD) present a high prevalence of polycystic ovary syndrome (PCOS) and other reproductive disorders even before diagnosis or treatment of the disease. Postulations on the potential molecular mechanisms of comorbid PCOS in women with BD remain limited to influence of medications and need further extension.

OBJECTIVES

This review focuses on evidence suggesting that common metabolic and immune disorders may play an important role in the development of BD and PCOS.

RESULTS

The literature covered in this review suggests that metabolic and immune disorders, including the dysfunction of the hypothalamic-pituitary-adrenal axis, chronic inflammatory state, gut microbial alterations, adipokine alterations and circadian rhythm disturbance, are observed in patients with BD and PCOS. Such disorders may be responsible for the increased prevalence of PCOS in the BD population and indicate a susceptibility gene overlap between the two diseases. Current evidence supports postulations of common metabolic and immune disorders as endophenotype in BD as well as in PCOS.

CONCLUSIONS

Metabolic and immune disorders may be responsible for the comorbid PCOS in the BD population. The identification of hallmark metabolic and immune features common to these two diseases will contribute to the clarification of the effect of BD on the reproductive endocrine function and development of symptomatic treatments targeting the biomarkers of the two diseases.

Early detection of bipolar disorders and treatment recommendations for help-seeking adolescents and young adults: Findings of the Early Detection and Intervention Center Dresden

Background

Early identification and intervention of individuals with risk factors for or subtle prodromal symptoms of bipolar disorders (BD) may improve the illness course and prevent adverse long-term consequences.

Methods

We examined sociodemographic, clinical and psychopathological characteristics of help-seeking adolescents and young adults who consulted the Early Detection and Intervention Center Dresden at the University of Dresden (Germany) and presented with or without pre-defined at-risk criteria for BD. The standardized diagnostic procedure for all help-seeking youth included a comprehensive psychiatric history and a structured clinical interview. When BD at-risk state was suspected, early detection instruments (EPIbipolar, BPSS-FP) were applied. Treatment recommendations were formulated in multi-professional case conferences.

Results

Out of 890 help-seeking persons between 05/2009 and 04/2018, 582 (65%) completed the diagnostic process. Of these, 24 (4%) had manifest BD and 125 (21%) fulfilled at-risk BD criteria (age = 23.9 ± 0.6 years, female = 62%). Of the pre-defined main risk factors, family history for BD was reported in 22% of the at-risk persons, (hypo-)mania risk state in 44%, and increasing cyclothymic mood swings with increased activity in 48%. The most common secondary risk factors were decreased psychosocial functioning (78%), lifetime diagnosis of depressive disorder (67%) and specific sleep/circadian rhythm disturbances (59%). Substance use was very common in subjects at-risk for BD (cannabis = 50%, alcohol = 33%) and highest in patients with BD (cannabis = 75%, alcohol = 40%). Psychiatric treatment history, including psychopharmacological therapy, was similar between the groups, while treatment recommendations differed, with more advice for psychotherapy and antidepressants in the at-risk group with a lifetime diagnosis of depression and more advice for specialized BD treatment including mood stabilizers in patients with BD.

Conclusion

This analysis on the phenomenology of different BD at-risk stages suggests that early detection of individuals presenting with suggested risk factors for the development of BD is feasible in help-seeking young people. Future research should further develop/test stage-specific prevention and early targeted intervention approaches that were described in a naturalistic setting.

Translational genomics and beyond in bipolar disorder

Genome-wide association studies (GWAS) have revealed multiple genomic loci conferring risk of bipolar disorder (BD), providing hints for its underlying pathobiology. However, there are still remaining questions to answer. For example, discordance exists between BD heritability estimated with earlier epidemiological evidence and that calculated based on common GWAS variations. Where is the "missing heritability"? How can we explain the biology of the disease based on genetic findings? In this review, we summarize the accomplishments and limitations of current BD GWAS, and discuss potential reasons for the "missing heritability." In addition, progresses of research for the biological mechanisms underlying BD genetic risk using brain tissues, reprogrammed cells, and model animals are reviewed. While our knowledge of BD genetic basis is significantly promoted by these efforts, the complexities of gene regulation in the genome, the spatial-temporal heterogeneity during brain development, and the limitations of different experimental models should always be considered. Notably, several genes have been widely studied given their relatively well-characterized involvement in BD (e.g., CACAN1C and ANK3), and findings of these genes are summarized to both outline possible biological mechanisms of BD and describe examples of translating GWAS discoveries into the pathophysiology.

An Extended Swedish National Adoption Study of Bipolar Disorder Illness and Cross-Generational Familial Association With Schizophrenia and Major Depression

IMPORTANCE

Information about how risk for bipolar disorder is transmitted across generations and how parental risk for bipolar disorder relates to their children's risk for schizophrenia and major depression is limited.

OBJECTIVE

To evaluate the sources of parent-offspring transmission of bipolar disorder and its familial cross-generational association with schizophrenia and major depression.

DESIGN, SETTING, AND PARTICIPANTS

Parents and offspring (born 1960-1990) from 4 family types were ascertained from Swedish national samples: intact (offspring, n = 2 175 259), not-lived-with biological father (n = 152 436), lived-with stepfather (n = 73 785), and adoptive (n = 15 624). Data analysis was conducted from October 28, 2019, to January 8, 2020.

EXPOSURES

Three sources of parent-offspring resemblance: genes plus rearing, genes only, and rearing only.

MAIN OUTCOMES AND MEASURES

Diagnosis of bipolar disorder, broad schizophrenia (ie, schizophrenia as a 3-level variable: unaffected, nonaffective psychosis, and schizophrenia) and major depression obtained from Swedish national registries. Parent-offspring resemblance was assessed primarily by tetrachoric correlation (ie, correlation of liability) and for key results, odds ratios (ORs) from logistic regression. Cross-generational associations of bipolar disorder with broad schizophrenia and major depression were assessed by their transmission from bipolar disorder in parents and transmission to bipolar disorder in offspring.

RESULTS

The study population included 2 417 104 individuals of 4 family types (51.8% male and 48.2% female; median age, 41 [range, 25-60] years). For bipolar disorder to bipolar disorder transmission, tetrachoric correlations for 3 types of parent-offspring relationships were statistically homogeneous across family type and mothers and fathers for genes plus rearing (0.25; 95% CI, 0.24-0.26), genes only (0.22; 95% CI, 0.18-0.26), and rearing only (0.07; 95% CI, -0.01 to 0.15). Parallel ORs were 5.20 (95% CI, 4.91-5.50), 3.66 (95% CI, 2.97-4.51), and 1.63 (95% CI, 0.96-2.78). Best-estimate, cross-disorder tetrachoric correlations for 3 types of parent-offspring relationships for bipolar disorder and broad schizophrenia were 0.12 (95% CI, 0.11-0.13) for genes plus rearing, 0.12 (95% CI, 0.09-0.14) for genes only, and -0.03 (95% CI, -0.11 to 0.04) for rearing only, with parallel ORs of 1.95 (95% CI, 1.93-1.97), 2.04 (95% CI, 1.75-2.38), and 0.76 (95% CI, 0.43-1.35). For bipolar disorder and major depression, the parallel tetrachoric correlations were 0.09 (95% CI, 0.07-0.10) for genes plus rearing, 0.04 (95% CI, 0.01-0.07) for genes only, and 0.05 (95% CI, 0.01-0.08) for rearing only; parallel ORs were 1.53 (95% CI, 1.50-1.57), 1.23 (95% CI, 1.13-1.34), and 1.25 (95% CI, 1.09-1.42). Heritability for bipolar disorder was estimated at 0.44 (95% CI, 0.36-0.48). Genetic correlations were estimated at 0.572 (95% CI, 0.560-0.589) between bipolar disorder and broad schizophrenia and 0.302 (95% CI, 0.001-0.523) between bipolar disorder and major depression.

CONCLUSIONS AND RELEVANCE

The findings of this study suggest that genes are largely responsible for bipolar disorder transmission across generations, although modest rearing effects are also likely present. Cross-generational transmission between bipolar disorder and broad schizophrenia appears to be entirely genetic with a moderate genetic correlation; for bipolar disorder and major depression, transmission appears to result equally from genes and rearing with a modest genetic correlation.

Improving early recognition and intervention in people at increased risk for the development of bipolar disorder: study protocol of a prospective-longitudinal, naturalistic cohort study (Early-BipoLife)

Background

Bipolar disorders (BD) belong to the most severe mental disorders, characterized by an early onset and recurrent, severe episodes or a chronic course with poor psychosocial functioning in a proportion of patients. Many patients with BD experience substantial symptomatology months or even years before full BD manifestation. Adequate diagnosis and treatment is often delayed, which is associated with a worse outcome. This study aims to prospectively evaluate and improve early recognition and intervention strategies for persons at-risk for BD.

Methods

Early-BipoLife is a prospective-longitudinal cohort study of 1419 participants (aged 15–35 years) with at least five waves of assessment over a period of at least 2 years (baseline, 6, 12, 18 and 24 months). A research consortium of ten university and teaching hospitals across Germany conducts this study. The following risk groups (RGs) were recruited: RG I: help-seeking youth and young adults consulting early recognition centres/facilities presenting ≥ 1 of the proposed risk factors for BD, RG II: in-/outpatients with unipolar depressive syndrome, and RG III: in-/outpatients with attention-deficit/hyperactivity disorder (ADHD). The reference cohort was selected from the German representative IMAGEN cohort. Over the study period, the natural course of risk and resilience factors, early symptoms of BD and changes of symptom severity (including conversion to manifest BD) are observed. Psychometric properties of recently developed, structured instruments on potential risk factors for conversion to BD and subsyndromal symptomatology (Bipolar Prodrome Symptom Scale, Bipolar at-risk criteria, EPIbipolar) and biomarkers that potentially improve prediction are investigated. Moreover, actual treatment recommendations are monitored in the participating specialized services and compared to recently postulated clinical categorization and treatment guidance in the field of early BD.

Discussion

Findings from this study will contribute to an improved knowledge about the natural course of BD, from the onset of first noticeable symptoms (precursors) to fully developed BD, and about mechanisms of conversion from subthreshold to manifest BD. Moreover, these generated data will provide information for the development of evidence-based guidelines for early-targeted detection and preventive intervention for people at risk for BD.

DSM-III criteria for affective disorders and schizophrenia : A preliminary appraisal using family interview findings

We performed a blind family interview study of 226 first-degree relatives of 63 probands meeting DSM-III criteria for schizophrenia, schizoaffective disorder, and bipolar disorder, as diagnosed by the National Institute ot Mental Health Diagnostic Interview Schedule (DIS). A small test-retest reliability study demonstrated good agreement between the proband interviewer and the principal family interviewer for the major diagnostic categories of psychotic disorders. Excellent compliance was obtained, with 85% of living relatives interviewed personally.

Three principal findings emerged front the study. First, as expected, bipolar disorder, as defined by DSM-III, displayed a strong familial comportent, comparable to that found by many studies using criteria other than those of DSM-III. Second, patients meeting DSM-III criteria for schizophrenia and schizoaffective disorder displayed a low familial prevalence of schizophrenia. Although initially suprising, this finding is in agreement with the results of several other recent lantily studies of schizophrenia. Upon comparing our results with those of other recent family studies of schizophrenia, it appears that the familial component in schizophrenia tnay be less than was estimated by earlier studies using older and “broader” definitions of schizophrenia.

Third, we found that patients meeting DSM-III criteria for schizophrenia appeared genetically heterogeneous. Those who had displayed a superimposed full affective syndrome at some tinte in the course of their illness, together with those probands meeting DSM-III criteria for schizoaffective disorder, displayed a high familial prevalence of major affective disorder, similar to that found in the families of the bipolar probands. On the other hand, “pure” DSM-III schizophrenie probands, who had never experienced a superimposed full affective syndrome, displayed a low familial prevalence of major affective disorder, similar to that found in the general population. These findings favor the possibility that probands meeting DSM-III criteria for schizophrenia, but displaying a superimposed full affective syndrome, may in sonie cases have a disorder genetically relatcd to major affective disorder.

Further prospective family interview studies, using DSM-III criteria and larger samples, will be necessary to test these preliminary impressions.

A multifactorial approach to depression : the inadequacy of pharmacologic inference and psychosocial hypotheses

The author has reviewed evidence generated during the past decade at the University of Tennessee and other affective disorders research units in support of a psychobiologic understanding of affective disorders as the final common pathway of various psychologic and biologic factors that impinge on midbrain centers of reward, circadian rhythms, and psychomotor function. In this model, inherited temperamental instability, based on a persistent diencephalic abnormality, provides the fertile soil for the development of major affective episodes. The pathogenesis of full-blown affective episodes is then the product of multiple factors, none of which alone is a necessary or sufficient cause. It is submitted that this unified theory, in bridging psychosocial and biologic factors, provides the most comprehensive etiologic understanding of depressive illness permitted by current data. Clinical implications of the theory are discussed.

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.

Childhood adverse life events and parental psychopathology as risk factors for bipolar disorder

Childhood adverse events are risk factors for later bipolar disorder. We quantified the risks for a later diagnosis of bipolar disorder after exposure to adverse life events in children with and without parental psychopathology. This register-based population cohort study included all persons born in Denmark from 1980 to 1998 (980 554 persons). Adversities before age 15 years were: familial disruption; parental somatic illness; any parental psychopathology; parental labour market exclusion; parental imprisonment; placement in out-of-home care; and parental natural and unnatural death. We calculated risk estimates of each of these eight life events as single exposure and risk estimates for exposure to multiple life events. Main outcome variable was a diagnosis of bipolar disorder after the age of 15 years, analysed with Cox proportional hazard regression. Single exposure to most of the investigated adversities were associated with increased risk for bipolar disorder, exceptions were parental somatic illness and parental natural death. By far the strongest risk factor for bipolar disorder in our study was any mental disorder in the parent (hazard ratio 3.53; 95% confidence interval 2.73-4.53) and the additional effects of life events on bipolar risk were limited. An effect of early adverse life events on bipolar risk later in life was mainly observed in children without parental psychopathology. Our findings do not exclude early-life events as possible risk factors, but challenge the concept of adversities as important independent determinants of bipolar disorder in genetically vulnerable individuals.

Characterization of bipolar disorder patient-specific induced pluripotent stem cells from a family reveals neurodevelopmental and mRNA expression abnormalities

Bipolar disorder (BD) is a common neuropsychiatric disorder characterized by chronic recurrent episodes of depression and mania. Despite evidence for high heritability of BD, little is known about its underlying pathophysiology. To develop new tools for investigating the molecular and cellular basis of BD, we applied a family-based paradigm to derive and characterize a set of 12 induced pluripotent stem cell (iPSC) lines from a quartet consisting of two BD-affected brothers and their two unaffected parents. Initially, no significant phenotypic differences were observed between iPSCs derived from the different family members. However, upon directed neural differentiation, we observed that CXCR4 (CXC chemokine receptor-4) expressing central nervous system (CNS) neural progenitor cells (NPCs) from both BD patients compared with their unaffected parents exhibited multiple phenotypic differences at the level of neurogenesis and expression of genes critical for neuroplasticity, including WNT pathway components and ion channel subunits. Treatment of the CXCR4(+) NPCs with a pharmacological inhibitor of glycogen synthase kinase 3, a known regulator of WNT signaling, was found to rescue a progenitor proliferation deficit in the BD patient NPCs. Taken together, these studies provide new cellular tools for dissecting the pathophysiology of BD and evidence for dysregulation of key pathways involved in neurodevelopment and neuroplasticity. Future generation of additional iPSCs following a family-based paradigm for modeling complex neuropsychiatric disorders in conjunction with in-depth phenotyping holds promise for providing insights into the pathophysiological substrates of BD and is likely to inform the development of targeted therapeutics for its treatment and ideally prevention.

Genetic relationships between schizophrenia, bipolar disorder, and schizoaffective disorder

There is substantial evidence for partial overlap of genetic influences on schizophrenia and bipolar disorder, with family, twin, and adoption studies showing a genetic correlation between the disorders of around 0.6. Results of genome-wide association studies are consistent with commonly occurring genetic risk variants, contributing to both the shared and nonshared aspects, while studies of large, rare chromosomal structural variants, particularly copy number variants, show a stronger influence on schizophrenia than bipolar disorder to date. Schizoaffective disorder has been less investigated but shows substantial familial overlap with both schizophrenia and bipolar disorder. A twin analysis is consistent with genetic influences on schizoaffective episodes being entirely shared with genetic influences on schizophrenic and manic episodes, while association studies suggest the possibility of some relatively specific genetic influences on broadly defined schizoaffective disorder, bipolar subtype. Further insights into genetic relationships between these disorders are expected as studies continue to increase in sample size and in technical and analytical sophistication, information on phenotypes beyond clinical diagnoses are increasingly incorporated, and approaches such as next-generation sequencing identify additional types of genetic risk variant.

Chromosome 18p11.2 harbors susceptibility marker: D18S452, for bipolar affective disorder

AIM

The aim of our study was to investigate whether the tandem repeat polymorphism in D18S452 microsatellite marker at locus 18p11.2 is a risk factor of bipolar affective disorder (BPAD) in Kashmiri population.

MATERIALS AND METHODS

The repeat polymorphism in D18S452 was evaluated by polymerase chain reaction (PCR) analysis of in 74 diagnosed BPAD patients and 74 controls subjects.

RESULTS

Tandem repeat (300 bp*) allele frequency was found to be 1.35% in controls and 8.108% in cases. The tandem repeat (250 bp*) allele frequency was found to be in 91.89% in cases and 98.65% in controls. The 252 bp/252 bp genotype was found to be present in 89.18% of cases and 98.64% of controls, the 300 bp/300 bp genotype in 5.40% of cases and 1.35% of controls and the 252 bp/300 bp variant in 5.40% of cases and none among the controls. Although the proportion of patients homozygous for tandem repeat (300 bp/300 bp) was higher in cases than in controls, the difference was not statistically significant when 252 bp/252 bp genotype was taken as reference (odds ratio [OR]=4.4242; 95% confidence interval [CI] 0.4822-40.5924); P=0.1529). However, when the frequency of heterozygous genotype (252 bp/300 bp) was compared with 252 bp/252 bp statistical significance was observed (OR=8.0603; 95% CI 1.1112-58.4646; P=0.0383).

CONCLUSION

This is the first study reporting a significant association between D18S452 maker with tandem repeat polymorphism in heterozygous condition (252 bp/300 bp) and the development of BPAD in Kashmiri population.

Gene expression alterations in bipolar disorder postmortem brains

OBJECTIVES

  Bipolar disorder (BD) is a mental illness of unknown neuropathology and has several genetic associations. Antipsychotics are effective for the treatment of acute mania, psychosis, or mixed states in individuals with BD. We aimed to identify gene transcripts differentially expressed in postmortem brains from antipsychotics-exposed individuals with BD (hereafter the 'exposed' group), non-exposed individuals with BD (hereafter the 'non-exposed' group), and controls.

METHODS

  We quantified the abundance of gene transcripts in postmortem brains from seven exposed individuals, seven non-exposed individuals, and 12 controls with the Affymetrix U133P2 GeneChip microarrays and technologies. We applied a q-value of ≤0.005 to identify statistically significant transcripts with mean abundance differences between the exposed, non-exposed and control groups.

RESULTS

  We identified 2191 unique genes with significantly altered expression levels in non-exposed brains compared to those in the control and exposed groups. The expression levels of these genes were not significantly different between exposed brains and controls, suggesting a normalization effect of antipsychotics on the expression of these genes. Gene ontology (GO) enrichment analysis showed significant (Bonferroni p ≤ 0.05) clustering of subgroups of the 2191 genes under many GO terms; notably, the protein products of genes enriched are critical to the function of synapses, affecting, for example, intracellular trafficking and synaptic vesicle biogenesis, transport, release and recycling, as well as organization and stabilization of the node of Ranvier.

CONCLUSIONS

  These results support a hypothesis of synaptic and intercellular communication impairment in BD. The apparent normalization of expression patterns with exposure to antipsychotic medication may represent a physiological process that relates both to etiology and improvement patterns of the disorder.

Hypomania spectrum disorders from adolescence to adulthood: a 15-year follow-up of a community sample

BACKGROUND

There is a lack of scientific knowledge about the broader spectrum of hypomania in adolescence and the course over time. To investigate this, we used longitudinal data spanning from adolescence to age 31 years.

METHOD

A community sample of adolescents (N=2300) was screened for depressive symptoms. Adolescents (16-17 years) with a positive screening and matched controls were interviewed with a structured diagnostic interview. A blinded follow-up assessment was conducted 15 years later, with a structured diagnostic interview covering the age span 19-31 years. Questions about treatment and family history were included.

RESULTS

Ninety adolescents (16-17 years) with a lifetime hypomania spectrum episode (3.9% of the total sample) were identified: 40 with fullsyndromal, 18 with brief-episode (<4 day), and 32 with subsyndromal (1-2 main symptoms and 1-2 additional symptoms) hypomania. The hypomania symptoms reported by the fullsyndromal and the brief-episode groups were similar, whereas the subsyndromal group per definition reported fewer symptoms. Of the 90 adolescents with a hypomania spectrum episode, 64 (71%) participated in the follow-up interview. Mania in adulthood was reported by 2 (3%), hypomania by an additional 4 (6%), and major depression by 38 (59%). Incidence of mood episodes in adulthood did not differ between the subgroups of hypomania spectrum.

LIMITATIONS

29% of the participants with hypomania spectrum were lost to follow-up.

CONCLUSION

The results indicate that only a small proportion of adolescents with hypomania spectrum episodes continue to have (hypo)mania in adulthood. Thus, maintenance or prophylactic treatment does not seem warranted for this group.

Re-sequencing of ankyrin 3 exon 48 and case-control association analysis of rare variants in bipolar disorder type I

OBJECTIVES

Genome-wide association studies (GWAS) recently identified ankyrin 3 (ANK3) as a candidate gene for bipolar disorder type I (BPD-I). Because the GWAS suggested multiple common haplotypes associated with BPD-I (with odds ratio ~1.3), we hypothesized that rare variants within these common haplotypes might increase risk for BPD-I.

METHODS

We undertook a project in which the serine-rich domain-tail domain (SRD-TD)-encoding exon of ANK3 was amplified from genomic DNA (gDNA) of 384 BPD-I patients and re-sequenced by next generation sequencing (NGS; SOLiD™).

RESULTS

We confirmed 18 novel mis-sense rare variants and one novel insertion/deletion variant within the SRD-TD exon, many of which change amino acid residues with extremely high evolutionary conservation. We genotyped most of these mis-sense variants in ≥ 1000 BPD-I and ≥ 1000 control individuals. We found no statistically significant association of any of the rare variants detected with BPD-I.

CONCLUSIONS

Thus, we conclude that rare variants within the re-sequenced structural domains of ANK3 exon 48 do not contribute to BPD-I.

Molecular linkage studies of bipolar disorder

Linkage studies have defined at least five bipolar (BP) disorder susceptibility loci that meet suggested guidelines for initial identification and subsequent confirmation. These loci, found on 18p11, 18q22, 21q21, 4p16, and Xq26, are targets for BP candidate gene investigations. Molecular dissection of expressed sequences for these regions is likely to yield specific BP susceptibility alleles in most cases, in all probability, these BP susceptibility alleles will be common in the general population, and, individually, will be neither necessary nor sufficient for manifestation syndrome. Additive or multiplicative oligogenic models involving several susceptibility loci appear most reasonable at present, it is hoped thai these BP susceptibility genes will increase understanding of many mysteries surrounding these disorders, including drug response, cycling patterns, age-of-onset, and modes of transmission.

Affective intensity and lability: heritability in adult male twins

BACKGROUND

Inability to monitor and self-regulate heightened levels of affect lability and affect intensity is associated with a range of mood, anxiety, and personality disorders, psychosomatic symptoms and socially maladaptive behaviors. Despite the importance of these aspects of affective regulation, there are no twin study data to shed light on the genetic and environmental components of these constructs.

METHODS

Affective Lability Scale (ALS) and Affect Intensity Measure (AIM) questionnaires were administered to 796 male twins in the Vietnam Era Twin Registry and subjected to twin and model-fitting analyses. Complete data were available from 182 monozygotic and 119 dizygotic twin pairs.

RESULTS

Biometrical genetic model-fitting estimates indicated that additive genetic influence accounted for 40% of the variance in affect intensity and 25% of the variance in the ALS subscale assessing anxiety-depression mood shifts. Nonadditive genetic influence was indicated for ALS subscales measuring shifts between normal mood and depression (29%) and anger (27%), respectively. There was negligible evidence of shared environmental influence on affect measures. In contrast, estimates of nonshared environmental influences ranged from 52% to 74%.

LIMITATIONS

Female were not included in this study due to the nature of the twin cohort. Data from subjects in a population cohort may not generalize to clinical populations. Measures of environment were not included.

CONCLUSIONS

These results provide evidence for moderate heritability of affect intensity and specific measures of affect lability. Individual differences in mood regulation may represent phenotypic variation in a core psychobiologic vulnerability (e.g., neurotransmitter systems).

Behavioral genetics of affective and anxiety disorders

As shown by clinical genetic studies, affective and anxiety disorders are complex genetic disorders with genetic and environmental factors interactively determining their respective pathomechanism. Advances in molecular genetic techniques including linkage studies, association studies, and genome-wide association studies allow for the detailed dissection of the genetic influence on the development of these disorders. Besides the molecular genetic investigation of categorical entities according to standardized diagnostic criteria, intermediate phenotypes comprising neurobiological or neuropsychological traits (e.g., neuronal correlates of emotional processing) that are linked to the disease of interest and that are heritable, have been proposed to be closer to the underlying genotype than the overall disease phenotype. These intermediate phenotypes are dimensional and more precisely defined than the categorical disease phenotype, and therefore have attracted much interest in the genetic investigation of affective and anxiety disorders. Given the complex genetic nature of affective and anxiety disorders with an interaction of multiple risk genes and environmental influences, the interplay of genetic factors with environmental factors is investigated by means of gene-environment interaction (GxE) studies. Pharmacogenetic studies aid in the dissection of the genetically influenced heterogeneity of psychotropic drug response and may contribute to the development of a more individualized treatment of affective and anxiety disorders. Finally, there is some evidence for genetic factors potentially shared between affective and anxiety disorders pointing to a possible overlapping phenotype between anxiety disorders and depression.

Association of genetic polymorphisms in the type II deiodinase gene with bipolar disorder in a subset of Chinese population

OBJECTIVE

Genetic factors play a critical role in the etiology of bipolar disorder (BPAD). Previous studies suggested an association between thyroid dysfunction and BPAD. We hypothesize that genetic variations in the type II deiodinase (DIO2) gene that possibly alter the bioactivity of thyroid hormones are associated with BPAD.

METHOD

A case-control association study was conducted in a subset of Chinese Han population. Two single nucleotide polymorphisms (SNP), open reading frame a (ORFa)-Gly3Asp (rs12885300) and Thr92Ala (rs225014) with potential functions on the activity of DIO2, were selected. The frequencies of allele, genotype and haplotype of the two SNPs were compared between the BPAD patients and the control group.

RESULTS

Statistical significance between the BPAD patients and the control group was observed for the allele (chi(2)=7.746, P=0.005, df=1) and genotype frequencies (chi(2)=8.158, P=0.017, df=2) at the locus of ORFa-Gly3Asp, and for the allele (chi(2)=15.838, P=7.00e-005, df=1) and genotype frequencies (chi(2)=17.236, P=0.0002, df=2) at Thr92Ala. Distribution of allele 3Gly and 92Ala were significantly higher in the BPAD patients, with odds ratios of 1.489 [95% confidence interval (CI)=1.124-1.973] and 1.616 [95% CI=1.275-2.048], respectively. Individuals with two copies of the variant 3Gly or 92Ala were at greater risk of BPAD than individuals with one copy (dose-response manner). Haplotypes ORFa-3Asp-92Ala and ORFa-3Gly-92Ala indicated higher susceptibility for BPAD with odds ratios of 3.759 (95% CI=2.013-7.020) and 1.292 (95% CI=1.017-1.642), respectively, while ORFa-3Asp-92Thr probably played a protective role with an odds ratio of 0.395 (95% CI=0.284-0.549).

CONCLUSION

Data generated from this study supported our hypothesis that genetic variations of the DIO2 gene were associated with BPAD and suggested further consideration on the possible involvement of these functionally active variants in the pathophysiology of BPAD.

Bipolar disorder: from genes to behavior pathways

Bipolar disorder (BPD) is a devastating illness that is characterized by recurrent episodes of mania and depression. In addition to these cyclic episodes, individuals with BPD exhibit changes in psychovegetative function, cognitive performance, and general health and well being. In this article we draw from neuroimaging findings in humans, postmortem data, and human genetic and pharmacological studies as well as data from animal models of behavior to discuss the neurobiology of BPD. We conclude with a synthesis of where the field stands and with suggestions and strategies for future areas of study to further increase our conceptual understanding of this complex illness.

Bipolar disorder: from genes to behavior pathways

Bipolar disorder (BPD) is a devastating illness that is characterized by recurrent episodes of mania and depression. In addition to these cyclic episodes, individuals with BPD exhibit changes in psychovegetative function, cognitive performance, and general health and well being. In this article we draw from neuroimaging findings in humans, postmortem data, and human genetic and pharmacological studies as well as data from animal models of behavior to discuss the neurobiology of BPD. We conclude with a synthesis of where the field stands and with suggestions and strategies for future areas of study to further increase our conceptual understanding of this complex illness.

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.

The proximal prodrome to first episode mania--a new target for early intervention

OBJECTIVE

Affective psychoses and bipolar disorders have been neglected in the development of early intervention strategies. This paper aims to gather current knowledge on the early phase of bipolar disorders in order to define new targets for early intervention.

METHODS

Literature review based on the main computerized databases (MEDLINE, PUBMED and PSYCHLIT) and hand search of relevant literature.

RESULTS

Based on current knowledge, it is likely that an approach aiming at the identification of impending first-episode mania is the most realistic and manageable strategy to promote earlier treatment. During the period preceding the onset of the first manic episode, patients go through a prodromal phase marked by the presence of mood fluctuation, sleep disturbance, and other symptoms such as irritability, anger, or functional impairment. Additionally, various risk factors and markers of vulnerability to bipolar disorders have been identified.

CONCLUSIONS

In the few months preceding first-episode mania, patients go through a prodrome phase (proximal prodrome) that could become an important target for early intervention. However, considering the low specificity of the symptoms observed during this phase, criteria defining high-risk profiles to first-episode mania should also include certain risk factors or markers of vulnerability. While more research is needed in high-risk groups (e.g., bipolar offspring), retrospective studies conducted in first-episode mania cohorts could provide valuable information about this critical phase of the illness.

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.

The End of Behavioral Genetics?

Although genetic models were in the ascendance within psychology during the early 20(th) century, the association of early behavioral genetic research with the eugenics movement served to discredit the field in the eyes of many. Twin and adoption studies throughout the latter half of the 20(th) century helped to reestablish the importance of behavioral genetic models and set the stage for the current focus of the field on developing and testing models of gene-environment interplay. Research findings on developmental behavioral genetic research, gene-environment interaction, and the use of behavioral genetic models to test causal hypotheses are used to highlight the contributions of contemporary behavioral genetic research to psychological research. It is argued that future efforts to investigate models of gene-environment interplay will depend heavily of the field's ability to identify the specific genetic variants that contribute to individual differences in behavior. The anticipated yield from genome-wide association studies gives much reason to be optimistic about the future vitality of behavior genetics.

Setting the stage: from prodrome to treatment resistance in bipolar disorder

Bipolar disorder is common, and both difficult to detect and diagnose. Treatment is contingent on clinical needs, which differ according to phase and stage of the illness. A staging model could allow examination of the longitudinal course of the illness and the temporal impact of interventions and events. It could allow for a structured examination of the illness, which could set the stage for algorithms that are tailored to the individuals needs. A staging model could further provide as structure for assessment, gauging treatment and outcomes. The model incorporates prodromal stages and emphasizes early detection and algorithm appropriate intervention where possible. At the other end of the spectrum, the model attempts to operationalize treatment resistance. The utility of the model will need to be validated by empirical research.

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.

Genetic analysis of psychiatric disorders in humans

Psychiatric disorders place a large burden not only on affected individuals and their families but also on societies and health services. Current treatment is only effective in a proportion of the patients, so considerable effort has been put into the development of new medications. The susceptibility to all major psychiatric disorders is, at least in part, genetic. Knowledge of the genes that underlie this susceptibility may lead to the identification of new drug targets and the development of more effective treatments. Therefore, numerous genetic studies in search for the genes involved in psychiatric disorders have been performed. Although results of both linkage and association studies have been inconsistent, several promising gene regions and candidate genes have been identified recently. In this article, we will review the strategies that proved to be successful in detecting genes for psychiatric disorders and we will provide some recommendations to increase the probability of detecting susceptibility genes in genetic studies of different designs.

Molecular genetics of bipolar disorder

Bipolar disorder (BPD) is an often devastating illness characterized by extreme mood dysregulation. Although family, twin and adoption studies consistently indicate a strong genetic component, specific genes that contribute to the illness remain unclear. This study gives an overview of linkage studies of BPD, concluding that the regions with the best evidence for linkage include areas on chromosomes 2p, 4p, 4q, 6q, 8q, 11p, 12q, 13q, 16p, 16q, 18p, 18q, 21q, 22q and Xq. Association studies are summarized, which support a possible role for numerous candidate genes in BPD including COMT, DAT, HTR4, DRD4, DRD2, HTR2A, 5-HTT, the G72/G30 complex, DISC1, P2RX7, MAOA and BDNF. Animal models related to bipolar illness are also reviewed, with special attention paid to those with clear genetic implications. We conclude with suggestions for strategies that may help clarify the genetic bases of this complex illness.

A prospective high-risk study of the association among maternal negativity, apparent frontal lobe dysfunction, and the development of bipolar disorder

In a previous paper, the authors found that impairment on the Wisconsin Card Sorting Test (WCST) in adolescence was predictive of bipolar disorder in young adulthood among offspring of mothers with bipolar illness. In the present study, the authors explore the contribution of maternal characteristics, beyond maternal mood disorder, to the prediction of offspring dysfunction on the WCST. Results showed that maternal bipolar disorder and maternal negativity were both predictive of impaired performance on the WCST during adolescence. The contribution of maternal negativity to offspring WCST impairment was not better explained by maternal personality disorder, mother's functional impairment, family loading for bipolar disorder, or offspring disruptive behavioral disturbance. Findings did not support a moderator model. However, support was found for a mediation model in which maternal negativity contributed to risk for offspring bipolar disorder through its negative association with apparent frontal lobe functioning, as measured by the WCST. Findings are discussed from the perspective of a vulnerability-stress model. In addition, the authors consider the possibility that maternal negativity and offspring impairment on the WCST may be reflective of a common heritable trait.

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.

Bipolar II and the bipolar spectrum

In studies made in the last decade, patients consulting doctors because of depression and anxiety have very often turned out to suffer from bipolar type II and similar conditions with alternating depression and hypomania/mania (the bipolar spectrum disorders - BP). Specifically, about every second patient seeking consultation because of depression has been shown to suffer from BP, mainly bipolar type II. BP is often concealed by other psychiatric conditions, e.g. recurrent depression, psychosis, anxiety, addiction, personality disorder, attention-deficit hyperactivity disorder and eating disorder. BP shows strong heredity. Relatives of patients with BP also have a high frequency of the psychiatric conditions just mentioned. Conversion ("switching") from recurrent unipolar depressions (recurrent UP) to BP is common in very long longitudinal studies (over decades). Mood-stabilizing medicines are recommended to a great extent in the treatment of BP, since anti-depressive medicines are often not effective and involve a substantial risk of inducing mood swings. Particularly in the long-term pharmacological treatment of depression in BP anti-depressive medicines may worsen the condition, e.g. inducing a symptom triad of dysphoria, irritability and insomnia: ACID (antidepressant-associated chronic irritable dysphoria).

Family, twin, adoption, and molecular genetic studies of juvenile bipolar disorder

Juvenile bipolar disorder (JBD) has been a subject of significant research and debate. Phenotypic differences between JBD and adult-onset bipolar disorder have led researchers to question whether or not similar neuropathologic mechanisms will be found. While much is known about the genetic and environmental contributions to the adult-onset phenotype, less is known about their contributions to JBD. Here, we review family, twin, adoption, and molecular genetic studies of JBD. Behavioral genetic data suggest both genetic and environmental contributions to JBD, while molecular genetic studies find linkage to age of onset of bipolar disorder to chromosomes 12p, 14q, and 15q. Additionally, changes associated with symptom age of onset have been recently reported in the brain-derived neurotrophic factor (BDNF) and glycogen synthase kinase 3-beta (GSK3-beta) genes. We contend that further progress in discovering the precise genetic and environmental contributions to JBD may depend on advances in phenotypic refinement, an increased appreciation of comorbid conditions, and more investigation of the longitudinal course of the disorder.

Dissecting the genetic etiology of major depressive disorder using linkage analysis

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

Genetics and genomics of depression

Depressive disorders are among the most common psychiatric diseases, with prevalence estimates ranging from 5% to a maximum of 20%. Despite their high prevalence and socioeconomic impact, little is known about their etiology. Heritability estimates demonstrate up to a 50% genetic component based on family aggregation and contrasting monozygotic and dizygotic twin studies. The low relative risk to siblings ( lambda sib <1.5) makes the search for their genetic determinants very tedious. Gene-environment interaction has been recognized for a long time in the pathophysiology of depression, and its best biological substratum at present is represented by the serotonin transporter (5-HTT) gene, where several copies of its short allele culminate in depression and suicide in response to lifelong stress events. Many total genome scans have been performed with variable results, the most authoritative being the one of Utah pedigrees with a strong family history of major depression. It identified a locus on chromosome 12 encompassing a gene cluster and sex-specific predisposition. Nevertheless, recent genome scan meta-analysis yielded somewhat disappointing conclusions with a relatively low significance for quantitative trait loci on chromosomes 9, 10, 14, and 18. Studies on animal models have contributed to the chromosomal mapping of many behavioral traits, including anxiety, the stress response, and depression. Although F2 crosses constitute a classical approach, novel models of recombinant inbred strain and recombinant congenic strain animals allow for a rapid initial localization of any traits. This type of analysis has led us to uncover significant loci for the stress response and anxiety in rats and mice.

Monoamine Oxidase A and Tryptophan Hydroxylase Gene Polymorphisms

Most of the candidate gene studies in bipolar disorder have focused on the major neurotransmitter systems that are influenced by drugs used in the treatment of this disorder. The monoamine oxidase A (MAOA) and the tryptophan hydroxylase (TPH1, TPH2) genes are two of the candidates that have been tested in a series of association studies using unrelated or family-based controls. This review summarizes the existing association studies regarding these genes. Most of these studies were based on the unrelated case-control design with samples of 50 to 600 subjects. Regarding MAOA, three meta-analyses with partially overlapping samples supported a modest effect of this gene in bipolar disorder in female Caucasians. However, as several studies could not replicate these findings, more work is necessary to demonstrate unequivocally the involvement of MAOA in bipolar disorder and establish the biological mechanism underlying the genetic association. With respect to TPH1 and TPH2, the majority of studies did not provide evidence for an association between these genes and bipolar disorder. The genes are more likely to be related to suicidal behavior than to bipolar disorder.

The epidemiology of mood disorders

This review provides an overview of the epidemiology, risk factors, and genetic epidemiology of mood disorders in adults and children. The magnitude and impact of mood disorders in the community outweighs that of most other chronic diseases. Although there is substantial knowledge regarding the sociodemographic risk factors for mood disorders, our understanding of the pathogenesis and classification still is evolving. Comorbidity of mood disorders with anxiety disorders and substance abuse has been documented widely. Whereas substance abuse and mood disorders seem to be independent etiologically, anxiety and mood disorders result from partially common etiologic factors. The results of family, twin, and adoption studies reveal that a positive family history is the most potent risk factor for mood disorders, particularly bipolar disorder. However, the specific factors that are transmitted in families still are unknown. The two areas that will inform future genetic research include phenomenologic studies that refine the validity of the current phenotypic classification of mood disorders, and application of study designs to elucidate specific factors that may explain the familial transmission of these 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.

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.

Molecular genetics of affective disorders

Evidence for familial aggregation in Affective Disorders (AD) has been provided in classical studies. Linkage and association genetic studies have been proposed to detect genetic factors implicated in AD. However, findings from molecular genetic studies remain inconclusive. Nevertheless, current research is focusing on the phenotypes, both sub- and endophenotypes. In addition, recent advances in technology, such as microarrays, provide new tools in psychiatric genetics. These different approaches offer a new optimism era in the search of genetic factors in AD.