Impact of gene polymorphisms on depression and its treatment

Various genetic alterations have been demonstrated to be associated with mood disorders and suicide in a number of studies, although there are many contradictory findings. The most studied genotype, with the largest number of replicated results, is the serotonin transporter genotype. The efficacy of antidepressants appears to be influenced by the presence of a functional polymorphism within the serotonin transporter gene. In addition, genetic variation has an influence on the occurrence of antidepressant-induced side effects. Although further studies using larger sample populations are needed, it is becoming clear that genetic tools will be a major factor in improving diagnosis and optimizing the treatment of depressive disorders in the near future.

Neurochemical and behavioral alterations in glucocorticoid receptor-impaired transgenic mice after chronic mild stress

Mice (GR-i) bearing a transgene encoding a glucocorticoid receptor (GR) antisense RNA under the control of a neuron-specific neurofilament promoter were used to investigate the effects of a 4 week chronic mild stress (CMS) on the hypothalamo-pituitary-adrenocortical (HPA) axis and the serotoninergic system in a transgenic model of vulnerability to affective disorders. GR-i mice showed a decrease in both GR-specific binding (hippocampus and cerebral cortex) and GR mRNA levels [hippocampus, cerebral cortex, and dorsal raphe nucleus (DRN)] as well as a deficit in HPA axis feedback control (dexamethasone test) compared with paired wild-type (WT) mice. In the latter animals, CMS exposure caused a significant decrease in both GR mRNA levels and the density of cytosolic GR binding sites in the hippocampus, whereas, in the DRN, GR mRNA levels tended to increase. In contrast, in stressed GR-i mice, both GR mRNA levels and the density of GR binding sites were significantly increased in the hippocampus, cerebral cortex, and DRN. Electrophysiological recordings in brainstem slices and [gamma-35S]GTP-S binding measurements to assess 5-HT1A receptor functioning showed that CMS exposure produced a desensitization of DRN 5-HT1A autoreceptors in WT, but not in GR-i, mice. In addition, CMS was found to facilitate choice behavior of WT, but not GR-i, mice in a decision-making task derived from an alternation paradigm. These results demonstrate that impaired GR functioning affects normal adaptive responses of the HPA axis and 5-HT system to CMS and alters stress-related consequences on decision-making behaviors.

Multiple dimensions of familial psychopathology affect risk of mood disorder in children of bipolar parents

The aim of our study was to determine whether familial loading of unipolar disorder, bipolar disorder, and substance use disorder are associated with DSM-IV mood disorders in adolescents at risk for bipolar disorder. One hundred and forty adolescents aged 12-21 years of 86 bipolar parents participated in the study. Lifetime DSM-IV diagnoses of the bipolar offspring were assessed with the Schedule for Affective Disorders and Schizophrenia for School Age Children Kiddie-SADS-Present and Lifetime Version (SADS-PL). Parents were interviewed using the Family History Research Diagnostic Criteria (FH-RDC) which were used to calculate a continuous familial loading score (FL) for unipolar disorder, bipolar disorder, and for substance use disorder in first- and second-degree relatives of the adolescents. FL for unipolar disorder and substance use disorder were strong and independent predictors for lifetime mood disorders in the adolescents. The gender adjusted hazard ratios for mood disorders in the children were 1.5 (95% confidence interval (CI) = 1.2-2.0) for FL of unipolar disorder and 1.8 (95% CI = 1.3-2.4) for FL of substance use disorder. Expression of mood disorders in children of bipolar parents varies with the degree of additional FL of unipolar disorder and substance use disorder in the extended family.

Das 22q11.2-Deletionssyndrom und seine Relevanz für die Kinder- und Jugendpsychiatrie

Zusammenfassung: Das 22q11.2-Deletionssyndrom ist das häufigste bekannte Mikrodeletionssyndrom beim Menschen. Betroffene Patienten können eine Vielzahl körperlicher Störungen zeigen, vor allem charakteristische dysmorphe Gesichtszüge, Herzfehler, Thymus- sowie strukturelle oder funktionelle Gaumenanomalien. Typisch sind auch deutliche Beeinträchtigungen der motorischen, sprachlichen, kognitiven und sozialen Entwicklung sowie psychiatrische Störungen. Nach dem aktuellen Forschungsstand treten bei Kindern und Jugendlichen mit einer Deletion 22q11.2 insbesondere Aktivitäts- und Aufmerksamkeitsstörungen, affektive Störungen sowie tiefgreifende Entwicklungsstörungen gehäuft auf. 2% aller schizophrenen Erkrankungen im Erwachsenenalter sollen durch eine Deletion 22q11.2 verursacht sein. Der Artikel gibt einen aktuellen Überblick über Ätiologie, körperliche Symptomatik, Entwicklungsaspekte und psychiatrische Komorbidität des 22q11.2-Deletionssyndroms. Es werden klinische Kriterien für die humangenetische Abklärung einer Deletion 22q11.2 bei Kindern und Jugendlichen mit psychiatrischen Störungen definiert. Außerdem werden Behandlungsmöglichkeiten für die beim 22q11.2-Deletionssyndrom häufigen psychiatrischen Störungen erörtert. Insgesamt wird bei psychisch kranken Kindern und Jugendlichen eine Deletion 22q11.2 bisher noch zu selten diagnostiziert - trotz ihrer klinischen Relevanz.

Affective disorders in the first-degree relatives of bipolar probands: results from the South Island Bipolar Study

The current study was performed to document observed rates of affective disorders in the first degree relatives of probands with bipolar I or II disorder; to determine whether bipolar II probands have an excess of bipolar II relatives; and to determine whether bipolar probands with a history of one or more suicide attempts have more relatives who have also made suicide attempts. Bipolar probands with positive family histories of affective disorder were recruited from a variety of sources for a study on the molecular genetics of bipolar disorder. Probands and relatives were interviewed with the Diagnostic Interview for Genetic Studies (DIGS) and blood was obtained for DNA extraction and genetic analyses. Among 423 first-degree adult relatives of 153 bipolar probands, 7% (29) had bipolar I disorder, 7% had bipolar II disorder, and 7% had bipolar not otherwise specified (NOS) disorder, making 21% of relatives with any bipolar disorder. A further 42% of relatives had a depressive disorder and only 38% had no affective disorder. A suicide attempt by a proband was not associated with any increase in suicide attempts by relatives. We conclude that while unipolar depressive disorders are the most common affective disorders in the first-degree relatives of bipolar probands, extension of the bipolar phenotype to include bipolar spectrum disorders results in 21% of relatives having any bipolar disorder.

Phosphoinositide deficiency due to inositol depletion is not a mechanism of lithium action in brain

The "inositol depletion hypothesis" has been widely held to be the explanation for both the effect of lithium on brain function, apropos of its use in mood disorders, and on the impairment of development and induction of embryonic malformations in diverse organisms. The essence of the hypothesis is that a deficiency in cellular myo-inositol (Ins), secondary to lithium inhibition of inositol monophosphatase and/or multiple inositol polyphosphate phosphatase activities with trapping of Ins as inositol phosphates, leads to a depression of phosphatidylinositol (PtdIns) and a secondary impairment in inositide signaling. However, the ability of relatively low micromolar levels of Ins to reduce mammalian PtdIns synthetase activity in vivo has never been adequately tested. We have generated a lethal murine brain Ins deficiency model and measured PtdIns content using a novel MALDI-TOF MS method. Our results show that in the most severe Ins deficiency ever recorded in a mammal, the brain PtdIns levels do not decrease. We conclude that PtdIns deficiency due to "inositol depletion" is not a mechanism of lithium action in brain, and that Ins plays another unidentified role in the mammalian brain.

Family study of chronic depression in a community sample of young adults

OBJECTIVE

The validity of the distinctions between dysthymic disorder, chronic major depressive disorder, and episodic major depressive disorder was examined in a family study of a large community sample of young adults.

METHOD

First-degree relatives (N=2,615) of 30 probands with dysthymic disorder, 65 probands with chronic major depressive disorder, 313 probands with episodic major depressive disorder, and 392 probands with no history of mood disorder were assessed by using direct interviews and informant reports.

RESULTS

The rates of major depressive disorder were significantly greater among the relatives of probands with dysthymic disorder and chronic major depressive disorder than among the relatives of probands with episodic major depressive disorder, who in turn exhibited a higher rate of major depressive disorder than the relatives of probands with no history of mood disorder. The relatives of probands with dysthymic disorder had a significantly higher rate of dysthymic disorder than the relatives of probands with no history of mood disorder, and the relatives of probands with chronic major depressive disorder had a significantly higher rate of chronic major depressive disorder than the relatives of probands with no history of mood disorder. However, the relatives of the three groups of probands with depression did not differ on rates of dysthymic disorder and chronic major depressive disorder.

CONCLUSIONS

Chronic depression is distinguished from episodic depression by a more severe familial liability. This familial liability may contribute to the more pernicious course of chronic depression.

Epigenetic studies of genomic retroelements in major psychosis

This work is dedicated to the exploration of the role of epigenetic (epiG) factors in major psychosis. One of the key functions of epigenetic modification of the genome of eukaryotic cells is to suppress transcriptional activity of the retroelements. Examples of retroelements are endogenous retroviral sequences (ERVs), Alu's, and LINEs, among others, which as a rule are hypermethylated. There is evidence from schizophrenia (SCH) and other human complex diseases that some of the genomic retroelements become transcribed in the affected tissues. Our goal was to screen DNA samples from post-mortem brain tissues of individuals who were affected with major psychiatric illness for retroelements that were located in the hypomethylated fraction of the genomic DNA. Over 100 Alu sequences were cloned, sequenced, and mapped to the human genome. A substantial portion of the cloned Alu's are located close to or within the genes that may be interesting targets for further genetic, transcription, and epigenetic studies.

Do maternal psychotic symptoms predict offspring's psychotic disorder? Findings from the Helsinki High-Risk Study

The Helsinki High-Risk (HR) Study is a follow-up study of 179 offspring born to mothers with DSM-IV-TR diagnoses of schizophrenia, schizoaffective disorder, other schizophrenia spectrum disorders, and affective psychoses. Mothers comprised all female patients born between 1916 and 1948 who had been treated with hospital diagnoses of schizophrenia, schizophreniform, or schizoaffective psychoses in any mental hospital in the city of Helsinki up to 1974, and who had given birth in Helsinki between 1960 and 1964. In this report we conducted a principal factor analysis of maternal symptoms using 12 items of the Major Symptoms of Schizophrenia Scale (MSSS), the global ratings of anhedonia-asociality and avolition-apathy from the Scale for the Assessment of Negative Symptoms (SANS), and the global rating of bizarre behavior from the Scale for the Assessment of Positive symptoms (SAPS), and examined whether the factor scores predicted the offspring's morbidity from psychotic disorders. We found a four-factor solution (negative, positive, catatonic, and affective symptom factors). High maternal positive symptom factor score significantly predicted decreased morbidity from schizophrenia among offspring (P=0.0098). Our result suggests that maternal positive symptoms are less harmful to the child than other maternal psychotic symptoms, and supports the view that positive symptoms are non-specific symptoms of psychosis rather than core features of schizophrenia.

Association study of a brain-derived neurotrophic-factor genetic polymorphism and mood disorders, age of onset and suicidal behavior

Brain-derived neurotrophic factor (BDNF), a member of the neurotrophin growth factor family, has been implicated in both mood disorders and suicidal behavior. This study has examined the association between the BDNF gene Val66Met polymorphism and mood disorders, age of onset and suicidal behavior in a Chinese sample population. The genotype and allele frequencies for the BDNF gene Val66Met polymorphism did not differ comparing depression groups (total, bipolar disorder or major depression) and control subjects. Furthermore, it was not demonstrated that this BDNF polymorphism was associated with age of onset or suicidal history in our mood disorder patients. Based on these results, it seems reasonable to suggest that this polymorphism is unlikely to play a major role in the genetic susceptibility to mood disorders. Given the fact that the positive association between BDNF gene Val66Met polymorphism and bipolar disorder has only been demonstrated for a Caucasian population but not for a Japanese analog or our Chinese sample, it appears likely that this association is ethnicity dependent.

Analysing the contributions of genes and parent-child interaction to childhood behavioural and emotional problems: a model for the children of twins

BACKGROUND

Despite the demonstrable influence of both genes and the family environment on children's behavioural and emotional development, the mechanisms by which these factors are transmitted from parents to their children are not known. Numerous aspects of the family have long been associated with behavioural and emotional problems in children; it is not clear, however, whether these family variables represent genuine environmental risks or secondary consequences of the underlying genetic liability shared between parents and their children.

METHOD

In this study we present a model for analysing the non-genetic contributions of family background to risk for childhood and adolescent depression and conduct disturbance using simulated data on adult MZ and DZ twins, their spouses and children.

RESULTS

The twin offspring design provides substantial power to detect remarkably small non-genetic effects on parent-offspring resemblance against the background of genetic transmission. As presented, the model is able to resolve the direction of transmission from both parent to child (passive genotype environment correlation) and child to parent (evocative genotype environment correlation).

CONCLUSIONS

Unlike many other genetic studies, a study of twins and their children can sort out which putative family environmental risk factors do actually have a significant environmental impact on the child and which ones only appear to do so because they are associated with genetic mediation.

The utility of the non-human primate; model for studying gene by environment interactions in behavioral research

Variation in the serotonin transporter gene-linked polymorphic region (5-HTTLPR) has been associated with anxiety and harm avoidance and is weakly associated with a number of neuropsychiatric disorders, including Type II alcoholism, which has a high rate of comorbidity with antisocial personality disorder. Studies have also demonstrated interactions between 5-HTLPR variation and environmental stress on the incidence of depression. As in humans, there is a serotonin transporter gene promoter length polymorphism in rhesus macaques that produces similar decreases in transcriptional efficiency. Macaques with histories of early-life stress have been shown to exhibit impulsive aggression, incompetent social behavior and increased behavioral and endocrine responsivity to stress. In this paper, we review studies performed previously in our lab and present preliminary data examining interactions between early rearing and serotonin transporter gene promoter variation on the incidences of play behavior and aggression in infant rhesus macaques. The data presented here highlight the importance of considering gene-environment interactions when studying childhood risk factors for aggression, anxiety and related neuropsychiatric disorders and support the use of the nonhuman primate for studing gene by environment interactions in behavioral research.

Possible association between a haplotype of the GABA-A receptor alpha 1 subunit gene (GABRA1) and mood disorders

BACKGROUND

The gamma-aminobutyric acid (GABA) neurotransmitter system has been implicated in the pathogenesis of mood disorders. The GABRA1 gene encodes one of the subunits of GABA-A receptor and is located on human chromosome 5q34-q35, which is a region reportedly linked to mood disorders. We examined the GABRA1 gene as a candidate for mood disorders.

METHODS

We performed mutation screening of GABRA1 in 24 Japanese bipolar patients and evaluated associations in Japanese case-control subjects consisting of 125 patients with bipolar disorder, 147 patients with depressive disorders, and 191 healthy control subjects. Associations were confirmed in the National Institute of Mental Health (NIMH) Initiative Bipolar Pedigrees, which consists of 88 multiplex pedigrees with 480 informative persons.

RESULTS

We identified 13 polymorphisms in the GABRA1 gene. Nonsynonymous mutations were not found. Association of a specific haplotype with affective disorders was suggested in the Japanese case-control population (corrected p=.0008). This haplotype association was confirmed in the NIMH pedigrees (p=.007).

CONCLUSIONS

These results indicate that the GABRA1 gene may play a role in the etiology of bipolar disorders.

Impulse control disorders: clinical characteristics and pharmacological management

This article reviews the current knowledge of the clinical characteristics and pharmacological management of pathological gambling, kleptomania, and compulsive buying. Specifically, the article summarizes the phenomenology and associated psychopathology of these disorders and presents study results of the various pharmacological agents used to treat these disorders--serotonin reuptake inhibitors, opioid antagonists, mood stabilizers, and atypical antipsychotics.

Hypothalamic-pituitary-adrenocortical system and mood disorders: highlights from mutant mice

In recent years, refined molecular technologies and the generation of genetically engineered mice have allowed to specifically target individual genes involved in the regulation of the hypothalamic-pituitary-adrenocortical (HPA) system. Given the fundamental role of the corticotropin-releasing hormone (CRH) system in anxiety, stress-associated pathologies, and mood disorders, we describe genetic modifications of the genes that encode proteins integral to the CRH/CRH receptor system with particular emphasis on conditional gene-targeting strategies. The profile of results, consistent with current knowledge of CRH function from more traditional assays, indicates that enhancement of the CRH function is associated with an activation of the HPA system, an anxious phenotype, alterations in cognitive performance, reductions in food intake, and disturbances of autonomic functions. In general, blockade of CRH activity produces the opposite effects, namely an anxiety-reduced phenotype. Molecular genetic strategies for conditional inactivation or overexpression of the glucocorticoid receptor contribute to our understanding of the genetics of endocrine activity and behavior, the most complex form of biological organization. In addition, we introduce mice with a genetic manipulation in the function of the blood-brain barrier as an animal model for the study of neuroendocrine regulation and, in particular, of HPA system activity. By use of mice deficient for abcb1- (also called multidrug resistance gene 1, mdr1-) type P glycoproteins, it was shown most recently that abcb1-type P glycoproteins control the access of endogenous glucocorticoids into the central nervous system. Thus, the ABCB1-type P glycoprotein function exerts a profound influence on activity and regulation of the HPA system under both basal conditions and during stress. Taken together, these genetically engineered mice are valuable tools for increasing our understanding of HPA system dysregulation in anxiety and stress-related pathologies, including human affective disorders. The identification and detailed characterization of these molecular pathways will ultimately lead to the development of novel neuropharmacological intervention strategies.

DISC1 and DISC2: discovering and dissecting molecular mechanisms underlying psychiatric illness

A balanced (1;11)(q42;q14) translocation co-segregates with schizophrenia and major affective disorders in a large Scottish family. The translocation breakpoint on chromosome 1 is located within the Disrupted in Schizophrenia 1 and 2 genes (DISC1 and DISC2). Consequently loss of normal function of these genes is likely to underlie the susceptibility to developing psychiatric disorders that is conferred by inheritance of the translocation. Additionally, a number of independent genetic studies highlight the region of chromosome 1q containing DISC1 and DISC2 as a likely susceptibility locus for both schizophrenia and affective disorders. These genes are thus implicated in the aetiology of major psychiatric disorders in several populations. Although the function of DISC1 was initially unknown, several recent reports have made significant progress towards understanding its role in the central nervous system. Intriguingly, all data obtained to date point towards an involvement in processes critical to neurodevelopment and function. DISC2 has not been studied in detail, but is likely to modulate DISC1 expression. Overall, it is clear from the combination of genetic and functional data that DISC1 and/or DISC2 are emerging as important factors in the molecular genetics of psychiatric illness.

BDNF and COMT Polymorphisms: Relation to Memory Phenotypes in Young Adults With Childhood-Onset Mood Disorder

Recent investigations in several species have suggested a role for brain-derived neurotrophic factor (BDNF) in memory, which may be mediated by the influence of BDNF on neuronal plasticity in the hippocampus. BDNF polymorphisms have also been associated with mood disorders. Catechol-O-methyltransferase (COMT) metabolizes dopamine and has been implicated in prefrontal function, another area of the brain relevant for memory. In a sample of 63 young adults with a history of childhood-onset mood disorder, we typed three BDNF polymorphisms, including the BDNF Val66Met single nucleotide polymorphism (SNP), and the COMT Val108/158Met SNP. Multivariate analysis of variance was used to test the association between BDNF and COMT markers and measures of declarative memory. Variants at the three BDNF markers and one COMT marker were not associated with declarative memory function p-values ranged from 0.25 to 0.98. Higher IQ (F = 6.18, df = 4, 58, p = 0.0003) and female gender (F = 4.41, df = 4, 58, p = 0.0035) were associated with more optimal performance on the memory tasks. This study did not provide evidence supporting an association between BDNF and COMT genes and declarative memory phenotypes.

Increased incidence of CYP2D6 gene duplication in patients with persistent mood disorders: ultrarapid metabolism of antidepressants as a cause of nonresponse. A pilot study

OBJECTIVE

Recent studies have revealed that genetic polymorphisms of cytochrome P(450) 2D6 (CYP2D6) are among the factors that determine the interindividual differences in the metabolism and response to antidepressants. We investigated the relationship between persistent mood disorders and the duplication of the CYP2D6 gene, which encodes an enzyme with increased activity.

METHODS

We screened the prevalence of the CYP2D6 genotypes in 108 patients with persistent mood disorders using long polymerase chain reaction (PCR) and the real-time PCR methods. Clinical correlates with the genotypes were also analyzed.

RESULTS

Among the 108 patients, 81 had failed to respond to antidepressants shown to be metabolized by CYP2D6. Of those 81, 8 had a CYP2D6 gene duplication (9.9%, 95% confidence interval 3.4-16.4%) which was higher than the 0.8-1.0% incidence previously observed in healthy Nordic Caucasians. The worst week scores of the Hamilton Depression Rating Scale were higher in the patients with the duplication compared with those without the duplication ( P=0.026, student's t-test).

CONCLUSION

These results suggest that the CYP2D6 gene duplication is a possible factor that influences the development of persistence in patients with mood disorders probably by ultrarapid drug metabolism.

Genetics of Schizophrenia and Affective Disorders

The molecular-genetic basis of non-mendelian, genetically influenced disorders (complex disorders) is beginning to be uncovered. Recently, major progress in localization and detection of disposition genes of schizophrenia and bipolar disorder was achieved. We provide a comprehensive overview of recent results of linkage and association studies in schizophrenia and bipolar disorder. Several disposition genes for schizophrenia (DTNBP1, NRG1, G72) were identified, whereas evidence for specific disposition genes in bipolar disorder is more limited. Multiple limitations of current research strategies in the search of disposition genes of complex disorders have to be considered; alternative phenotype definitions, genome-wide association studies and parallel investigation of epigenetic misregulations might overcome these limitations.

The human genetics of anorexia nervosa

Anorexia nervosa is a severe eating disorder characterised by restricted eating, the relentless pursuit of thinness and obsessive fears of being fat. The involved risk factors are probably numerous, but the existence of a genetic vulnerability has been proposed for decades. The heritability in the broad sense is computed on the basis of aggregation studies, treated twin samples and twin studies from the general population. Many difficulties make this heritability estimation problematic, but the convergence of the results (from family studies and two types of twin studies) gives the most convincing evidence in favour of a major role of genetics in the vulnerability to anorexia nervosa, with a heritability around 70%. Regarding the analysis of candidate genes, the most frequently studied is the 5-HT(2A) gene, with positive and negative results. We thus propose a meta-analysis showing that a large heterogeneity between samples exists, but the main effect of the -1438A allele persists even when extracting this contaminating effect (p=0.003). Furthermore, the absence of significant correlation between odds ratio and time after first publication of each sample, and size of each sample, is in accordance with the fact that the A allele is a risk factor. In order to explain the high heterogeneity between the nine studies yet performed, an alternative explanation such as a "modifying the phenotype" effect is proposed.

ABCB1 (MDR1)-type P-glycoproteins at the blood-brain barrier modulate the activity of the hypothalamic-pituitary-adrenocortical system: implications for affective disorder

Multidrug-resistance gene 1-type P-glycoproteins (ABCB1-type P-gps) protect the brain against the accumulation of many toxic xenobiotics and drugs. We recently could show that the access of the endogenous glucocorticoids corticosterone and cortisol to the brain are regulated by ABCB1-type P-gps in vivo. ABCB1-type P-gp function, therefore, is likely to exert a profound influence on the regulation of the hypothalamic-pituitary-adrenocortical (HPA) system. Hyperactivity of the HPA system is frequently observed in human affective disorder, and a considerable amount of evidence has been accumulated suggesting that normalization of the HPA system might be the final step necessary for stable remission of the disease. To examine whether blood-brain barrier (BBB) function influences neuroendocrine regulation, we investigated HPA system activity in abcb1ab (-/-) mice under basal conditions and following stress. Abcb1ab (-/-) mice showed consistently lower plasma ACTH levels and lower evening plasma corticosterone levels. CRH mRNA expression in the hypothalamic paraventricular nucleus was decreased and pituitary POMC mRNA expressing cells were significantly reduced in number in abcb1ab (-/-) mutants; however, they showed a normal activation of the HPA system following CRH stimulation. Lower doses of dexamethasone were required to suppress plasma corticosterone levels in mutants. Our data thus provide evidence for a sustained suppression of the HPA system at the hypothalamic level in abcb1ab (-/-) mice, suggesting that BBB function significantly regulates HPA system activity. Whether naturally occurring polymorphisms in the human ABCB1 gene might result in persistent changes in the responsiveness and regulation of the HPA system will be the subject of future investigations, correlating both genetic information with individual characteristics of the neuroendocrine phenotype.

The corticotropin-releasing hormone binding protein is associated with major depression in a population from Northern Sweden

BACKGROUND

Recent research suggests that central corticotropin releasing hormone hyperdrive is an important neurobiological risk factor for developing major depression. The availability of free corticotropin releasing hormone in the central nervous system is tightly regulated by the expression of corticotropin releasing hormone binding protein. Therefore, the gene encoding for corticotropin releasing hormone binding protein is a functional candidate gene for major depression.

METHODS

We present a systematic study of single nucleotide polymorphisms in the corticotropin releasing hormone binding protein gene and their role in the liability for major depression. Seven single nucleotide polymorphisms were genotyped in a well-diagnosed sample of 89 patients with recurrent major depressions and matched controls.

RESULTS

Two single nucleotide polymorphisms within the corticotropin releasing hormone binding protein gene were significantly associated with the disease (p <.05). An expectation-maximization algorithm estimated a specific haplotype to have a frequency of 53% in patients and 35% in controls (p <.001).

CONCLUSIONS

The corticotropin releasing hormone binding protein gene is likely to be involved in the genetic vulnerability for major depression.