Ildikó Baji

Brain-derived neurotrophic factor variants are associated with childhood-onset mood disorder: confirmation in a Hungarian sample

Brain-derived neurotrophic factor (BDNF) is a nerve growth factor that has been implicated in the neurobiology of depression. Our group has previously reported an association between a BDNF variant and childhood-onset mood disorder (COMD) in an adult sample from Pittsburgh. We hypothesize that variants at the BDNF locus are associated with COMD. Six BDNF polymorphisms were genotyped in 258 trios having juvenile probands with childhood-onset DSM-IV major depressive or dysthymic disorder. BDNF markers included the (GT)n microsatellite, Val66Met and four other single-nucleotide polymorphisms (SNPs) distributed across the BDNF gene. Family-based association and evolutionary haplotype analysis methods were used. Analysis of linkage disequilibrium (LD) revealed substantial LD among all six polymorphisms. Analyses of the Val66Met polymorphism demonstrated significant overtransmission of the val allele (χ2=7.12, d.f.=1, P=0.0076). Consistent with the pattern of LD, all other SNPs showed significant biased transmission. The (GT)n microsatellite alleles also indicated a trend towards biased transmission (170 bp: Z=2.095, P=0.036). Significant haplotypes involved Val66Met and BDNF2 (P=0.0029). In this Hungarian sample, we found all five BDNF SNPs tested and a haplotype containing the BDNF Val66Met Val allele to be associated with COMD. These results provide evidence that BDNF variants affect liability to juvenile-onset mood disorders, supported by data from two independent samples.

Cytokine Genes TNF, IL1A, IL1B, IL6, IL1RN and IL10, and Childhood-Onset Mood Disorders

Background/Aims: Inflammatory cytokines induce a behavioral syndrome, known as sickness behavior, that strongly resembles symptoms typically seen in depression. This resemblance has led to the theory that an imbalance of inflammatory cytokine activity may be a contributing factor in depressive disorders. Support for this is found in multiple lines of evidence, such as the effects of cytokines on the activities of the hypothalamic-pituitary-adrenal axis, serotonin and brain-derived neurotrophic factor, and hippocampal function, all of which are implicated in the etiology of depression. In addition, associations between inflammatory activity and depressive symptomology have been documented in a number of studies, and the depressogenic effects of cytokine therapy are well known. Accordingly, given that depression has a substantial genetic basis, genes involved in the regulation of inflammatory cytokine activity are strong candidates for involvement in genetic susceptibility to depressive disorders. Here, we have tested 6 key genes of this type, TNF, IL1A, IL1B, IL6, IL1RN and IL10, as candidates for involvement in childhood-onset mood disorders. Methods: In this study of 384 families, each ascertained through a child with depression diagnosed before the age of 15 years, 11 polymorphisms of known or likely functional significance (coding and regulatory variants) were analyzed. Results: Testing for biased transmission of alleles from parents to their affected offspring, we found no evidence for an association between childhood-onset mood disorders and any of the polymorphisms, either individually or as haplotypes. Conclusion: The present study does not support the involvement of the TNF, IL1A, IL1B, IL6, IL1RN and IL10 variants as major genetic risk factors contributing to early-onset mood disorders.

Association Study of the Estrogen Receptor Alpha Gene (ESR1) and Childhood-Onset Mood Disorders

Depressive disorders are heterogeneous psychiatric disorders involving deficits in cognitive, psychomotor, and emotional processing. Depressive disorders have a significant genetic component, with severe, recurrent and early‐onset forms demonstrating elevated heritability. In this study we genotyped eleven single nucleotide polymorphisms (SNPs) spanning the estrogen receptor alpha gene (ESR1) in a large family‐based childhood‐onset mood disorder (COMD) sample. None of the individual SNP or global haplotype analyses was significant in the entire COMD sample, but haplotype analysis of three SNPs in strong linkage disequilibrium (rs746432, rs2077647, and rs532010) uncovered an association with COMD, specifically in females. Our data are consistent with previous studies demonstrating a female‐specific association between ESR1 and neurobehavioral phenotypes. These results suggest the existence of sex‐specific etiological factors in depressive disorders, related to estrogen, with onset in childhood.

Association of the GABRD gene and childhood-onset mood disorders

The chromosome 1p36 region was previously indicated as a locus for susceptibility to recurrent major depressive disorder based on a linkage study in a sample of 497 sib pairs. We investigated the gamma‐aminobutyric acid A (GABAA) δ receptor subunit gene, GABRD, as a susceptibility gene to childhood‐onset mood disorders (COMD) because of substantial evidence implicating GABAergic dysfunction in mood disorders and the position of this gene near the 1p36 linkage region. Using a sample consisting of 645 Hungarian families with a child/adolescent proband diagnosed with a mood disorder with the onset of the first episode before age 15, we found some evidence for the association of two polymorphisms located within the gene, rs2376805 and rs2376803, as well as significant evidence for biased transmission of the haplotypes of these two markers (global χ2 test for haplotypes = 12.746, 3 df, P = 0.0052). Furthermore, significant evidence of association was only observed in male subjects (n = 438) when the results were analyzed by sex (χ2 = 9.000 1 df, P = 0.003 for rs2376805). This was in contrast with the previous linkage findings, as LOD scores exceeding 3 were only in female–female pairs in that study. These findings point to the GABRD gene as a susceptibility gene for COMD; however, this gene may not explain the previous linkage finding.

Association study of neurotrophic tyrosine kinase receptor type 2 (NTRK2) and childhood-onset mood disorders.

Childhood‐onset mood disorders (COMD) are often familial, and twin studies of COMD provide compelling evidence that genetic factors are involved. Deficits in neural plasticity have been suggested to underlie the development of depression. The receptor tropomyosin related kinase B (TrkB) and its ligand, brain derived neurotrophic factor (BDNF), play essential roles in neural plasticity, and mRNA expression of both of these genes has been shown to be influenced by stress and chronic antidepressant treatment. In addition, TrkB knock‐out mice display inappropriate stress coping mechanisms. Having previously shown that BDNF is associated with COMD, in this study we investigated the gene encoding TrkB, neurotrophic tyrosine kinase, receptor, type 2 (NTRK2) as a susceptibility factor in COMD. We tested for association of NTRK2 with COMD in two independent samples: (a) a case‐control sample matched on ethnicity and gender, consisting of 120 cases who met DSM III/IV criteria for major depressive or dysthymic disorder before age 14 or bipolar I/II before the age of 18, and controls, and (b) a family based control sample of 113 families collected in Hungary, identified by a proband between the age of 7 and 14 who met DSM IV criteria for major depressive disorder or bipolar I/II disorder. There was no evidence for an allelic or genotypic association of three polymorphisms of NTRK2 with COMD in the case‐control sample. Also, in the family based sample, using the transmission disequilibrium test (TDT), we did not identify any evidence of allelic association for each marker individually or when haplotypes were analyzed. Based on these results, using these three polymorphisms, we do not find support for NTRK2 as a susceptibility gene for COMD.

The Association between Major Depressive Disorder in Childhood and Risk Factors for Cardiovascular Disease in Adolescence

Objective Depression in adults is associated with risk factors for cardiovascular disease (CVD). It is unclear, however, when the association between clinical depression and cardiac risk factors develops or how early in life this association can be detected. Methods In an ongoing study of pediatric depression, we compared CVD risk factors including smoking, obesity, physical activity level, sedentary behavior, and parental history of CVD across three samples of adolescents: probands with established histories of childhood-onset major depressive disorder (n = 210), never-depressed siblings of probands (n = 195), and controls with no history of any major psychiatric disorder (n = 161). Results When assessed during adolescence, 85% of the probands were not in a major depressive episode. Nevertheless, at that assessment, probands had a higher prevalence of regular smoking (odds ratio [OR] = 12.54, 95% confidence interval [CI] = 4.36–36.12) and were less physically active than controls (OR = 0.59, CI = 0.43–0.81) and siblings (OR = 0.70, CI = 0.52–0.94) and had a higher rate of obesity than did controls (OR = 3.67, CI = 1.42–9.52). Parents of probands reported high rates of CVD (significantly higher than did parents of controls), including myocardial infarction and CVD-related hospitalization (ORs = 1.62–4.36, CIs = 1.03–15.40). Differences in CVD risk factors between probands and controls were independent of parental CVD. Conclusions Major depression in childhood is associated with an unfavorable CVD risk profile in adolescence, and risks for pediatric depression and CVD may coincide in families. Effective prevention and treatment of childhood depression may be a means to reduce the incidence of adult CVD.

Further genetic evidence implicates the vasopressin system in childhood‐onset mood disorders

Studies in both animals and humans advocate a role for the vasopressin (AVP) system in the aetiology of depressive symptoms. Attention has particularly focused on the role of AVP in the overactivation of the hypothalamic‐pituitary‐adrenal (HPA)‐axis in mood disorders. Elevated AVP plasma levels have been found in mood disorder patients, which are often positively correlated with the severity of symptoms. We recently reported an association between childhood‐onset mood disorders (COMD) and polymorphisms in the receptor responsible for the AVP‐mediated activation of the HPA‐axis (AVPR1B). As genetic variation in the vasopressinergic system could provide a mechanism to explain the endocrine alterations observed in mood disorders, we investigated other genes in this system. The gene encoding AVP is the strongest candidate, particularly as genetic variation in this gene in rodents is associated with anxiety‐related behaviours. Six single‐nucleotide polymorphisms (SNPs) were genotyped across the AVP gene in a sample comprised of 586 Hungarian nuclear families ascertained through affected probands with a diagnosis of COMD. In addition, AVP coding and putative regulatory regions were screened for mutations using denaturing high‐performance liquid chromatography. One SNP, 3′ to the AVP, gene reached significance (P = 0.03), as did the overtransmission of a five‐marker haplotype with a frequency of 22% (P = 0.0001). The subsequent mutation screen failed to identify any putative functional polymorphisms. The outcome of this study, combined with our previous association between COMD and AVPR1B, implicates genetic variation in vasopressinergic genes in mediating vulnerability to COMD.

Stressful life events in a clinical sample of depressed children in Hungary

BACKGROUND There is limited information on the characteristics of stressful life events in depressed pediatric clinical populations and the extent to which sex, age, and their interactions may influence the relations of life events and depression. Using a very large clinical sample of children and adolescents with major depressive disorder (MDD), we therefore examined life events in various ways, as well as their relations to age and sex. METHODS The study included a clinic-based sample of 434 children (ages 7-14) with a DSM-IV diagnosis of MDD and their mothers, and a school-based comparison sample of 724 children and their mothers. Life event information was obtained from the mothers. RESULTS Children with MDD had twice the number of lifetime stressful events than did the comparison group, with very high levels of stressors by the age of 7-9 that stabilized across adolescence. In contrast, the comparison sample experienced a gradual increase in stressful life events as a function of age up to mid-adolescence. Parental health events, death of close relatives, and intrafamilial events were significantly associated with MDD diagnosis. There were significantly stronger associations between parental health- as well as death-event clusters and MDD diagnosis among younger children than adolescents. LIMITATIONS Geographical differences between the clinical and comparison samples, as well as possible parental reporting biases may affect the generalizability of these findings. CONCLUSION The association between some stressful life events and MDD seems to be moderated by age, underscoring the need to examine specific events, as well as clusters of events. Better understanding of such interactions may facilitate early identification of possible risk factors for pediatric MDD.

Age and sex analyses of somatic complaints and symptom presentation of childhood depression in a Hungarian clinical sample

OBJECTIVE To determine whether the symptom presentation of major depressive disorder (MDD) in a large clinical sample of youngsters is influenced by age, sex, and the interaction of age and sex. METHOD The sample included 559 children (mean age = 11.69 years; range, 7-14 years; 247 girls) with MDD recruited from 23 mental health facilities across Hungary. Psychiatric evaluations were conducted via the semistructured Interview Schedule for Children and Adolescents-Diagnostic Version (ISCA-D). Final DSM-IV diagnoses were rendered via the best-estimate diagnostic procedure. Evaluations were conducted between April 2000 and May 2005. RESULTS Six depression symptoms increased with age: depressed mood (odds ratio [OR] = 1.10, P < .05), hypersomnia (OR = 1.17, P < .05), psychomotor retardation (OR = 1.11 P < .05), fatigue (OR = 1.13, P < .01), thoughts of death (OR = 1.11, P < .05), and suicidal ideation (OR = 1.18, P < .01), while psychomotor agitation decreased with age (OR = 0.91, P < .05). Boys were less likely to evidence anhedonia (OR = 0.67, P < .05), insomnia (OR = 0.68, P < .05), and hypersomnia (OR = 0.56, P < .05) but more likely to have psychomotor agitation (OR = 1.59, P < .01). There were no age-by-sex interactions. Rates of somatic complaints did not decrease with age (OR = 1.01, P > .05). CONCLUSIONS The symptom presentation of MDD becomes somewhat more neurovegetative as children get older. However, girls display more affective and atypical symptoms across all age groups. Somatic complaints were common regardless of age and should be considered an associated feature of depression in children and adolescents.

G72/G30 (DAOA) and juvenile-onset mood disorders

The chromosome 13q region has been linked to bipolar disorder in a number of genome scans as well as focused linkage studies. Previously we identified linkage to the 13q32 region in a genome scan of 146 affected sibling pair families from Hungary with juvenile‐onset mood disorders. Within this region are the overlapping genes G72/G30, with G72 now officially named as D‐amino‐acid oxidase activator (DAOA). This locus has been associated with panic disorder, schizophrenia, and bipolar disorder. In this study, we tested for association to 11 markers in these genes and mood disorders in a sample of 646 nuclear families identified with a proband with onset of a mood disorder before 14.9 years of age. We identified evidence for association to three markers within the gene (rs2391191, rs3918341, rs1935062), two of which had been associated with bipolar disorder in previous studies. When corrected for the number of markers tested, the results were no longer significant, however the prior evidence for association of this gene in multiple studies points to this gene as a potential contributor to juvenile‐onset mood disorders.