Eniko Kiss

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 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.

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.

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.

Genome scan in sibling pairs with juvenile-onset mood disorders: Evidence for linkage to 13q and Xq.

Mood disorders (bipolar and depressive disorders) in children and adolescents are associated with significant morbidity and mortality. Twin and family studies, for the most part, indicate higher familiality and heritability for mood disorders that onset in childhood/adolescence than those that onset in adulthood. To identify the genetic contribution to mood disorders that onset in childhood/adolescence, we performed a genome scan on 146 nuclear families from Hungary containing an affected proband and affected siblings. In total, the pedigrees contained 303 affected children: 146 probands, 137 siblings with a first episode of mood disorder before 14.9 years of age, and 20 siblings with onset of their first episode after 14.9 years of age but before the age of 18. The results of the genome scan using 405 microsatellite markers did not provide evidence for linkage at the recommended genome wide significance level for any novel loci. However, markers on two chromosomes, 13q and Xq, provided evidence for linkage in regions previously identified as linked to bipolar disorder in multiple studies. For the marker on chromosome 13q the peak non‐parametric multipoint LOD score was at the marker D13S779 (LOD = 1.5, P = 0.004). On chromosome Xq, evidence for linkage was observed across a large region spanning two regions previously linked to bipolar disorder; Xq24 to Xq28, with a peak at marker TTTA062 (LOD 2.10, P = 0.0009) in Xq28. Results for these regions exceed the recommended P‐value for a replication study of P < 0.01 and thus provide evidence for these two loci as contributing to mood disorders with juvenile onset.

Association study of serotonin system genes in childhood-onset mood disorder

Background The serotonin system has been implicated in neuropsychiatric disorders, including mood disorders. Methods We investigated polymorphisms in two serotonin-receptor genes, HTR1B and HTR2A, and the serotonin transporter (SLC6A4) in two independent samples of patients with childhood-onset mood disorders (COMD): 203 patients from Pittsburgh, USA with matched controls and 448 small families from Hungary. Results Case–control and family-based analyses showed no association between COMD and any of the studied polymorphisms (all P values >0.05). Haplotype analysis of SLC6A4 was also negative in both samples. Conclusions Overall, the examination of genetic variants at the HTR1B, HTR2A, and SLC6A4 loci indicated no association between the selected polymorphisms and COMD.

Parasympathetic nervous system activity predicts mood repair use and its effectiveness among adolescents with and without histories of major depression.

Depressive disorders that onset in the juvenile years have been linked to far-reaching adverse consequences, making it imperative to elucidate key mechanisms and contributory factors. Excessive use of regulatory responses that exacerbate sadness (maladaptive mood repair) or insufficient use of regulatory responses that reduce it (adaptive mood repair) may reflect behavioral mechanisms of depression risk. Cardiac vagal control, indexed by patterns of respiratory sinus arrhythmia (RSA), has received attention as a putative physiological risk factor for depression. Although mood repair and RSA are related, the nature of this relationship is not well characterized in the context of depression risk. Therefore, we tested alternative models of the relationships between RSA patterns (at rest and in response to a sad film), trait mood repair, and the effectiveness of a mood repair response in the laboratory (state mood repair) among adolescents with depression histories (n = 210) and emotionally healthy peers (n = 161). In our data, a mediation model best explained the association between the key constructs: Adolescents with normative RSA patterns exhibited lower levels of depression and trait maladaptive mood repair, and benefited more from instructed (state) mood repair in the laboratory. By contrast, adolescents with atypical RSA patterns exhibited higher levels of depression and dispositional maladaptive mood repair, which, in turn, mediated the relations of RSA patterns and depression symptoms. Atypical RSA patterns also predicted reduced benefits from laboratory mood repair.

Positive Affectivity Is Dampened in Youths With Histories of Major Depression and Their Never-Depressed Adolescent Siblings

Although hedonic capacity is diminished during clinical depression, it is unclear whether that deficit constitutes a risk factor or persists after depression episodes remit. To examine these issues, adolescents with current/past major depression (probands; n = 218), never-depressed biological siblings of probands (n = 207), and emotionally well controls (n = 183) were exposed to several positively valenced probes. Across baseline and hedonic probe conditions, controls consistently reported higher levels of positive affect than high-risk siblings, and siblings reported higher levels of positive affect than probands (remitted and depressed probands’ reports were similar). Extent of positive affect across the protocol predicted adolescents’ self-reports of social support network and parental reports of offspring’s use of various adaptive mood repair responses in daily life. Attenuated hedonic responding among youths remitted from depression offers partial support for anhedonia as a trait, whereas its presence among never-depressed high-risk siblings argues for anhedonia as a potential diathesis for clinical depression.

Juvenile onset depression alters cardiac autonomic balance in response to psychological and physical challenges

Cardiac autonomic balance (CAB) indexes the ratio of parasympathetic to sympathetic activation (Berntson, Norman, Hawkley, & Cacioppo, 2008), and is believed to reflect overall autonomic flexibility in the face of environmental challenges. However, CAB has not been examined in depression. We examined changes in CAB and other physiological variables in 179 youth with a history of juvenile onset depression (JOD) and 161 healthy controls, in response to two psychological (unsolvable puzzle, sad film) and two physical (handgrip, and forehead cold pressor) challenges. In repeated measures analyses, controls showed expected reductions in CAB for both the handgrip and unsolvable puzzle, reflecting a shift to sympathetic relative to parasympathetic activation. By contrast, JOD youth showed increased CAB from baseline for both tasks (ps<.05). No effects were found for the forehead cold pressor or sad film tasks, suggesting that CAB differences may arise under conditions requiring greater attentional control or sustained effort.