Disruptions in circadian rhythms have been described in mood disorders (MD), but the involvement of genetic variation in genes pertaining to the molecular circadian machinery in the susceptibility to MD has not been conclusively determined. We examined 209 single-nucleotide polymorphisms (SNPs) covering 19 circadian genes (ADCYAP1, ARNTL, ARNTL2, BHLHB2, BHLHB3, CLOCK, CRY1, CRY2, CSNK1E, DBP, NPAS2, NR1D1, PER1, PER2, PER3, RORA, TIMELESS, VIP, and VIPR2) in a sample of 534 MD patients (335 with unipolar major mood depression (MDD) and 199 with bipolar disorder (BD)) and 440 community-based screened controls. Nominally, statistically significant associations were found in 15 circadian genes. The gene-wide test, corrected for the number of SNPs analyzed in each gene, identified significant associations in CRY1 (rs2287161), NPAS2 (rs11123857), and VIPR2 (rs885861) genes with the combined MD sample. In the MDD subsample, the same SNPs in CRY1 and NPAS2 of the combined sample remained associated, whereas in the BD subsample CLOCK (rs10462028) and VIP (rs17083008) were specifically associated. The association with an SNP located 3′ near CRY1 gene in MDD remained statistically significant after permutation correction at experiment level (p=0.007). Significant additive effects were found between the SNPs that were statistically significant at the gene-wide level. We also found evidence of associations between two-marker haplotypes in CRY1 and NPAS2 genes and MD. Our data support the contribution of the circadian system to the genetic susceptibility to MD and suggest that different circadian genes may have specific effects on MD polarity.

Previous studies in mice have reported five different microRNAs (miRNAs; miR-219-1/132/183/96/182) to be modulators of the endogenous circadian clock and have presented experimental evidence for some of the genes involved in the molecular clock machinery as target sites. Moreover, disruption of circadian rhythms has long been implicated in the pathophysiology of major depression (MD). We investigated these miRNAs and some of their target sites at the sequence and functional levels as possible predisposing factors for susceptibility to MD and related chronobiological subphenotypes. Mutational screening was performed in a sample of 359 MD patients and 341 control individuals. We found a significant association between the T allele of the rs76481776 polymorphism in the pre-miR-182 and late insomnia in MD patients. Previous studies have reported an association between insomnia and CLOCK gene, a predicted miR-182 target site. A significant overexpression of miR-182 was detected by quantitative real-time polymerase chain reaction in cells transfected with the mutated form of the pre-miR-182 when compared with wild-type form. Moreover, a significant reduction in luciferase activity of plasmids with 3′ UTR of ADCY6, CLOCK and DSIP genes was shown when transfecting cells with the mutated form of pre-miR-182 compared with cells that did not express miR-182. These data indicate that abnormal processing of pre-miR-182 in patients carrying the T allele of the rs76481776 polymorphism may contribute to the dysregulation of circadian rhythms in MD patients with insomnia, which could influence expression levels of the mature form of miR-182 and might increase downregulation in some of its target genes.

A fundamental difficulty in human genetics research is the identification of the spectrum of genetic variants that contribute to the susceptibility to common/complex disorders. We tested here the hypothesis that functional genetic variants may confer susceptibility to several related common disorders. We analyzed five main psychiatric diagnostic categories (substance‐abuse, anxiety, eating, psychotic, and mood disorders) and two different control groups, representing a total of 3,214 samples, for 748 promoter and non‐synonymous single nucleotide polymorphisms (SNPs) at 306 genes involved in neurotransmission and/or neurodevelopment. We identified strong associations to individual disorders, such as growth hormone releasing hormone (GHRH) with anxiety disorders, prolactin regulatory element (PREB) with eating disorders, ionotropic kainate glutamate receptor 5 (GRIK5) with bipolar disorder and several SNPs associated to several disorders, that may represent individual and related disease susceptibility factors. Remarkably, a functional SNP, rs945032, located in the promoter region of the bradykinin receptor B2 gene (BDKRB2) was associated to three disorders (panic disorder, substance abuse, and bipolar disorder), and two additional BDKRB2 SNPs to obsessive‐compulsive disorder and major depression, providing evidence for common variants of susceptibility to several related psychiatric disorders. The association of BDKRB2 (odd ratios between 1.65 and 3.06) to several psychiatric disorders supports the view that a common genetic variant could confer susceptibility to clinically related phenotypes, and defines a new functional hint in the pathophysiology of psychiatric diseases.

Recent research suggests that neuroplastic and neuroinflammatory changes may account for the mode of action of electroconvulsive therapy (ECT), although extant data do not allow for a clear disambiguation between these two hypotheses. Multimodal neuroimaging approaches (for example, combining structural and metabolic information) may help in clarifying this issue. Here we aimed to assess longitudinal changes in (i) regional gray matter (GM) volumes and (ii) hippocampal metabolite concentrations throughout an acute course of bitemporal ECT, as well as (iii) to determine the association between imaging changes and clinical improvement. We assessed 12 patients with treatment-resistant depression (TRD) at four time points (pre-treatment, after the first ECT session, after the ninth ECT session and 15 days after ECT course completion) and 10 healthy participants at two time points, 5 weeks apart. Patients with TRD showed bilateral medial temporal lobe (MTL) and perigenual anterior cingulate cortex volume increases. Left MTL volume increase was associated with (i) a hippocampal N-acetylaspartate concentration decrease, (ii) a hippocampal Glutamate+Glutamine concentration increase and (iii) significant clinical improvement. The observed findings are, in part, compatible with both neuroplastic and neuroinflammatory changes induced by ECT. We postulate that such phenomena may be interrelated, therefore reconciling the neuroplasticity and neuroinflammatory hypotheses of ECT action.