Lithium is a first-line treatment in bipolar disorder, but individual response is variable. Previous studies have suggested that lithium response is a heritable trait. However, no genetic markers of treatment response have been reproducibly identified. Here, we report the results of a genome-wide association study of lithium response in 2563 patients collected by 22 participating sites from the International Consortium on Lithium Genetics (ConLiGen). Data from common single nucleotide polymorphisms (SNPs) were tested for association with categorical and continuous ratings of lithium response. Lithium response was measured using a well established scale (Alda scale). Genotyped SNPs were used to generate data at more than 6 million sites, using standard genomic imputation methods. Traits were regressed against genotype dosage. Results were combined across two batches by meta-analysis. A single locus of four linked SNPs on chromosome 21 met genome-wide significance criteria for association with lithium response (rs79663003, p=1·37 × 10(-8); rs78015114, p=1·31 × 10(-8); rs74795342, p=3·31 × 10(-9); and rs75222709, p=3·50 × 10(-9)). In an independent, prospective study of 73 patients treated with lithium monotherapy for a period of up to 2 years, carriers of the response-associated alleles had a significantly lower rate of relapse than carriers of the alternate alleles (p=0·03268, hazard ratio 3·8, 95% CI 1·1-13·0). The response-associated region contains two genes for long, non-coding RNAs (lncRNAs), AL157359.3 and AL157359.4. LncRNAs are increasingly appreciated as important regulators of gene expression, particularly in the CNS. Confirmed biomarkers of lithium response would constitute an important step forward in the clinical management of bipolar disorder. Further studies are needed to establish the biological context and potential clinical utility of these findings. Deutsche Forschungsgemeinschaft, National Institute of Mental Health Intramural Research Program.

This review will discuss the role of childhood trauma in bipolar disorders. Relevant studies were identified via Medline (PubMed) and PsycINFO databases published up to and including July 2015. This review contributes to a new understanding of the negative consequences of early life stress, as well as setting childhood trauma in a biological context of susceptibility and discussing novel long-term pathophysiological consequences in bipolar disorders. Childhood traumatic events are risk factors for developing bipolar disorders, in addition to a more severe clinical presentation over time (primarily an earlier age at onset and an increased risk of suicide attempt and substance misuse). Childhood trauma leads to alterations of affect regulation, impulse control, and cognitive functioning that might decrease the ability to cope with later stressors. Childhood trauma interacts with several genes belonging to several different biological pathways [Hypothalamic–pituitary–adrenal (HPA) axis, serotonergic transmission, neuroplasticity, immunity, calcium signaling, and circadian rhythms] to decrease the age at the onset of the disorder or increase the risk of suicide. Epigenetic factors may also be involved in the neurobiological consequences of childhood trauma in bipolar disorder. Biological sequelae such as chronic inflammation, sleep disturbance, or telomere shortening are potential mediators of the negative effects of childhood trauma in bipolar disorders, in particular with regard to physical health. The main clinical implication is to systematically assess childhood trauma in patients with bipolar disorders, or at least in those with a severe or instable course. The challenge for the next years will be to fill the gap between clinical and fundamental research and routine practice, since recommendations for managing this specific population are lacking. In particular, little is known on which psychotherapies should be provided or which targets therapists should focus on, as well as how childhood trauma could explain the resistance to mood stabilizers.

The hypothesis that the S allele of the 5-HTTLPR serotonin transporter promoter region is associated with increased risk of depression, but only in individuals exposed to stressful situations, has generated much interest, research and controversy since first proposed in 2003. Multiple meta-analyses combining results from heterogeneous analyses have not settled the issue. To determine the magnitude of the interaction and the conditions under which it might be observed, we performed new analyses on 31 data sets containing 38 802 European ancestry subjects genotyped for 5-HTTLPR and assessed for depression and childhood maltreatment or other stressful life events, and meta-analysed the results. Analyses targeted two stressors (narrow, broad) and two depression outcomes (current, lifetime). All groups that published on this topic prior to the initiation of our study and met the assessment and sample size criteria were invited to participate. Additional groups, identified by consortium members or self-identified in response to our protocol (published prior to the start of analysis) with qualifying unpublished data, were also invited to participate. A uniform data analysis script implementing the protocol was executed by each of the consortium members. Our findings do not support the interaction hypothesis. We found no subgroups or variable definitions for which an interaction between stress and 5-HTTLPR genotype was statistically significant. In contrast, our findings for the main effects of life stressors (strong risk factor) and 5-HTTLPR genotype (no impact on risk) are strikingly consistent across our contributing studies, the original study reporting the interaction and subsequent meta-analyses. Our conclusion is that if an interaction exists in which the S allele of 5-HTTLPR increases risk of depression only in stressed individuals, then it is not broadly generalisable, but must be of modest effect size and only observable in limited situations.