Both genetic factors and family environment contribute to risk for chronic pain, and contributions of many genes contribute to risk of both chronic pain and major depressive disorder (MDD), according to a new study published in PLOS Medicine. The research was conducted by Andrew McIntosh of the University of Edinburgh, and colleagues and utilized data from 23,960 individuals in the Generation Scotland: Scottish Family Health Study, as well as 112,151 individuals with genotyping and phenotypic data from the United Kingdom Biobank. They found that heritability accounted for 38.4% of the variation in chronic pain risk, and that shared environment with spouses accounted for 18.7% of the variation in susceptibility to chronic pain. They also found that chronic pain was correlated with depression. Finally, McIntosh and colleagues found evidence that polygenic risk contributes to chronic pain and MDD. Data from two independent genome wide association studies, Pfizer-23andMe and the Psychiatric Genomics Consortium Major Depressive Disorder Working Group, suggested that chronic pain risk arises through the combined effect of many different genetic risk factors and that the cumulative effects of genetic risk factors for depression increased an individual's chance of having chronic pain. The researchers note that assortative mating (choosing a spouse who is similar to oneself) may be responsible for some of the spousal effects, and that these associations do not identify mechanisms through which the genes might be contribute chronic pain. Nevertheless, the study suggests strong genetic and environmental links in risk for MDD and chronic pain and that identifying the shared causal mechanisms may be relevant to finding new treatments.

The researchers say: "The answer to these key questions are likely to signpost new directions for therapeutic interventions and highlight the symptoms that are most amenable to treatment, as well as to prevention."