Chronic pain, often defined as pain lasting longer than three months, may affect between one-third and one-half of U.K. adults. It can result from a variety of conditions, including arthritis, cancer and back problems, yet its genetic and environmental risk factors are poorly understood.
In a new PLOS Medicine study, Andrew McIntosh and colleagues used two major U.K. population studies and two genome-wide association studies to examine the contributions of genetics and shared family environments to the risk of suffering chronic pain, and to elucidate any correlation between chronic pain and major depressive disorder (MDD).
The authors found that multiple genes contribute to the risk of developing chronic pain, but shared family environments are also important. They also found a correlation between chronic pain and MDD, with some of the same genetic and environmental factors contributing to the risk of developing both conditions. Interestingly, the presence of chronic pain makes MDD more likely not only in an individual but also in their partner or spouse.
Why does living with a spouse with chronic pain make you more likely to be severely depressed? A number of factors may be involved:
- You may choose a spouse similar to yourself, with similar existing predispositions to the conditions (assortative mating).
- It’s possible that caring for a spouse with chronic illness makes you more likely to develop depression.
- The environment you share with your spouse may contribute to both your risks of chronic pain and MDD; shared environmental factors could include diet, infectious diseases, and hobbies.
The study could not determine the extent to which such factors might contribute to the spousal effect. However, identifying the environmental and genetic causal mechanisms that link chronic pain and MDD could help to prevent and treat these debilitating conditions.
Research Article: McIntosh AM, Hall LS, Zeng Y, Adams MJ, Gibson J, Wigmore E, et al. (2016) Genetic and Environmental Risk for Chronic Pain and the Contribution of Risk Variants for Major Depressive Disorder: A Family-Based Mixed-Model Analysis. PLoS Med 13(8): e1002090. doi:10.1371/journal.pmed.1002090
Additional Research: Fayaz A, Croft P, Langford RM, Donaldson LJ, Jones GT. (2016). Prevalence of Chronic Pain in the UK: A Systematic Review and Meta-Analysis of Population Studies. BMJ Open 2016;6:e010364. doi:10.1136/bmjopen-2015-010364