Genetic Influences on the Dynamics of Pain and Affect in Fibromyalgia

Objective: The purpose of the present investigation was to determine if variation in the catechol- O-methyltransferase (COMT) and mu-opioid receptor (OPRM1) genes is associated with pain-related positive affective regulation in fibromyalgia (FM). Design: Forty-six female patients with FM completed an electronic diary that included daily assessments of positive affect and pain. Between- and within-person analyses were conducted with multilevel modeling. Main Outcome Measure: Daily positive affect was the primary outcome measure. Results: Analyses revealed a significant gene × experience interaction for COMT, such that individuals with met/met genotype experienced a greater decline in positive affect on days when pain was elevated than did either val/met or val/val individuals. This finding supports a role for catecholamines in positive affective reactivity to FM pain. A gene × experience interaction for OPRM1 also emerged, indicating that individuals with at least one asp ⁴⁰ allele maintained greater positive affect despite elevations in daily pain than those homozygous for the asn ⁴⁰ allele. This finding may be explained by the asp ⁴⁰ allele's role in reward processing. Conclusions: Together, the findings offer researchers ample reason to further investigate the contribution of the catecholamine and opioid systems, and their associated genomic variants, to the still poorly understood experience of FM.