Investigating the Interaction Between Self-Reported Measures of Pain and COMT and BDNF Polymorphisms in the Setting of Chronic Low Back Pain

PURPOSE Chronic low back pain (CLBP) is now the leading cause of disability worldwide and is the second most common reason for health care visits. The etiology of CLBP is multifactorial, from molecular to psychosocial factors. Single genetic polymorphisms (SNPs) of catechol-o-methyltransferase (COMT) and brain derived neurotrophic factor (BDNF) have been shown to moderate pain outcomes. Also, certain cognitive responses of pain have been shown to amplify pain intensity. Current literature lends support to the predictive value of a bio-psychosocial model on pain outcomes. Thus, it is hypothesized that cognitive pain responses and COMT and BDNF SNPs interact to modulate pain outcomes. METHODS: This cross-sectional study included 424 subjects with CLBP. Subjects provided biological samples for analysis and completed cognitive measures of pain, the pain self-efficacy (PSE) and pain catastrophizing (PCS). A one-way ANOVA was run for rs4680 (COMTVal158Met) and rs6265 (BDNFVal66Met) using the Numerical Rating Scale (NRS), PCS and PSE as phenotypes. LSD post hoc analyses were completed for the rs4680 and r56263 genotypes that showed a statistically significant difference (p RESULTS: One-way ANOVA showed a statistically significant difference in the rs4680 genotypes and NRS pain outcomes (p=0.03). A LSD post hoc analysis of rs4680 revealed that the AG group (p=0.017) had lower pain outcomes compared to the AA group. The one-way ANOVA did not present a relationship between rs6265 genotypes and pain outcomes (p=0.40). Neither pain catastrophizing nor self-efficacy were associated with rs4680 and rs6265. CONCLUSIONS: Results indicate that pain outcomes in rs4680 AG heterozygotes are statistically reduced when compared to AA homozygotes. Thus, the AG genotype of rs4680 could be a significant predictor of pain outcomes in the setting of CLBP.