Association of herbal cannabis use with negative psychosocial parameters in patients with fibromyalgia.

OBJECTIVE Patients with chronic pain, including fibromyalgia (FM), may seek treatments outside of mainstream medicine. Medicinal cannabinoids are popularly advocated for pain relief but with limited evidence for efficacy in FM. The extent of use of cannabinoids in FM is unknown. METHODS We have documented the self-reported prevalence of cannabinoid use in 457 patients with the diagnosis of FM and referred to a tertiary care pain center. We validated the diagnosis of FM and examined the associations of cannabinoid use in these patients. RESULTS Cannabinoids were being used by 13% of all patients, of whom 80% used herbal cannabis (marijuana), 24% used prescription cannabinoids, and 3% used both herbal cannabis and prescription cannabinoids. One-third of all men used cannabinoids. Current unstable mental illness (36% versus 23%; P = 0.002), opioid drug-seeking behavior (17% versus 4%; P = 0.002), and male sex (26% versus 7%; P = 0.0002) were all associated with herbal cannabis use. There was a trend for cannabinoid users to be unemployed and receiving disability payments. The diagnosis of FM was validated in 302 patients, with 155 assigned another primary diagnosis. When the FM group was analyzed separately, significant associations were lost, but trends remained. CONCLUSION Cannabinoids were used by 13% of patients referred with a diagnosis of FM. The association of herbal cannabis use with negative psychosocial parameters raises questions regarding the motive for this self-medication practice. Although cannabinoids may offer some therapeutic effect, caution regarding any recommendation should be exercised pending clarification of general health and psychosocial problems, especially for those self-medicating.