A Systematic Review and Meta-Analysis of Cognitive Performance among People with Chronic Use of Opioids for Chronic Non-Cancer Pain.

OBJECTIVE: Opioids, often prescribed for chronic non-cancer pain, may adversely affect cognition. Research has not been synthesized in recent years, during which time academic interest has increased. This study presents meta-analyses on cognitive performance in people taking opioids for chronic non-cancer pain (CNCP). METHODS: We ran systematic literature searches in EMBASE, Medline, and PsycINFO. Eligible studies included people taking opioids for CNCP, an opioid-free group (i.e., case-control) or session (e.g., pre-post), and objective cognitive assessments. Using random-effects meta-analyses, we computed pooled effect sizes for differential task performance for each study design across five domains (motor performance, attention, working memory, executive functions, memory). RESULTS: Seventeen studies were included. Case-control studies covered three control types (healthy, CNCP, taper-off). Pre-post studies were grouped into five follow-ups (four to six and six to nine weeks; three, six, and 12 months). Effect sizes ranged from 0.02-0.62. Cases showed small magnitude impairments in attention and memory compared with healthy controls. Although limited by small sample sizes, there was no clear evidence of impairment in cases compared with opioid-free controls with CNCP. Cases showed some cognitive improvements from opioid-free baseline to follow-up. Effects were strongest for attention and working memory and were apparent from four weeks to six months follow-up. Other effects were small and nonsignificant. CONCLUSIONS: Opioid therapy for CNCP did not worsen cognitive performance and improved it for some domains. People who take opioids for CNCP may evidence deficits in attention and memory, but this is unlikely to translate to global impairment and likely relates to pain more so than opioids.