Improvement in Cognitive Performance after One Year of Methadone Maintenance Treatment.

Individuals with substance use disorders are known to suffer from stress, poor sleep, and cognitive impairment. We investigated whether individuals with opioid use disorder would improve cognitive performance following a year of methadone maintenance treatment (MMT). Perceived Stress Scale (PSS), the Pittsburgh Sleep Quality Index (PSQI), and a standardized computerized cognitive battery were administered at admission (T0) to 29 patients, and repeatedly following one year of MMT (T1) by 19 patients. Admission measures did not differ between those who studied once or twice. Patients who perceived very high stress levels (PSS ≥24) at T0 (11, 37.9%) had lower computerized global cognitive scores (67.6±16.2 vs. 90.9±12.5 p≤0.0005). At T1, PSS and PSQI scores improved significantly among 11 patients with no substance abuse, but worsened among 8 with substance abuse (PSS p(interaction)=0.009, p(groups)=0.005, PSQI p(interaction)=0.01, p(groups)=0.04). Global cognitive score improved at T1 for the entire sample (81.8±20.1 to 89.2±13.8, p=0.05). Differentiation by high stress at T0 or by substance abuse at T1 subgroups showed that improvement was observed by those with very low cognitive scores at T0. Patients with poor cognition may improve following one year of MMT, due to stress and substance abuse reduction. Interventions for stress reduction are recommended.