Six-month buprenorphine-naloxone treatment is associated with neurocognitive function improvement in opioid dependence

Background and Aim: The number of longitudinal studies on cognitive functions in patients on buprenorphine-based agonist treatment is limited. Our objective was to assess the change in neurocognitive functions over the first 6 months of buprenorphine-naloxone (BNX) treatment for opioid dependence (OD) and compare cognitive functions on BNX and controls. Methods: We selected 60 patients with OD aged 18 to 55 years and 20 sex-matched controls; and excluded patients with other substance dependence, human immunodeficiency virus (HIV), head injury, epilepsy, and severe mental illness. We assessed patients thrice: at baseline, 3, and 6 months and Controls once. Cognitive tests included Wisconsin card sorting test (WCST), Iowa gambling task (IGT), trail making tests A and B (TMT-A and B), verbal and visual N-back test (NBT), and standard progressive matrices (SPM). We measured with-in group effect size with Cohen's D (d). Results: A total of 24 participants completed at least one follow-up; 17 completed both follow-up assessments. All participants were men. At baseline, the patients performed worse than healthy controls in IGT, TMT-A, and B, and visual and verbal NBT. At 3 months, the performance of visual NBT improved significantly (d = 1.2 for NBT1; 1.3 for NBT2). At 6 months, additional performance improvements were seen in WCST ("perseverative error" d = 1.2), IGT ("net total score" d = 1.2), TMT-A (d = 1.1), and verbal NBT ("omission error" d = 1.7). Except for visual-NBT, results did not differ between patients and controls at both follow-ups. Conclusion: Cognitive flexibility, decision making, attention, working memory, and psychomotor speed showed improvements over 6 months of a stable dose of BNX.