Cognitive function is largely intact in methadone maintenance treatment patients

Objectives: To confirm our previous findings of less cognitive impairments (based on cognitive screening tools) among methadone maintenance treatment (MMT) patients who achieved take-home dose (THD) privileges. Methods: a random sample of 65 Israeli MMT patients were studied using computerised, age and education standardised, cognitive domains (attention, executive function, memory, motor skills), and non-computerised phonetic and semantic verbal fluency. Results: Cognitive scores were within +/- 1 standard deviation (SD) of average for most domains, including non-verbal IQ, attention and motor skills. Verbal fluency and memory were >1 SD below average (mean = 84; z = -1.1 for both). Females were younger than the males and had poorer motor skills (P = 0.005) but better verbal memory (P < 0.0005). Opiate usage duration correlated with reaction time (P = 0.05) and inversely with verbal memory (P = 0.01). Overall cognitive function was poorest among 25 (38.5%) current drug users, and 6 (9.2%) lifetime schizophrenia patients. Cognitive domains were comparable between THD privileges subgroups. Conclusions: Despite heterogeneity in MMT duration, abuse duration, substance use and psychiatric comorbidity, all performed within +/- 1 SD of average for age and education in most cognitive domains. Our findings challenge the notion of MMT as being synonymous with compromised cognition and may lead to reduced bias regarding cognitive function of MMT patients.