Cognitive impairment in drug-dependent patients receiving methadone (MMP) maintenance treatment has been reported previously. We assessed cognitive functioning after at least 14 days of stable substitution treatment with buprenorphine (BUP) or MMP and after 8 to 10 weeks. We performed a randomized, nonblinded clinical trial in 59 drug-dependent patients receiving either BUP or MMP maintenance treatment and healthy normal controls (n = 24) matched for sex, age, and educational level. Thirteen patients dropped out of the study before the second testing was performed (BUP, n = 22; MMP, n = 24). A neuropsychological test battery was used to measure selective attention, verbal memory, motor/cognitive speed, and cognitive flexibility. In addition, subjective perceived stress was assessed with a questionnaire. Patients in both treatment groups performed equally well in all of the cognitive domains tested. Both BUP and MMP patients showed significantly improved concentration and executive functions after 8 to 10 weeks of stable substitution treatment. The control group achieved better results than the BUP and MMP groups in most cognitive domains, indicating cognitive impairment in the patients. Perceived stress did not show any significant change after 8 to 10 weeks of treatment, and no major differences were detected between the 3 groups. No effects of perceived stress on cognitive function were found. Our results indicate a cognitive impairment in patients receiving maintenance treatment with BUP or MMP compared with healthy controls. Selective attention improved in both patient groups during treatment. We propose that the improvement of attention may facilitate rehabilitation of drug-dependent patients.
*Psychiatric Hospital, University of Munich, Munich, Germany; †Private Hospital Meiringen, Meiringen, Switzerland; and ‡Institute for Therapy Research IFT, Munich, Germany.
Received April 16, 2008; accepted after revision July 28, 2008.
This article has been prepared in the context of the project F9 "Optimizing substitution treatment outcome by allocating substitution substances and psychosocial treatment components to patient profiles" (short title: OSTD) of the Addiction Research Network ASAT ("Allocating Substance Abuse Treatments to Patient Heterogeneity" [Buehringer et al. Suchtmed 2004;6:7-13]). Contact information: e-mail: firstname.lastname@example.org (www.asat-verbund.de). ASAT is sponsored by a federal grant of the Federal Ministry of Education and Research (01 EB 0440-0441, 01 EB 0142). This study was also supported by a grant from the Justin Rockola Foundation.
Address correspondence and reprint requests to Michael Soyka, MD, Private Hospital Meiringen, PO Box 612, CH-3860 Meiringen, Switzerland. E-mail: email@example.com.