Psychopharmacology, Feb, 2010, Vol.208(2), p.353(11)
Byline: Thomas Wobrock (1), Alkomiet Hasan (1), Berend Malchow (1), Claus Wolff-Menzler (1), Birgit Guse (1), Nicolas Lang (2), Thomas Schneider-Axmann (1), Ullrich K. H. Ecker (3), Peter Falkai (1) Keywords: Schizophrenia; Substance abuse; Cortical inhibition; Transcranial magnetic stimulation (TMS); Cannabinoids; Electrophysiology Abstract: Rationale/objectives There is a high prevalence of substance use disorder (SUD) in first-episode schizophrenia (SZ), but its contribution to the underlying SZ pathophysiology remains unclear. Several studies using transcranial magnetic stimulation (TMS) have observed abnormalities in human motor cortex (M1) excitability in SZ. Studies on cortical excitability comparing SZ patients with and without comorbid substance abuse are lacking. Methods A total of 29 first-episode SZ patients participated in this study 12 had a history of comorbid cannabis abuse (SZ-SUD) and 17 did not (SZ-NSUD). We applied TMS to right and left M1 areas to assess the resting motor threshold (RMT), short-interval cortical inhibition (SICI), intracortical facilitation (ICF), and the contralateral cortical silent period (CSP). Results In SICI and ICF conditions, right M1 stimulation led to significantly higher motor evoked potential ratios in SZ-SUD compared to SZ-NSUD. This suggests lower cortical inhibition and increased ICF in first-episode SZ with previous cannabis abuse. There were no group differences in RMT and CSP duration. Neither were there any significant correlations between psychopathology (as indexed by Positive and Negative Syndrome Scale), disease characteristics, the extent of cannabis abuse, and TMS parameters (SICI, ICF, and CSP). Conclusions Comorbid cannabis abuse may potentiate the reduced intracortical inhibition and enhanced ICF observed in first-episode SZ patients in some previous studies. This finding suggests an increased alteration of GABA.sub.A and NMDA receptor activity in cannabis-abusing first-episode patients as compared to schizophrenia patients with no history of substance abuse. This may constitute a distinct vulnerability factor in this special population. Author Affiliation: (1) Department of Psychiatry and Psychotherapy, Georg-August-University Gottingen, Von-Siebold-Strasse 5, 37075, Gottingen, Germany (2) Department of Neurology, Christian-Albrechts-University Kiel, 24195, Kiel, Germany (3) School of Psychology, University of Western Australia, Crawley, WA, 6009, Australia Article History: Registration Date: 18/11/2009 Received Date: 09/07/2009 Accepted Date: 16/11/2009 Online Date: 09/12/2009 Article note: T. Wobrock and A. Hasan contributed equally.
Marijuana ; Cannabinoids ; Substance Abuse ; Gaba ; N-methyl-d-aspartate ; Schizophrenia ; Comorbidity ; Psychotherapy