title: Differential effects of chronic cannabis use on preattentional cognitive functioning in abstinent schizophrenic patients and healthy subjects.
abstract: BACKGROUND
  A number of studies indicate a higher risk for psychosis as well as for neurocognitive deficits in healthy cannabis users. However, little is known about the impact of cannabis use on outcome in schizophrenia. In fact, there is growing evidence that cannabis-using schizophrenic patients may show preserved or even better neurocognitive performance compared to schizophrenic non-users.
  
  
  METHODS
  We measured mismatch negativity (MMN) to investigate preattentional neurocognitive functioning in long-term abstinent chronic cannabis users with (SZCA n=27) and without schizophrenia (COCA n=32) compared to schizophrenic patients (SZ n=26) and healthy controls (CO n=34) without any chronic drug use.
  
  
  RESULTS
  Healthy cannabis users showed reduced frontal MMN compared to controls (p=0.036). In contrast, cannabis-using schizophrenic patients showed increased frontal MMN compared to schizophrenic patients without cannabis use (p=0.038). Comparing non-cannabis users, schizophrenic patients showed reduced frontal MMN (p=0.001). No significant differences were found between CO and SZCA (p=0.27), and COCA and SZCA (p=0.50).
  
  
  CONCLUSIONS
  Results suggest that chronic cannabis use may have different effects on preattentional neurocognitive functioning in schizophrenic patients when compared to healthy subjects. This may be related to preexisting differences in the endocannabinoid system between schizophrenic patients and healthy subjects. However, due to the naturalistic design of the study, the results must be interpreted with caution.
authors.affiliation: Charité-Universitätsmedizin Berlin, Department of Psychiatry and Psychotherapy, Campus Mitte, Charitéplatz 1, 10177 Berlin, Germany. johannes.rentzsch@charite.de
authors.forename: Johannes
authors.initials: J
authors.lastname: Rentzsch
authors.forename: Elise
authors.initials: E
authors.lastname: Buntebart
authors.forename: Ada
authors.initials: A
authors.lastname: Stadelmeier
authors.forename: Jürgen
authors.initials: J
authors.lastname: Gallinat
authors.forename: Maria C
authors.initials: MC
authors.lastname: Jockers-Scherübl
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D001288:Attention / Q000502:physiology*; D003072:Cognition Disorders / Q000209:etiology*; D003265:Contingent Negative Variation / Q000502:physiology; D004569:Electroencephalography; D005072:Evoked Potentials, Auditory / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D002189:Marijuana Abuse / Q000150:complications* / Q000523:psychology*; D008875:Middle Aged; D009483:Neuropsychological Tests; D012559:Schizophrenia / Q000150:complications*; D012565:Schizophrenic Psychology; D055815:Young Adult