Preattentive information processing in schizophrenia with cannabis abuse: an ERP study

Introduction: Cannabis abuse is discussed as an independent risk factor for schizophrenia. Little is known about the influence of cannabis use on the disrupted preattentive information processing in schizophrenia. In a preliminary study we found a partial deficit in the late phase of the attentive sensory gating process in a group of healthy cannabis users. This deficit could not be demonstrated in schizophrenic patients with and without cannabis use. In the prestent study we investigated the preattentive phase of the sensory gating process in patients with and without cannabis-use in a much larger sample.

Methods: Clinically stable, medicated schizophrenic patients with and without former cannabis abuse, former cannabis users and healthy controls were examined in a auditory paired stimulus paradigm. The sensory gating for the evoked potentials P50 was measured.

Results: In contrast to our preliminary results on the attentive sensory gating process we found no gating deficit in the early phase of the information processing in this larger sample of healthy cannabis users. However, the schizophrenic cannabis users showed a significantly lower amplitude of P50 compared to the schizophrenic patients without cannabis use.

Discussion: Cannabis seems to impair auditory evoked potentials in schizophrenia even further which might correspond to its disease-deteriorating properties.