Effects of cannabis use on event related potentials in subjects at ultra high risk for psychosis and healthy controls

• Healthy cannabis using controls and UHR subjects show similar P3 amplitude reductions.
• Cannabis use is associated with prolonged ERP latencies.
• In cannabis users, ERP abnormalities are associated with more severe UHR symptoms.

Cannabis use has consistently been associated with psychotic symptoms as well as cognitive impairments. Moreover, its use may provoke subclinical psychotic symptoms and is associated with neuropsychological dysfunctions in subjects at ultra high risk (UHR) for developing psychosis. However, to our knowledge, no data are yet available on the relationship between cannabis use, UHR symptoms and information processing as assessed with event related potentials (ERP) in UHR subjects. This cross-sectional study therefore aimed to investigate N100, N200, P200 and P300 ERP components in 48 UHR subjects (19 cannabis users; UHR + C) and 50 healthy controls (21 cannabis users; HC + C). Results showed smaller P300 amplitudes in HC + C and UHR subjects compared to HC − C. Moreover, HC + C showed prolonged P300 and N200 latencies compared to HC − C and UHR − C. No significant ERP differences were found between UHR + C and UHR − C. Regarding the relationship between information processing and psychopathology, we found associations between ERP components and severity of UHR symptoms, findings being most pronounced for N100 latencies and P300 amplitudes and severity of general psychopathology and positive symptoms. We conclude that UHR subjects and healthy cannabis users demonstrate similar P300 amplitude reductions compared to non-using control subjects. In addition, the interrelation of cannabis use with prolonged ERP latencies may signify reduced information processing speed associated with cannabis use. Finally, our findings cautiously support the hypothesis that the clinical phenomena of the UHR state may be associated with abnormalities in stimulus processing.