Healthy cannabis users and people at ultra-high risk for psychosis both showed reduced P300 brain wave amplitudes compared to non-using controls, suggesting overlapping effects on information processing.
Read this if you are interested in how cannabis affects brain function in people who may be vulnerable to psychosis.
Cannabis users and ultra-high-risk subjects showed similar P300 brain wave reductions
What the researchers found
Researchers measured brain wave responses (event-related potentials, or ERPs) in 48 ultra-high-risk (UHR) subjects and 50 healthy controls, split into cannabis users and non-users within each group. Healthy cannabis users and UHR subjects both showed smaller P300 amplitudes compared to non-using healthy controls.
Healthy cannabis users also showed delayed P300 and N200 latencies, suggesting slower information processing speed associated with cannabis use. However, within the UHR group, cannabis users and non-users did not differ on any ERP measure.
Associations between brain wave abnormalities and clinical symptoms were found, particularly between N100 latencies and P300 amplitudes and the severity of positive symptoms and general psychopathology.
Why it matters
The P300 brain wave reflects attention and information processing capacity. Finding similar reductions in both healthy cannabis users and UHR subjects raises questions about whether cannabis produces information processing changes that resemble those seen in early psychosis-related states.
The numbers in context
48 UHR subjects (19 cannabis users) and 50 healthy controls (21 cannabis users) were studied. Both UHR subjects and healthy cannabis users showed reduced P300 amplitudes compared to non-using controls.
How the study worked
Cross-sectional study comparing ERP components (N100, N200, P200, P300) across four groups: UHR cannabis users (n=19), UHR non-users (n=29), healthy control cannabis users (n=21), and healthy control non-users (n=29). Standard oddball paradigm was used to elicit ERPs.
What this study cannot tell us
Small sample sizes, particularly in the cannabis-using subgroups. Cross-sectional design cannot determine whether cannabis caused the ERP changes or whether pre-existing differences led to cannabis use. Cannabis use was not standardized for frequency, quantity, or potency.
How to read the evidence
Cross-sectional ERP study with relatively small subgroups. Interesting findings that require replication.
When this study was published
Published in 2013. Neurophysiological research on cannabis and psychosis risk has continued to develop.
The bigger picture
Understanding how cannabis affects brain information processing in people already at risk for psychosis is relevant to the ongoing debate about whether cannabis can trigger psychotic episodes. The overlap in brain wave changes between cannabis users and UHR subjects is intriguing but does not prove a causal pathway.
Questions still open
- Do the ERP changes in healthy cannabis users normalize with abstinence? Does cannabis use in UHR individuals affect the rate of transition to full psychosis? Are the similar P300 reductions in cannabis users and UHR subjects produced by the same underlying neural mechanisms?
Common questions
What is the P300 brain wave?
Does cannabis affect brain waves the same way psychosis risk does?
Read the original research
Effects of cannabis use on event related potentials in subjects at ultra high risk for psychosis and healthy controls.
International journal of psychophysiology : official journal of the International Organization of Psychophysiology, 88(2), 149-56
Citation
van Tricht, Mirjam J; Harmsen, Emma C; Koelman, Johannes H T M; Bour, Lo J; van Amelsvoort, Thérèse A; Linszen, Don H; de Haan, Lieuwe; Nieman, Dorien H. (2013). Effects of cannabis use on event related potentials in subjects at ultra high risk for psychosis and healthy controls.. International journal of psychophysiology : official journal of the International Organization of Psychophysiology, 88(2), 149-56. https://doi.org/10.1016/j.ijpsycho.2013.03.012
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