Interaction of schizophrenia and chronic cannabis use on reward anticipation sensitivity

Abstract

Chronic cannabis use and schizophrenia are both thought to affect reward processing. While behavioural and neural effects on reward processing have been investigated in both conditions, their interaction has not been studied, although chronic cannabis use is common among these patients. In the present study eighty-nine participants divided into four groups (control chronic cannabis users and non-users; schizophrenia patient cannabis users and non-users) performed a two-choice decision task, preceded by monetary cues (high/low reward/punishment or neutral), while being scanned using functional magnetic resonance imaging. Reward and punishment anticipation resulted in activation of regions of interest including the thalamus, striatum, amygdala and insula. Chronic cannabis use and schizophrenia had opposing effects on reward anticipation sensitivity. More specifically control users and patient non-users showed faster behavioural responses and increased activity in anterior/posterior insula for high magnitude cues compared to control non-users and patient users. The same interaction pattern was observed in the activation of the right thalamus for reward versus punishment cues. This study provided evidence for interaction of chronic cannabis use and schizophrenia on reward processing and highlights the need for future research addressing the significance of this interaction for the pathophysiology of these conditions and its clinical consequences.

Fig. 1. Reaction time (RT) differences between groups.

Mean RT difference (ms) for magnitude contrast for each group. ms milliseconds, HC−C non-cannabis user healthy controls, HC + C cannabis-user healthy controls, SZ−C non-cannabis user schizophrenia patients, SZ + C cannabis-user schizophrenia patients. Error bars indicate standard errors of the mean differences.

Fig. 2. Validation analysis.

Clusters of higher activation for reward + punishment versus neutral conditions for the valence (a) and magnitude (b) cue period as well as high versus low + neutral for the magnitude cue period (c). Clusters thresholded at p < 0.005 for visualisation purposes. Red = thalamus; green = caudate; cyan = nucleus accumbens; peach = amygdala; brown = dorsal anterior insula; yellow = ventral anterior insula.

Fig. 3. Main analysis.

Clusters showing significant modulation by the interaction of cannabis and schizophrenia for the reward versus punishment contrast (a) and the magnitude contrast (b). Clusters thresholded at p < 0.005 for visualisation purposes. Red = thalamus; yellow = ventral anterior insula; brown = dorsal anterior insula; violet = posterior insula. The bar plots show mean beta values for each cluster for each group and error bars show standard errors of the mean beta values. HC−C non-cannabis user healthy controls, HC + C cannabis-user healthy controls, SZ−C non-cannabis user schizophrenia patients, SZ + C cannabis-user schizophrenia patients.