Drug and Alcohol Dependence 112 (2010) 27–32 Contents lists available at ScienceDirect Drug and Alcohol Dependence journal homepage: www.elsevier.com/locate/drugalcdep Processing dynamic facial affect in frequent cannabis-users: Evidence of deficits in the speed of identifying emotional expressions Bradley Platt ∗ , Sunjeev Kamboj, Celia J.A. Morgan, H. Valerie Curran Clinical Psychopharmacology Unit, Research Department of Clinical, Educational and Health Psychology, University College London, Gower Street, London WC1E 6BT, UK article info Article history: Received 22 October 2009 Received in revised form 1 May 2010 Accepted 4 May 2010 Available online 17 June 2010 Keywords: Cannabis Depression Affective processing Drug abuse abstract Background: While heavy cannabis-users seem to show various cognitive impairments, it remains unclear whether they also experience significant deficits in affective functioning. Evidence of such deficits may contribute to our understanding of the interpersonal difficulties in cannabis-users, and the link between cannabis-use and psychological disorders (Moore et al., 2007). Method: Emotion recognition performance of heavy cannabis-users and non-using controls was com- pared. A measure of emotion recognition was used in which participants identified facial expressions as they changed from neutral (open-mouth) to gradually more intense expressions of sadness, neutral, anger or happiness (open or closed mouth). Reaction times and accuracy were recorded as the facial expressions changed. Participants also completed measures of ‘theory of mind,’ depression and impulsivity. Results: Cannabis-users were significantly slower than controls at identifying all three emotional expressions. There was no difference between groups in identifying facial expressions changing from open-mouth neutral expressions to closed-mouth neutral expressions suggesting that differences in emotion recognition were not due to a general slowing of reaction times. Cannabis-users were also significantly more liberal in their response criterion for recognising sadness. Conclusion: Heavy cannabis-use may be associated with affect recognition deficits. In particular, a greater intensity of emotion expression was required before identification of positive and negative emotions. This was found using stimuli which simulated dynamic changes in emotion expression, and in turn, suggests that cannabis-users may experience generalised problems in decoding basic emotions during social interactions. The implications of these findings are discussed for vulnerability to psychological and interpersonal difficulties in cannabis-users. © 2010 Elsevier Ireland Ltd. All rights reserved. 1. Introduction Adolescents and adults in the United Kingdom are among the world’s heaviest users of cannabis, with a lifetime prevalence of 38% and a previous month prevalence of 9% (European Monitoring Centre for Drugs and Drug Addiction – EMCDDA, 2008; World Health Organisation, 1997). This is of concern, since cannabis-use is associated with a number of negative mental health outcomes (Moore et al., 2007). While considerable attention has focused on the possible link between heavy cannabis-use and psychosis, recent meta-analyses also suggest a dose–response association between cannabis-use and depression (Degenhardt et al., 2003; Moore et al., 2007). There is also increasing concern about the rising num- bers of young people seeking treatment for cannabis dependence (EMCDDA, 2008). Cannabis contains about 70 ingredients – called cannabinoids – which are unique to the plant. Delta-9-tetrahydrocannabinol ( 9 - ∗ Corresponding author. E-mail address: bradley.platt@live.com (B. Platt). THC) is the principle constituent of cannabis and its effects are those that users generally seek. However, another main constituent is cannabidiol (CBD) which has very different effects to THC. Whilst  9 -THC induces positive emotional states in users, it also acutely produces anxiety and psychosis-like symptoms. CBD on the other hand is anxiolytic and may have anti-psychotic properties (D’Souza et al., 2004). Currently, many available strains of cannabis, like skunk’, are very high in  9 -THC but contain little if any CBD (Potter et al., 2008). Although cannabis-users report increased feelings of friend- ship, empathy and interpersonal warmth whilst experiencing the acute effects of  9 -THC (Galanter et al., 1974; Tart, 1971), intoxi- cation may impair individual’s ability to perceive others emotions (Clopton et al., 1979). The specific behavioural effects of cannabis on emotion perception are at present, unclear. Studies investigating the neuronal effects of cannabis using functional magnetic reso- nance imaging (fMRI) have shown  9 -THC (Fusar-Poli et al., 2009; Phan et al., 2008) and chronic cannabis-use (Gruber et al., 2009) to attenuate amygdala activation during emotion perception. This is consistent with the role of the endocannabinoid system in modu- lating the activity of the monoaminergic neurotransmitter systems 0376-8716/$ – see front matter © 2010 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.drugalcdep.2010.05.004