Tsen Vei is as SSA academic fellow in the Department of Psychiatry at the University of Cambridge. With a background in experimental psychology and cognitive neuroscience, his research investigates the neuropsychological mechanisms underlying addictive disorders, with the ultimate goal of translating these insights into effective, targeted interventions. His current research integrates computational modelling, behavioural paradigms, and neuroimaging to study the biobehavioural processes that drive addictive behaviours. He holds a PhD in Psychiatry from the University of Cambridge (UK) and a BSc in Psychology from the University of Bath (UK).

Abstract

Unravelling the effects of regular cannabis, alcohol, and cocaine use on neuropsychological functioning

Regular substance use can become dysfunctional when it disrupts the neuropsychological processes that control behaviour. However, determining their specific harms is challenging because people often use multiple drugs together and have co-occurring mental illnesses. Through selective recruitment, we characterised how commonly used substances (alcohol, cannabis, and cocaine) affect neuropsychological functions that regulate behaviour. Given their distinct pharmacology, we hypothesised that behaviour profiles vary across substances. We recruited individuals who regularly used either cannabis (n=44), alcohol (n=57), or cocaine (n=48), and those with minimal drug use (n=109). Participants completed clinical scales of drug use severity (alcohol: Alcohol-Use-Disorder-Identification-Test; cannabis: Cannabis-Use-Disorder-Identification-Test-Revised; cocaine: Obsessive-Compulsive-Drug-use-Scale), and established paradigms of reinforcement learning, reward/loss processing, decision-making, and delay discounting. We used Bayesian multivariable regression models to investigate the effects of drug use severity on these neuropsychological functions. Greater severity of cannabis and cocaine use predicted poorer reinforcement learning. By contrast, alcohol use severity did not predict poorer reinforcement learning but instead predicted reduced reward and loss processing. Both cannabis and alcohol use severity, but not cocaine, predicted steeper delay discounting. Neither financial nor social decision-making were associated with any severity index. Through targeted recruitment and comprehensive neuropsychological profiling, our data revealed the distinct effects of commonly used substances on basic neuropsychological functions, demonstrating how their regular use can adversely affect behaviour. These findings offer novel insights into the extent of harm from regular substance use, which could identify candidate psychological processes to target for early intervention.