Dr Michal Graczyk is a clinical academic foundation trainee at Oxford University Hospitals. He studied Medicine and Natural Sciences (Psychology and Neuroscience) at the University of Cambridge, graduating with first-class honours. His research investigates the neurobiology and genetics of drug addiction, using large population datasets, computational modelling, and neuroimaging to examine brain-behaviour mechanisms underlying addiction. Michal has presented his work at national and international conferences and is committed to bridging clinical practice and research to advance understanding of substance use disorders and inform more effective approaches to treatment.

Abstract

Cocaine and opioid addictions show distinct patterns in delay discounting: What drug type and abstinence reveal

Delay discounting, a tendency to devalue rewards delayed in time, is widely considered a marker of impulsive decision-making and a shared feature of substance use disorders. However, it remains unclear whether abnormal discounting is expressed differently between drug types. Here we aimed to compare delay discounting in 1) addicted and non-addicted opioid users; 2) active opioid users with comorbid cocaine addiction and patients in recovery. Delay discounting was assessed using Kirby’s 27-item Monetary Choice Questionnaire. First sample comprised opioid-addicted patients (n=24), non-addicted prescription opioid users (n=26) and control participants (n=38) from Hamburg, Germany. Second sample included active (n=77) and abstinent (n=27) patients with comorbid cocaine and opioid addiction, and control participants (n=164) from Cambridgeshire, UK. Hierarchical Bayesian model was used to estimate discounting rates (log10k) and choice sharpness (log10b). Opioid-addicted patients showed increased discounting rates (log10k) than opioid non-addicted patients and controls (F2,85=8.92, p<0.001), with no difference in log10k between the latter groups. Choice consistency (log10b) did not differ across groups. Actively using patients with comorbid cocaine and opioid addiction had increased log10k (F2,265=102.0, p<0.001) and decreased log10b compared with controls (F2,265=107.8, p<0.001). Abstinent patients showed intermediate values on both measures (post hoc p<0.001). Steep delay discounting appears characteristic of addiction rather than a consequence of long-term opioid use, while reduced choice consistency is specific to comorbid cocaine use. Both impairments only partially recover with abstinence. Our findings point towards drug-type specific discounting patterns in patients addicted to cocaine and opioids, underscoring the importance of stratifying decision-making profiles in the assessment and treatment of different substance use disorders.