It’s often difficult to recruit and retain individuals with alcohol- or drug dependency in multi-session research studies, yet this is particularly important when pharmacological interventions are being assessed. To overcome this problem, the Imperial College Cambridge Manchester (ICCAM) platform was established. This experimental medicine approach spanned multiple sites across the UK, including the University of Cambridge and aimed to characterise behavioural and neural functioning in alcohol and drug dependence. The project, which spanned two years, was made up of several testing sessions, each examining the effects of a pharmacological treatment targeting distinct neurotransmitter systems.
The ICCAM platform study included 155 participants at baseline and aimed to examine reward processing, impulsivity and emotional reactivity, which have each been implicated in the progression and maintenance of addiction. The group assessed the effects of certain medications on these behaviours and on the brain, including selective antagonists for µ-opioid receptor, dopamine D3 receptor and neurokinin 1 receptor, in a randomised, placebo-controlled crossover design.
One of the first articles from this endeavour was published last month in Psychopharmacology. The report examines several self-reported and behavioural measures of impulsivity, a test of attentional shifting, as well as a measure of motor control during functional MRI. Participants included 86 abstinent substance dependent individuals, made up of alcohol dependence only (27), and those with a history of dependence to multiple substances or polydrug dependence (59), alongside 57 control individuals. These large sample sizes are a substantial benefit of this cross-centre study design.
Substance dependent individuals scored significantly higher on self reported measures of impulsivity, but the alcohol and polydrug dependent individuals were not different from each other. There were differences, however, in a measure of decisional impulsivity: delay discounting. To measure delay discounting, participants are given choices of either a small monetary reward immediately or a larger reward after a delay. The tendency to choose the smaller reward over the larger but later reward marks a form of decisional impulsivity. Polydrug dependent individuals scored higher on this measure than both alcohol dependent and healthy control individuals. There were no group differences on other behavioural measures or during functional MRI.
Eleanor Taylor, the lead author of the study commented:
“This study highlights the importance of platforms like ICCAM because they enable us to compare large and varied samples of substance dependent individuals across the same cognitive measures. This enables us to identify subtle differences between users and develop more targeted treatment.”
Written by Laurel Morris.