Deficits in behavioural inhibitory control are attracting increasing attention as a factor behind the development and maintenance of substance dependence. However, evidence for such a deficit is varied in the literature. A meta-analysis of published results indicated that substance use disorders and addiction-like behavioural disorders are associated with impairments in inhibitory control, although the size of this effect varies between drug classes and inhibitory tasks.
Dr Sharna Jamadar
The results reported in the literature to date are contradictory and suffer from small sample sizes. Previous meta-analyses have either considered only one drug type (e.g., alcohol) or collapsed across several types of drug. We conducted a meta-analysis to find the overall effect for several classes of drugs, as well as for addiction-like behavioural disorders.
To provide a weighted mean effect size estimate for several classes of drugs, for inhibitory measures as well as general performance measures.
A literature search revealed 97 papers suitable for inclusion in the meta-analysis. We considered two measures of behavioural inhibition and three other general performance measures.
Inhibitory deficits were small-to-medium on the whole, and stronger for stimulants (cocaine, methamphetamine, ecstasy, and to a lesser extent, tobacco). Small deficits were observed for alcohol dependence and non-dependent heavy drinking. Opioid users, cannabis users and internet addicts showed no deficit in inhibition, while gamblers displayed a strong deficit. For the most part, these performance deficits were specific to inhibition, and not displayed for general performance measures.
Smith JL, Mattick RP, Jamadar SD & Iredale JM (2014) Deficits in behavioural inhibition in substance abuse and addiction: A meta-analysis. Drug and Alcohol Dependence, 145, 1-33.
The project has found solid support for the concept of a behavioural control deficit in abusers of some but not all substances. This will contribute to a narrowing of theory concerning the importance of inhibitory control to the development and maintenance of substance abuse disorders.