The efficacy of a working memory training in substance use patients: A randomized double-blind placebo-controlled clinical trial

Introduction: Substance use disorder patients show impairments in working memory (WM) functioning. Previous findings indicate that a WM training results in improvements of working memory capacity (WMC) and in decreased clinical symptoms in a range of mental disorders, including alcohol use disorder. Method: The aim of the current study is to investigate the efficacy of a 24-session WM training in addition to treatment as usual on craving, WMC, substance use, impulsivity, attention bias, and psychopathology using a randomized double-blind placebo-controlled trial. Inpatients (n=180) diagnosed with an alcohol, cocaine, or cannabis use disorder were included. Results: Although the WM training resulted in better scores on the trained tasks in both groups, the placebo training resulted in a better or equal WMC compared to the experimental training, as measured with two nontrained transfer tasks. The WM training had no effect on craving, substance use, impulsivity, attention bias, and psychopathology. Conclusion: Overall, we did not find evidence for the efficacy of WM training on WMC or clinical symptoms as compared to a placebo training in a population of substance use disorder patients. Future research needs to investigate further whether WMC is an important factor that is associated with substance-abuse-related behavior, and whether working memory training could be useful in substance use disorders.