Repetitive bilateral (left cathodal/ right anodal) transcranial Direct Current Stimulation (tDCS) over the dorsolateral prefrontal cortex (DLPFC) reduces craving and seems to decrease relapse risk in addiction. However, little is known about the relapse rates in cocaine addiction after tDCS, despite the need for neurobiological treatments to reduce the high relapse rates in this population. The current study explores the effects of repetitive tDCS in a larger sample (N=60) of cocaine addicted patients on number of relapse days after three months. We expect that a decrease in relapse risk after tDCS is associated with cognitive control functioning. Therefore, risky decision making and inhibitory control will be measured before and after the interventions, and at three months follow-up. Ecological momentary assessment (EMA) will be used as a reliable measure for relapse, craving and mood.

For this study, 60 cocaine addicted patients will receive real or sham bilateral tDCS (left cathodal/right anodal) over the DLPFC after one week in detox. The participants will receive this two times daily for 5 consecutive days. It is expected that this particular tDCS method will reduce relapse probability, as was previously seen in alcohol addicted patients. Furthermore, it is hypothesized that this therapeutic effect is associated with diminished craving and enhanced cognitive control. Craving, temptations and relapse, will be explored by means of Ecological Momentary Assessment (EMA). The mixed results in previous studies of tDCS on craving may be explained by the fact that craving in addiction is a momentary phenomenon which is difficult to reliably measure with more traditional methods like retrospective self-reports, for which EMA provides a solution. Cognitive control will be measured by means of inhibitory control during a Go/NoGo task and reward processing during a gambling task. The tasks will be performed at baseline, one day after the tDCS sessions and at three months follow up.

Inclusion Criteria:

• Aged between 18 and 65 years
• Meeting the DSM-V criteria for cocaine dependence
• The ability to speak, read, and write in Dutch at an eight-grade literacy level
• No severe withdrawal signs or symptoms at baseline

Exclusion Criteria:

• Indications of severe psychopathology (psychosis, severe mood disorder) as assessed by a physician
• A diagnosis of epilepsy, convulsions or delirium tremens during abstinence of cocaine use
• Any contraindication for electrical brain stimulation procedures such as electronic implants or metal implants
• Pregnancy or breast-feeding.