The aim of this research is to evaluate the efficacy of a new treatment for chemsex or chemical sex, the use of psychoactive substances to modify sexual experience and performance. This treatment, called Transcranial direct current stimulation (tDCS) aims to modulate the cortical activity of brain areas involved in the desire to use psychoactive substances, or drugs, and the desire for uncontrolled sexual intercourse. This treatment should therefore lead to a reduction in the craving for consumption of psychoactive substances and/or the practice of uncontrolled sexual activity. The stakes of this new treatment are high, because chemsex exposes people to health risks for themselves and others. These risks include the risk of infection (skin infections, HIV infection, hepatitis viruses), psychological harms (anxiety attacks, depression, suicide risk), risk of addiction (addiction to the psychoactive product used, sex addiction), and toxicological harm (overdose, dangerous combination of psychoactive substances) or trauma (blows, trauma to the genitals or anorectal trauma). To date, there is no proven therapeutic treatment for people wishing to reduce or stop chemsex. 40 participants will be randomized into 2 groups: * 20 patients will receive active stimulation * 20 patients will receive sham stimulation The total duration of the study for each patient will be 13 weeks: 1 week of stimulation and 12 weeks of follow-up.