Examining tDCS Effect on Cannabis Use Disorder in Patients With Schizophrenia

Stimulation will be performed using a Neurocan DC-Stimulator Plus with two 7×5 cm sponge electrodes soaked in a saline solution. Electrodes will be placed in accordance with the international 10-20 electrode placement system: the anode over F4 (right DLPFC), the cathode over Fp1 (MPFC). The stimulation level will be set at 2 mA for 20 minutes during stimulation sessions twice a day (separated by at least 3 hours) for 5 consecutive weekdays.

The control group will receive the sham stimulation following the same regimen, using the sham procedure which has been developed by the manufacturer of the tDCS material, allowing sensations to be felt in the scalp which are the equivalent to those of the active stimulation. The same device will be used for both the sham and the active procedures.

Inclusion criteria

• Schizophrenia diagnostic according to DSM (Diagnostic and Statistical Manual of mental disorder) 5 criteria, without change in psychotropic treatment since at least 4 weeks
• Moderate to severe cannabis use disorder according to DSM 5 criteria and active consumption during the last 7 days
• Subjects motivated to reduce or quit their cannabis consumption
• Patients with ambulatory compulsory care may be included

Exclusion criteria

• Other substance use disorder, excluding nicotine, according to DSM 5 criteria
• Other current psychiatric disorder according to DSM 5 criteria, excluding personality disorder
• Inpatient hospitalization
• History of head injury, neurological disorder with cerebral consequence or severe unstable somatic disorder
• Pregnancy or no contraception
• Contraindications for tDCS and/or MRI (implanted material, uncontrolled epilepsy, intracranial hypertension)