Investigation of possible benefits of transcranial direct current stimulation (tDCS) as a treatment of depression in patients with Parkinson's Disease, through a randomized placebo-controlled clinical trial.

We aim to investigate the effects of transcranial direct current stimulation (tDCS) as treatment for depression in patients with Parkinson's Disease. We have designed a clinical trial in which volunteers that fulfill inclusion criteria will receive 15 sessions of tDCS during 1 week (3 sessions a day, with 30 minutes interval in between). Subjects will be randomly allocated into two groups, one that will receive the real intervention (active) and the other that will receive the placebo intervention (sham). The collaborator in charge of administering the session will not participate in the evaluations, keeping both subjects and evaluators blinded to the nature of the sessions. Subjects will be evaluated at baseline, and after the end of sessions, 1 week, 4 weeks and 8 weeks, the latter being the main outcome.

We aim to enroll 50 subjects, 25 for each arm. The sample size calculation took into consideration previous clinical trials using tDCS for depression in different settings.

Inclusion Criteria:

• Idiopathic Parkinson's Disease
• Geriatric Depression Scale - 15 higher that 5
• Major Depression Disorder

Exclusion Criteria:

• CNS disease other than Parkinson's Disease (i.e. epilepsy, stroke)
• Mental disorder other than depression on anxiety disorder (i.e. bipolar disorder, schizophrenia)
• Previous neurosurgical intervention (i.e. DBS)
• Current use of antidepressant drug
• High suicidality risk
• Limited capacity of understanding written and spoken Portuguese