Prader-Willi Syndrome (PWS) is a multisystemic genetic disease characterized by hypotonia, mental retardation, hyperphagia, and uncontrollable hunger due to hypothalamic dysfunction, caused by dysregulation of genes located in chromosome 15q11-q13. The goal of this study is to evaluate the effects of Transcranial Direct Current Stimulation (tDCS) on hyperphagia and behavior in PWS. Forty children and adolescents (11-24 years) with clinical and cytogenetic-molecular diagnosis of Prader-Willi syndrome will be assessed before and after 10 tDCS session with: Food Craving Questionnaire (FCQ), Aberrant Behavior Checklist (ABC), Dykens hyperphagia questionnaire. Caregivers self-reported the participant's behaviors at home and, lately, they will be categorized and quantified. tDCS will be applied for 20 minutes with electrodes of 25cm2 wrapped in cotton material soaked in saline solution. The anode at the left dorsolateral prefrontal cortex (F3) and the cathode at the contralateral area (F4). Children from 11-12 years will receive a current of 1mA; above 13 years, 2mA.

Prader-Willi syndrome (PWS) is a complex neurodevelopmental disorder that affects about 1 in 20,000 births, regardless of sex or race. PWS is characterized by two clinical phases. In the first, the cardinal symptoms are: neonatal hypotonia, feeding difficulty, lethargy, weak crying and hyporeflexia. The second, from six months, presents gradual improvement of hypotonia, weight gain and progressive development of hyperphagia and obesity. A recent trend is the use of transcranial Direct Current Stimulation (tDCS), a very simple, safe and inexpensive technique of cerebral stimulation, noninvasive and painless. It is based on the application of low intensity direct current (0-2 mA) through electrodes. tDCS has been shown to be a safe, easily tolerable method, allowing its therapeutic use in several clinical situations involving sustained cortical dysfunction such as in neurological or psychiatric disorders, including Schizophrenia, Alzheimer's Disease, Parkinson's Disease and major depression. These and other studies have been shown to be consistent with tDC's therapeutic methodology, thus favoring more accurate conclusions about the efficacy and efficiency of the method. The general objective of this research is to evaluate the effects of tDCS on the treatment Obsessive Compulsive Behavior and depressive symptoms in PWS; evaluate and compare the participants' cerebral activation pattern through electroencephalographic mapping with resting-quantitative EEG (qEEG), before and after the intervention; check if the changes (if any) last 3 months after the end of the intervention (follow up). 40 individuals will be invited to participate in this study, divided into 2 groups: 20 patients with PWS, in the age group between 11 and 35 years of age diagnosed and 20 obese individuals without the diagnosis of PWS. All will receive the same pacing protocol in terms of number of sessions and pacing time, tDCS intensity will be adjusted to 1mA in subjects aged 11 to 13 years and up to 2mA in subjects aged 14-35 years. The project will include Neuropsychological evaluation for each patient and electroencephalographic mapping with resting qEEG, before and after the intervention at the beginning of the experiment, at the end of the experiment and 30 days after (follow up).

Inclusion Criteria:

• Adolescents aged above 11 years old;
• BMI > 30Kg/m²
• Agreement and Consent of parents and/or guardians and adolescent to participate of the study.

Exclusion Criteria:

• Cognitive inability to understand instructions, as assessed by the psychiatrist, due to severe cognitive impairment;
• Presence of other associated syndromes in addition to PWS;
• Inability to travel to the research site due to complications due to obesity; for convenience, as they seek specialized centers for the care of this population and associations of Prader Willi they will be referred by those responsible for participation in the program.