Inclusion Criteria:
* Patients will be evaluated initially in a clinical interview by a specialized psychiatrist and then by a second interviewer who will use a semi-structured interview to check the DSM-5 criteria for Video Game Disorder (VGD) modeled in the standard format of Schedules for clinical assessment in neuropsychiatry (SCID). Only a specific subgroup of VGD will be included in our sample, which will be called VGDa, a sample that represent a framework of behavioral dependence in essence. Patients in this sample must necessarily have the following symptoms: salience, withdrawal, relapse, conflict, mood modification and fissure. The criteria to delimit this subgroup are listed below:
* Patients diagnosed with Internet Gaming Disorder according to DSM-5
* Patients who have a score of 4 or higher on the following questions on the IGDS9-SF scale (Internet Gaming Disorder Scale 9 - Short Form):
Question 1: Salience assessment. Question 2: Abstinence assessment. Question 4: Relapse assessment. Question 6: Conflict assessment. Question 8: Mood modification assessment.
* Patients with craving according to the adaptation of the Gambling Follow-up Scale (GFS) described below.
An adaptation of the GFS scale, originally used to evaluate patients with Gambling Disorder, was made in order to allow the evaluation of the craving symptom in a patient with VGD. It will only be used the fourth question on this scale as follows.
"4) In the past 4 weeks, how was your desire to play?
1. I felt an irresistible urge to play.
2. I felt a strong desire to play, sometimes resistable, sometimes not.
3. I felt a strong desire to play, but resistable most of the time.
4. I felt a slight desire to play.
5. I didn't feel like playing. " It will considered that the patient has craving if he answers this question by selecting items 1, 2 or 3.
Patients must meet the following criteria before randomization:
* Have read and signed the informed consent form after the nature of the study has been fully explained and before carrying out any procedures related to the study;
* Age between 18 and 60 years old, inclusive;
* Female patients must be:
1. In post-menopause for at least one year, or;
2. Being surgically incapable of becoming pregnant (undergoing bilateral hysterectomy or oophorectomy or tubal ligation or otherwise being unable to become pregnant), or;
3. Be practicing an acceptable method of birth control (defined as: hormonal contraceptives, spermicide plus barrier, a single vasectomized partner and / or intrauterine device).
4. If a patient with the potential to become pregnant is practicing an acceptable method of birth control (as mentioned above), she must have a negative urine pregnancy test at the enrollment stage, as well as, at baseline, before receiving the study drug.
Exclusion Criteria:
* \- Established contraindication to naltrexone (opioid dependence, in the process of opioid withdrawal or current use of opioid analgesics) or hypersensitivity to naltrexone;
* Exposure to any other drug or experimental device in the 30 days prior to inclusion, except for occasional use of benzodiazepines;
* Pregnancy, breastfeeding or patients who intend to become pregnant during the study;
* Evidence of renal failure, defined as serum creatinine levels\> 133 mmol / L in men and\> 124 mmol / L in women, which correspond to\> 1.51 mg / dl and\> 1.41 mg / dl, respectively on Week 1 of inclusion;
* Evidence of clinically significant liver failure (defined as AST or ALT\> 2 times the upper limit of normal) in Week 1 of inclusion;
* Significant cardiovascular disease, including a history of myocardial infarction in the last 5 years, stroke, clinically significant heart valve disease, unstable angina, clinically abnormal ECG, arrhythmia or congestive heart failure, determining functional class III or IV (NYHA, 1964);
* Uncontrolled hypertension (defined as a diastolic blood pressure of 100 mm / Hg and / or a systolic blood pressure of 180 mm / Hg with or without medication). Hypertensive patients receiving medication should be receiving the same dose of the same antihypertensive medication for at least two months;
* Evidence of uncontrolled thyroid disorders, including hyper or hypothyroidism or abnormal TSH level. Patients who are known to have thyroid hormone replacement need to have had a stable dose for at least three months prior to inclusion and a normal TSH level upon inclusion
* History or current comorbidity with bipolar affective disorder, obsessive compulsive disorder, psychotic disorder, schizophrenia or severe depression, additionally verified through the Patient Health Questionnaire 9 (PQH-9\> 19), current suicide risk, or any other neuropsychiatric condition in severe cognitive impairment;
* Current or previous history (in the previous two years) of abuse / dependence on alcohol or other psychoactive substance (except nicotine);
* If at any moment the clinician responsible for the patient identifies suicidal ideation with risk of self-harm, or death;
* Clinically significant hematological or immunological disorder;
* Patients currently receiving psychotropic medications, except for the episodic use of benzodiazepines;
* Illiteracy, or any other condition that prevents the reading and understanding of the research instruments;
* Do not have a telephone line available for remote monitoring;
* Living alone, or not being able to present a family member capable of providing collateral information on gaming behavior;
* To be followed up in another therapeutic program.
The Mini International Neuropsychiatric Interview (MINI) will be used to verify the psychiatric exclusion diagnoses. This is a structured diagnostic interview, with quick application - approximately 45 minutes - compatible with the DSM-IV criteria. Its objective is the verification and standardization of the main Psychiatric Disorders of Axis 1 of DSM IV. It is performed by clinicians after rapid training (1 to 3 hours). The translated and adapted Brazilian version showed globally satisfactory reliability.
