The aim of this research is to explore the efficacy of the opiate antagonist, naltrexone as combined with CBT-intervention in the treatment of pathological gambling (PG). The study period is 2011-2014 during which one hundred Pathological Gamblers will be recruited to participate to this placebo-controlled double-blind trial.

All participants have to be able to read and understand the patient information sheet and sign the informed consent. All participants are free to stop being in the study whenever they wanted. The patients are not paid or reimbursed for participation.

The study periods is 21 weeks during which the participant's have 8 appointments with the researchers. During the meetings research data will be collected and the participant is having Controlled Behavioral Therapy (CBT) consulting from a trained therapist. At the study visits, the subjects are given written instructions for the proper use of naltrexone and advised to take 50 mg naltrexone approximately one hour before gambling or feeling urges to gamble (and to refrain from taking naltrexone at other times). In this study the maximal daily dose is 50mg of naltrexone. The medication is free for the subjects.

Inclusion Criteria:

• pathological gambling (scores 5+ from SOGS-R and DSM-IV criteria)

Exclusion Criteria:

• acute hepatitis
• severe liver or kidney dysfunction
• suicide risk or severe depression or other untreated mental health problem
• participation to other gambling research at the same time
• the use of drugs (especially opiates)
• pregnancy
• prisoners
• retarded and mentally ill patients were also excluded