This study will test the effects of an add-on mindfulness intervention for patients with gambling problems, added to treatment as usual, compared to a waitlist control condition. The study will primarily aim to decrease gambling behaviour compared to the control condition which receives the intervention later, after two months, and secondarily to decrease symptoms of depressive and anxiety symptoms. In addition, patients who have undergone the mindfulness intervention will be offered participation in a qualitative interview study aiming to deepen the understanding of feasibility and challenges of a mindfulness add-on intervention against gambling problems.

Inclusion Criteria:

• Enrolled in any kind of treatment for problem gambling at a regional health care unit for problem gambling or at any municipal social service unit for problem gambling, and who provides informed consent

Exclusion Criteria:

• Inability to provide informed consent due to language difficulties or due to severe mental health problems, or because of mental health problems requiring urgent psychiatric management (such as suicidal, homicidal, delirious or psychotic behavior)