 The intervention both DM and CR is spread over four sessions of 100 min each taking place within two weeks i.e. two sessions per week and includes intensive homework assignments for the patients. The intervention will be delivered by MSc-level clinical psychologists completing the clinical training for becoming a licenced psychotherapist in Germany Psychologischer Psychotherapeut. The diagnostic assessment involves clinical interviews and a number of questionnaires and will be conducted by independent assessors who have a qualification similar to the study therapists. Assessment involves pre-, post- and follow-up assessment. Additionally, assessment comprises data collection via ecological momentary assessment EMA in order to measure OCD symptoms intrusions, emotions and coping strategies, the degree to which participants apply the newly learned strategy DM or CR in everyday life and the amount of relief experienced from applying it. There will be one EMA before Pre-EMA and one after the intervention Post-EMA. For EMA, participants receive a smartphone for four days each Friday to Monday and are randomly prompted ten times per day to fill in a short questionnaire. The average amount of time necessary to fill in the questionnaire is assumed to be less than 2 min, based on a sample trial with mentally healthy participants. 