Inclusion Criteria:  Bipolar disorder (type 1 or 2), with diagnoses confirmed by SCAN interview. Age 18-65 years Speaks and writes Danish at a level equal to mother tongue Habile (i.e. able to give informed consent)  Exclusion Criteria:  Chronic kidney disease with GFR 0-10 ml/min Severe cardiac insufficiency (NYHA IIIb-IV) History of gastric ulcers, gastro-intestinal bleeding or other pathological bleeding tendency (thrombocytopenia, hemophilia, vitamin K deficiency) Asthma or other allergic symptoms developed after intake of salicylates, paracetamol or other NSAID or any of the excipients Patients already on aspirin or other NSAID, anticoagulants or SSRIs.  For fertile females:  Reluctance to use effective contraception during enrollment, including a safety period of one week following last medication day/trial completion Pregnancy; pregnancy ruled out by HCG test before enrollment Breastfeeding Planned major surgery during trial period. If a subject has scheduled major surgery (i.e. with bleeding risk), enrollment will be postponed until this is completed