Clep_a_241249 193..202

1Department of Research, Cancer Registry of Norway, Oslo, Norway; 2Oslo Centre for Biostatistics and Epidemiology, Department of Biostatistics, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway; 3Division of Emergencies and Critical Care, Oslo University Hospital, Oslo, Norway; 4Institute of Clinical Medicine, Faculty of Medicine, University of Oslo, Oslo, Norway; 5Oslo Ischemia Study, Oslo University Hospital, Oslo, Norway; 6Department of Chronic Diseases and Ageing, Norwegian Institute of Public Health, Oslo, Norway; 7Department of Radiation Biology, Institute for Cancer Research, Oslo University Hospital, Oslo, Norway; 8Department of Rheumatology, Dermatology and Infectious Diseases, Oslo University Hospital, Oslo, Norway; 9Department of Registration, Cancer Registry of Norway, Oslo, Norway; 10QIMR Berghofer Medical Research Institute, Brisbane, Australia; 11CRUK Manchester Institute, University of Manchester, Manchester, UK Purpose: Melanoma is the cancer with the most rapidly rising incidence rate in Norway. Although exposure to ultraviolet radiation (UVR) is the major environmental risk factor, other factors may also contribute. Antidepressants have cancer inhibiting and promoting side effects, and their prescription rates have increased in parallel with melanoma incidence. Thus, we aimed to prospectively examine the association between use of antidepressants and melanoma by using nation-wide data from the Cancer Registry of Norway, the National Registry, the Norwegian Prescription Database and the Medical Birth Registry of Norway. Patient and Methods: All cases aged 18–85 with a primary cutaneous invasive melanoma diagnosed during 2007–2015 (n=12,099) were matched to population controls 1:10 (n=118,467) by sex and year of birth using risk-set sampling. We obtained information on prescribed antidepressants and other potentially confounding drug use (2004–2015). Conditional logistic regression was used to estimate adjusted rate ratios (RRs) and 95% confidence intervals (CIs) for the association between overall and class-specific use of antidepressants and incident melanoma. Results: Compared with ≤1 prescription, ≥8 prescriptions of antidepressants overall were negatively associated with melanoma (RR 0.81 CI 0.75–0.87). Class-specific analyses showed decreased RRs for selective serotonin reuptake inhibitors (RR 0.82 CI 0.73–0.93) and mixed antidepressants (RR 0.77 CI 0.69–0.86). The negative association was found for both sexes, age ≥50 years, residential regions with medium and highest ambient UVR exposure, all histological subtypes, trunk, upper and lower limb sites and local disease. Conclusion: Use of antidepressants was associated with decreased risk of melanoma. There are at least two possible explanations for our results; cancer-inhibiting actions induced by the drug and less UVR exposure among the most frequent users of antidepressants.