different ICD editions. Third, because outpatient data were only introduced in the Swedish registers in 2001, during years 1969–2000 the cohort only included individuals whose attempted suicide led to inpatient care, potentially leaving out attempts of lower lethality. In addition, patients with OCD included in the NPR register may not be representative of all OCD cases in the population as the register is biased towards inpatients and only includes specialist care visits and not patients seen in general practitioner clinics. In the same way, the NPR does not include patients diagnosed by professionals other than physicians. These limitations also apply to the identification of the comorbid psychiatric conditions. Finally, despite the large dataset, some of the specific methods of suicidal behavior were rare. Thus, these comparisons based on small numbers should be cautiously interpreted.
