To access personal data on history of admission to psychiatric hospitals, we linked the personal identifiers of cases to the Danish Psychiatric Central Register to ascertain if they were recorded from 1969 to the time of suicide or matching. We recorded personal data on 4 specific aspects of psychiatric hospitalization. The first one was the time since recent admission or discharge, which was grouped into 12 categories reflecting the detailed time distance (Table 1). The second was the main diagnosis at the recent hospitalization, which was categorized into 4 major groups as schizophrenia spectrum disorders (ICD-8 codes 295, 297, 298.29, 298.39, 298.89, 298.99, 299.05, 299.09, 301.09, 301.29, and 301.83 and ICD-10 codes F20, F21, F22, F23, F24, F25, F28, F29, F60.0, and F60.1), affective disorders (ICD-8 codes 296, 298.09, 298.19, 300.49, and 301.19 and ICD-10 codes F30, F31, F32, F33, F34, F38, and F39), substance abuse disorders (ICD-8 codes 303 and 304 and ICD-10 codes F10.2, F10.3, F10.4, and F1x.2), and other psychiatric disorders. The third variable was the length of hospital treatment, indicating if the inpatient stay was less than the median length (in days) according to the distribution of the total psychiatric hospitalizations in the calendar year. The last variable referred to the total number of admissions to psychiatric hospitalization before the suicide or matching.