Trends in Suicide Risk Associated With Hospitalized Psychiatric Illness: A Case-Control Study Based on Danish Longitudinal Registers

Objective: In light of the consistent reduction in suicide rate during the past 20 years in Denmark, this study aims to investigate trends in suicide risk associated with hospitalized psychiatric illness and to explore differences in the changes with regard to clinical phases of illness, sex, age, and diagnosis.

Method: This population-based study includes all of 21,169 suicides in Denmark during the years 1981 through 1997 and 423,128 controls matched for sex, age, and time (using a nested case-control design). Personal data on psychiatric history and socioeconomic status were retrieved from Danish longitudinal registers. Data were analyzed using conditional logistic regression.

Results: This study shows that the reduction in suicide rate is generally faster among individuals with a history of psychiatric admission than among individuals without such a history. However, this substantial reduction is mainly accounted for by the reduction among patients who had been discharged from psychiatric hospitals for more than 1 year. For patients who had been discharged from hospitals within 1 year, the reduction is similar to that of the general population; while for patients hospitalized for treatment at the time of suicide or the index date, the reduction in suicide rate is relatively slower. Such trends hold for all diagnostic groups. Further analyses stratified by age indicate that the faster reduction in suicide rate associated with history of hospitalized psychiatric illness is more pronounced among patients aged 36 years and older.

Conclusion: The reduction in suicide rate is substantial for patients who have been discharged from psychiatric hospitals for more than 1 year and for middle-aged and older patients. Recent improvement in psychiatric care and treatment and promotion of new generation antidepressants may contribute to these changes.