A comprehensive nationwide study of the incidence rate and lifetime risk for treated mental disorders

Abstract

Importance: Understanding the epidemiologic profile of the life course of mental disorders is fundamental for research and planning for health care. Although previous studies have used population surveys, informative and complementary estimates can be derived from population-based registers.

Objective: To derive comprehensive and precise estimates of the incidence rate of and lifetime risk for any mental disorder and a range of specific mental disorders.

Design, setting, and participants: We conducted a follow-up study of all Danish residents (5.6 million persons), to whom all treatment is provided by the government health care system without charge to the patient, from January 1, 2000, through December 31, 2012 (total follow-up, 59.5 million person-years). During the study period, 320,543 persons received first lifetime treatment in a psychiatric setting for any mental disorder; 489,006 persons were censored owing to death; and 69,987 persons were censored owing to emigration. Specific categories of mental disorders investigated included organic mental disorders, substance abuse disorders, schizophrenia, mood disorders, anxiety, eating disorders, personality disorders, mental retardation, pervasive developmental disorders, and behavioral and emotional disorders.

Exposures: Age and sex.

Main outcomes and measures: Sex- and age-specific incidence rates and cumulative incidences and sex-specific lifetime risks.

Results: During the course of life, 37.66% of females (95% CI, 37.52%-37.80%) and 32.05% of males (31.91%-32.19%) received their first treatment in a psychiatric setting for any mental disorder. The occurrence of mental disorders varied markedly between diagnostic categories and by sex and age. The sex- and age-specific incidence rates for many mental disorders had a single peak incidence rate during the second and third decades of life. Some disorders had a second peak in the sex- and age-specific incidence rate later in life.

Conclusions and relevance: This nationwide study provides a first comprehensive assessment of the lifetime risks for treated mental disorders. Approximately one-third of the Danish population received treatment for mental disorders. The distinct signatures of the different mental disorders with respect to sex and age have important implications for service planning and etiologic research.