The incidence and onset-age of hospitalized bipolar affective disorder in Finland.

Background: Some studies have indicated that there are wide variations on incidence and prevalence of bipolar disorder in specific populations.

Methods: The occurrence of bipolar affective disorder and the age at onset was studied in both genders among the hospitalized Finnish population.

Results: The annual rate of all hospitalized patients with bipolar disorder was 0.03%. Of these, 2% were under 20 years, 14% under 30 years, 61% under 50 years and 81% under 60 years of age. The 1-year incidence was highest in the age group 50-59 years in males and 40-49 years in females.

Conclusions: The low prevalence and incidence of bipolar disorder in Finland may be due to late onset-age.

Limitation: The study is based on hospital-treated bipolar disorder patients.

Clinical Relevance: We have presented previously unreported differences between the age of onset of bipolar disorder in Finland compared with other countries.