Period prevalence rates of specific mental disorders in an Icelandic cohort.

This paper presents the 1-month, 6-month and 1-year prevalence rates for mental disorders in a random sample of people born in Iceland in 1931 and interviewed at the age of 55-57 years. The diagnoses were made according to DSM-III, on the basis of the National Institute of Mental Health's Diagnostic Interview Schedule (DIS) used by trained lay interviewers. The period prevalence rates were found to be similar to those obtained by other studies using the DIS as a survey instrument. The highest rates were among the widowed, separated or divorced. The 1-year symptom-free rates were high for alcohol abuse and alcohol dependence, 74% and 71%, respectively. For depressive disorders, the 1-year symptom-free rate was only 50% and for the anxiety disorders, 50%-65%. The most common psychiatric disorders had a chronic course.