Across the adult years, the 12-month prevalence of most mental disorders increases from young adulthood to middle adulthood and then declines, with the lowest rates being , berglund, demler, et al., 2005).

After 75 years of age.

According to the study:

"Half of all lifetime cases start by age 14 years and three fourths by age 24 years. Later onsets are mostly of comorbid conditions, with estimated lifetime risk of any disorder at age 75 years (50.8%) only slightly higher than observed lifetime prevalence (46.4%)."

(Kessler et al., 2005)