The HPA axis is believed to be involved in the neurobiology of mood disorders.
... out with 24.7% under the age of 18, 7.4% from 18 to 24, 32.6% from 25 to 44, 23.2% from 45 to 64, and 12.2% who are 65 years of age or older. The median age is 37 years. ...