One of the Reasons Serious and Persistent Mental Illness Declines

One of the reasons serious and persistent mental illness declines with age is that

A) depression is a normal and healthy response to developmental changes of aging
B) life expectancy of people with serious mental illness is considerably lower than the general population
C) older adults are more likely to become asymptomatic
D) older adults experience less substance abuse than younger adults
E) there aren't enough service providers to diagnose it