Introduction

Aging may variably affect cognition, memory, intelligence, personality, and behavior. However, many changes in mental health are difficult to attribute to aging per se; they are often the result of disease. Decreases in mental capacity or performance (eg, cognition, behavior) that are viewed as age related may instead be due to treatable illnesses (eg, depression, hypothyroidism). A rapid decrease in cognition is almost always due to disease.

The effects of aging on mental health may also be related to socioenvironmental factors, including the care setting. For example, the prevalence of psychiatric disorders is 15 to 25% among persons aged 65 living in the community and 27 to 55% among those in the hospital. Psychiatric disorders are a primary or secondary diagnosis in 70 to 80% of nursing home residents; in one study, 94% of nursing home residents had a psychiatric disorder. Brain disorders causing dementia (most commonly, Alzheimer's disease) affect about 10% of persons aged 65 and at least 25% of those aged 85.