Failure to differentiate disease-related psychiatric changes from manifestations of normal aging has blurred the understanding of mental funclion in healthy older adults. Many decrements in capacity or performance viewed as age related—particularly those associated with cognition and behavior—actually reflect modifiable consequences of illness.
NORMAL CHANGES OF AGING

Changes in Cognition
A longitudinal study of cognitive capacity in a cohort of men followed from 1919 to 1961 described increments in verbal ability and total intellectual performance from age 20 to age 50. although mathematical ability declined slightly. From 50 to 60 yr of age, scores of intellect showed little change. These studies were among the first to raise serious doubts about the presumed normal decline in mental ability with aging, which had been inferred from earlier cross-sectional research.
A 12-yr longitudinal study of older men (median age, 71 yr) con-dueled by the National Institute of Mental Health examined a broad range of variables. Physical and psychiatric disease was absent or minimal; the goal was to separate the impact of aging from that of illness. As these healthy men moved from their 70s to their 80s. various intellectual functions declined while others improved. For example, quality of cognitive operations, draw-a-person exercises, and sentence completions declined, while vocabulary and picture arrangement ability improved. This suggests that older persons may have difficulty with activities requiring a quick reaction lime or a high degree of precision, although they maintain the ability to understand their situation and learn from new experiences.
Moreover, men who developed arteriosclerotic cardiovascular disease had significantly greater decrements in intellectual performance than those who remained healthy. Therefore, significant changes in intellectual performance should not be dismissed as normal consequences of aging but should be evaluated as potentially modifiable manifestations of disease (psychiatric as well as general medical). For example, both depression and hypothyroidism are treatable problems that can be covert and cause cognitive impairment.
Changes in Behavior and Personality
Corresponding to the stereotype of inevitable intellectual decline with aging are stereotypes of regressive behavior and increasing inflex-ibilily of personality traits. However, these are more a sign of psychiatric disturbance than a manifestation of aging. Consider the issue of cautiousness. Research shows that (he elderly are more cautious than younger adults about risk taking when the payoff is predictable and constant. If the size of the payoff depends on the degree of risk, however, older persons are no more cautious than younger persons.
Anxiety can resull in cautiousness, causing delays in decision making and reactions. In other words, excessive cautiousness in the elderly may signal underlying anxiety or a related clinicaldisorder. However, it is entirely appropriate for a frail or disabled older person to he more careful in general. A maladaptive overcautiousness resulting from anxiety must be distinguished from an appropriate, adaptive response to reality.
If older adults appear to be more rigid lhan younger adults, then cohort differences (ie, generational differences that stem from having grown up during different hisloric periods)—and no! age differences— are more likely involved. Research shows no( only that personalities remain stable with aging but also that behavioral and psychologic adap-tiveness continues and docs not normally give way to regression or rigidity. If certain behaviors or traits become increasingly exaggerated, maladaptive, and unmodifiable, neurosis rather than normal aging may be to blame. Treatment rather than acceptance is in order.