Longitudinal analyses of psychological well-being in a national sample: stability of mean levels.

Maturational changes, cohort differences, and time of measurement effects on psychological well-being were examined in data from the National Health and Nutrition Examination Survey (NHANES) I Epidemiologic Followup Study. A 9-year longitudinal study of 4,942 men and women initially aged 25 to 74 was supplemented by cross- and time-sequential analyses using an independent sample of 4,986 participants who were first administered the well-being measures at the time of the follow-up. Older participants in the study tended to be lower in both Positive and Negative Affect, but longitudinal changes in these two subscales were not found, and Total Well-Being showed no significant age, birth cohort, or time effects in any of the analyses. Given the size and representativeness of the sample, this is strong evidence of the stability of mean levels of psychological well-being in adulthood, and points to the importance of enduring personality dispositions and processes of adaptation in determining levels of well-being.