Stability and change in religiousness during emerging adulthood.

Understanding the development of religiousness is an important endeavor because religiousness has been shown to be related to positive outcomes. The current study examined mean-level, rank-order, and individual-level change in females' religiousness during emerging adulthood. Genetic and environmental influences on religiousness and its change and stability were also investigated. Analyses were completed with an epidemiological study of 2 cohorts of twins: 1 assessed at ages 14 and 18 and a 2nd at 20 and 25. Mean levels of religiousness decreased significantly with age, while rank-order stability was high. Individual-level change was also evident. Analyses also supported the hypotheses that more change would occur in the younger cohort compared with the older cohort and that more change would occur in religious service attendance than the general index of religiousness. Twin analyses suggested that the heritability of religiousness increased with age, while the shared environmental influences decreased. For the younger cohort, change was genetic in origin, while stability was environmental. In the older cohort, change was influenced by nonshared environment and stability by both genes and family environment.