As presented in Table 1, on average males reported higher levels of problem alcohol use symptoms than females at both waves; however, this difference reached significance only in young adulthood. Moreover, consistent with previous studies, on average females reported significantly higher religiosity than males at both waves. Furthermore, the mean levels of religion significantly decreased for both males and females from wave 1 to wave 2, as determined using the Mann Whitney U test (males: z = 5.61, p < 0.001; females: z = 6.70, p < 0.001), and levels of problem alcohol use significantly increased across wave (males: z = 16.28, p < 0.001; females: z = 21.02, p < 0.001). A significant negative correlation was detected between religiosity and problem alcohol use; for males correlations were −0.11 and −0.20 in adolescence and young adulthood respectively, while for females the correlations between religiosity and problem alcohol use were −0.15 (adolescence) and −0.13 (young adulthood). Correlations of the twin-pair differences for religiosity and alcohol problem use provide a within-family replication of the between-family correlations described above. That is, we analyzed
