Figure 1. Salivary Cortisol levels within 90 minutes after awakening in different groups.

The solid lines indicate cortisol levels within 90 minutes after awakening for participants from low family conflict groups. Group differences were tested by repeated measures ANOVA. (a) shows that adult parents with high family conflict had marginally lower cortisol levels than adult parents with low family conflict. (b) shows that cortisol levels were lower in adolescents at late/post puberty with high family conflict than those adolescents at late/post puberty with lower family conflict, which were generally consistent with findings from adults. However, there were no differences in cortisol levels between high family conflict and low family conflict in adolescents at pre/early puberty (c). The findings by using mixed effect modeling (XTREG module of Stata version 14.0) were consistent with the findings by using repeated measures ANOVA, which show that the effect of family conflict on cortisol levels within 90 minutes upon awakening (4 time points) was −1.51 ± 0.69 for adults (z value = −2.17, p = 0.03), −1.95 ± 0.89 for adolescent at late/post puberty (z value = −2.17, p = 0.03), and 1.03 ± 0.93 for adolescent at pre/early puberty (z value = 1.10, p = 0.27).