Previous studies have suggested that meaning in life may buffer the negative effects of stress. This study is the first to investigate the moderating role of meaning in life in the relationship between the perception of stress and diurnal cortisol in two independent samples of healthy adults. In study 1 (n = 172, men = 82, women = 90, age range = 21-55 years, mean age = 37.58 years), the results of moderated regression analyses revealed that there was a significant positive relationship between overall perceived stress in the past month and both diurnal cortisol levels (area-under-the-curve with respect to the ground; AUCg) and the diurnal cortisol slope (DCS) only in individuals with low levels of meaning in life conceptualized as the degree to which one engages in activities that are personally valued and important. In study 2 (n = 259, men = 125, women = 134, age range = 18-54 years, mean age = 29.06 years), we found a non-significant interaction term between meaning in life conceptualized as having goals and a sense of excitement regarding one's future and perception of stress in a model of both adjusted AUCg and DCS. The results were independent of age, sex, body mass index, education, and race. The results shed light on the importance and the complexity of the construct of meaning in life and offer a possible explanation for why some people who face stressors may be more vulnerable than others to developing stress-related health problems.
Keywords: HPA axis; Perceived stress; diurnal cortisol levels; diurnal cortisol slope; meaning in life.