Early life stress (ELS) is associated with altered stress reactivity and an increased risk for the development of psychopathological conditions in later life. However, depending on whether autonomic or endocrine measures were used as indicators of stress reactivity, previous studies reported conflicting findings of either increased or decreased stress reactivity after ELS experience. In the present study we therefore aimed to investigate the effect of ELS on both autonomic and endocrine indicators (heart rate and salivary cortisol) of individual stress reactivity and applied a psychosocial stress task in a sample of healthy participants with and without exposure to mild to moderate ELS. Results showed no significant effects of ELS on autonomic and endocrine indicators of individual stress reactivity. Importantly though, heart rate proved as more sensitive than salivary cortisol with regard to differentiating between stress and control conditions and thereby as a more feasible indicator of an individual's stress reactivity. Accordingly, our data suggest that sole reliance on salivary cortisol as an indicator of stress reactivity might lead to an oversight of more subtle effects of psychosocial stress.
Keywords: Early life stress; Heart rate; Salivary cortisol level; Stress reactivity.