The effect of selective serotonin reuptake inhibitors (SSRI) on healthy individuals remains unclear. We tested the hypothesis that escitalopram decreases perceived stress and salivary cortisol. The trial has a randomised, blinded, placebo-controlled, parallel-group design. After informed consent 80 healthy first-degree relatives to patients with depression were randomly allocated to receive daily tablets of escitalopram 10mg or placebo for 4 weeks. The area under the curve (AUC) for awakening and all day salivary cortisol was analysed in samples taken immediately after awakening and at 15-min intervals for the next hour, and at 12:00, 18:00 and 23:00. The salivary cortisol awakening response, all day salivary cortisol, and scale scores on sleep, pain, aggression, quality of life, and perceived stress assessed at entry were compared to values following 4 weeks of intervention. Statistically significant decreases were found in awakening salivary cortisol (P=0.04) and in all day salivary cortisol (P=0.02) in the escitalopram group compared with the placebo group. There were no statistically significant differences in perceived stress between the intervention groups. These findings from a randomised clinical trial suggest that a long-term escitalopram administration to healthy participants results in a decrease in the hypothalamic-pituitary-adrenal (HPA) activity measured by salivary cortisol compared with inert placebo. However, change in salivary cortisol was one out of multiple outcome measures. The results of the present trial do not refute salivary cortisol as a potential endophenotype for depression.