Elevated evening cortisol secretion due to underlying psychiatric disorders independent of the sleep-related disease

Recent research focussed on the interaction between chronic insomnia and functions of the HPA axis. However, it is still unclear whether the increase of cortisol secretion is a function of disturbed sleep independent of the origin of the sleep disorder or reflects the postulated cognitive hyperarousal. We therefore investigated polysomnographically registered sleep and saliva cortisol secretion in 79 patients suffering from insomnia, hypersomnia and sleep disorders related to organic factors. Accompanying mild to moderate psychiatric disorders were found in 33 patients (group 1), but not in the remaining 46 patients (group 2).

Sleep differed only with respect to REM-sleep parameters between both groups. Independent of the complaint (insomnia or hypersomnia) and sleep diagnosis, evening (AUC: 5.54±3.21 vs. 3.38±2.25, p<0.01) and daytime cortisol levels were significantly increased in group 1. Daytime anxiety was increased and correlated with cortisol secretion of the preceding evening (p<0.05) only in group 1.

The results indicate that cortisol secretion is increased in sleep disorders accompanied by psychiatric disorders independent of the sleep complain or main sleep diagnosis including organic factors. The correlation with daytime functioning supports the hypothesis of a cognitive hyperarousal in these patients which requires a special treatment.