We investigated the predictive validity of the cortisol awakening response (CAR) in patients with non-seasonal major depression.
Patients were treated with sertraline in combination with bright or dim light therapy for a 5-week period. Saliva cortisol levels were measured in 63 patients, as an awakening profile, before medication and light therapy started. The CAR was calculated by using three time-points: awakening and 20 and 60 min after awakening.
Patients with low CAR had a very substantial effect of bright light therapy compared with dim light therapy, whereas patients with a high CAR had no effect of bright light therapy compared with dim light therapy.
High CAR was associated with an impairment of the effect of bright light therapy. This result raises the question of whether bright light acts through a mechanism different from that of antidepressants.