Sleep deprivation in bright and dim light: antidepressant effects on major depressive disorder.

Twenty-three patients with a major depressive disorder were deprived of a night's sleep twice weekly, one week staying up in the dimly lit living room of the ward (less than 60 lux), and one week in a brightly lit room (greater than 2000 lux). Immediate, but transient beneficial effects of sleep deprivation were observed primarily in eight patients (the 'responders'). The immediate effects did not differ greatly for the two conditions, indicating that exposure to light at night is an implausible explanation for the antidepressant effects of total sleep deprivation. There was some evidence that the bright light condition led to a more prolonged improvement of the responders.