Wake therapy is a form of sleep deprivation

Sleep deprivation

Sleep deprivation is the condition of not having enough sleep; it can be either chronic or acute. A chronic sleep-restricted state can cause fatigue, daytime sleepiness, clumsiness and weight loss or weight gain. It adversely affects the brain and cognitive function. Few studies have compared the...

 used as a treatment for depression

Clinical depression

Major depressive disorder is a mental disorder characterized by an all-encompassing low mood accompanied by low self-esteem, and by loss of interest or pleasure in normally enjoyable activities...

. The subject is woken at 1AM and stays awake all morning, and the next full day. While sleepy, patients find that their depression vanishes, until they sleep again. Combining this with bright light therapy make the beneficial effects last longer than one day.