What is it?
The use of prolonged periods of wakefulness, with intervening periods of recovery sleep, to induce rapid improvement in depressive symptoms.
Wake therapy is best used as an antidepressant response inducer or accelerator; it jump starts the improvement in depression. When employed with other interventions, this antidepressant response can be maintained and solidified over months.
Originally demonstrated in Europe in the 1970's. Initial research documented rapid but transient improvement in depressive symptoms.
Relapse back into depression occurred after sleep or even brief dozing.
Beginning in the mid-1980's, researchers from Italy and Germany sought to identify methods to sustain the initial antidepressant response and prevent relapse.
It is not the absolute amount of sleep reduction that is important. Therapeutic effects mainly occur when sleep is prevented in the second half of the night. 
When combined with complementary chronotherapeutic (bright light therapy or sleep phase advance) or pharmacologic (antidepressants or mood stabilizers) interventions, wake therapy combinations produce sustained remissions that can last for months. [11, 13, 14, 15, 20, 21, 38]
Wake therapy has a broad spectrum of antidepressant activity: it has been found to be effective in unipolar, bipolar, and melancholic types of depression. 
One to three cycles (the night and entire following day) of complete sleep avoidance, separated by intervening nights of recovery sleep. The treatments vary between two to five days in duration depending on the number of cycles used.
We use a combination of wake and bright light therapy along with sleep phase advance – termed triple chronotherapy – as our standard protocol whenever wake therapy is prescribed. This treatment is a full, three-day process during which all waking hours are spent under our care and the prescribed sleeping periods take place in private apartments adjacent to the clinic area or hotels in the immediate vicinity. A detailed description of this three component process can be found in the Triple Chronotherapy Protocol section of this website.
Patients are able to go to work or manage home responsibilities on the days following their recovery sleep. Many patients are often able to do computer-based or online work or make business-related phone calls during the mornings after their sleepless nights when they are likely to be feeling better.
Our wake therapy program uses an entire floor of a residential building in downtown Chicago. Patients check into a reserved and private conference room where they register and start the process. A series of adjoining areas are available including a TV lounge, private library, full kitchen, complete business center, and an fully-equipped athletic facility including locker rooms and showers.
The program staff are psychiatric nurses and advanced graduate students in clinical psychology. These clinicians will be present throughout the treatment to assist with and monitor levels of wakefulness, track mood changes, identify and manage side-effects and maintain personal contact. A psychiatrist will be on-call throughout the process.
14. Colombo, C., et al., Total sleep deprivation combined with lithium and light therapy in the treatment of bipolar depression: replication of main effects and interaction. Psychiatry Research, 2000. 95(1): p. 43-53.
15. Berger, M., et al., Sleep deprivation combined with consecutive sleep phase advance as a fast-acting therapy in depression: an open pilot trial in medicated and unmedicated patients. The American Journal Of Psychiatry, 1997. 154(6): p. 870-872.