Wake Therapy is the most rapid antidepressant treatment in current clinical use. 
Compared to standard antidepressant treatments that usually require between 2 to 8 weeks to show effects, Wake Therapy produces improvement within hours.
Broadly active in most depressive subtypes including unipolar, bipolar, and melancholic forms.
Comparable effectiveness to antidepressants in non-seasonal depression. 
When used with one of several other chronotherapeutic interventions and/or psychiatric medications, the initial response to Wake Therapy becomes cemented, generating a sustained remission that can last for months. [10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21]
As a biological treatment, chronotherapy shares the same psychiatric risks as any other antidepressant treatment. 
As a non-pharmacologic therapy, it avoids the drug side-effects associated with medications.
Though chronotherapy is often used with antidepressant and/or mood-stabilizing medications, it can be used on its own, affording the option of a fully non-pharmacologic treatment.
The therapeutic action of chronotherapeutic treatment depends on its time of administration. Time-sensitive treatments and chronotherapeutic principles are increasingly being used in cardiology, oncology and sleep medicine. [23, 24, 25, 26, 27, 28]
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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.
17. Voderholzer, U., et al., Is the antidepressive effect of sleep deprivation stabilized by a three day phase advance of the sleep period? A pilot study. European Archives of Psychiatry & Clinical Neuroscience, 2003. 253(2): p. 68-72.
18. Benedetti, F., et al., Antidepressant effects of light therapy combined with sleep deprivation are influenced by a functional polymorphism within the promoter of the serotonin transporter gene. [see comment]. Biological Psychiatry, 2003. 54(7): p. 687-92.
23. Abolmaali, K., et al., Circadian variation in intestinal dihydropyrimidine dehydrogenase (DPD) expression: a potential mechanism for benefits of 5FU chrono-chemotherapy. Surgery, 2009. 146(2): p. 269-73.
24. Liao, C., et al., Chronomodulated chemotherapy versus conventional chemotherapy for advanced colorectal cancer: a meta-analysis of five randomized controlled trials. International Journal of Colorectal Disease, 2010. 25(3): p. 343-50.
27. Morgenthaler, T.I., et al., Practice parameters for the clinical evaluation and treatment of circadian rhythm sleep disorders. An American Academy of Sleep Medicine report. Sleep, 2007. 30(11): p. 1445-59.