Planned drug holidays are used in numerous fields of medicine. They are perhaps best known in HIV therapy, after a study showed that stopping medication may stimulate the immune system to attack the virus.
A 2006 HIV literature review noted that "two studies suggested that so-called drug holidays were of no benefit and might actually harm patients, while a third study suggested that the idea might still have value and should be revisited.
In addition to drug holidays that are intended for therapeutic effect, they are sometimes used to reduce drug side effects so that patients may enjoy a more normal life for a period of time such as a weekend or holiday, or engage in a particular activity. For example, it is common for patients using SSRI anti-depressant therapies to take a drug holiday to reduce or avoid side effects associated with sexual dysfunction.
In the treatment of mental illness, a drug holiday may be part of a progression toward treatment cessation. The idea of a holiday is an acknowledgement that longer term psychoactive drug formulations may represent risks not apparent in early phases of use. The holiday is also a tool to assess a drugs benefits against unwanted side effects, assuming that both will end after an extended vacation (some psychoactive drugs have extended side effects long after cessation, however).