Antidepressants should be gradually tapered and should not be abruptly discontinued. Abruptly stopping an antidepressant in some patients can cause discontinuation syndrome.
For example, abruptly stopping an SSRI such as paroxetine can cause dizziness, nausea, flu-like symptoms, body aches, anxiety, irritability, fatigue, and vivid dreams. These symptoms typically occur within days of abrupt cessation, and can last one to two weeks (up to 21 days). Among the SSRIs, paroxetine and fluvoxamine cause more pronounced discontinuation symptoms than fluoxetine, sertraline, and citalopram. Some patients experience discontinuation symptoms despite gradual tapering of the SSRI. Abrupt cessation of venlafaxine, duloxetine, or desvenlafaxine can cause discontinuation symptoms similar to those of SSRIs.

Abruptly stopping MAOIs can lead to irritability, agitation, and delirium. Similarly, abruptly stopping a TCA can cause agitation, irritability, and abnormal heart rhythms.