How can antidepressant withdrawal symptoms last so long, when it only takes a few days for the drug to leave your body?

Most antidepressants do leave your body in a few days, but the changes to the brain that they cause can last for much longer. While these adaptations re-adjust towards your body’s factory settings (returning to its pre-drug state), you may have withdrawal symptoms. Withdrawal symptoms are a sign that your brain and body are hard at work to settle down.