Most antidepressants take time to reach their full effect. This includes SSRIs such as sertraline, escitalopram, and fluoxetine, and SNRIs such as venlafaxine and duloxetine. Many people notice early changes in sleep, energy, or appetite within the first one to two weeks. Improvement in mood usually builds over four to eight weeks.
That delay is one of the most common reasons people stop a medication too soon. Feeling no change after a couple of weeks doesn’t mean the medicine has failed. Your psychiatrist may adjust the dose before considering a switch, since many people respond once they reach the right dose for their body.
Close follow-up during the first month or two is important. For people under 25, the FDA advises extra monitoring during this period, because a small number experience increased suicidal thoughts when starting an antidepressant. These check-ins help your provider track your response and catch concerns early.