How long does it take for antidepressants to reach full therapeutic effect?

Most antidepressants take four to six weeks to reach full therapeutic effect, although some improvement in sleep, appetite, and energy may occur within one to two weeks. This delay occurs because the therapeutic benefit requires downstream changes in receptor sensitivity and neuroplasticity, not just acute increases in neurotransmitter levels. Patients must be counseled about this timeline to prevent premature discontinuation. If no improvement occurs after six to eight weeks at an adequate dose, the clinician may increase the dose, switch medications, or add an augmenting agent.