It depends on what type of medication you are prescribed.
Antidepressants are taken daily and typically take 4 to 6 weeks for people to notice a difference. It may take additional time to find the best dosage or to try other medications or combinations if the one you are initially prescribed does not work for you.
Other names for drugs in this category include: Selective Serotonin Reuptake Inhibitors (SSRIs); Serotonin and Norepinephrine Reuptake Inhibitors (SNRIs); Norepinephrine and Dopamine Reuptake Inhibitors (NDRIs); Atypical antidepressants; Tricyclic antidepressants (TCAs); and Monoamine Oxidase Inhibitors (MAOIs).
Other types of drugs sometimes used to treat depression including mood stabilizers and atypical antipsychotics also take about 4 to 6 weeks for individuals to notice a difference.
Drugs like ketamine are showing potential for quicker treatment of depression, but they are still being researched.