People may react differently to the same antidepressant. For example, a particular drug may work better — or not as well — for you than for another person. Or you may have more, or fewer, side effects from taking a specific antidepressant than someone else does.
Inherited traits may play a role in how antidepressants affect you. In some cases, where available, results of special blood tests may offer clues about how your body may respond to a specific antidepressant. However, other variables besides genetics can affect your response to medication.
When choosing an antidepressant, your doctor takes into account your symptoms, any health problems, other medications you take, and what's worked for you in the past.
Typically, it may take several weeks or longer before an antidepressant is fully effective and for initial side effects to ease up. Your doctor may recommend dose adjustments or different antidepressants, but with patience, you and your doctor can find a medication that works well for you.