A number of factors will go into your doctor's choice of medication for your mood disorder. For example, if a certain medication has worked well for you or a relative in the past, it may be worth trying now.
Your doctor may have to eliminate some medication choices because they could react with drugs you're already taking for other health conditions. He or she may choose a medication based on the cost or dosing schedule or even because he or she has prescribed the medication to other patients with great success.
Psychiatrists occasionally may recommend a blood testcalled the cytochrome P450which can help identify genetic factors that predict your response to certain medications, including antidepressants. The test won't show which antidepressants will be most helpful, but it can suggest which ones may not work well or may be most likely to cause side effects.
All things considered, however, many doctors begin by trying selective serotonin reuptake inhibitors (SSRIs), since they typically work well and usually have fewer and milder side effects than some other medications.
Keep in mind that choosing a medication is not an exact science, and it may require some trial-and-error to find the drug, dosage, or combination of drugs that works best for you.