If you're one of the 12 million women diagnosed with depression in the last year, there's a good chance your doctor wrote you a prescription for a selective serotonin reuptake inhibitor (SSRI), the most common type of antidepressant. But if you don't feel 100 percent after a few months, don't worry: A study from the University of Michigan found that while SSRIs, like Paxil and Zoloft, can improve mood, boost energy, and reduce insomnia within three months, it may take up to six months for feelings of despondency or pessimism to lift. Some patients may give up on the drugs too soon, say researchers. But if it's been six months and you're still feeling down, ask your M.D. about additional treatments, such as therapy.