The question of whether to try an antidepressant depends on a number of medical and personal factors. Suppose you've never had depression before, but find yourself upset over some life trauma, such as a divorce or the death of a loved one. Experts generally say you should avoid antidepressants in that case so long as you can still work and otherwise function. In fact, many doctors worry that antidepressants are over-prescribed for such "situational" depression—cases that result from a specific event—and for very mild cases of depression, both of which may resolve on their own or with counseling and family support.

On the other hand, studies clearly show that serious major depression is often undertreated. Only 30 to 40 percent of sufferers get adequate care, in part because many people are reluctant to seek treatment for emotional or mental problems. So if you suspect you are clinically depressed, don't delay consulting a doctor or mental health professional.

Which drugs work best

The earliest antidepressants, like amitriptyline and nortriptyline (brand names: Aventyl and Pamelor) were developed in the 1950s and 1960s. They are still occasionally prescribed, but have been superceded by newer drugs that generally have fewer side effects. Our analysis includes only the newer drugs.

The new antidepressants were introduced in the late 1980s and early 1990s. No doubt you've heard of some of them, such as Prozac, Paxil, Zoloft, and Wellbutrin. What you may not know is that most of the newer antidepressants are now available as lower-cost generics. (See Newer Antidepressants)

Indeed, of the 9 newer antidepressants, only three (Cymbalta, Lexapro, and the newest, Pristiq) are still available only in higher-priced branded forms. The rest can be bought for somewhere between $25 and $100 per month. And studies suggest that all of the newer drugs —generic or branded—are roughly equally effective at controlling depression.

As a result, if you were choosing only on those factors, your task would be easy: pick the one you can afford. Importantly, though, the drugs do differ on side effects (see Newer Antidepressants). Because of that, our choice of the following three Best Buys is based primarily on cost and variations in side effects, safety indicators, and convenience:

Bupropion (generic Wellbutrin)

Citalopram (generic Celexa)

Fluoxetine (generic Prozac)

In choosing these or any other antidepressants, here are several points to keep in mind. First, antidepressants take a while to work, often as long as six to eight weeks. So don't get discouraged if the drug doesn't seem to have much effect at first. Only with time can you tell if the medication is doing its job.

You should also be aware that about 40 percent of patients do not respond at all to the first antidepressant they try. Generally, your doctor or mental health therapist will wait 12 weeks or so before advising you to switch to a different drug, and may even boost the dose first just to give the original medication a better chance. But it's not uncommon to try three or four different medicines before finding one that works. In some cases, doctors recommend taking two antidepressants at the same time to improve effectiveness.

A more sobering fact to bear in mind: some 30 to 45 percent of people get little or no help from any antidepressant. And some studies suggest that the percentage might be even higher if you add those with mild depression who more than likely would have gotten better without drugs. The good news is that the majority of people (55 to 70 percent) who take antidepressants report that their depressive symptoms were reduced, generally by at least one-half according to a self-rating scale.