How long does it take for Zoloft to work?

For a small amber or blue oval pill, Zoloft sure generates a lot of buzz -- and so do other members of its family of antidepressants.

A study released in 2011 by the National Center for Health Statistics reports that from 2005 to 2008, one in 10 Americans age 12 and older took antidepressant medication, making antidepressants the third most commonly prescribed drug taken by Americans of all ages during and the No. 1 medication of adults age 18 to 44. Overall, the rate of antidepressant usage in the U.S. -- among all ages -- skyrocketed 400 percent between 1988 and 2008 [source: NCHS].

Zoloft -- also known by its generic name sertraline hydrochloride -- is a prescription antidepressant classified as a selective serotonin reuptake inhibitor (SSRI), as we mentioned. This class of antidepressants affects receptors in the brain that absorb serotonin.

Serotonin -- 5-Hydroxytryptamine or 5-HT -- is a naturally occurring chemical found in intestines, blood platelets, certain cells and the brain. Serotonin is a derivative of tryptophan, a natural amino acid, and is concentrated in the midbrain and hypothalamus -- two areas responsible for mood, sleep and aggression. When there isn't enough serotonin, either because it is absorbed too quickly or in too great a quantity by the brain's neurons, depression can occur.

An SSRI antidepressant like Zoloft acts as an air traffic controller in the brain. It commands serotonin to circle the runway before landing, causing a critical delay that allows the brain's neurons to more effectively absorb the optimal amount of mood-boosting serotonin. The air traffic controller opens more runways, in this case receptors in the brain, so more serotonin can reach its intended destination. And, because (as its name suggests) an SSRI is "selective," it targets only serotonin and allows other chemicals to continue their normal flight pattern in the brain. In effect, it inhibits the reabsorption or reuptake of serotonin from happening too quickly [source: Bussing, Crowe].

The first generation of antidepressants in the 1950s boosted the levels of several brain neurotransmitters or chemicals. Later scientists concentrated on drugs that could improve the uptake of just one chemical. In 1987, the first SSRI -- Prozac -- was approved by the FDA, followed by fluvoxamine maleate (Luvox), paroxetine (Paxil), Zoloft and, in 1998, citalopram (Celexa) [source: Bussing].

The newest class of antidepressants is serotonin norepinephrine reuptake inhibitors (SNRIs), called dual-action antidepressants because they increase levels of serotonin and norepinephrine (both neurotransmitters). This class includes duloxetine (Cymbalta), venlafaxine (Effexor) and desvenlafaxine (Pristiq). For some people, this combination works better than an SSRI [source: Medicine Net].

Zoloft isn't only for major depression. It's also used to treat obsessive-compulsive disorder, panic disorder, post-traumatic stress disorder, premenstrual dysphoric disorder (PMDD) and social anxiety disorder.

Zoloft, an oral antidepressant pill made of compressed crystalline powder, is usually prescribed to first-time users in a 50-milligram-per-day dose for depression and PMDD and 25 milligrams per day for other disorders. Dosages can be increased with time and medical supervision up to 200 milligrams per day. It's also available in liquid form [source: RX List].

Within just a few hours of taking an SSRI for the first time, the levels of serotonin in the brain and bloodstream increase. Yet, we don't feel immediate results. Zoloft takes weeks to work. Why?

The answer is us. Our bodies need time to adapt to the new normal created by taking a pill laced with sertraline that is designed to increase serotonin levels in the brain. Not only does this SSRI medication help the brain absorb serotonin into the blood stream more effectively, but it may actually change the makeup of the brain. The brain needs new receptors to help absorb the additional serotonin; it builds and installs additional receptors -- a biological process that can take up to eight weeks. So, even though Zoloft increases the levels of serotonin in our bodies nearly immediately, our brains aren't immediately equipped to absorb it [source: Crowe].

If, however, after six to eight weeks, Zoloft doesn't seem to be positively affecting your mood, anxiety -- or other condition for which it was prescribed -- it's time to alert your physician. Not every antidepressant will work the same for every person, and an estimated 50 percent of people who try an antidepressant will need to take a different brand or class before finding one that works for them. Or, it could just be that your dosage needs to be increased [source: Grohol].

Your physician will help determine your type and dosage of antidepressant by considering your symptoms, other medications you are taking, health conditions, potential side effects, and whether you are pregnant or breastfeeding. In addition, she may inquire as to whether a particular antidepressant has been taken by a close relative, and what the results were. If your brother's depression, for example, lifted after taking Zoloft, yours probably will, too [source: Mayo Clinic].