We know antidepressants are effective. But what about the effect of taking them for decades?

SHOW TRANSCRIPT

Depression is rampant. It's the leading cause of disability in the United States for people 15 to 44 years old. So, it's no wonder that the use of antidepressants — Prozac, Celexa, Paxil, Zoloft and other SSRIs — is high.

SSRI stands for selective serotonin reuptake inhibitor. Serotonin is a brain chemical — a neurotransmitter — that helps regulate mood. It's sometimes called the "happy chemical." People with depression often have low serotonin levels, although it is unclear whether depression results in lower serotonin levels or if low levels trigger depression.

Here's how an SSRI works: Imagine a brain cell sending serotonin to another cell. The chemical crosses a gap — a synapse — to reach the receiver that's branched out like tree roots. The serotonin that is not sucked up by the receiving cell is naturally reabsorbed and deactivated by the original cell. An SSRI blocks that natural reuptake, which allows more active serotonin to hang out in the synapse, ready to be used.

Related Story Psychedelics Show Promise In Treating Depression And Anxiety

One other detail: SSRIs are called "selective" because they seem to primarily affect serotonin, not other neurotransmitters. The number of people taking SSRIs is surging.

A New York Times analysis found that 15.5 million Americans have been taking the medications for at least five years. The rate has almost doubled since 2010 and more than tripled since 2000. The Times report also showed that more than 34.4 million adults took antidepressants in recent years, up from 13.4 million as the decade began.

That's in line with a CDC survey, showing antidepressant use increased nearly 65 percent over that 15-year time frame. Antidepressants aren't an overnight cure. Some people feel less depressed within two weeks after starting medication, and others don't feel the full effects for six to eight weeks.

Side effects vary from patient to patient including drowsiness, nausea and low sex drive. Some patients also report withdrawals when they try to stop taking the pills, leading to dizziness, confusion and fatigue. Antidepressants that have a short half-life — that is, they break down and leave the body quickly — are more likely to be troublesome when a patient stops taking them.

There is an ongoing debate over how effective antidepressants are. Are they less effective over time in the body? The answer seems to be that it depends on the patient, the particular medication taken and the intensity of a patient's depression.

The director of a study published in The Lancet, a respected medical journal, leaves little doubt about her conclusion: "Antidepressants are an effective tool for depression. Untreated depression is a huge problem because of the burden to society."

So depression is pervasive. Antidepressants are in millions of medicine cabinets. Yet, we don't know the true effect of taking these pills for decades.