How do antidepressants work?

People suffering from depression are thought to have lower levels of some of the chemical messengers in the brain, called neurotransmitters. The three neurotransmitters believed to be involved in depression are serotonin, dopamine, and norepinephrine. Neurons in the brain constantly produce, release, and reabsorb these brain chemicals. Antidepressants increase the levels of these neurotransmitters in the brain by blocking their reabsorption. Watch the video Antidepressants — How they help relieve depression for an illustration of how this works.
 
While this has led to the popular belief that depression is the result of a chemical imbalance in the brain that can be corrected with drugs, the reality is more complex. It is not yet known whether low levels of neurotransmitters cause depression, or whether depression causes this imbalance in brain chemistry. For more, read Causes of Depression and The Brain and Depression.

How effective is medication for depression?

While antidepressants provide relief for some people, they are not a “magic bullet” for depression. Antidepressants reduce symptoms in approximately 70 percent of people. This leaves nearly 1 out of 3 people who don't get relief. Even in those who respond to medication, complete remission is rare. More commonly, their symptoms are reduced but not cured. This is important because, as Psychology Today notes, unless a full remission is achieved, depression is very likely to recur.

Placebo Effect

Some of the improvement that people experience from antidepressants can be attributed to the placebo effect. In fact, recent research suggests that antidepressants don't work much better than sugar pills. For more information, read Placebo Power and Antidepressants: A Triumph of Marketing Over Science?. 

Medication vs. Therapy

While antidepressants may improve mood by boosting the “feel-good” chemicals in your brain, they don't treat the actual cause of the depression. Because of this, relapse rates are high once drug treatment is stopped. In contrast, the emotional insights and coping skills acquired during therapy can have a more lasting effect on depression. A University of Pennsylvania study backs up this claim. It found that cognitive therapy works just as well as antidepressants and is more effective than medication in preventing relapse once treatment ends.

In a moderate to severe depression, medications may be useful in the short term, but should be accompanied by therapy to address underlying issues. Sometimes the heaviness of a depression serves to mask painful emotions, which may then come to the surface when medications are taken. The result can be an unexpected sadness – yet another reason that psychotherapy is so important when using antidepressants.

Can antidepressants make depression worse?

There is a risk that antidepressant treatment will cause an increase, rather than a decrease, in depression. In fact, all depression medications are required by the FDA to carry a warning about the increased risk of suicide, hostility, and agitation. The FDA advises that all individuals on antidepressants be closely watched for increases in suicidal thoughts and behaviors.

Monitoring is especially important if this is the person’s first time on depression medication or if the dose has recently been changed. If the depression appears to be getting worse, an evaluation by a mental health professional should be scheduled as soon as possible. New problems with anxiety, insomnia, aggressiveness, irritability, impulsivity, and restlessness—particularly if the symptoms are severe or appeared abruptly—are red flags as well, and should be evaluated immediately.