Antidepressant use among Americans is skyrocketing. Adults in the U.S. consumed four times more antidepressants in the late 2000s than they did in the early 1990s. As the third most frequently taken medication in the U.S., researchers estimate that 8 to 10 percent of the population is taking an antidepressant. But this spike does not necessarily signify a depression epidemic. Through the early 2000s pharmaceutical companies were aggressively testing selective serotonin reuptake inhibitors (SSRIs), the dominant class of depression drug, for a variety of disorders—the timeline below shows the rapid expansion of FDA-approved uses.

As the drugs' patents expired, companies stopped funding studies for official approval. Yet doctors have continued to prescribe them for more ailments. One motivating factor is that SSRIs are a fairly safe option for altering brain chemistry. Because we know so little about mental illness, many clinicians reason, we might as well try the pills already on the shelf.

Common Off-Label Uses

Doctors commonly use antidepressants to treat many maladies they are not approved for. In fact, studies show that between 25 and 60 percent of prescribed antidepressants are actually used to treat nonpsychological conditions. The most common and well-supported off-label uses of SSRIs include:

Abuse and dependence

ADHD (in children and adolescents)

Anxiety disorders

Autism (in children)

Bipolar disorder

Eating disorders

Fibromyalgia

Neuropathic pain

Obsessive-compulsive disorder

Premenstrual dysphoric disorder

Investigational Uses

SSRIs have shown promise in clinical trials for many more disorders, and some doctors report using them successfully to treat these ailments: