A new analysis of US data shows a strong correlation between increased use of antidepressants over the past 20 years and a marked nationwide decrease in suicide rate, according to an article in the June issue of PLoS Medicine.

Julio Licinio, MD, the new chairman of the Department of Psychiatry and Behavioral Sciences at the University of Miami Leonard M. Miller School of Medicine, and colleagues analyzed federal data on overall suicide rates since the early 1960s and sales of the selective serotonin reuptake inhibitor fluoxetine since the antidepressant's introduction in 1988.

The data show the US suicide rate held fairly steady for 15 years prior to the introduction of fluoxetine, then dropped steadily over 14 years as sales of the antidepressant rose. The research team found the strongest effect among women.
Mathematical modeling of probable suicide rates from 1988 to 2002, based on pre-1988 data, suggests a cumulative decrease in expected suicide mortality of 33,600 people since the introduction of the antidepressant.

"Our findings certainly suggest that the introduction of SSRIs has contributed to reduction of suicide rates in the United States," Licinio said. "However, the findings do not preclude the possibility of increased risk of suicide among small populations of individuals."

The Food and Drug Administration introduced "black box warnings" on the most popular members of the drug class in 2004 amid rising concerns in the United States and United Kingdom concerning the relationship between suicide and antidepressant use in children and adults.

A key unanswered question involves whether antidepressants increase suicide over and above the underlying disorder, such as major depression.

"Much of the psychiatric community fears that the absence of treatment may prove more harmful to depressed individuals than the effects of the drugs themselves," Licinio said. "Most people who commit suicide suffer from untreated depression. Our goal is to explore a possible SSRI suicide link while ensuring that effective treatment and drug development for depression is not halted without cause."

The study examined age-adjusted suicide rate data from the Centers for Disease Control and the U.S. Census Bureau from the early 1960s until 2002. Data show suicide rates fluctuated between 12.2 and 13.7 per 100,000 people for the entire U.S. population until 1988. Since then, suicide rates have gradually declined, with the lowest rate at 10.4 per 100,000 in 2000. The decline is significantly associated with increased numbers of fluoxetine prescriptions dispensed, from 2.47 million in 1988 to 33.32 million in 2002.

Major depressive disorder affects approximately 10 percent of American men and 20 percent of women over their lifetimes. Because the prevalence is so high and treatment lasts several months or years, antidepressant medications are the most common form of treatment. Fluoxetine is the most widely prescribed antidepressant medication in the world and the only antidepressant that is FDA-approved for treatment of depression in children.