People under age 25 who take antidepressants have a higher risk of suicide, but adults older than that do not, an analysis by U.S. Food and Drug Administration researchers released on Tuesday showed.

The report by the FDA scientists confirms earlier studies and supports the agency's age-related warnings on the drugs' labeling.

U.S. and European regulators have been sounding alarms on the use of antidepressant drugs since 2003 after clinical trials showed they increased the risk of suicidal thoughts and behaviors in those under age 18.

In February 2005, the FDA added a so-called black box warning -- the agency's strongest warning -- on the use of all antidepressants in young children and teens to draw attention to the possible risks of these medications. In May 2007, it extended the warnings to young adults aged 18 to 24.

Many psychiatrists have criticized the warnings, saying they scare people away from effective treatment for depression, the leading cause of suicide. In fact, recent studies have suggested the warnings triggered an 8 percent rise in suicide among youth and teens in 2004, the biggest one-year gain in 15 years.

A LASTING DECLINE

A study published in June in the journal Archives of General Psychiatry said the FDA's decision to impose black box warnings for children and young adults had a spillover effect on depression care in older adults, resulting in a lasting decline in depression diagnosis and treatment.

Those researchers urged the FDA to revise its policy.

The FDA analysis by Dr. Marc Stone, Dr. Thomas Laughren and colleagues involved a review of data from eight drug makers on 372 clinical trials involving nearly 100,000 adults.

Overall, they found the risk of suicide was strongly age-dependent, with higher risks in people under 25, no difference among those 25 to 64, and lower risks in people 65 and older.

The researchers said the findings, published on the British Medical Journal website, support the agency's warnings on antidepressant drug labeling for people under 25, and they also support the notion that antidepressant drugs can have two distinct effects.

In some patients, they can promote suicidal thoughts or behavior -- but this risk appears to diminish with age. In others, the drugs provide relief from depression, reducing the risk of suicide. They said more research is needed to understand these differences.

John Geddes from the University of Oxford and colleagues said in a commentary the findings were not new and noted that the trials studied by the FDA excluded sicker patients. The study did, however, make clear differences in risks among specific antidepressants, they said.

They noted specific differences in commonly used drugs called selective serotonin reuptake inhibitors, or SSRIs.

For example, the odds of suicidal behavior by people taking Pfizer Inc's Zoloft, or sertraline, were around half of those who took placebo. By comparison, Forest Laboratories Inc's Celexa, or citalopram, and Lexapro, or escitalopram, seem to increase the risk of suicidal events, Geddes and colleagues wrote.

Increased risk is probably restricted to younger people and varies greatly between individual medicines.