WASHINGTON — Young adults face an increased risk of suicidal thoughts and behavior when they first begin taking antidepressants and should be warned about the danger, federal health officials said Wednesday.

The Food and Drug Administration asked makers of the drugs to expand its warning labels to include adults age 18-24. The labels already include similar warnings for children and adolescents.

Eli Lilly and Co., the maker of Prozac, Zoloft manufacturer Pfizer Inc. and other pharmaceutical companies said they would comply with the FDA’s request.

“We believe this step will help ensure that the millions of people with depression who are young adults age 24 and under and their families can make informed treatment decisions while minimizing the fear and stigma associated with depression,” Eli Lilly said in a statement.

Pfizer spokeswoman Shreya Prudlo said the company would update its label, which she said already calls for close monitoring of patients when they begin taking Zoloft. She added, however, “There is no established causal link between Zoloft and suicide in adults, young adults or children.”

The proposed labeling changes would note that studies have not shown this increased risk in adults older than 24 and that adults 65 and older taking antidepressants have a decreased risk of suicidal thoughts and behavior.

The expanded warnings would emphasize that depression and certain other serious psychiatric disorders are themselves the most important causes of suicide.

“Antidepressant medications benefit many patients, but it is important that doctors and patients are aware of the risks,” said Dr. Steven Galson, the FDA’s drugs chief.

The FDA advises that patients of all ages starting on antidepressants should be “monitored appropriately and observed closely” for worsening symptoms, suicidal thoughts or behaviors or unusual changes in behavior.

Still, any risks are small. For every 1,000 patients 18-24 treated with antidepressants, the FDA would expect there would be five additional patients who have suicidal thoughts or exhibit suicidal behavior, said Dr. Thomas Laughren, who oversees psychiatric drugs for the FDA. The FDA analysis was based on studies of 11 antidepressants in more than 77,000 patients.

The proposed changes came with the endorsement of FDA expert advisers. Some experts have argued that the changes are overdue while others maintain they could keep drugs from those who need them.

Last month, a comprehensive analysis of antidepressants for children and teenagers found the benefits of treatment trump the small risk of increasing suicidal thoughts and behaviors in some patients. The Journal of the American Medical Association study also found that risk is lower than what the FDA identified in 2004, the year the agency warned the public about the risks of the drugs in children.

After that warning, doctors wrote children fewer prescriptions for antidepressants, and U.S. youth suicides increased.

That suggests the warnings could have a net effect that is harmful if they keep the drugs from patients who would benefit from them, said Dr. David Brent, a University of Pittsburgh School of Medicine psychiatry professor and co-author of the JAMA study.

“When you have a black-box warning and within it you caution people that the biggest risks are from the disease and not being treated, people will still pay attention to the headline and not the small print,” Brent said.

Laughren said the FDA’s doesn’t know if the previously strengthened warnings led to the decrease in prescriptions or the increase in youth suicides.

“These are data that are hard to reach any conclusion about in terms of causality, but obviously it is something we are concerned about,” Laughren said.