Washington ? Federal health officials are preparing stronger warnings for some anti-depressants used in children after new analyses back a possible link to suicide.

Exactly what those warnings will say, and which drugs will be affected, hasn’t been settled, according to Food and Drug Administration documents released Friday. The agency will ask its scientific advisers next month for help in deciding.

“While there remains a signal of risk … for some drugs in some trials, it is important to note that the data are not black-and-white in providing a clear and definitive answer,” FDA psychiatric drugs chief Dr. Thomas Laughren wrote the advisory panel this week.

The question is how strong the warnings will be, and whether any of the drugs will come with specific instructions not to use them in children and teenagers.

The controversy erupted last year, when British health authorities declared that most popular anti-depressants might sometimes increase the risk of suicidal behavior in children and teenagers. They declared all but one, Prozac, unsuitable for depressed youth, but stopped short of a pediatric ban.

It’s difficult to sort out because depression itself can lead to suicide, and studies show anti-depressants can help adults recover.

Here, only Prozac is FDA-approved to treat pediatric depression, and a taxpayer-funded study earlier this week showed that Prozac plus therapy was more effective for depressed teenagers than either approach alone. The latest FDA analyses don’t link Prozac to increased suicidal tendencies.

But while doctors widely prescribe anti-depressants for children, which is legal despite the lack of FDA approval, there is little evidence that any other than Prozac work for pediatric depression, thus deepening concern about even potential risks.

The FDA in March urged close monitoring of patients for suicide warning signs, especially when they first start the pills or change a dose. The reason: The drugs may cause agitation, anxiety and hostility in a subset of patients unusually prone to rare side effects.

Now, FDA and Columbia University psychiatric specialists have re-evaluated 25 studies involving more than 4,000 young people and eight anti-depressants.

There were no completed suicides. But, when all the results were lumped together, young anti-depressant users were about 1.8 times more likely to have suicidal thoughts or behaviors than patients given dummy pills, say analyses released Friday.