WASHINGTON — No one under age 18 should be prescribed the drug Paxil for major depression because the adult antidepressant may increase a child's risk of suicide, the U.S. government said.

The Food and Drug Administration's recommendation came a week after Britain issued an even stronger warning against pediatric use of Paxil, sold there under the name Seroxat. Paxil is also sold in Canada. Children and teenagers already taking Paxil should not suddenly stop the pills, the FDA stressed. Some doctors may feel the drug is helping enough to keep a particular patient on the medication, which the FDA warning doesn't forbid. Those who do stop taking Paxil need medical supervision to taper off and avoid rebound side-effects, such as abnormal dreams and shock-like sensations.

Paxil is approved for adult treatment of a number of psychiatric illnesses, including depression. While there have been lawsuits alleging Paxil caused violent or suicidal reactions, the FDA said Thursday there is no scientific evidence linking the drug to increased suicide risk among adults.

The FDA has never approved use of Paxil in children or teens. But some doctors prescribe the adult drug for children anyway.

The FDA had asked all makers of adult antidepressants to submit research showing how their drugs affect children. Three studies of Paxil found it didn't seem to help pediatric depression - but FDA scientists spotted some safety concerns and ordered manufacturer GlaxoSmithKline to re-analyse the data.

That new analysis - submitted last month, first to the British government and then to the FDA - found the risk of suicidal thoughts and suicide attempts was three times greater among Paxil users, mostly teens, than among children given dummy pills, the FDA said.

There were no deaths during the studies, but FDA officials wouldn't release the actual number of suicide attempts, citing manufacturer confidentiality.

GlaxoSmithKline would detail only the rate of all "emotional side-effects," ranging from mood swings to suicide attempts: 3.2 per cent of pediatric Paxil patients compared with 1.5 per cent of those given dummy pills in studies that included about 1,000 children and teens.

The FDA cautioned that it still is investigating and hasn't definitively concluded there is a suicide risk to children.

"There is no definitive action or even decision about what ought to be done," said the FDA's Dr. Russell Katz. But "we wanted to let people know" about the possible risk.

Why would Paxil cause such a side-effect in depressed children but not adults?

The FDA said it's not clear, but noted that childhood depression itself is different from adult depression, probably because of changes the child's brain undergoes as it grows. A number of adult antidepressants have failed to work in children. Plus, children often suffer different side-effects from a variety of medications than adults do.

GlaxoSmithKline couldn't provide prescription data Thursday, but spokeswoman Mary Anne Rhyne said an extremely small percentage of Paxil users are children with depression. The company is seeking FDA approval to sell Paxil to treat another illness, obsessive-compulsive disorder, in children. Rhyne said studies found no sign that giving the drug to those patients triggered suicidal thoughts.

There is one FDA-approved treatment for depression in children, the competing drug Prozac.