Some antidepressant drugs could cause irritability and other abnormal behaviour in teenagers and more research is required to study their effect on children, say scientists.
Kereshmeh Taravosh-Lahn of the University of Texas at Austin, US, and colleagues gave injections of the drug fluoxetine (sold in pill form as Prozac) to pubescent and mature hamsters.
They injected either a low dose (10 milligrams per kilo of body weight) or a high dose (20 milligrams per kilo body weight), while other hamsters received a placebo.
The researchers then introduced a smaller, same-sex hamster into the cage of each experimental hamster and filmed all the fights between the two rodents that were initiated by the subject animals, reported the online edition of New Scientist.
The pubescent hamsters on a higher dose of drug appeared calmer, initiating about 65 percent fewer attacks than those on placebo. But surprisingly, those on lower dose of antidepressant became more aggressive, initiating 40 percent more fights than those on a placebo.
Adult hamsters on either dose of the drug initiated fewer fights than those on placebo.
Prozac can make "adolescent" hamsters more aggressive towards their cage-mates, despite the antidepressant drug producing the opposite effect in adult hamsters, making them calmer, the researchers said.
Some young people with depression receive lower doses of antidepressant drugs because of their relatively small weight and size. But Taravosh-Lahn says the findings of the hamster study should prompt a closer look at the effects of this practice.
"We underestimate the differences between the juvenile brain and the adult brain," he said. "It seems there is more research needed on the effects of antidepressants on kids."