Canadian researchers, who examined the impact of the medications on the whole body, say common anti-depressants could be doing patients more harm than good.

Researchers at McMaster University examined previous patient studies into the effects of anti-depressants and determined that the benefits of most anti-depressants compare poorly to the risks, which include premature death in elderly patients.

“We need to be much more cautious about the widespread use of these drugs,” said study leader and evolutionary biologist Paul Andrews.

“It’s important because millions of people are prescribed anti-depressants each year, and the conventional wisdom about these drugs is that they’re safe and effective.”

Anti-depressants are designed to relieve the symptoms of depression by increasing the levels of serotonin in the brain, where it regulates mood.

The vast majority of serotonin that the body produces, though, is used for other purposes, including digestion, forming blood clots at wound sites, reproduction and development.

The researchers, whose study was published in the online journal Frontiers in Psychology, found that anti-depressants had negative health effects on all processes normally regulated by serotonin.

This included a higher risk of developmental problems in infants, problems with sexual function, digestive problems and abnormal bleeding and stroke in the elderly.

The authors reviewed three recent studies showing that elderly anti-depressant users are more likely to die than non-users, even after taking other important variables into account. The higher death rates indicate that the overall effect of these drugs on the body is more harmful than beneficial.

The higher death rates among anti-depressants users indicate that the overall effect of these drugs on the body is more harmful than beneficial

“Serotonin is an ancient chemical. It’s intimately regulating many different processes, and when you interfere with these things you can expect, from an evolutionary perspective, that it’s going to cause some harm,” Paul Andrews said.

Millions of people are prescribed anti-depressants every year, and while the conclusions may seem surprising, Paul Andrews says much of the evidence has long been apparent and available.

“The thing that’s been missing in the debates about anti-depressants is an overall assessment of all these negative effects relative to their potential beneficial effects,” he says.

“Most of this evidence has been out there for years and nobody has been looking at this basic issue.”

In previous research, Paul Andrews and his colleagues had questioned the effectiveness of anti-depressants even for relieving depression. They found patients were more likely to suffer relapse after going off their medications as their brains worked to re-establish equilibrium.

Paul Andrews says it is important to look critically at their continuing use.

“It could change the way we think about such major pharmaceutical drugs,” he said.

“You’ve got a minimal benefit, a laundry list of negative effects – some small, some rare and some not so rare. The issue is: does the list of negative effects outweigh the minimal benefit?”