Common anti-depressants could be doing patients more harm than good, according to researchers examined the impact of the medications on the whole body.
A team from 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, 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.
"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," Andrews said.
Millions of people are prescribed anti-depressants every year, and while the conclusions may seem surprising, 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.
"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?"
In June 2011, Andrews and his colleagues had questioned the effectiveness of anti-depressants even for relieving depression.
They found patients were nearly twice as likely to suffer relapse after going off their medications as their brains worked to re-establish equilibrium.
The team studied dozens of previous papers to compare depressed patients who used anti-depressants compared to those who used placebos.
The analysis suggested that people who have not been taking any medication are at a 25 per cent risk of relapse, compared to 42 per cent or higher for those who have taken and gone off an anti-depressant.
"We found that the more these drugs affect serotonin and other neurotransmitters in your brain - and that's what they're supposed to do - the greater your risk of relapse once you stop taking them," Andrews said.
"All these drugs do reduce symptoms, probably to some degree, in the short-term. The trick is what happens in the long term.
"Our results suggest that when you try to go off the drugs, depression will bounce back. This can leave people stuck in a cycle where they need to keep taking anti-depressants to prevent a return of symptoms."
Rethink Mental Illness CEO Paul Jenkins said, "There is a place for medication, and for some people affected by mental illness it can be life-saving or can help them maintain a good quality of life.
"However, it can also impact on people’s physical health, so it is crucial that health professionals explain the potential side-effects so people can make an informed choice. It’s also vital that GPs take extra care in monitoring the physical health of people taking such medication.
"Too often, people with depression are fobbed off with medication alone.
"People with mild to moderate depression should always be offered talking therapies before medication and people with severe depression should always be offered talking therapies along with medication.
"Sadly, access to psychological therapies, although improving, is still nowhere near good enough, and people are waiting months or even years to get access to the treatment they need."
–Daily Mail, London