Their use is dramatically increasing, with 64.7million prescriptions given out in England last year, double the number of a decade ago.
Critics are increasingly concerned that many of these patients may not actually need the drugs, with doctors prescribing the pills as a stop-gap because of long waiting lists for therapy.
The new analysis suggests people who take the pills may be at greater risk than previously thought.
HOW WAS THE STUDY CARRIED OUT?
Scientists at McMaster Universty in Canada combined the results from 17 previous studies, analysing the impact on a pool of nearly 380,000 people.
Their initial analysis suggested just a 9 per cent increased risk of death among those who took antidepressants - a result they admitted was not statistically significant.
But they then removed the people suffering from cardiovascular disease from the findings, and found the chance of death among the remaining patients who took antidepressants jumped up to 33 per cent when compared to those who did not take the drugs.
The scientists think this is because antidepressants are also a blood thinner - which actually protects the health of people with heart disease because it stops blood clotting.
But among people without heart disease, this is dangerous because it increases the risk of a major haemmorage or internal bleed.
The researchers found that among people without cardiovascular disease, taking antidepressants increased the risk of heart attacks and strokes by 14 per cent.
They believe the protective impact of the drugs among patients with cardiovascular disease has been masking the impact on other patients for years.
But the scientists stressed that although the relative risk of death was high, this would not actually affect many people, because the initial risk was very low.
WHAT DO THE STATS SAY?
They calculated that eight people in every 1,000 over-50s would usually expect to die every year if they did not take antidepressants.
This would increase to 10.64 per 1,000 for those taking the pills - fewer than three extra deaths per year.
British experts stressed that all medicines have side effects - and antidepressants are crucial for countless patients.
A spokesman for the Royal College of Psychiatrists said: 'All medicines have side effects.
"Countless studies over the years have shown that antidepressants are a life saver for many, reducing the risk of suicide in depressed patients. It is down to a patient and their doctor to decide together whether the benefits of a medicine outweigh the risks."
But Canadian study leader Paul Andrews said the risks are extremely serious.
"We are very concerned by these results," he said.
"They suggest that we shouldn't be taking antidepressant drugs without understanding precisely how they interact with the body.
"I do think these drugs for most people are doing more harm than good and that physicians ought not to generally prescribe them."
HOW DO THE DRUGS WORK?
The researchers think the way antidepressants work - by altering the uptake of serotonin, dopamines and other natural mood-enhancing chemicals in the brain - harms other parts of the body.
They said these chemicals are vital for other major organs of the body, including the heart, kidneys, lungs, and liver, which use serotonin and other chemicals from the bloodstream.
Antidepressants block the absorption of these chemicals throughout the body, and the researchers warn that antidepressants could increase the risk of death by preventing organs from functioning properly.
Benoit Mulsant, a psychiatrist at the University of Toronto who was also involved in the study, said the findings point to the need for more research on how antidepressants actually do work.
He said: "I prescribe antidepressants even though I do not know if they are more harmful than helpful in the long-term.
"I am worried that in some patients they could be, and psychiatrists in 50 years will wonder why we did not do more to find out."
WHAT DID THE CRITICS SAY?
Critics, however, questioned the results of the study. They said people who take antidepressants are already at increased risk even before they start taking the drugs.
Professor David Baldwin, a psychiatrist at Southampton University and chairman of the psychopharmacology committee of the Royal College of Psychiatrists, said: "Unfortunately this study has major flaws.
"Depressed patients have higher risks of a range of physical health problems, all of which carry a risk of increased mortality, and antidepressants are often prescribed for a range of problems other than depression, including chronic pain and insomnia, which also increase mortality."
He added: "The small number of papers included in the meta-analysis included patients who were prescribed antidepressants at any dose and for any duration, but the analysis takes no account of this."
GOOGLE'S DEPRESSION TOOL
Google's screening tool that enables people to check online whether they are clinically depressed could do more harm than good, an expert has warned.
Last month, the tech giant released a self-assessment quiz, called the Patient Health Questionnaire-9, which pops up as a result for the search query 'Am I depressed?' on a computer or cell phone.
Google developed its test in partnership with the National Alliance on Mental Illness (NAMI) but one professor claims that the quiz could just lead to over-treatment of depression amid the US's opioid epidemic.
He warns the tool's development was funded by major drug company Pfizer, which profits from the sale of antidepressants.
