A new study that suggests commonly prescribed antidepressants may be linked to an increased risk of certain types of cancers also finds a potential bias in research funded by makers of those drugs.

Researchers from Harvard University compiled data from 26 epidemiological and 35 pre-clinical studies studies between 1965 and 2010 that analyzed what impact antidepressants known as SSRIs had on cancer risk. They found that the drugs may be linked to a slight increased risk of breast and ovarian cancers, even at low doses.

What they also found was that the conclusions of the studies differed depending on whether or not they were funded by the drug manufacturers.

Of the 61 studies included, 41 did not find a link between the antidepressants and cancer, while 20 did find an association between the drugs and disease risk.

When the results of all the 61 were pooled, the analysis found an 11 per cent higher chance of women taking antidepressants developing the diseases later in life. The increased risk was particularly stronger for women taking newer, selective-serotonin re-uptake inhibitor drugs (SSRIs) compared to older antidepressants.

The analysis also showed that more than one third of the studies funded by the manufacturers found no link between the drugs and cancer risk. However, all of the studies not funded by the drug makers found an association between the antidepressants and cancer risk.

The drug companies involved weren't identified in the report, which appears in the journal, PLoS One.

"We found that researchers with industry tries were far less likely to publish studies with adverse side effects," study author Dr. Lisa Cosgrove of the Edmond J. Safra Center for Ethics at Harvard told CTV News.

Her team concludes that the results point to a need for more study of SSRIs and their link to cancer in women.

Previous studies have called into question the reliability of research funded by industry.

Dr. David Henry, a researcher with the Institute for Clinical Evaluative Sciences, called the latest findings worrying.

"This is a feature that we have found fairly broadly in the literature that shows where industry ties exist, where the researchers themselves have association with the industry, they're more likely to find in favour of the product that is being tested," Henry told CTV News.

Jennifer Foulds, a Toronto woman who relies on SSRIs to treat her anxiety and depression, says the study is compelling her to rethink her use of the drugs because the findings "give the suggestion that we are not getting the full picture."

"I am definitely going to talk to my doctor," she told CTV News.

Despite the findings and the concerns over biased research, doctors say patients should not stop taking the drugs, which help millions of patients cope with chronic mood disorders, as well as a range of ailments from hot flashes to headaches associated with chronic pain.

Dr. Lorne Brandes, a breast cancer specialist and researcher at the University of Manitoba, calls the implication that drug company-sponsored research may be skewed "stunning," even though he, like other researchers, is aware of the ongoing controversy surrounding industry-funded studies.

But he said the latest study does not provide a definitive answer to the question of whether antidepressants increase cancer risk.

"I do believe that they must do much longer studies that they will have to carry out to get an answer," Dr. Lorne Brandes, a breast cancer specialist and researcher at the University of Manitoba, told CTV News.

"But I do believe that the study by the Harvard group will get more people thinking about this issue and what needs to be done."

With a report from CTV's medical specialist Avis Favaro and producer Elizabeth St. Philip