The bacteria injected by a cat can include a strain common in animals, which is particularly hard to fight with antibiotics.

London - People who have been bitten by a cat should be screened for depression, suggest United States researchers.

This follows findings that those who had been treated for a cat bite were five times more likely to develop depression than people who hadn’t.

The figures come from a study conducted by the University of Michigan based on data from a million people. They found that more than 40 percent of those who’d had a cat bite went on to be diagnosed with depression.

The risk appears to be greater in women than men - 47 percent compared with 24.2 percent. This compares with an 8.8 percent depression rate in the general adult population.

It isn’t just cat bites that are linked to a higher risk - dog bites are, too, say the researchers. While 41 percent of people with cat bites went onto have depression, the figure was 28.7 percent for those bitten by dogs, a proportion that was still higher than normal.

“It may seem counter-intuitive to consider screening in someone who seeks treatment for an acute injury from a household pet, but our findings suggest that it could be beneficial,” says Dr David Hanauer, who led the research.

“Although we found an association between bites and depression, our work does not show that cat bites cause depression.”

This latest research follows a study - from Lund University, Sweden, and centres in the US - which last year discovered that a parasite found in cats’ brains may drive people to suicide.

Researchers found that those infected with the bug called toxoplasma gondii (T gondii), which breeds in cats’ stomachs, were seven times more likely to commit suicide. One theory is that a T gondii infection leads to the release of the inflammatory compounds in the brain that may cause depression. Previous studies have suggested that the parasite may contribute to human psychiatric disorders such as schizophrenia, obsessive compulsive disorder, and personality changes.

On the possible link to depression, Dr Carmine Pariante, professor of biological psychiatry at King’s College London’s Institute of Psychiatry, said: “Much more work is needed.

“Essentially, they found that people who had cats were more likely to have depression. One explanation, for example, might be that people who are lonely are more likely to have a pet, and be more prone to depression.”

This is the first report of the possibility of some kind of link between cats and depression in humans. Previously, studies have found that pet ownership results in physical and mental health benefits.

It has been shown to be better at reducing high blood pressure caused by stress than medication, while a study in Switzerland reported that cats can improve the mood of people living alone. - Daily Mail