“There’s fresh evidence that cats can be a threat to your mental health,” according to a post on yesterday’s NPR health blog, Shots. The threat, reporter Jon Hamilton explains, is not the cats themselves by the Toxoplasma gondii parasite that some cats pass in their feces.*

“A study of more than 45,000 Danish women found that those infected with [Toxoplasma gondii] were 1.5 times more likely to attempt suicide than women who weren’t infected.” [1]

“Still,” Hamilton continues, “the absolute risk of suicide remains very small. Fewer than 1,000 of the women attempted any sort of self-directed violence during the 30-year study span. And just seven committed suicide.” [1]

In fact, it may well be that T. gondii infection has no bearing on the risk of suicide at all.

As the researchers themselves point out in a paper published in this month’s issue of the Archives of General Psychiatry, “we cannot say with certainty whether the observed association between T. gondii infection and self-directed violence is causal.”

“T. gondii infection is likely not a random event and it is conceivable that the results could be alternatively explained by people with psychiatric disturbances having a higher risk of becoming T. gondii infected prior to contact with the health system.” [2]

In other words, it’s possible that mental illness is a risk factor for T. gondii infection, rather than the other way around. Read more