A common parasitic organism that lives in our brains and spreads through infected kitty litter and undercooked meat may increase the risk of suicide in mothers, a new study has found.
Toxoplasma gondii is a widespread but poorly understood disease that affects an estimated 30 percent of people worldwide, with most experiencing symptoms no worse than a severe flu.
In rare cases it can cause severe problems and even death in people with compromised immune systems or if it is passed to unborn babies.
However, there is a growing body of evidence suggesting that once it takes up residence in your brain — seemingly dormant — it can cause long-term neurological changes — messing with your mind.
A 2011 study found that infected mice lost their fear of cats — the rationale being they were more likely to be eaten by cats, the parasite's primary host.
Researchers have also raised links between Toxoplasma gondii and schizophrenia and other behavioural changes.
Now a study of more than 45,000 infected mothers in Denmark has found they were one and a half times more likely to attempt suicide than non-infected mothers.
"We can't say with certainty that T. gondii caused the women to try to kill themselves, but we did find a predictive association between the infection and suicide attempts later in life that warrants additional studies," the study's author Dr. Teodor T. Postolache, from the University of Maryland School of Medicine, told the US ABC News.
Dr Chris Tonkin, from the Walter and Eliza Hall Institute of Medical Research's infection and immunity division, says there is little current data on how common the parasite is.
A study done to estimate the value of mandatory screening of expectant mothers to prevent related birth defects found it was not worthwhile.
However, he said it was likely rates were similar to the United States where about one in five people were infected.
Dr Tonkin, who is researching ways to stop the organism invading human cells, said there was no known treatment for people with the dormant form of the parasite.
"We really want the smoking gun before we spend too much effort (finding a cure) but there is more and more evidence that toxo is modulating some sort of process in the brain and this is worthy of further investigation," he said.
"If it is true then finding new treatments to cure you of the chronic form could help with treatment options of psychiatric illness."