Toxoplasma gondii, which can cause toxoplasmosis, is easily transmitted to humans, with most catching it by consuming undercooked meat or anything contaminated with cat faeces, a major newspaper reported.
A group of 54 patients of both sexes in a Swedish hospital, all with a history of attempting suicide, were studied, along with 30 control subjects.
It found that people who were exposed to toxoplasmosis were seven times more likely to attempt suicide.
Scientists have linked toxoplasmosis to behavioural changes and even the development of schizophrenia.
Infected people become more expedient, suspicious, jealous and dogmatic.
The report said identifying toxoplasmosis as a risk factor for suicide could be of benefit in suicide prevention.
Czech scientist Jaroslav Flegr has claimed to be a living example of toxoplasma gondii causing schizophrenia.
The 63-year-old said he had contracted the parasite, and that it had led him to behave in strange, self-destructive ways.
Signs of toxoplasmosis include mild flu-like symptoms such as a high temperature, sore throat or aching muscles, although the infection often causes no symptoms at all.
The study will be published in the Journal of Clinical Psychiatry.