(ORDO NEWS) — Owning a cat outdoors as a child is associated with an increased risk of psychotic experiences in adulthood – but only in men, new research shows.
The researchers found that male children who owned outdoor cats had a slightly but significantly higher risk of psychotic experiences as adults than their peers who did not have cats as children or had a pet cat.
The culprit is not thought to be the cat itself, but exposure to Toxoplasma gondii (T. gondii), a common parasite carried by rodents and sometimes found in cat feces. This study adds to a growing body of evidence suggesting that T. gondii infection may be a risk factor for schizophrenia and other psychotic disorders.
“This is small evidence, but it’s interesting to think that there could be combinations of risk factors,” study lead author Vincent Pakin, MD, a psychiatric resident at McGill University, told Medscape Medical News.
“And even if the magnitude of the risk is small at the individual level,” he added, “cats and Toxoplasma gondii are so present in our society that if you add up all these small potential effects, it becomes a potential public health issue.”
T gondii infects about 30% of the human population and is usually transmitted from cats. Most infections are asymptomatic, but T. gondii can cause toxoplasmosis in humans, which has been associated with an increased risk of schizophrenia, suicide attempts, and, more recently, mild cognitive impairment.
Although some studies show a link between cat ownership and an increased risk of mental illness, research findings have been inconsistent.
“The data on the relationship between cat ownership and the severity of psychosis is mixed, so our approach was to consider whether specific factors or combinations of factors could explain this mixed data,” Paquin said.
For the study, 2,206 people aged 18-40 completed the Community Assessment of Psychic Experiences (CAPE-42) questionnaire and a questionnaire to collect information on cat ownership at any time from birth to age 13, and whether cats lived exclusively in indoors (not hunted) or they were allowed to go outside (hunted rodents).
Participants were also asked about the number of moves from birth to age 15, date and place of birth, lifetime history of head trauma, and smoking history.
Owning a rodent-hunting cat was associated with a higher risk of developing psychosis in men compared to those who did not own or hunt a cat. When the researchers added head injuries and house moves to hunting rodent ownership, the risk of psychosis increased in both men and women.
Regardless of cat ownership, younger age, moving more than three times during childhood, a history of head trauma, and smoking were associated with an increased risk of psychosis.
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