Having a cat in childhood could lead to psychosis, study shows.
Recent research has found that owning a cat early on in life could be linked to psychosis in adulthood. More specifically, the team found male children who owned cats allowed to be outside had a greater chance of experiencing psychotic episodes in adulthood versus those who had no cat or who had a solely indoor cat. The researchers believe that the significance of having a psychotic episode is not related to the animal itself but due to exposure to Toxoplasma gondii (T. gondii), a parasite found in rodents and cat feces.
According to the Centers for Disease and Control and Prevention (CDC), “The only known definitive hosts for Toxoplasma gondii are members of family Felidae (domestic cats and their relatives). Unsporulated oocysts are shed in the cat’s feces.” Other potential causes might include eating undercooked meat of animals harboring tissue cysts, consuming food or water contaminated with cat feces or by contaminated environmental samples (such as fecal-contaminated soil or changing the litter box of a pet cat), the agency explains.
The current study shows that T gondii infects approximately 30% of the human population. Most infections are asymptomatic and go undetected, but T. gondii has been linked to increased risk of schizophrenia, suicide attempts, and cognitive impairment.
The CDC also explains that “In the human host, the parasites form tissue cysts, most commonly in skeletal muscle, myocardium, brain, and eyes; these cysts may remain throughout the life of the host. Diagnosis is usually achieved by serology, although tissue cysts may be observed in stained biopsy specimens.” The diagnosis is made by serologic testing, which measures immunoglobulin G (IgG) levels.
The results of the current study was published in an online issue of the Journal of Psychiatric Research.
“These are small pieces of evidence but it’s interesting to consider that there might be combinations of risk factors at play,” lead author Vincent Paquin, MD, psychiatry resident at McGill University, said. “And even if the magnitude of the risk is small at the individual level, cats and Toxoplasma gondii are so present in our society that if we add up all these small potential effects then it becomes a potential public health question. The evidence has been mixed about the association between cat ownership and psychosis expression, so our approach was to consider whether specific factors or combinations of factors could explain this mixed evidence.”
In order to evaluate the effects of cat ownership on adult mental health disorders, more than 2200 individuals aged 18 to 40 years completed the Community Assessment of Psychic Experiences (CAPE-42) and a questionnaire inquiring about cat ownership. Participants were also asked about how many moves were made between birth and age 15, date and place of birth, whether there was a history of head trauma, and if they smoked tobacco.
The study concludes, “Rodent-hunting cat ownership was associated with higher risk of psychosis in male participants, compared with owning no cat or a nonhunting cat. When investigators added head trauma and residential moves to rodent-hunting cat ownership, psychosis risk was elevated in both men and women.”