New medical research suggests that owning a cat could double the risk of developing schizophrenia.
To reach that conclusion, scientists in Australia analyzed 17 studies published over the last 44 years from 11 different countries, including the US and the UK.
“Our findings support an association between cat exposure and an increased risk of broadly defined schizophrenia-related disorders,” the authors wrote in their analysis, published in the journal Schizophrenia Bulletin.
“We found that individuals exposed to cats had approximately twice the odds of developing schizophrenia,” wrote the research team from the Queensland Centre for Mental Health Research.
Schizophrenia is a complex mental illness that often runs in families, according to Johns Hopkins Medicine.
The illness can cause troubling symptoms such as hearing voices, having trouble thinking clearly and relating to others. It typically starts suddenly in a person’s late teens or early adulthood.
Some research suggests there's a link between exposure to cats and schizophrenia.
Symptoms of schizophrenia can also include:
Delusions or false beliefs not based on reality
Hallucinations or seeing, hearing, smelling or feeling things that are not real
Disorganized speech and behavior
Lack of emotion, withdrawal from others
Worldwide, the illness is estimated to be found in one of every 300 people, or about 24 million people, according to the World Health Organization. Schizophrenia can be managed with medicine and supportive therapy, but there’s no known cure for it.
The idea that cat ownership could be linked to schizophrenia risk isn’t new and was first proposed in a 1995 study. That report suggested exposure to a parasite called Toxoplasma gondii could be the cause.
The parasite is believed to enter a person’s body through a cat’s bite or contact with a its bodily fluids or feces. It can also be ingested through contaminated water or undercooked meat.
It’s estimated that about 40 million people in the US may be infected with T. gondii, usually without any symptoms. However, the parasite can infiltrate the central nervous system and influence neurotransmitters.
A parasite in cats, known as Toxoplasma gondii, might be the cause of neurological changes in humans.
In earlier studies, T. gondii had been linked to personality changes, the emergence of psychotic symptoms and some neurological disorders, including schizophrenia.
The parasite, however, has been proven to have other serious effects on human health, especially for pregnant women, who can pass the parasite through the placenta to the fetus, according to the Cleveland Clinic
T. gondii increases the risk of miscarriage, stillbirth or serious health problems for the child, including vision problems, blindness, developmental delays and learning differences.
The study authors noted that more research is needed before anyone can make any final interpretations.
“Our review provides support for an association between cat ownership and schizophrenia-related disorders,” the authors wrote.
“There is a need for more high-quality studies, based on large, representative samples to better understand cat ownership as a candidate risk-modifying factor for mental disorders.