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— 16 November 2025 | By Rebecca Dyer

Having a cat as a pet is linked to an increased risk of schizophrenia-related conditions, according to an analysis of 17 studies.

Psychiatrist John McGrath and colleagues at the Queensland Centre for Mental Health Research in Australia looked at papers published over the last 44 years in 11 countries, including the US and the UK.

Their 2023 review found "a significant positive association between broadly defined cat ownership and an increased risk of schizophrenia-related disorders." "There is a need for more high-quality studies in this field," the authors emphasize in their published paper.

This idea that cat ownership could be linked to schizophrenia risk was proposed in a 1995 study, with exposure to a parasite called Toxoplasma gondii suggested as a cause. But the research so far has put forth mixed conclusions.

Studies have found that being around cats during childhood might make a person more likely to develop schizophrenia; however, not all research has found an association.

Lifecycle: Toxoplasmosis is only known to reproduce in cats (1), but can be spread to humans through intermediate hosts (2, 5, 7) as well. (CDC) ***

Some papers also link cat exposure to higher scores on scales that measure traits related to schizophrenia - which affects a person's thoughts, feelings, and behaviors - and psychotic-like experiences, but again, other studies don't show this connection.

To get a clearer picture, McGrath and his team say there's a need for a thorough review and analysis of all the research on these topics. T. gondii is a mostly harmless parasite that can be transmitted through undercooked meat or contaminated water. It can also be transmitted through an infected cat's feces.

Estimates suggest that T. gondil infects about 40 million people in the US, typically without any symptoms. Meanwhile, researchers keep finding more strange effects that infections may have.

Once inside our bodies, T. gondii can infiltrate the central nervous system and influence neurotransmitters. The parasite has been linked to personality changes, the emergence of psychotic symptoms, and some neurological disorders, including schizophrenia.

However, a link doesn't prove T. gondii causes these changes or that the parasite was passed on to a human from a cat.

Cat Feces Could Be The Source of Toxoplasmosis.

"After adjusting for covariates, we found that individuals exposed to cats had approximately twice the odds of developing schizophrenia," the Australian team writes. There are some important things to keep in mind here, like the fact that 15 of the 17 studies were case-control studies.

This kind of research can't show cause and effect, and it often doesn't account for factors that may have affected both the exposure and the outcome. The researchers also highlight the low quality of a number of the examined studies.

Results were inconsistent across studies, but those of higher quality suggested that associations in unadjusted models might have been due to factors that could have influenced the results.

One study found no significant association between owning a cat before age 13 and later developing schizophrenia, but it did identify a significant link when narrowing down cat ownership to a specific period (ages 9 to 12). This inconsistency suggests that the critical window for cat exposure is not well defined.

A study in the US, which involved 354 psychology students, didn't find a connection between owning a cat and schizotypy scores. However, those who had received a cat bite had higher scores when compared to those who had not.

Another study, which included people with and without mental disorders, discovered a connection between cat bites and higher scores on tests measuring particular psychological experiences. But they suggested other pathogens, such as Pasteurella multocida, may be responsible instead.

Before we can make any firm interpretations, the researchers reiterate that we need better and broader research. "Our review provides support for an association between cat ownership and schizophrenia-related disorders," the authors conclude.

"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."

— The research was published in Schizophrenia Bulletin.

Toxoplasmosis ***:

Causal Agents: Toxoplasma gondiiis a protozoan parasite that infects most species of warm-blooded animals, including humans, and causes the disease toxoplasmosis.

The only known definitive hosts for Toxoplasma gondil are members of family Felidae (domestic cats and their relatives). Unsporulated oocysts are shed in the cat's feces 1. Although oocysts are usually only shed for 1-3 weeks, large numbers may be shed. Oocysts take 1-5 days to sporulate in the environment and become infective. Intermediate hosts in nature (including birds and rodents) become infected after ingesting soil, water or plant material contaminated with oocysts 2. Oocysts transform into tachyoites shortly after ingestion. These tachyoites localize in neural and muscle tissue and develop into tissue cyst bradyzoites 3. Cats become infected after consuming intermediate hosts harboring tissue cysts 4. Cats may also become infected directly by ingestion of sporulated oocysts. Animals bred for human consumption and wild game may also become infected with tissue cysts after ingestion of sporulated oocysts in the environment 5. Humans can become infected by any of several routes:

Eating undercooked meat of animals harboring tissue cysts 6.

Consuming food or water contaminated with cat fees or by contaminated environmental samples (such as fecal-contaminated soil or changing the litter box of a pet cat) 7.

Blood transfusion or organ transplantation 8.

Transplacentally from mother to fetus 9.

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 10. Diagnosis of congenital infections can be achieved by detecting T. gondii DNA in amniotic fluid using molecular methods such as PCR 11.

Geographic Distribution

Serologic prevalence data indicate that toxoplasmosis is one of the most common human infections throughout the world. A high prevalence of infection in France has been related to a preference for eating raw or undercooked meat, while a high prevalence in Central America has been related to the frequency of stray cats in a climate favoring survival of oocysts and soil exposure. The overall seroprevalence in the United States among adolescents and adults, as determined with specimens collected by the third National Health and Nutrition Examination Survey (NHANES III) between 1988 and 1994, was found to be 22.5%, with a seroprevalence among women of childbearing age (15 to 44 years) of 15%. In a more recent evaluation using data from NHANES 2009-2010, the overall age-adjusted T. gondii antibody seroprevalence among persons ≥6 years of age was 12.4%, and among women 15-44 years of age was 9.1%.

Clinical Presentation

Acquired infection with Toxoplasma in immunocompetent persons is generally an asymptomatic infection. However, 10% to 20% of patients with acute infection may develop cervical lymphadenopathy and/or a flu-like illness. The clinical course is usually benign and self-limited; symptoms usually resolve within a few weeks to months. In rare cases ocular infection with visual loss can occur. Immunodeficient patients often have central nervous system (CNS) disease but may have retinochoroiditis, pneumonitis, or other systemic disease. In patients with AIDS, toxoplasmic encephalitis is the most common cause of intracerebral mass lesions and is thought to usually be caused by reactivation of chronic infection. Toxoplasmosis in patients being treated with immunosuppressive drugs may be due to either newly acquired or reactivated latent infection.

Congenital toxoplasmosis results from an acute primary infection acquired by the mother during pregnancy. The incidence and severity of congenital toxoplasmosis vary with the trimester during which infection was acquired. Because treatment of the mother may reduce the incidence of congenital infection and reduce sequelae in the infant, prompt and accurate diagnosis is important. Many infants with subclinical infection at birth will subsequently develop signs or symptoms of congenital toxoplasmosis. Ocular Toxoplasma infection, an important cause of retinochoroiditis in the United States, can be the result of congenital infection, or infection after birth. In congenital infection, patients are often asymptomatic until the second or third decade of life, when lesions develop in the eye.