Could Cat Ownership and Adolescent Psychosis Be Linked?

A study published in Psychological Medicine reported no evidence of an association between cat ownership during pregnancy or early childhood and increased risk of adolescent psychotic experiences (PEs). This finding could provide some reassurance on T. gondii infection from a public health perspective, the authors wrote.

T. gondii is a protozoal parasite whose primary host is the house cat. Intermediate hosts, including humans, can become infected with T. gondii in utero or by ingesting parasitic oocysts or tissue cysts. Once inside the body, T. gondii can encyst in brain tissue. In children, a T. gondii brain infection can negatively affect neurodevelopment and increase the risk of adolescent PEs, which, in turn, can increase the risk of adult schizophrenia.

Previous studies have reported a possible link between T. gondii infection and schizophrenia. In one study, people infected with T. gondii demonstrated cognitive impairments commonly associated with schizophrenia. A potential link between T. gondii infection and schizophrenia led some researchers to propose a hypothesis regarding cat ownership and increased psychosis risk. Currently, though, little empirical evidence exists to support this hypothesis.

The current study’s authors gathered birth data from England’s Avon Longitudinal Study of Parents and Children (ALSPAC). Women in the ALSPAC study provided information on pet ownership, including cat ownership, during pregnancy and at specific time points thereafter.

At ages 13 and 18, the women’s children participated in a psychotic-like symptoms interview, which screened for PEs. Children with complete data of psychotic symptoms from these interviews (age 13, n=6705; age 18, n=4676) were included in the study’s analysis. Data on PE were reported for these two ages.

Age Group Characteristics

Overall, the majority of children aged 13 and 18 were female, white, and had mothers who were married. Approximately 30% of mothers in both age groups reported cat ownership during pregnancy and at 4 and 10 years after pregnancy.

Several characteristics were found to be more more prevalent in children with suspected or definite PEs:

Age 13

• Female
• Crowded home environment
• Frequent house moves
• Younger, single, less educated mother

Age 18

• Female
• Crowded home environment
• Younger, single, less educated mother
• Non-white ethnicity

Notably, authors observed that PE prevalence decreased from age 13 to age 18.

Association Between Cat Ownership and PEs

Authors performed regression analysis to analyze the association between cat ownership and adolescent PEs. Before performing this analysis, they identified several factors, including child ethnicity and maternal education, that could have confounded this association.

The following associations between cat ownership and adolescent PEs were identified:

Cat ownership during pregnancy

• No significant association with PEs at ages 13 or 18

Cat ownership at age 4

• No significant association with PEs at age 13, only after multivariable adjustment
• No significant association with PEs at age 18, regardless of multivariable adjustment

Cat ownership at age 10

• As for cat ownership at age 4

The authors noted that their findings contrasted with those of previous studies on cat ownership and schizophrenia. Methodological differences could explain this contrast. The current study was prospective; the previous studies were retrospective and did not evaluate cat ownership at specific time points.

Taken together, the study’s results—namely, decreased PE prevalence at age 18 and the lack of association between cat ownership and PEs—“may have the strongest implications for likely effects of early life cat ownership on clinical disorder.” Because of possible T. gondii exposure, authors still advised pregnant women not to handle soiled cat litter.

Dr. JoAnna Pendergrass received her doctorate in veterinary medicine from the Virginia-Maryland College of Veterinary Medicine. Following veterinary school, she completed a postdoctoral fellowship at Emory University’s Yerkes National Primate Research Center. Dr. Pendergrass is the founder and owner of JPen Communications, LLC, a medical communications company.