Background: It has been proposed that cat ownership may be a risk-modifying factor for schizophrenia-related disorders and psychotic-like experiences (PLE). This study aimed to systematically review and meta-analyze publications that reported the relationship between cat ownership and schizophrenia-related outcomes.
Methodology: We searched MEDLINE, Embase, CINAHL, Web of Science, and gray literature for publications between January 1, 1980, and May 30, 2023, regardless of geographical location and language. Backward citation search methods were used to locate additional articles. We included studies that reported original data on cat ownership and schizophrenia-related outcomes. We meta-analyzed estimates based on broad definitions (cat ownership, cat bites, and cat contact) with estimates with or without covariate adjustments. We pooled comparable estimates using random-effects models and assessed the risk of bias, heterogeneity, and study quality.
Results: We identified 1,915 studies, of which 106 were chosen for full-text review, ultimately resulting in the inclusion of 17 studies. We found an association between broadly defined cat ownership and increased odds of developing schizophrenia-related disorders. The unadjusted pooled odds ratio (OR) was 2.35 (95% CI: 1.38–4.01), while the adjusted pooled estimate was 2.24 (95% CI: 1.61–3.12). We were unable to aggregate the estimates for the PLE outcomes because of the broad range of measures.
Conclusions: Our findings support an association between cat exposure and an increased risk of broadly defined schizophrenia-related disorders; however, the findings related to PLE as an outcome are mixed. There is a need for more high-quality studies in this field.
PROSPERO registration: PROSPERO 2023 CRD42023426974.
…With respect to heterogeneity, both meta-analyses identified statistically-significant heterogeneity (the Q-statistic and I2 are presented for each forest plot). The unadjusted and adjusted Q-statistics estimates for schizophrenia-related disorders were 106.8 (p-value < 0.01) and 12.48 (p-value = 0.03), respectively. The corresponding I2 values were 94.5% and 56.2%, respectively. The quality scores for the included studies ranged 0–8 (total score of 9) (Supplementary Table 2), with 8 studies scoring 4 or less and 9 studies scoring 5 or higher. In keeping with recommendations about the minimal number of estimates required to interpret funnel asymmetry plots (>10),35 we were not able to assess potential publication bias in the included data.