Does having a pet in early childhood reduce the risk of mental illness in adolescence?

Having a pet dog or cat during early childhood is associated with a reduced risk of mental illnesses in adolescence, a retrospective cohort study in the US has shown.

“In our prior study of 643 children aged 4–11 years, children with pet dogs had lower anxiety scores than children without pet dogs. This follow-up study examines whether exposure to pet dogs or cats during childhood reduces the risk of adolescent mental disorders,” wrote the researchers.

To create a patient-level analytic database, the researchers merged their prior study database with electronic medical records (EMRs). Subjects from the prior study were followed up for 8 years to identify common adolescent mental disorder diagnoses (eg, anxiety, depression, attention deficit hyperactivity disorder [ADHD]) using International Classification of Diseases (ICD)-9 and ICD-10 codes. Sixty subjects with pre-existing mental disorder diagnosis or missing screen for child anxiety-related disorders 5-item (SCARED5) score at baseline were excluded. [Prev Chronic Dis 2015;12:E205; BMC Pediatr 2022;22:572]

The current study included 571 youths (mean age, 14 years; male, 53 percent; having a pet dog at baseline, 58 percent; having a cat at baseline, not ascertained). After a mean follow-up of 7.8 years, 191 youths were diagnosed with a mental disorder (anxiety, 52 percent; ADHD, 32 percent; depression, 11 percent; combined mental disorders, 5 percent).

“After adjusting for significant confounders, having a pet dog at baseline was associated with a lower risk of any mental disorder diagnosis [hazard ratio (HR), 0.74; 95 percent confidence interval (CI), 0.56–0.99; p=0.04], but not of anxiety or any mental disorder diagnosis with a psychotropic prescription [both p>0.05],” reported the researchers.

Furthermore, cumulative exposure to pet dogs was marginally associated with a reduced risk of any mental disorder diagnosis (HR, 0.74, 95 percent CI, 0.54–1.02; p=0.06), but cumulative exposure to pet cats was not (HR, 0.87, 95 percent CI, 0.68–1.11; p=0.28).

“[Notably], exposure to the most attached pet [dog or cat] was significantly associated with a 43 percent risk reduction in anxiety [HR, 0.57; 95 percent CI, 0.38–0.85; p=0.006] and a 36 percent risk reduction in any mental disorder diagnosis [HR, 0.64; 95 percent CI, 0.44–0.91; p=0.013],” pointed out the researchers.

Although the underlying mechanism for this protective effect is unknown, two mechanisms have been proposed. Firstly, interaction with pet reduces cortisol levels, most likely through oxytocin release, which may attenuate physiologic responses to stress. Secondly, pets transfer beneficial microbes to infants and young children, which may result in increased microbiome diversity and thereby improving the gut-microbiota-brain axis.

“This study adds to the growing evidence supporting the potential benefits of companion animal interaction for youths’ socioemotional development,” wrote the researchers. “This study also underscores the need to measure and account for the level of child or youth pet attachment and duration of exposure, rather than simply studying the pet ownership.”