Ever since humans teamed up with dogs, lo the many millennia ago, they have been not just our invaluable co-workers but have offered us their companionship and aided in our emotional well-being. There are also so many studies about the healthful benefits that dogs bring to us from our birth and through our whole lives. Now we might add another reason why dogs are truly our first and best friends. A new study from the Johns Hopkins School of Medicine has shown that exposure to a pet dog from an early age may lessen the development of schizophrenia as an adult.
As Dr Robert Yoken, chair of the Stanley Division of Pediatric Neurovirology and professor of neurovirology in pediatrics at the Johns Hopkins Children’s Center, and lead author of this research paper noted they decided to pursue this study because: “Serious psychiatric disorders have been associated with alterations in the immune system linked to environmental exposures in early life, and since household pets are often among the first things with which children have close contact, it was logical for us to explore the possibilities of a connection between the two.”
Previous research has identified early life exposures to dogs as environmental factors that may alter the immune system through various means, including allergic responses, contact with zoonotic (animal) bacteria and viruses, changes in a home’s microbiome, and pet-induced stress reduction effects on human brain chemistry. But the association between exposure to dogs and subsequent risk of schizophrenia had not been extensively studied.
Some suspect that this “immune modulation” may alter the risk of developing psychiatric disorders to which a person is genetically or otherwise predisposed.
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The results of this current study, that involved a population of 1,371 men and women between the ages of 18 and 65 that consisted of 396 people with schizophrenia, 381 with bipolar disorder and 594 controls, were surprising even to the researchers—people exposed to a pet dog before their 13th birthday are significantly less likely—as much as 24%—to be diagnosed later with schizophrenia. “The largest apparent protective effect was found for children who had a household pet dog at birth or were first exposed after birth but before age 3,” Yolken said.
He added that, “There are several plausible explanations for this possible ‘protective’ effect from contact with dogs—perhaps something in the canine microbiome that gets passed to humans and bolsters the immune system against or subdues a genetic predisposition to schizophrenia.” Research into understanding the associations between “pet exposure and psychiatric disorders” will, hopefully, “lead to better prevention and treatment strategies.”
Robert Yolken, Cassie Stallings, Andrea Origoni, Emily Katsafanas, Kevin Sweeney, Amalia Squire, Faith Dickerson. Exposure to household pet cats and dogs in childhood and risk of subsequent diagnosis of schizophrenia or bipolar disorder. PLOS ONE, 2019; 14 (12): e0225320 DOI: 10.1371/journal.pone.0225320