Dogs and Disorders: The Benefits of Canines on our Neurology.
They might be man's best friend but our canine companions may also be significantly more beneficial for our neurobiological health than previously thought with new research suggesting that having a pet dog as a child reduces the chances of developing schizophrenia as an adult.
Science has long understood the health benefits of owning a pet dog, from encouraging regular exercise and enhanced immune systems to lowering both stress levels and blood pressure; however, the effect that they have upon our neurology is less well understood. This was the topic of a fascinating paper that was recently published in PLOS One by researchers from John Hopkins Children's Medical Centre and Sheppard Pratt Health System in Baltimore, United States.
"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," says Robert Yolken, lead author of the paper and professor at the John Hopkins Centre.
The research team sampled a total of 1,371 men and woman between the ages of 18 and 65 years from the local area: 396 of those people were diagnosed with schizophrenia, 381 with bipolar disorder and the remaining 594 being control subjects. Researchers recorded a variety of variables from participant surveys, from their place of birth and socioeconomic status to their childhood exposure to animals in the form of household pets.
Astonishingly, they found that people who had lived with a dog before the age of 13 were up to 24% less likely to be diagnosed with schizophrenia as adults. Furthermore, the largest reduction in diagnosis was found for children who had a pet dog at birth or were first exposed after birth but before three years old.
"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," Yolken says.
Interestingly, this finding did not correlate with either the diagnosis of bipolar disorder or for having a pet cat in childhood. In fact, there was a slight increased risk of developing both disorders [schizophrenia and bipolar] for those exposed to felines between 9 and 12 years of age, suggesting that "the time of exposure may be critical to whether or not it alters the risk."
One theory around why cats may increase the risk of developing schizophrenia concerns the toxoplasmosis disease: a condition caused by a cat transmitting a parasite to humans which has already been documented to induce psychiatric disorders in children who are born to infected mothers.
Whilst this may sound like dogs are the key to a healthy neurology, this research still needs confirming by more in-depth investigations before the results can be applied to our households. According to Yolken, "A better understanding of the mechanisms underlying the associations between pet exposure and psychiatric disorders would allow us to develop appropriate prevention and treatment strategies."
On the other hand, if these results are an accurate reflection of risk and considering that approximately 3.5 million people in the United States suffer from schizophrenia, over 800,000 of these cases could have been prevented if they had a pet pooch as a kid.
Author: Thomas Llewellyn
Reference: 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