Owning a Dog in Childhood May Reduce Risk of Developing Schizophrenia Later in Life, Study Finds

Childhood exposure to dogs may reduce a person's likelihood of developing schizophrenia as an adult, according to a study published this month by researchers from Johns Hopkins Medicine.

However, the researchers stressed that their findings were not conclusive. More research, they said, needs to be conducted to confirm whether the correlation is directly caused by exposure to dogs, as well as to more clearly define the risk of developing psychiatric problems that may result from exposing children to pets.

The study, published December 2 in the online journal PLOS One, was conducted to determine the relationship between the development of bipolar disorder and schizophrenia and a person's interaction with dogs and cats before age 13.

However, the researchers' data suggested that only people exposed to dogs in childhood were less likely to become schizophrenic. They did not observe a similar trend in the likelihood of developing bipolar disorder after being exposed to dogs in childhood, and not any trend related to exposure to cats and either disorder.

According to the Mayo Clinic, schizophrenia is a mental disorder that distorts the affected person's perception of reality. Among its symptoms are hallucinations, delusions and disorganized speech or thought. Most patients need lifelong treatment for the symptoms, including prescribed antipsychotic medication.

In an email to Newsweek, the study's lead author, Robert Yolken, wrote that his research group focuses on the role inflammation and infections play in the development of psychiatric disorders. He said that they chose to examine schizophrenia and bipolar disorder because people with those disorders comprise the largest group that can be compared with people who have no psychiatric disorder.

For the study, researchers examined a total of 1,371 people between the ages of 18 and 65. Of that group, 594 had no history of a psychiatric disorder, 396 had been diagnosed with schizophrenia or the related schizoaffective disorder, and 381 had been diagnosed with bipolar disorder.

Researchers asked respondents if they had had a dog or a cat living in their households before the age of 13. Those who replied affirmatively were as much as 24 percent less likely to have developed schizophrenia in their late years.

"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," Robert Yolken, the study's lead author, said in a press release.

Researchers admitted that there were some limits to the study. Among these were the fact that pet exposure was self-reported by the people in the study group—and that people may not be able to remember all of the exposure they had to animals when they were young children. Further, they were unable to discern precisely how sociodemographic factors such as race may have affected the findings on bipolar disorder and exposure to dogs.

Yolken told Newsweek that future studies will likely examine the microbiomes of people diagnosed with schizophrenia or bipolar disorder to determine if there are patterns there that correlate with a higher likelihood of developing psychiatric disorders.

A girl pets a cocker spaniel during an American Kennel Club and Westminster Kennel Club event on February 9 in New York. Timothy A. Clary/Getty