Ask the Doctors: Can a pet dog in childhood protect against developing schizophrenia later in life?

Dear Doctors: My wife read that, when kids grow up with a dog in the house, it can keep them from getting schizophrenia. Is this based on psychology?

Dear Reader: Your wife is referring to a study several years ago that found a link between living with a dog in very early childhood and a reduced risk of schizophrenia later.

Schizophrenia is a mental illness that interferes with a person’s sense of reality. The condition usually shows up between 16 and 30 years old. Early symptoms often include visual and auditory hallucinations, disordered thought patterns, delusions and paranoia.

Though the causes aren’t known, genetics and brain structure have been shown to play a role. Researchers have begun to explore a potential link to the gut microbiome — whether certain environmental exposures might influence brain development and thus play a role in who develops a serious psychiatric illness.

Childhood pets are an early source of exposure to a range of harmless microbes as well as to potential allergens. We’re learning that, via the gut microbiome, such exposure might have a positive effect on some children’s immune systems.

This made the researchers in this study curious about whether living with a cat or a dog during the first 12 years of life might have an effect on mental health. They were looking for a correlation with a diagnosis of schizophrenia or bipolar disorder.

The latter is a mental health condition marked by sudden and extreme shifts in mood, energy and concentration. Like schizophrenia, bipolar disorder often arises in adolescence and makes it difficult toy manage day-to-day life.

In this study, the researchers used data from 396 adults diagnosed with schizophrenia and 381 adults diagnosed with bipolar disorder. They also included 594 adults with no mental health disorders as the control group. Participants ranged from 18 to 65, were in good health and had no history of drug use. All were asked to detail their history with childhood pets.

The researchers were surprised to find a statistically significant connection between having a dog in early childhood and a decrease in the risk of developing schizophrenia. They did not find the same link in participants with bipolar disorder or among those whose childhood pet was a cat.

More study is needed. One of the theories getting a closer look will be whether beneficial microorganisms in the microbiomes of dogs might provide protection against developing schizophrenia.

Dr. Eve Glazier and Dr. Elizabeth Ko are internists at UCLA Health.