Exposure to household pets during childhood may be linked to altered rates of psychiatric disorders in later lifeSerious psychiatric disorders during adulthood have been associated with environmental exposures in early life. Some such disorders – including schizophrenia and bipolar disorder -- also have a high rate of familial association. Household pet ownership during childhood is one environmental condition shared by members of a family. This study investigated the relationship between exposure to a household pet cat or dog during the first 12 years of life and having a diagnosis of schizophrenia or bipolar disorder during adulthood.
Data for this study was based on 396 adults with schizophrenia, 381 with bipolar disorder, and 594 individuals without a history of a psychiatric disorder (controls). All of the participants lived in the same geographic area, were between the ages of 18 and 65, and had neither mental retardation nor a serious medical disorder that would affect their cognitive functioning. All of the participants provided information about having a pet cat and/or pet dog in their household during childhood.
The most robust findings related to household pet dog exposure and protection against schizophrenia. This protective effect was strongest if the household pet dog was present at birth or was added to the household before the end of the child’s second year of life. Exposure during these time points was associated with an approximately 50% reduction in the relative risk of a schizophrenia diagnosis. Results showed that having a pet dog during the first 12 years of life was associated with an approximately 25% decreased chance of having schizophrenia as an adult. These associations remained even after a range of demographic factors were considered, such as age, gender, race, etc. There was no significant relationship between household exposure to a pet dog and bipolar disorder. Having a pet cat did not change these associations.
Some evidence revealed trends towards an increased risk of both disorders (schizophrenia and bipolar disorder) at defined periods of pet exposure. There was, for example, some evidence of an increased risk of adult schizophrenia in individuals first exposed to a pet cat between the ages of 9 and 12. Results also showed an association between an increased risk of a bipolar disorder diagnosis and first exposure to a pet cat from the period after birth through age 3.
This research indicates that exposure to household pets during infancy and childhood “may be associated with altered rates of development of psychiatric disorders in later life.” Further research focusing on the mechanisms underlying these associations could help inform appropriate interventions. Such research would make an important contribution to the literature, as the association between exposure to dogs and subsequent risk of schizophrenia or bipolar disorder has not been extensively studied.
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