Nature, Not Nurture, the Culprit in OCD

Obsessive-compulsive disorder (OCD) is transmitted from parent to child mostly through genetics and not the way a child is raised, new research suggests.

This finding from a large, register-based study is particularly surprising because results from previous studies of major depression and anxiety disorder have shown a significant effect of parenting and a child’s home environment on the risk for these disorders, the investigators note.

While the results likely won’t change patient treatment, one expert said it could alleviate concerns of some parents with OCD who fear that witnessing their obsessive behaviors might put their children at higher risk for the disorder.

Dr Kenneth S. Kendler

“The evidence is consistent with the idea that the psychological transmission of OCD from parent to child, if it exists, is really pretty weak,” lead author Kenneth S. Kendler, MD, professor of psychiatry and director of the Virginia Institute for Psychiatric and Behavioral Genetics, Virginia Commonwealth University, Richmond, told Medscape Medical News.

The findings were published online February 1 in JAMA Psychiatry.

Family Analysis

The study is the first to include adoptive parents in an analysis of OCD transmission, which allowed investigators to answer the nature vs nurture question that is often difficult to decipher.

Working with Swedish population registries, researchers identified more than 2.4 million offspring. Of these, 27,141 individuals (1.1%) had a lifetime diagnosis of OCD.

Families were divided into four types: intact families, with kids who lived at home with their biological parents from birth to at least age 15 years; families with kids who never lived with their biological father; families with children who did not live with their biological fathers between birth and age 15 years but who lived with a stepfather for at least 10 of those years; and families with children who were adopted before the age of 5 by people with no biological connection to the child.

After analyzing data from all parent-child relationships, researchers found that genes plus rearing (odds ratio [OR], 3.94; 95% confidence interval [CI], 3.58 – 4.33) and genes only (OR, 3.34; 95% confidence interval [CI], 2.27 – 4.93) were significantly more likely to be correlated to transmission of OCD from parent to offspring than rearing alone. Rearing only (OR, 1.4; 95% CI, .45 – 4.39) was not significantly correlated with OCD transmission

“It appears from our data that the only substantial transmission that occurs is in the genes parents transmit, not by the modeling of behavior,” Kendler said.

“There’s an idea that you can learn some things from your parents from psychopathology, but we didn’t see that kids picked that up much in the case of OCD,” he added.

However, there was one outlier. Researchers found that children raised by stepparents or adoptive parents with an anxiety disorder had a greater risk of developing OCD.

Given the lack of evidence of a strong rearing effect in other analyses, Kendler noted that this rogue finding could be due to an underpowered sample; researchers plan to study the data further.

“Psychiatric disorders, like many other conditions, are often correlated with neighboring conditions,” he said. “Our study would suggest that some of the molecular genetic variants between OCD and generalized anxiety disorder or other anxiety disorders would be shared, but some would be unique.”

Answers an Old Question

Dr Jon Grant

Commenting for Medscape Medical News, Jon Grant, JD, MD, MPH, professor of psychiatry and director of the Addictive, Compulsive, and Impulsive Disorders Research Lab at the University of Chicago, Illinois, said the findings fill an important gap in what is known about OCD.

“I think the findings are really answering this old question of: ‘Is OCD due to the rearing patterns in a family vs genetics?’ This was able to get at that information showing that it’s virtually all due to genetics within families, and that’s really good to know,” said Grant, who was not a part of the study.

He was also struck by the finding of a strong genetic relationship between OCD and generalized anxiety disorder (GAD).

While identifying that OCD and GAD are genetically linked likely won’t change clinical care, “I think it at least allows clinicians to know when we see that comorbidity that it may be much more genetically linked in the case of GAD,” Grant said.

JAMA Psychiatry. Published online February 1, 2023. Abstract

The study was funded by the Swedish Research Council, as well as Avtal om Läkarutbildning och Forskning funding from Region Skåne. Kendler and Grant report no relevant financial relationships.

Kelli Whitlock Burton is a reporter for Medscape Medical News, covering psychiatry and neurology.

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