We've known for some time that anxiety runs in families, but research now suggests that anxiety disorders are passed down from mother to daughter and that having a father without anxiety protects sons from developing the condition.

Researchers looked at the role of nature versus nurture in the development of anxiety, examining a dataset of around 400 Canadian children aged around 10 who had previously participated in a study focused on families at risk for mood disorders.

If genetics played a larger role, anxiety disorders would presumably occur in children of both sexes at the same rate regardless of whether the mother or father was the parent passing down the anxiety condition.

If kids were developing anxiety disorders because they were modeling themselves on and learning from a same-sex parent, a distinct pattern of transmission from mother to daughter and father to son would be expected.

The latter is what the researchers found – at least to an extent. 

In the study, the kids who had a same-sex parent with an anxiety disorder had almost three times the chance of developing the same condition compared with their peers. (To our knowledge, the study did not include transgender children or adults.)

A mother's anxiety disorder (but not a father's) increased their daughter's risk of being diagnosed with an anxiety condition in the study.

Sons were no more likely to have an anxiety disorder if their father had one, but if their father didn't have an anxiety disorder, that lowered the son's risk of developing one. 

Overall, having an opposite-sex parent without an anxiety condition was not protective in the same way as having a same-sex parent without the condition.

The study could not demonstrate cause and effect because it was observational and retrospective. 

If there were a causal link, it would be hard to say which direction it was operating "given the two-way feedback loop", the researchers wrote, meaning that children may be making their parents anxious instead of the other way around.

However, if a causal link is established, it may be possible to prevent the intergenerational transmission of anxiety disorders by treating parents for anxiety, the researchers say. 

Previous studies have demonstrated that anxiety can be a learned behavior that children pick up from their parents.

For example, an experiment where parents were randomly instructed to either act anxiously or calmly while a child prepared for a spelling test, showed that kids mirrored that attitude and developed anxious cognitions and avoidance behaviors. 

Other studies have connected parental anxiety disorders with a higher chance of anxiety disorders in their children. 

The paper was published in JAMA Network Open.