In Nestadt et al.'s family study on OCD, first-degree relatives of OCD sufferers had what percentage chance of developing the disorder compared to relatives of healthy parents?

• A. 11.7% vs 2.7%
• B. 5% vs 0%
• C. 20% vs 10%
• D. 1% vs 0.1%

Answer: (A)

This question looks at familial risk for OCD and how much the disorder clusters in families. The study found that about 11.7% of first-degree relatives of OCD patients develop the disorder, whereas about 2.7% of first-degree relatives of healthy controls do. This shows a clear increase in risk for relatives of OCD sufferers, suggesting genetic factors contribute to the disorder because first-degree relatives share about half their genes. The finding isn’t near certainty, which fits a complex, polygenic risk with environmental influences as well.

In simple terms, the correct pattern is a substantially higher risk for relatives of OCD patients (around 12% vs around 3%), indicating familial aggregation and a genetic contribution to OCD.