Nestadt et al. found that first-degree relatives of OCD sufferers had approximately what increased risk?

Nestadt et al. found that first-degree relatives of OCD sufferers had approximately what increased risk?

• A. 11.7% compared to 2.7% in controls
• B. 1% compared to 0.1% in controls
• C. 50% vs 25%
• D. 0% vs 0%

Answer: (A)

The idea is that OCD shows familial clustering, pointing to a genetic contribution. Nestadt and colleagues did a family study and found that first-degree relatives of people with OCD have a much higher lifetime risk—about 11.7%—compared with roughly 2.7% in people without an affected relative. In other words, close relatives are about four to five times more likely to develop OCD. This supports heritability because close relatives share about half of their genes, so the increase suggests genetic factors play a role, while still leaving room for environmental influences. The figures in other options would imply far smaller or far larger differences than what the study found, which isn’t consistent with the observed familial aggregation.

The idea is that OCD shows familial clustering, pointing to a genetic contribution. Nestadt and colleagues did a family study and found that first-degree relatives of people with OCD have a much higher lifetime risk—about 11.7%—compared with roughly 2.7% in people without an affected relative. In other words, close relatives are about four to five times more likely to develop OCD. This supports heritability because close relatives share about half of their genes, so the increase suggests genetic factors play a role, while still leaving room for environmental influences. The figures in other options would imply far smaller or far larger differences than what the study found, which isn’t consistent with the observed familial aggregation.