Boys who grow up with a sister have stress levels that are 78% higher

Contradicted by strong evidence

What we can confirm

There is no credible evidence that boys who grow up with a sister have stress levels that are specifically and quantifiably “78% higher”; available research on sibling effects shows more nuanced and often opposite patterns, with several studies indicating that having sisters can be protective for mental health and stress coping, not a large, fixed increase in stress levels.

Sources

Checked July 4, 2026