Sam Tuckett, an associate director for post-16 and skills at the institute, said girls were more susceptible to problematic social media use, issues with sleep and not feeling safe at school.
He told The Telegraph: “These things are undoubtedly going to have an effect on the ability to do well in assessments, and particularly high stakes assessments.
“It stands to reason that if you are struggling with mental health issues, that is only going to harm your ability to work and prepare for exams.”
After the introduction of modular A-levels in 2000, girls led boys in achieving A* or A grades for the first 16 years, opening up a gap of nearly 3 percentage points at their peak in 2003.
Boys briefly took the lead in 2017 and 2018 before girls surged ahead during the pandemic, leading by nearly 5 percentage points in 2021. However, boys have closed the gap since the pandemic and have stretched ahead.
Official data show that teenage girls are now more likely to have mental health disorders than boys.