This study used modelled estimates from the Global Burden of Disease project, covering 204 countries from 1990 to 2019. The estimates draw on population surveys and span all ages. In 2019 the project put the global rate of people living with ADHD at about 1.13% and the rate of new cases at about 0.061%. Both rates had fallen since 1990; the prevalence rate dropped by 8.75%. ADHD was recorded 2.5 to 2.6 times more often in males than females. New cases peaked at ages 5 to 9, and prevalence and disease burden peaked at ages 10 to 14.
The authors then re-analysed the raw studies that actually collected data in children and teenagers aged 18 or younger. Pooling 136 studies from before 2013, they found a much higher rate, about 5.41%, roughly double the project's own 2.68% estimate for 2013. They concluded the project underestimated ADHD, mainly because it filled gaps for countries with no data by imputing from nearby places. These raw studies disagreed with each other a great deal. The authors also noted the project set ADHD deaths to zero, even though one meta-analysis found deaths from unnatural causes were about 2.81 times higher than expected in people with ADHD.
Source: Cortese S, Song M, Farhat L, et al.. Incidence, prevalence, and global burden of ADHD from 1990 to 2019 across 204 countries: data, with critical re-analysis, from the Global Burden of Disease study. Molecular Psychiatry (2023). doi:10.1038/s41380-023-02228-3