Something like 30% of the population has ADHD, for example.
No, they don't.
ADHD is a neurodevelopmental disorder.
Attention deficit hyperactivity disorder is a neurodevelopmental disorder characterised by..
https://www.nature.com/articles/s41572-024-00495-0
Neurodevelopmental disorders (NDDs) affect
around 15% of children and adolescents globally
https://pmc.ncbi.nlm.nih.gov/articles/PMC8985496/
So all NDD's — including ADHD — affect around ~15% of the population, but you're claiming ADHD alone affects ~30% of the population?

^ps ^I've ^an ^excellent ^therapist