According to Dr. Thomas E. Brown, ADHD is not uncommon in young adults; especially males. He states "The National Comorbidity Survey of Adolescents found the prevalence rate of ADHD to be 9% in a large sample of 17- to 18-year-olds. In that group the ratio of males to females was 3 to 1. About half of the 9% were identified as having severe ADHD." However, for most people with ADHD treatment begins and end while in pediatric care; meaning the majority of these young adults go without services.
The lack of ADHD and mental health treatment in adulthood can have disastrous implications. Dr. Brown shares "The National Comorbidity Survey Replication found that adults aged 18 to 44 years with ADHD had more than 6 times the likelihood of having at least one additional psychiatric disorder at some point in their life relative to adults without ADHD."
Click the link for Dr. Brown's full article and to gain a new understanding of ADHD and its treatment.