Prevalence and developmental course
ADHD is common, with worldwide prevalence estimated at
approximately 5% (Polanczyk et al. 2007). Although originally
seen as a disorder of childhood, the lifelong prevalence of
ADHD is now widely acknowledged. Symptoms and neuropsychological
impairments associated with ADHD are evident
in preschool children (Daley et al. 2009) and although symptoms
may decline with age in some cases, ADHD symptoms
and impairments can persist into adulthood (Geissler &
Lesch 2011). Prevalence rates in adult community samples are estimated at approximately 2.5% (Simon et al. 2009). It is likely
that a substantial number of young people accessing services for
ADHD will require transition into adult services (Taylor et al.
2010). Consequently, adult ADHD services are now developing
in parts of the UK.