The diagnostic validity of attention-deficit/hyperactivity disorder

Despite considerable research, the validity of attention-deficit/hyperactivity disorder (ADHD) remains controversial. This paper summarizes the results of a comprehensive review of the internal and external validity of ADHD as defined in the fourth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV). Results indicate that for most individuals DSM-IV ADHD is a valid disorder in the sense that it is associated with significant impairment in social, academic, and occupational functioning and increased risk of accidental injury across the life span. Additional research is needed, however, to clarify the diagnostic validity of the hyperactive-impulsive type and the discriminant validity of the combined and inattentive subtypes. Other areas in need of further study include potential modifications to the diagnostic conceptualization of the inattentive subtype, developmental trajectories of the subtypes, and methods to address cross-informant diagnostic inconsistencies. Such research is likely to benefit from an etiologically informed approach to examining heterogeneity both across and within subtypes.