Recent studies have suggested that late-onset adult ADHD is valid and that the DSM-IV’s age-at-onset criterion of age 7 is too stringent. Given the lack of empirical evidence supporting the age-at-onset criteria of ADHD, combined with practical difficulties in demonstrating impairment before age 7 in older adolescents and adults, some experts have argued that the criterion should be abandoned or redefined to include the broader age period of childhood, specifically to age 12 (McGough, 2004).The DSM-IV field trial also demonstrated that all individuals with ADHD in that study developed their disorder by the more generous age at onset.

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