Is the diagnosis of ADHD influenced by time of entry to school? An examination of clinical, familial, and functional correlates in children at early and late entry points.

OBJECTIVE: The authors examined the proposed immaturity hypothesis, which suggests that younger children may have developmental immaturity and not ADHD, using data from a large, clinically referred population of individuals with and without ADHD.
METHOD: The sample consisted of individuals with and without an ADHD diagnosis, ascertained from ongoing studies in our laboratory, born in August (Younger Cohort N = 562) and born in September (Older Cohort N = 529). The authors compared studywide diagnosis rates of ADHD, ADHD familiality patterns, ADHD symptoms, psychiatric comorbidity, and functional impairments between the two cohorts.
RESULTS: Studywide rates of ADHD diagnosis, ADHD-associated symptoms, ADHD-associated impairments, ADHD-associated comorbid disorders, and familiality were similar in the two age cohorts.
CONCLUSION: Results showed that ADHD-associated familial, clinical, and functional correlates are similar irrespective of age at entry to school, indicating that when ADHD symptoms are present, a diagnosis of ADHD should be considered rather than attributing these symptoms to developmental immaturity.