Category: ADHD - Adult

Symposium

Late-Onset ADHD Reconsidered: Results From the Multimodal Treatment of ADHD Study

Keywords: ADHD - Adult | Adolescents | Longitudinal
Presentation Type: Symposium

Presenter(s)

• MS

  Margaret Sibley, Ph.D.

  Florida International University

  Guilford Press: Book Royalties

Recent birth-cohort studies report 2.5%-10.7% prevalence for late-onset ADHD, departing from a traditional conceptualization of the disorder. These studies were limited either by relying on screening instruments to assess ADHD, not considering alternative sources of symptoms, or possessing incomplete participant psychiatric histories. This study investigated late-onset ADHD with a design that overcomes these limitations by examining longitudinal psychiatric assessments in the local normative comparison group (LNCG) of the Multimodal Treatment of ADHD (MTA) Study. Individuals without childhood ADHD (N=238) were administered eight assessments from LNCG baseline (M age=10.35) to the final MTA adult assessment (M age=24.40). The diagnostic procedure utilized parent, teacher, and self-reports of ADHD symptoms, impairment, substance use, and other mental health disorders with consideration of symptom context and timing.

Approximately 95% of adolescents and adults who screened positive on symptom checklists were excluded from late-onset ADHD diagnosis due to failure to demonstrate impairment or symptom pervasiveness, onset traced to childhood, or symptoms that were better explained by another mental disorder or heavy substance use. Late-onset ADHD prevalence was 2.9% in this sample.  Most late-onset cases displayed an adolescence-limited presentation that remitted by age 19 and above average childhood symptoms compared to sample means. There was also evidence of a late-identified (rather than late-onset) presentation that was associated with a superior IQ. There was no evidence for adult-onset ADHD independent of a complex psychiatric history. This presentation discusses implications for clinicians and researchers including: (1) recommendations for the assessment of suspected late-onset ADHD, (2) potential explanations for an adolescent-limited ADHD presentation, (3) how to treat and categorize late-onset ADHD cases within the DSM-5 system, and (4) in light of the high number of false positive diagnoses, actions the field might consider to prevent ADHD from becoming a catchall diagnosis for executive dysfunction in adolescence and adulthood.