How Should We Diagnose and Treat Late Onset and
Subthreshold ADHD Adults?
by Richard Rubin, MD
Clinical Associate Professor, University of Vermont
College of Medicine
Two common factors prevent adults from meeting full
clinical ADHD diagnosis criteria: 1) lack of onset
before age seven, and 2) fewer than six core
symptoms. These conditions are currently described
as late onset and subthreshold ADHD types. These
categories are appropriately applied when all other
ADHD criteria are met. The popular term “borderline”
ADHD had no research or clinical usefulness. Yet
how are clinicians to decide diagnosis and plan
treatment in these circumstances?
Drs Faraone, Biederman, Spencer et al studied if
late-onset and subthreshold adult ADHD diagnoses are
valid, and what are the implications for treatment
decisions (Am J Psychiatry, 163:10, Oct. 2006).
Groups of adults recruited from the community with
1) full ADHD by DSM-IV criteria, 2) late-onset ADHD,
3) subthreshold ADHD, and 4) without ADHD were
compared for significant characteristics besides
core symptoms associated with ADHD problems:
patterns of psychiatric comorbidity, functional
impairment, and familial transmission rates. Results
showed that late-onset and full ADHD people had
similar patterns of psychiatric comorbidity,
functional impairment, and familial transmission. In
other words, having onset by age 12 (83% of the
group) led to similar ADHD characteristics and
problems as a full DSM diagnosis with onset by age
7. This included rates of mood and anxiety
disorders, substance use, and disruptive behavior.
In addition, learning disability, school grade
repeat, special classes, legal difficulties, lower
occupational levels, traffic accidents, and
relatives’ ADHD were more common. The subthreshold
ADHD people had milder impairments and less familial
transmission.
This research supports practicing clinicians’
confidant diagnosis and treatment of late onset ADHD
in adults. The authors found that 39% of their full
ADHD group and 59% of the late onset group had never
been treated, and current rates of treatment were
even lower: 17% for full ADHD and 10% for
late-onset. The methods for diagnosis are no
different for these groups, and the multiple
treatment modalities available now promise better
outcomes.
Dr. Rubin practices Child and Adult Psychiatry,
directs The Clinical Study Center in Burlington
Vermont, and serves as Clinical Associate Professor
at the University of Vermont College of Medicine.
