Is age-at-onset criterion relevant for the response to methylphenidate in attention-deficit/hyperactivity disorder?
OBJECTIVE
Since DSM-IV criteria for attention-deficit/hyperactivity disorder (ADHD) require that some symptoms causing impairment must be present before 7 years of age, clinicians are faced with a diagnostic and treatment dilemma on how to proceed with late-onset ADHD patients. We aimed to compare the response to methylphenidate between a group of patients fulfilling all DSM-IV ADHD criteria (full ADHD diagnosis) and a group of patients fulfilling all DSM-IV criteria except the age-at-onset criterion (late-onset ADHD).


METHODS
We evaluated 180 children and adolescents (4-17 years old) and 111 adults from our ADHD unit. All ADHD diagnoses were assessed using DSM-IV criteria. Methylphenidate was administered twice daily (8 a.m. and noon), but an extra dose was allowed between 5 and 6 p.m. for children and adolescents needing extra coverage in the evening. The minimum dose was 0.30 mg/kg/day. Response to treatment was assessed in methylphenidatenaive subjects using the Swanson, Nolan, and Pelham Scale-version IV (SNAP-IV) at baseline and after 1 month of treatment. Data were collected from January 2000 to January 2006.


RESULTS
In both samples, subjects with the full ADHD diagnosis did not have a better response to methylphenidate at doses around 0.5 mg/kg/day than the late-onset ADHD subjects. In fact, adults with late-onset ADHD had a better response to methylphenidate than adults with the full diagnosis, even after adjustment for confounders (baseline SNAP-IV total score and ADHD types) (children and adolescents: F = 0.865, p = .354; adults: F = 5.760, p = .018).


CONCLUSIONS
These results concur with recent literature questioning the validity of the DSM-IV age-at-onset criterion for the diagnosis of ADHD and suggest that clinicians should consider implementing methylphenidate treatment for subjects with late-onset ADHD.
ADHD Outpatient Program, Federal University of Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brazil.
Marcelo C
MC
Reinhardt
Lucia
L
Benetti
Marcelo M
MM
Victor
Eugenio H
EH
Grevet
Paulo
P
Belmonte-de-Abreu
Stephen V
SV
Faraone
Luis A
LA
Rohde
D000293:Adolescent; D000328:Adult; D017668:Age of Onset; D001289:Attention Deficit Disorder with Hyperactivity / Q000175:diagnosis / Q000188:drug therapy*; D000697:Central Nervous System Stimulants / Q000008:administration & dosage*; D002648:Child; D002675:Child, Preschool; D039721:Diagnostic and Statistical Manual of Mental Disorders; D005260:Female; D006801:Humans; D008297:Male; D008774:Methylphenidate / Q000008:administration & dosage*; D011379:Prognosis; D016896:Treatment Outcome
D000697:Central Nervous System Stimulants; D008774:Methylphenidate