Processing speed can monitor stimulant-medication effects in adults with attention deficit disorder with hyperactivity
Sammanfattning
Background: Treatment responses to methylphenidate by adults with ADHD are generally monitored
against DSM-IV/DSM-V symptomatology, rating scales or interviews during reviews.
Aims: To evaluate the use of single- and dual-dimension processing-speed and efficiency measures to
monitor the effects of pharmacological treatment with methylphenidate after a short period off
medication.
Methods: A Quick Test of Cognitive Speed (AQT) monitored the effects of immediate-release methylphenidate
in 40 previously diagnosed and medicated adults with ADHD. Processing speed was evaluated
with prior prescription medication, without medication after a 2-day period off ADHD
medication, and with low-dose (10/20 mg) and high-dose (20/40 mg) methylphenidate hydrochloride
(Medikinet IR).
Results: Thirty-three participants responded to the experimental treatments. One-way ANOVA with
post-hoc analysis (Scheffe) indicated significant main effects for single dimension colour and form and
dual-dimension colour–form naming. Post-hoc analysis indicated statistical differences between the noand
high-dose medication conditions for colour and form, measures of perceptual speed. For colour–-
form naming, a measure of cognitive speed, there was a significant difference between no- and lowdose
medication and between no- and high-dose medications, but not between low- and high-dose
medications.
Conclusions: Results indicated that the AQT tests effectively monitored incremental effects of the
methylphenidate dose on processing speed after a 2-day period off medication. Thus, perceptual (colour
and form) and cognitive speed (two-dimensional colour–form naming) and processing efficiency
(lowered shift costs) increased measurably with high-dose medication. These preliminary findings warrant
validation with added measures of associated behavioural and cognitive changes.