Processing speed can monitor stimulant-medication effects in adults with attention deficit disorder with hyperactivity

Abstract

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 no- and 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 low-dose 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.

Keywords:

• Attention deficit disorder with hyperactivity
• adults
• central nervous system stimulant
• cognition

Acknowledgements

Our gratitude goes to Evolan Pharma AB, Danderyd, Sweden for supporting this clinical study with funding and experimental medication.

Disclosure statement

Dr Niels Peter Nielsen reports grants for participation in professional meetings and conferences from Evolan Pharma AB, Danderyd, Sweden, during the conduct of the study. Professor Elisabeth H. Wiig reports assistance with travel expenses from Evolan Pharma AB, Danderyd, Sweden, during the conduct of the study. Nielsen and Wiig are co-authors of A Quick Test of Cognitive Speed (AQT). The copyright is held by AQT Assessments Aps. Copenhagen, Denmark. Dr Svante Bäck reports grants for participation in professional meetings and conferences from Evolan Pharma AB, Danderyd, Sweden, during the conduct of the study. Jan Gustafsson, Medical Education Manager, initiated and co-ordinated funding to the Psychiatric Clinic in the Västervik-Vimmerby region for the study from Evolan Pharma AB, Danderyd, Sweden.

Additional information

Funding

EVOLAN PHARMA AB, Danderyd, Sweden.