Modafinil increases the latency of response in the Hayling Sentence Completion Test in healthy volunteers: a randomised controlled trial.
BACKGROUND
Modafinil is a medication licensed for the treatment of narcolepsy. However, it has been reported that healthy individuals without wakefulness disorders are using modafinil off-label to enhance cognitive functioning. Although some studies have reported that modafinil improves cognitive task performance in healthy volunteers, numerous other studies have failed to detect cognitive enhancing effects of modafinil on several well-established neuropsychological tasks. Interestingly, several clinical and preclinical studies have found that improved cognitive task performance by modafinil is accompanied by slower response times. This observation raises the question as to whether this slowing of response time in healthy volunteers is a necessary and sufficient condition for cognitive enhancement with modafinil. The aim of the current experiment was to explore this question by investigating the effects of modafinil on the Hayling Sentence Completion Test (HSCT).


METHODS
Sixty-four healthy volunteers received either a single dose (200 mg) of modafinil (n = 32) or placebo (n = 32) in a randomized, double-blind, placebo-controlled, parallel group study in which the principal outcome measures were response latencies on the response initiation and response inhibition sections of the HSCT.


RESULTS
Participants dosed with modafinil had significantly longer mean response latencies on the HSCT for both the response initiation and response inhibition compared to participants dosed with placebo. However, participants in both groups made a similar number of errors on each of these measures, indicating that modafinil did not enhance the accuracy of performance of the task relative to placebo.


CONCLUSIONS
This study demonstrated that administration of single 200 mg doses of modafinil to healthy individuals increased the latency of responses in the performance of the HSCT, a task that is highly sensitive to prefrontal executive function, without enhancing accuracy of performance. This finding may provide important clues to defining the limitations of modafinil as a putative cognitive enhancer.


BACKGROUND
ClinicalTrials.gov NCT02051153.
Department of Psychiatry, School of Clinical Medicine, University of Cambridge, Cambridge, United Kingdom; The School of Psychology, Cognitive and Sensory Systems Group, Faculty of Science, University of Nottingham Malaysia Campus, Selangor, Malaysia; Clare Hall College, Cambridge, United Kingdom.
Ahmed Dahir
AD
Mohamed
Department of Psychology, Towson University, 8000 York Road, Towson, Maryland, 21252-0001, United States of America.
Chris Roberts
CR
Lewis
D000328:Adult; D001559:Benzhydryl Compounds / Q000737:chemistry*; D003071:Cognition / Q000187:drug effects*; D004311:Double-Blind Method; D056344:Executive Function / Q000187:drug effects; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D007802:Language; D007807:Language Tests; D008297:Male; D000077408:Modafinil; D018697:Nootropic Agents / Q000494:pharmacology; D011930:Reaction Time / Q000187:drug effects*; D014851:Wakefulness / Q000187:drug effects; D055815:Young Adult
D001559:Benzhydryl Compounds; D018697:Nootropic Agents; D000077408:Modafinil