Annual variation in attentional response after methylphenidate treatment

Madelon A. Vollebregt, J. Leon Kenemans, Jan K. Buitelaar, Tom Deboer, Sean W. Cain, Donna Palmer, Glen R. Elliott, Evian Gordon, Kamran Fallahpour, Martijn Arns

Research output: Contribution to journalArticlepeer-review


Prevalence rates of attention-deficit/hyperactivity disorder (ADHD) differ with geographical areas varying in sunlight intensity. Sun- or daylight reaching the retina establishes entrainment of the circadian clock to daylight. Changes herein, hence, alterations in clock alignment, could be reflected indirectly in inattention via sleep duration. We here studied (1) annual variation in inattention at treatment initiation; (2) annual variation in response to ADHD treatment [methylphenidate (MPH)] by day of treatment initiation; and (3) dose dependence. We predicted least baseline inattention during a period of high sunlight intensity implying more room for improvement (i.e., a better treatment response) when sunlight intensity is low. These hypotheses were not confirmed. High-dose treated patients, however, had significantly better attention after treatment than low-dosed treated patients, only when treated in the period from winter to summer solstice. Change in solar irradiance (SI) during low-dosed treatment period was negatively related to attentional improvement. The above described findings were primarily found in inattention ratings and replicated in omission errors on a continuous performance task. Daylight and inattention have been proposed to be related via mediation of the circadian system. One mechanism of MPH may be to enhance sensitivity to the diurnal entrainment to sunlight and the question can be raised whether appropriate lighting could potentiate the effects of stimulants.

Original languageEnglish
Pages (from-to)1231-1236
Number of pages6
JournalEuropean Child and Adolescent Psychiatry
Issue number9
StatePublished - 1 Sep 2020


  • ADHD
  • Annual variation
  • Inattention
  • Methylphenidate
  • Sunlight


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