ADHD itself is associated with sleep difficulties, independent of ADHD medications. Thus, it is very important that sleep quality is assessed prior to treatment so that the changes due to treatment can be correctly inferred.

In clinical trials of stimulant medications for ADHD, insomnia is typically noted a side effect of the medications. But most of these studies have used subjective patient or parent reports of sleep quality. A new meta analysis, reviews 9 studies of a total of 246 patients enrolled in randomized controlled trials of a stimulant medication. To be included, studies must have had an objective measure of sleep quality, either polysomnography or actigraphy. The analysis showed that stimulant medications led to a) a longer time to get to sleep; b) worse sleep efficiency and c) a shorter duration of sleep. Some of these sleep measures worsened with an increasing number of doses and a shorter time on medication.
Given the adverse effects that lack of sleep can have on cognition and behavior, these data provide further impetus for clinicians, parents and patients to monitor the effects of stimulant ADHD medication on sleep and to take appropriate action (e.g., dose reduction, change of medication) as warranted.
 

REFERENCES
http://www.ncbi.nlm.nih.gov/pubmed/?term=PMID%3A+26598454
http://www.ncbi.nlm.nih.gov/pubmed/?term=cortese%5Bau%5D+sleep%5Bti%5D+meta%5Bti%5D