The relationship of sleep disorders, attention deficit hyperactivity disorder (ADHD), comorbidity associated with ADHD, and treatment with stimulant medications was determined using 2 sleep questionnaires completed by the parents in a study of children aged 6 to 12 years treated at the Hospital for Sick Children, Toronto, Canada. Sleep problems and factors associated with sleep difficulties were compared in ADHD unmedicated patients (n=79), medicated ADHD (n=22), and 2 control groups. The percentage of subjects with 1 or more sleep problems was highest in the medicated ADHD group (95.5%) and unmedicated ADHD group (86.1%); it was 82.9% in the clinical comparison group, and 55.5% in the nonclinical comparison group. Three sleep problems were evident by factor analysis: dysomnias (difficulty getting up, going to bed, and/or falling asleep; parasomnias (sleep walking, night waking, sleep terrors); and sleep related involuntary movements.
Dysomnias were related to comorbid oppositional defiant disorder and stimulant medication, but not to ADHD. Parasomnias were similar in clinical and nonclinical controls. Sleep-related involuntary movements were increased in frequency in children with the combined subtype of ADHD and in those with anxiety. Although children with ADHD had more sleep problems than normal children, they did not differ from those in the control group referred for a clinical assessment. 
COMMENT. Children with ADHD, in comparison with normal children, experience more sleep problems evidenced by dyssomnias and involuntary movements, but the frequency of parasomnias is similar to that in normally developing peers. Except for the association of sleep-related involuntary movements and the combined subtype of ADHD, sleep problems in ADHD children do not differ from those in clinical comparison groups without ADHD. Dysomnias in children with ADHD occur especially in those with comorbid ODD or in children taking stimulant medication. Involuntary movements during sleep are strongly associated with anxiety, especially separation anxiety.
The International Classification of Children’s Sleep Disorders, a more comprehensive and current listing than the DSM, includes 1) dyssomnias, or primary sleep disorders (eg. obstructive sleep apnea, narcolepsy, periodic limb movements, inappropriate environment and parenting, circadian sleep-wake rhythm disorders); 2) parasomnias (eg. sleepwalking and sleep terrors - arousal from deep NREM sleep, headbanging - sleep-wake transition disorders, nightmares - with REM sleep; and 3) sleep disorders associated with neuropsychiatric or other medical disorders (eg. depression, epilepsy, asthma) . The effects of sleep disorders on cognition, emotional state and behavior are discussed, and the need for a greater professional awareness of the problem is stressed.