Sleep and Childhood Depression Introduction According to the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition

ACCORDING TO THE DIAGNOSTIC AND STATISTICAL MANUAL OF MENTAL DISORDERS, FOURTH EDITION (DSM-IV), INDIVIDUALS MUST HAVE AT LEAST 5 OF 9 criterion depressive symptoms for a major depressive episode, and sleep disturbance is 1 of the 9 symptoms. Although sleep disturbance is not a necessary symptom for the diagnosis of major depressive episode, research has shown that up to 90% of depressed adults have sleep complaints1,2 and at least two thirds of depressed children and adolescents have significant sleep-onset or sleep-maintenance problems.3-5 Depressed patients may present with various forms of sleep disturbance, such as difficulty falling asleep (initial insomnia), difficulty maintaining sleep or poor sleep quality (middle insomnia), waking up too early (terminal insomnia), prolonged sleep episodes at night or increased daytime sleep (hypersomnia), and circadian reversal.2,3,6 Although sleep electroencephalogram changes characterized by impaired sleep efficiency, reduced slow-wave sleep sleep, and disinhibited rapid eye movement sleep have been consistently demonstrated in adult depression,2,7 findings of polysomnographic studies in child depression are equivocal3,8 and sleep electroencephalogram abnormalities appear to occur less frequently in child and adolescent depression than in adult depression.9 Notably, 1 recent study compared subjective sleep complaints and sleep electroencephalogram parameters and found no evidence that depressed children had more disturbed sleep than the controls; paradoxically, depressed children with the greatest subjective sleep disturbance showed the best sleep.10 The variability of sleep disturbances from patient to patient and discrepancy between subjective complaints and objective sleep parameters raise several important clinical questions. For example, although sleep disturbance in depression can take various forms, the DSM focuses on whether there has been some deviation in the “quantity” of usual sleep; that is, it specifies insomnia and hypersomnia as 1 criterion symptom. Although insomnia has received much research attention, far less is known about hypersomnia.10 One epidemiologic study indicated that about half of hypersomnia in young adults occurred in conjunction with insomnia.11 In some cases, a depressed child may complain about sleep disturbance at night and excessive sleepiness during the day.9 However, researchers tend to report the rates of insomnia and hypersomnia separately but not their co-occurrence.5,12 The relationship between sleep disturbance and depression is complex: bidirectional or comorbid.2,3 However, little is known about whether depressed children without and with sleep disturbance manifest Insomnia and Hypersomnia Associated with Depressive Phenomenology and Comorbidity in Childhood Depression