Table 1 Characteristic sleep-wake and circadian features of selected mood disorders

Major depression

● Subjective sleep-wake complaints (often preceding the onset or recurrence of depressive episodes)

Difficulty falling asleep, staying asleep or early morning awakening [131, 132]

Disturbing dreams [133]

Unrefreshing shallow sleep [132, 134]

Daytime fatigue and sleepiness [132, 134, 135]

● Macro and microarchitecture of sleep

Abnormal sleep duration [136]

Prolonged sleep onset latency [136]

Shortened REM latency and increased rapid eye movements [136–140]

Increased sleep fragmentation [136, 138]

Decreased SWS and increased REM sleep and (especially in the first sleep cycle) [136, 140]

Reduced slow wave activity and number of slow waves [136]

High comorbidity with sleep-related breathing disorders [141, 142]

● Biological rhythms

Abnormal sleep phase [71, 143 ]

Reduced melatonin secretion [144–149]

Increased 24-hour levels and variability of cortisol secretion [145, 150, 151]

Reduced circadian amplitude and increased nighttime body temperature [147, 151, 152]

Reduced heart rate circadian amplitude [153–155]

Depressive symptoms associated with increased nocturnal blood pressure in males

Abnormal cytokines, neurotransmitters, endocrine (for example, melatonin, cortisol, thyrotropin) and neuroimmune circadian rhythms [97, 144–148, 151, 156–168]

Abnormal circadian mood variations [157, 159, 169–171]

Possible seasonal variations (not exclusive to seasonal affective disorder) [172]

● Increased depressive symptoms are associated with more pronounced misalignment between melatonin, temperature and sleep-wake rhythms [173]

Depression in youth

● Subjective sleep-wake complaints

Difficulty falling asleep and staying asleep [174]

Difficulty waking up in the morning [175]

● Macro and microarchitecture of sleep

Lower intra- and inter-hemispheric coherence in delta and beta activity, especially in girls [176, 177]

Otherwise similar features to those seen in adult depression, but expressed to a lesser degree [177–184]

● Biological rhythms

Higher levels of ‘eveningness’ preference [70]

Lower circadian amplitude [185]

Delayed sleep phase and melatonin onset, especially in those with bipolar disorder [123, 212]

Elevated evening/nighttime cortisol levels [186, 187]

Late-life depression

● Macro and microarchitecture of sleep

Lower increase in REM sleep duration [136]

Otherwise similar features to that seen in adult depression, but more pronounced [136]

● Biological rhythms

Increased early morning awakenings [188]

Abnormal melatonin levels [189]

High prevalence of abnormal blood pressure circadian rhythms [190]

● Sleep and circadian disturbances have been associated with cognitive decline, relapses and mood deterioration [43, 116]

Bipolar disorders

● Characterized by episodic periods of sleep loss (that is, switching from wake to normal duration sleep state and back again over a 24-hour period) [191, 192]

● High prevalence of hypersomnia, especially ‘morning hypersomnia’ [193–195]

● Insomnia often occurring before and during manic episodes [196]

● Insomnia or hypersomnia often occurring before and during depressive episodes [196]

● Macro and microarchitecture of sleep

Depressive phase: longer sleep onset latency and greater REM fragmentation, but otherwise similar to people with unipolar depression [197–200]

Manic phase: Prolonged sleep onset latency, decreased sleep duration, lower sleep efficiency, shortened REM sleep latency and increased REM activity and density [201, 202]

● Disturbed biological rhythms

Short circadian period [203]

Possible hypersensitivity to light suppression of melatonin [204, 205]

Diurnal variations in the direction of mood cycle switch [206]

Possibly enhanced disturbances in thyrotropin rhythms [207]

Onset of mania episodes at key points in seasonal transitions [72, 208]

High prevalence of evening chronotypes (that is, preference for late bed and wake times) and late sleep onset, especially in younger individuals [209, 210]

In youth, the delay in sleep-wake cycles and dim light melatonin onset (DLMO) is more pronounced than what is seen in unipolar depression [123, 211]

Seasonal affective disorder

● Disrupted sleep

Hypersomnia (typically in winter-onset) [212–214]

Insomnia (typically in summer-onset) [212, 214]

● Disrupted biological rhythms

Delayed melatonin, cortisol and temperature rhythms [215–217]

Seasonal pattern of changes in symptoms [218]

Increased sensitivity of melatonin to light in the winter and decreased sensitivity in the summer [219]

Dysthymia

● Similar features to that seen in major depression expressed to a lesser degree [220]