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Sleep Loss and Mood

Authors: Ruth M. Benca, MD, PhDFaculty and Disclosures

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Question

How does sleep loss affect mood?

Response from Ruth M. Benca, MD, PhD

Individuals with insomnia are known to have significantly elevated rates of depression, and insomnia is a predictive factor for the future development of depression, both for new onset of a depressive disorder as well as recurrence of depression.[1] Conversely, some patients with depression report significant worsening of depressive symptomatology following a night of poor sleep. It is not definitively known whether (1) insomnia causes depression, (2) depression leads to insomnia, or (3) insomnia and depression are both caused by a common underlying process. Nevertheless, insomnia is more closely related to depression than to any other medical disorder, and the fact that insomnia most commonly precedes depression suggests a possible causal association between sleep disturbance and depressed mood.

One approach to study the relationship between sleep and mood is to assess the effects of sleep deprivation. Normal subjects typically show acute worsening of mood, with complaints of irritability, depression, and decreased motivation.[2] Some depressed patients, however, show a seemingly paradoxical response to sleep deprivation; about half of depressives will show an acute antidepressant response following total sleep deprivation, or even partial sleep deprivation, usually involving the second half of the night.[3] Unfortunately, depressive symptoms recur following even a short amount of recovery sleep. Patients with bipolar disorder may have episodes of mania triggered by periods of sleep restriction or sleep deprivation and, conversely, they may report excessive sleep during periods of depression.

The mechanisms for the antidepressant effects of sleep deprivation are not known, but have been attributed either to activating effects[4] or the build-up of pressure for rapid eye movement (REM)[5] and/or slow-wave sleep (SWS).[6] Recently, it has been suggested that sleep deprivation and antidepressants both may act by increasing expression of brain plasticity genes, with sleep deprivation leading to acute induction of these genes and antidepressant treatment increasing expression of these genes only after chronic administration, paralleling the clinical effects of the drugs.[7]

The association of insomnia with depression and sleep deprivation with antidepressant effects or even mania seems contradictory on the surface. This may be related to essential differences between sleep deprivation (inability to obtain sufficient sleep due to lack of opportunity) and insomnia (inability to obtain sufficient quantity and/or quality of sleep despite adequate opportunity). Although patients with insomnia may experience chronic sleep deprivation, it is possible that the deprivation is not severe enough to trigger a sleep rebound response, and in fact sleep restriction therapy is often helpful for treating insomnia. Alternatively, a subset of depressives may have a qualitatively different response to sleep loss. For most normal individuals and many depressives, however, sleep loss -- either through insomnia or sleep deprivation -- is associated with a worsening of mood.