Abstract
The present paper aims at reviewing and commenting on the relationships between sleep and circadian phasing alterations and neurodegenerative/neuroprogressive processes in mood disorder. We carried out a systematic review, according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, in PubMed, PsycINFO, and Embase electronic databases for literature related to mood disorders, sleep disturbances, and neurodegenerative/neuroprogressive processes in relation to (1) neuroinflammation, (2) activation of the stress system, (3) oxidative stress, (4) accumulation of neurotoxic proteins, and (5) neuroprotection deficit. Seventy articles were collectively selected and analyzed. Experimental and clinical studies revealed that insomnia, conditions of sleep loss, and altered circadian sleep may favor neurodegeneration and neuroprogression in mood disorders. These sleep disturbances may induce a state of chronic inflammation by enhancing neuroinflammation, both directly and indirectly, via microglia and astrocytes activation. They may act as neurobiological stressors that by over-activating the stress system may negatively influence neural plasticity causing neuronal damage. In addition, sleep disturbances may favor the accumulation of neurotoxic proteins, favor oxidative stress, and a deficit in neuroprotection hence contributing to neurodegeneration and neuroprogression. Targeting sleep disturbances in the clinical practice may hold a neuroprotective value for mood disorders.
Highlights
Mood disorders refer to a spectrum of conditions, including major depressive unipolar and bipolar disorders, which are amongst the most prevalent and severe psychiatric diseases with a tendency to be recurrent, chronic, and disabling.[1,2] These disorders constitute major public health concerns and leading conditions in the global burden of disease in terms of disability, morbidity, and premature mortality conferring high-suicidality risk.[1,2,3,4] mood disorders are very common mental disorders, their etiology is still unclear.[5]
We set out to systematically review the published literature on the topic in accordance with the PICOS process as follows: P—population: adult female and male patients with insomnia, short sleep duration, chronic sleep deprivation, sleep restriction, insufficient sleep, circadian sleep alterations, we included studies conducted in animals—Iintervention: not applicable, C—comparison: patients with insomnia, short sleep duration, chronic sleep deprivation, sleep restriction, insufficient sleep, circadian sleep alterations vs patients without these disorders; O—outcome: index of neuroinflammation, of activation of the stress system, of oxidative stress, of accumulation of neurotoxic proteins of neuroprotection deficit in relation with these sleep disturbances in mood disorders; S—study design: we included randomized controlled trials, cohort studies, case-control studies, follow-up studies, pilot studies, experimental studies, case series, or case reports
Clinical data are reviewed elsewhere[45,46,47,48,50,51] it is of importance to underlie that sleep disturbances, including short or long sleep duration, poor sleep quality, circadian rhythm abnormalities, and insomnia are associated with a significant increase in the risk ratio for cognitive impairment and preclinical Alzheimer Diseases.[45,46,47,48,50,51]
Summary
Mood disorders refer to a spectrum of conditions, including major depressive unipolar and bipolar disorders, which are amongst the most prevalent and severe psychiatric diseases with a tendency to be recurrent, chronic, and disabling.[1,2] These disorders constitute major public health concerns and leading conditions in the global burden of disease in terms of disability, morbidity, and premature mortality conferring high-suicidality risk.[1,2,3,4] mood disorders are very common mental disorders, their etiology is still unclear.[5]. It plays an important role in relapses and recurrences, it is considered an independent risk factor, as well as an early sign occurring prior to both depressive and manic episodes.[8,9,10,11,12,19,20,21,22] Recently, it has been shown that targeting sleep alterations such as insomnia may improve insomnia, but it may favorably impact on the trajectory of the disorder itself.[23,24,25]
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