Potential mechanisms of the sleep therapies for depression

Association between Sleep Quality and Depression Symptoms in Chinese College Students during the COVID-19 Lockdown Period

Background: The outbreak of COVID-19 has seriously threatened the health of people around the world. To prevent the spread of the epidemic, Chinese universities have implemented closed management of campuses. The implementation of restrictive measures has gradually caused changes in the quality of sleep and the psychological state of college students. In addition, college students are faced with the dual pressure of employment and study, and the psychological pressure is huge. Therefore, it is necessary to investigate sleep and depressive symptoms among college students. Methods: Using the method of stratified cluster sampling, 6695 college students were selected from three universities in Jiangxi, Anhui, and Xinjiang provinces from April to May 2022. The Chinese version of the Pittsburgh sleep quality index (PSQI) and the self-rating depression scale (SDS) were used for the survey. Hierarchical logistic regression analysis was used to analyze the relationship between the PSQI and the SDS. Results: Overall, during the outbreak of COVID-19, 69.0% of males and 73.5% of females had poor sleep quality among Chinese college students and the detection rate of depressive symptoms was 43.6% for males and 47.8% for females, respectively. Taking students with good sleep quality as references, after controlling for covariates, hierarchical logistic regression shows that Chinese college students with poor sleep quality have a higher OR value (OR = 12.0, 95%CI: 10.2~14.1, p < 0.001), especially in males (OR = 43.8, 95%CI:30.2~63.6, p < 0.001). For both males and females, the OR value of college students with the following characteristics was higher: rural college students (males, OR = 50.32, 95%CI: 32.50−77.93; females, OR = 8.03, 95%CI: 6.45−9.99), overweight college students (males, OR = 62.17, 95%CI: 19.47−198.53; females, OR = 16.67, 95%CI: 6.48−42.88), and college students drinking sugar-sweetened beverages (males, OR = 59.00, 95%CI: 36.96−94.18; females, OR = 8.16, 95%CI: 6.63−10.05) (p < 0.001). Conclusions: Poor sleep quality is associated with depressive symptoms among Chinese college students, especially college males. Our research suggests that it is necessary to consider the improvement of sleep quality and depressive symptoms among college students during the COVID-19 epidemic.

Circadian depression: A mood disorder phenotype

Major mood syndromes are among the most common and disabling mental disorders. However, a lack of clear delineation of their underlying pathophysiological mechanisms is a major barrier to prevention and optimised treatments. Dysfunction of the 24-h circadian system is a candidate mechanism that has genetic, behavioural, and neurobiological links to mood syndromes. Here, we outline evidence for a new clinical phenotype, which we have called 'circadian depression'. We propose that key clinical characteristics of circadian depression include disrupted 24-h sleep-wake cycles, reduced motor activity, low subjective energy, and weight gain. The illness course includes early age-of-onset, phenomena suggestive of bipolarity (defined by bidirectional associations between objective motor and subjective energy/mood states), poor response to conventional antidepressant medications, and concurrent cardiometabolic and inflammatory disturbances. Identifying this phenotype could be clinically valuable, as circadian-targeted strategies show promise for reducing depressive symptoms and stabilising illness course. Further investigation of underlying circadian disturbances in mood syndromes is needed to evaluate the clinical utility of this phenotype and guide the optimal use of circadian-targeted interventions.

Diurnal variation of cerebrospinal fluid hypocretin-1 (Orexin-A) levels in control and depressed subjects

BACKGROUND

Hypocretins, excitatory neuropeptides at monoaminergic synapses, appear to regulate human sleep-wake cycles. Undetectable cerebrospinal fluid hypocretin-1 levels are seen in narcolepsy, which is frequently associated with secondary depression. Shortened rapid eye movement latency is observed in both narcolepsy and depression. Cerebrospinal fluid hypocretin-1 levels have not been reported in mood disorders.

METHODS

We examined hypocretin-1 levels in 14 control and 15 depressed subjects. Cerebrospinal fluid was drawn continuously in supine subjects for 24 hours with an indwelling intrathecal catheter under entrained light-dark conditions. Depressed subjects were studied before and after 5 weeks of sertraline (n=10, three nonresponders) or bupropion (n=5, two nonresponders).

RESULTS

Hypocretin-1 levels varied slightly (amplitude 10%) but significantly across the diurnal cycle in control subjects, with amplitude significantly reduced in depression (3%). Levels were lowest at midday, surprising for a hypothetically wake-promoting peptide. Mean hypocretin levels trended higher in depressive than in control subjects. Hypocretin-1 levels decreased modestly but significantly after sertraline (-14%) but not bupropion.

CONCLUSIONS

Our results are consistent with previous physiologic findings in depression indicating dampened diurnal variations in hypocretin-1. The finding that sertraline but not bupropion slightly decreased cerebrospinal fluid hypocretin-1 indicates a serotoninergic influence on hypocretin tone.

No Influence of a functional polymorphism within the serotonin transporter gene on partial sleep deprivation in major depression

Sleep deprivation exerts transient antidepressant efficacy. As a potential mechanism of action an enhancement of serotonergic and dopaminergic neurotransmission within the CNS is discussed. Because genetic variations influencing neurotransmission could have an impact on therapeutic outcome and stability of improvement, we investigated the functional polymorphism of the serotonin transporter (5-HTT) gene, the 5-HTT-linked polymorphic region (5-HTTLPR), to examine the serotonergic pathway. We included 56 patients with major depression (DSM-IV). Psychiatric ratings including the HAM-D21 and HAM-D6 scale were assessed on the day prior to partial sleep deprivation (PSD) and on day 1 and 2 after PSD and related to the different genotypes. The 5-HTTLPR variants were determined following PCR amplification using genomic DNA. 58.1% of the patients were responders to PSD. A significant overall reduction in depression scores could be observed on day 1. Subdivision according 5-HTTLPR gene variants showed no differences in clinical outcome on day 1. As expected the therapeutical effect of PSD was only transient and most patients experienced an exacerbation of depressive symptoms on day 2. 5-HTTLPR variants had no influence on reduction of depressive symptoms on day 2 or relapse on day 3. Thus, the previously reported influence of the serotonin transporter gene on PSD outcome in bipolar depression could not be confirmed in unipolar depressed patients.

Timing is everything: does the robust upregulation of noradrenergically regulated plasticity genes underlie the rapid antidepressant effects of sleep deprivation?

The mechanisms by which sleep deprivation brings about rapid antidepressant effects remain to be elucidated. Biological rhythms have the capacity to temporally dissociate biochemical processes, and imposing a temporal coincidence on normally dissociated events can have striking and unexpected effects. In this context, it is noteworthy that the locus coeruleus (LC) noradrenergic projection is quiescent only during rapid-eye-movement (REM) sleep, when the target tissues display their greatest sensitivity; indeed, the temporal dissociation between the firing of the LC noradrenergic neurons and the sensitivity of its postsynaptic targets in the cortex may have considerable relevance for the antidepressant effects of sleep deprivation. Sleep deprivation rapidly upregulates several plasticity-related genes, effects that are noradrenergically mediated; these are the very same genes that are upregulated by chronic antidepressants. Thus, activating the norepinephrine system during REM sleep (by infusing an alpha(2) antagonist) may allow an interaction with a primed, sensitized postsynaptic milieu, thereby rapidly increasing the expression of plasticity genes and consequently a rapid antidepressant response.