The role of sleep in major depressive disorder (MDD) is a chicken-and-egg puzzle. To get to the root of potential depression in patients, clinicians need to inquire about sleep, diet, and exercise.1

Lack of Sleep Yields Depression and Poor Performance

In an anonymous survey of 558 college students (mean age, 20.4 years; 71% women) Lina Begdache, PhD, RDN, CDN, CNS-S, FAND, assistant professor at the Decker School of Nursing at Binghamton University in New York, and colleagues  asked about students’ sleeping habits, academic performance, and mood.1 

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The study found that students who reported poor sleeping habits also had poor academic performance (P <.001).1 Likewise, students who reported more severe mental distress also had worse daytime sleepiness, as well as a lower grade point average (P <.05).1

Exacerbating the situation in young adulthood is the imbalance between the excitatory glutamate and the inhibitory gamma-aminobutyric acid.1 It is also a period during which the prefrontal cortex has not yet fully matured.1 In addition, the researchers hypothesized that poor diet can lead to low-grade inflammation, which in turn can promote mental distress.1

“Sleep disorders could arise from an amalgamation of poor dietary choices (the diet provides precursors for brain chemicals), use of stimulants such as caffeine or depressants such as alcohol, which also disrupt the normal circadian rhythm,” said Dr Begdache. “Therefore, clinicians need to assess these variables along with others like stress.”

The Attempt to Objectify Depression With Biomarkers

Because the atypical symptoms of MDD are heterogeneous, researchers sought to determine whether biomarkers could detect the neurovegetative symptoms of MDD, such as appetite and sleep changes.2 Some patients with MDD experience tremendous weight gain, while others may lose weight due to loss of appetite.2 Sleep, too, has a similar variability.

A 29-study review of the MDD biomarker literature included neuroendocrine, inflammation, neurotransmitters, hypothalamic neuropeptides, and growth factors.2 Specific metabolic and endocrine biomarkers merit further research in MDD: leptin, adiponectin, ghrelin, cortisol, growth hormone, triglycerides, high density lipoprotein, glucose, insulin, and albumin.2

Other biomarker candidates to investigate in sleep behavior include serotonin and melatonin because of their regulation in the hypothalamus.2 The leading candidates for investigation of appetite changes include ghrelin, which regulates body weight, and leptin, because it is secreted in depressed patients.2

Biomarkers for Sleep and MDD

To find the root of depression, Rebecca Strawbridge, PhD, from the Institute of Psychiatry, Psychology and Neuroscience at King’s College London, United Kingdom, and colleagues reviewed the literature on biomarkers for MDD.3 They posited that more clarity in defining treatment resistant-depression by its biologic correlates may help clinicians provide more targeted treatments.3

While biomarkers may help researchers identify targets for MDD, they have yet to yield specific diagnoses in MDD. “The evidence to date has not discovered any biomarkers that are sufficiently accurate to diagnose depression, and the identification of such seems unexpected at this time,” said Dr Strawbridge. “If a biomarker reliably and accurately detected depression before the typical symptoms occurred, this would clearly be valuable for preventive and early intervention care.”

Micronutrients Affect Mood and Sleep

To demonstrate the benefits of a micronutrient diet as part of an employee wellness program, 71 participants at two employer sites were instructed on how a sound diet could improve overall health.4 While no dietary recommendations to reduce depression exist, the study did demonstrate that a micronutrient-dense plant-rich diet containing phytochemicals, vitamins, antioxidants, and minerals could improve mood in people with depression.4

Jay T. Sutliffe, PhD, RD, from Northern Arizona University in Flagstaff, and colleagues conducted a nonrandomized study that included 14 hours of live lectures, educational materials, online study, 1-hour meetings for 7 weeks, and 1-hour monthly meetings for a total of 6 months. The study assessed weight, waist circumference,  blood pressure, total cholesterol, triglycerides, blood glucose, hemoglobin A1c, gastroesophageal reflux disease, depression, sleep, pain, and worksite productivity before, during, and after the intervention.4

Depressive symptoms, measured by the Patient Health Questionnaire 9, had a mean reduction of 2.0 (P <.001) and sleep quality, measured by the Pittsburgh Sleep Quality Index, also improved by a mean of 1.3 (P <.001).4

“We would recommend a holistic approach to depression that addresses health habits that are often disrupted in major depression,” said Dr Sutliffe. He recommended a Harvard diet and depression blog and a National Alliance on Mental Illness blog for sleep hygiene.

Sleep Disparities Affect Minorities

Recognizing that health disparities in individuals of lower socioeconomic status, racial or ethnic minorities, affect sleep quality, Dr Shazia Jehan of the department of  population health, New York University School of Medicine, and colleagues sought to characterize how sleep deficits factor into poor health outcomes.5 Lack of sleep is associated with cardiometabolic diseases, obesity, depression, and anxiety.5

White women get the most sleep, while black men sleep the least.5 This is especially troubling because blacks who are deprived of sleep have double the risk of getting diabetes.5 One of the contributing factors in poor sleep in blacks is obstructive sleep apnea (OSA). Beyond race and ethnicity, being female and having low socioeconomic status also increased the risk for poor sleep and concomitant psychiatric and physical disturbances.5

Summary and Clinical Applicability

The roots of depression may be found in patients’ poor sleeping habits, diet, and exercise. Clinicians need to inquire about sleep and other lifestyle habits when they suspect depression.

References

1. Begdache L, Kianmehr H, Sabounchi N, Marszalek A, Dolma N. Principal component regression of academic performance, substance use and sleep quality in relation to risk of anxiety and depression in young adults. Trends Neurosci Educ. 2019;15:29-37.

2. Caroleo M, Carbone EA, Primerano A, Foti D, Brunetti A, Segura-Garcia C. The role of hormonal, metabolic and inflammatory biomarkers on sleep and appetite in drug free patients with major depression: a systematic review. J Affect Disord. 2019;250:249-259.

3. Strawbridge R, Young AH, Cleare AJ. Biomarkers for depression: recent insights, current challenges and future prospects. Neuropsychiatr Dis Treat. 2017;13:1245-1262.

4. Sutliffe JT, Gardner JC, Gorman MM, et al. Impact of a 6-month micronutrient-dense plant-rich nutrition intervention on health and well-being at the worksite. J Nutr Metab. 2019;2019:2609516.

5. Jehan S, Myers AK, Zizi F, et al. Sleep health disparity: the putative role of race, ethnicity and socioeconomic status. Sleep Med Disord. 2018;2(5):127-133.