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The Epidemiology of Insomnia and Sleep Duration Across Mental and Physical Health: The SHoT Study.
Sivertsen, Børge, Hysing, Mari, Harvey, Allison G et al. · Frontiers in psychology · 2021 · DOI
Quick Summary
This study looked at sleep problems in over 50,000 Norwegian college students and found that insomnia (difficulty sleeping) is much more common in people with both mental and physical health conditions. Students with ME/CFS had particularly high rates of insomnia—about 65% of women and an unspecified percentage of men experienced insomnia when they also had ME/CFS. The study also found that people with these conditions slept shorter amounts overall.
Why It Matters
This study provides epidemiological evidence that sleep disturbance is a prominent comorbidity in ME/CFS using formal diagnostic criteria. For ME/CFS patients, understanding the prevalence and severity of insomnia can help validate their experiences and guide clinical assessment and treatment prioritization. The strong association (RR = 2.66 in women) suggests that sleep dysfunction deserves attention as both a symptom and potential therapeutic target in ME/CFS management.
Observed Findings
Among female students, 65.4% with ME/CFS met DSM-5 insomnia criteria (adjusted RR = 2.66, 95% CI: 2.44–2.89), the second-highest among physical conditions studied.
Insomnia prevalence was generally higher in mental disorders (61–83% in females) compared to physical conditions (20–74% in females).
Both weekday and weekend sleep duration were significantly shorter across many physical and most mental disorders.
Insomnia associations with physical conditions showed sex differences; fibromyalgia in males (74.2%, adj. RR = 4.35) and ME/CFS in females (65.4%, adj. RR = 2.66) showed the strongest associations among physical conditions in their respective sexes.
Inferred Conclusions
Insomnia and short sleep duration are strongly comorbid with a broad range of mental and physical disorders, with mental disorders showing particularly high associations.
Physical conditions characterized by psychological or psychosomatic components (such as ME/CFS and fibromyalgia) show stronger insomnia associations than other physical conditions.
The sex differences in insomnia prevalence across conditions suggest that biological or psychosocial factors may moderate the relationship between specific disorders and sleep disturbance.
Remaining Questions
What mechanisms link ME/CFS specifically to insomnia? Are they related to autonomic dysfunction, inflammatory cytokines, circadian rhythm disruption, or psychological factors?
What This Study Does Not Prove
This cross-sectional study cannot establish whether insomnia causes ME/CFS, results from ME/CFS, or shares common underlying biological mechanisms with it. The study also does not explain why insomnia prevalence differs between sexes or which specific features of ME/CFS (e.g., post-exertional malaise, autonomic dysfunction) drive sleep disturbance. Additionally, self-reported diagnoses may not reflect clinically confirmed ME/CFS cases, limiting specificity.
About the PEM badge: “PEM required” means post-exertional malaise was an explicit required diagnostic criterion for participant inclusion in this study — not that PEM was studied, observed, or discussed. Studies using criteria that do not require PEM (e.g. Fukuda, Oxford) are tagged “PEM not required”. How the atlas works →
Does insomnia worsen ME/CFS symptoms or post-exertional malaise, or is it primarily a secondary consequence?
Why do insomnia prevalence rates differ markedly between males and females with the same conditions?
Would targeted insomnia treatment improve outcomes in ME/CFS patients, and if so, which therapeutic approaches (behavioral, pharmacological, or other) would be most effective?