Sleep Apnoea & Mental Health: The Connection You Need to Know About
This World Mental Health Day, one of the most important questions Australians can ask is not just how their mental health is, but also how their sleep is. The two are more deeply connected than most people realise, and for the millions of Australians living with undiagnosed obstructive sleep apnoea, that connection could be the missing piece in a mental health puzzle that has gone unsolved for years.
The Sleep-Mental Health Relationship Is Bidirectional
The Sleep Health Foundation of Australia is unequivocal on this point: chronic sleep disturbance is a significant risk factor for the development of mental health problems including depression, paranoia, anxiety, post-traumatic stress disorder, and even suicidal behaviours (1). The risk increases with insomnia, habitual sleep loss, and obstructive sleep apnoea. Research suggests that 60-90% of patients with depression have insomnia, and approximately 20% of people with depression also have sleep apnoea (1).
What makes this relationship particularly complex is that it operates in both directions. Poor sleep worsens mental health, and mental health conditions disrupt sleep. When obstructive sleep apnoea is layered on top of this, the cycle becomes even harder to break.
What Obstructive Sleep Apnoea Does to the Brain
Obstructive sleep apnoea causes repeated partial arousals throughout the night as the brain works to restore breathing after each airway collapse. Although these arousals are typically too brief to be remembered, they nonetheless fragment sleep architecture and can produce significant daytime impairment even when total sleep duration appears adequate (2). This fragmentation prevents adequate time in the deep NREM and REM stages where emotional processing, memory consolidation, and cognitive restoration occur, and research confirms that both stages play complementary and functionally distinct roles in overnight emotional regulation and the consolidation of newly encoded memories (3,4).
The result is a brain that is chronically under-restored, emotionally dysregulated, and poorly equipped to manage the ordinary stressors of daily life, with evidence that apnoea-related disruption of REM sleep alone can impair the overnight consolidation of spatial navigational memory⁵.
A 2024 systematic review and dose-response meta-analysis published in Sleep and Breathing found a clear association between obstructive sleep apnoea severity and depression risk, with risk increasing in a dose-dependent manner as the apnoea-hypnoea index (AHI) worsens (6). An Australian study presented at SLEEP Advances found that depression and anxiety were frequently comorbid with sleep-disordered breathing in patients referred for diagnostic sleep studies at an Australian tertiary centre, with both conditions linked to AHI severity and sleep quality measures (7).
What this means is sleep apnoea fragments sleep through repeated brief arousals that limit time in restorative deep NREM and REM sleep, leaving the brain under-restored and impairing emotional regulation, memory and cognition, even independent of oxygen desaturation. As a result, depression and anxiety are more common in people with sleep apnoea, and the more severe the apnoea, the higher the risk.
How Sleep Apnoea Mimics and Worsens Depression
The symptoms of untreated sleep apnoea overlap significantly with the symptoms of depression: persistent fatigue, low motivation, difficulty concentrating, irritability, withdrawal from social activities, and a pervasive sense that something is wrong that is difficult to articulate (8,9). This overlap means that sleep apnoea is frequently attributed to depression, and the underlying airway problem goes uninvestigated and untreated.
A 2025 Frontiers in Psychiatry study confirmed that the overlap of symptoms between depression and OSA can complicate the diagnostic and treatment process and may result in OSA being underdiagnosed in patients presenting with mental health concerns (10).
Critically, research consistently shows that treating sleep apnoea produces meaningful improvements in depressive symptoms, often independently of any change in antidepressant medication. A systematic review and meta-analysis published in The Lancet eClinicalMedicine, drawing on 20 randomised controlled trials including 4,255 participants, confirmed a significant benefit of OSA treatment in reducing depressive symptoms, independent of improvements in daytime sleepiness (11). A further meta-analysis confirmed that both CPAP and mandibular advancement splints produce statistically significant improvements in depressive symptoms in patients with OSA (12).
For patients whose depression has not responded adequately to treatment, undiagnosed sleep apnoea should always be considered as a possible contributing or maintaining factor.
The Anxiety Connection
The physiological stress of repeated apnoea events, including oxygen desaturation, cortisol surges, and activation of the sympathetic nervous system, creates a state of chronic hyperarousal that mirrors and amplifies anxiety (13). Patients with untreated sleep apnoea frequently report a sense of being permanently on edge, with heightened reactivity and reduced tolerance for stress that has no obvious external cause7. Addressing the airway problem can, for many patients, produce a meaningful reduction in anxiety in some patients that no amount of cognitive intervention alone was achieving (11).
Brain Fog, Cognitive Decline, and the Long-Term Risk
Beyond mood, untreated sleep apnoea is associated with measurable impairment of cognitive function, including memory, concentration, and decision-making (2,8). Chronic intermittent hypoxia, the repeated drops in blood oxygen caused by apnoea events, is neurotoxic over time, and research has found associations between severe untreated sleep apnoea and elevated risk of mild cognitive impairment (14,15). The Sleep Health Foundation has noted that looking after sleep to promote good mental health is imperative, given the bidirectional relationship between sleep disorders and psychiatric conditions (1).
What You Can Do
If you are experiencing depression, anxiety, or cognitive difficulties that have not responded adequately to treatment, and you also snore, wake unrefreshed, or feel excessively sleepy during the day, please speak to your GP about a sleep study. A custom oral appliance, the treatment offered at SleepWise Clinic, is a comfortable, evidence-based option that can significantly improve sleep quality and, with it, mental health.
This World Mental Health Day, take our free online sleep apnoea test or call SleepWise Clinic on 1300 101 505 to start finding out more about how you can help improve your sleep. What feels like a mental health problem might have a very treatable physical cause.
References1. Sleep Health Foundation. Mental health and sleep. Available from: https://www.sleephealthfoundation.org.au/sleep-topics/mental-health-sleep
2. AASM Foundation. Sleep apnoea effects on memory: consequences and mechanisms. Available from: https://foundation.aasm.org/sleep-apnea-effects-on-memory-consequences-and-mechanisms
3. Sio YK, Lustri MR. Both slow wave and rapid eye movement sleep contribute to emotional memory consolidation. Communications Biology. 2025. Available from: https://www.nature.com/articles/s42003-025-07868-5
4. Schoenfeld J, et al. REM sleep as a modulator of emotional processing. Frontiers in Psychology. 2021;12:730924.
5. Varga AW, et al. Apnea-induced rapid eye movement sleep disruption impairs human spatial navigational memory. J Neurosci. 2014;34(44):14571-7.
6. Zhao, D. F., Zhang, Y. Z., Sun, X., Su, C. Y., & Zhang, L. Q. (2024). Association between obstructive sleep apnea severity and depression risk: a systematic review and dose-response meta-analysis. Sleep & breathing = Schlaf & Atmung, 28(5), 2175–2185
7. Gordon, A., Pradeepan, S., & Paech, G. (2022). O013 Anxiety and depression in adults referred for diagnostic sleep studies at an Australian tertiary sleep referral centre. Sleep Advances: A Journal of the Sleep Research Society, 3(Suppl 1), A6.
8. Garbarino S, et al. Fatigue is distinct from sleepiness and negatively impacts individuals living with obstructive sleep apnoea. Health and Quality of Life Outcomes. 2021.
9. Grandner, M. A., & Malhotra, A. (2017). Connecting insomnia, sleep apnoea and depression. Respirology (Carlton, Vic.), 22(7), 1249–1250.
10. Chen X, Qiu Z, Hu C and Liu Z (2025) Prevalence and risk factors of obstructive sleep apnea in depression: an observational retrospective study. Front. Psychiatry 16:1568830.
11. Zheng, D., Xu, Y., You, S., Hackett, M. L., Woodman, R. J., Li, Q., Woodward, M., Loffler, K. A., Rodgers, A., Drager, L. F., Lorenzi-Filho, G., Wang, X., Quan, W. W., Tripathi, M., Mediano, O., Ou, Q., Chen, R., Liu, Z., Zhang, X., Luo, Y., … Anderson, C. S. (2019). Effects of continuous positive airway pressure on depression and anxiety symptoms in patients with obstructive sleep apnoea: results from the sleep apnoea cardiovascular Endpoint randomised trial and meta-analysis. EClinicalMedicine, 11, 89–96.
12. Povitz M, et al. Effect of treatment of obstructive sleep apnoea on depressive symptoms: systematic review and meta-analysis. PLoS Medicine. 2014;11(11):e1001762. Available from:
13. Narkiewicz, K., & Somers, V. K. (2003). Sympathetic nerve activity in obstructive sleep apnoea. Acta physiologica Scandinavica, 177(3), 385–390
14. Leng, Y., McEvoy, C. T., Allen, I. E., & Yaffe, K. (2017). Association of Sleep-Disordered Breathing With Cognitive Function and Risk of Cognitive Impairment: A Systematic Review and Meta-analysis. JAMA neurology, 74(10), 1237–1245.
15. Yaffe, K., Laffan, A. M., Harrison, S. L., Redline, S., Spira, A. P., Ensrud, K. E., Ancoli-Israel, S., & Stone, K. L. (2011). Sleep-disordered breathing, hypoxia, and risk of mild cognitive impairment and dementia in older women. JAMA, 306(6), 613–619.
