Clinically reviewed by Bülent Ada, BSc.(Psychol.)(Hons.), MAPS · Updated March 2025

Poor sleep makes everything worse. Anxiety feels more intense. Depression feels more heavy. Stress feels less manageable. The research is clear: sleep is not a passive activity or a luxury — it is a critical biological function that underpins virtually every aspect of mental and physical health.

And yet sleep is frequently the last thing addressed in mental health treatment, even though it is often the first thing to deteriorate when mental health suffers — and one of the most direct levers for improving it.

This article explores the relationship between sleep and mental health in depth: the disorders involved, the cycle that maintains them, and the evidence-based approach that most people haven’t heard of but research suggests works better than sleeping tablets.

(For practical sleep hygiene tips — the basics of creating conditions for better sleep — see our complementary article: How to Sleep Better: 12 Science-Backed Tips.)

The Bidirectional Relationship Between Sleep and Mental Health

Sleep and mental health are deeply intertwined — and the relationship runs in both directions.

Poor sleep causes or worsens mental health difficulties. Sleep deprivation impairs emotional regulation, increasing reactivity, reducing resilience, and making negative experiences feel more intense. It impairs cognitive functioning — concentration, memory, decision-making. Chronic sleep insufficiency is associated with increased risk of depression, anxiety, and other mental health conditions.

Mental health difficulties impair sleep. Depression often involves early morning waking and difficulty returning to sleep, or conversely, hypersomnia (sleeping excessively without feeling rested). Anxiety fuels a racing mind at bedtime and hyperarousal that prevents the nervous system from settling into sleep. PTSD disrupts sleep through nightmares, hypervigilance, and avoidance of the vulnerability of sleep. Burnout disrupts the ability to “switch off.”

The result is a cycle in which poor sleep worsens mental health, and worse mental health further disrupts sleep — each feeding the other.

Common Sleep Disorders and Their Mental Health Connections

Insomnia Disorder

Insomnia disorder is the most common sleep disorder. It is characterised by persistent difficulty falling asleep, staying asleep, or returning to sleep after early waking — combined with significant daytime impairment (fatigue, mood disruption, difficulty concentrating, reduced function).

Insomnia affects approximately one-third of Australian adults to some degree, with around 10–15% meeting criteria for a clinical disorder. It is both caused by mental health conditions and a risk factor for developing them.

The role of learned arousal: One of the key mechanisms maintaining chronic insomnia is conditioned arousal — the bed and bedroom gradually become associated with wakefulness and anxiety rather than rest, through a process of classical conditioning. Lying in bed becomes a cue for the fight-or-flight system rather than for sleep.

The thought-behaviour cycle: Anxiety about sleep (“If I don’t sleep I’ll be useless tomorrow”) leads to attempts to control sleep (trying harder, watching the clock), which increases arousal, which makes sleep less likely, which confirms the feared outcome.

Sleep and Depression

Sleep disturbance is among the most consistent symptoms of clinical depression — present in approximately 75% of people with a depressive episode. The most common pattern in depression is early morning waking (waking significantly earlier than intended, often with racing rumination that makes return to sleep impossible).

Hypersomnia (excessive sleeping) can also occur — particularly in atypical depression and bipolar depression — and represents a different presentation that requires a different approach.

Critically, research shows that treating insomnia in people with co-occurring depression significantly improves depression outcomes — even when the insomnia treatment is delivered separately from depression treatment. This suggests sleep is not merely a symptom to wait out, but an active treatment target.

Sleep and Anxiety

Anxiety and sleep have a particularly obvious connection: the bedtime period, with its quietness and absence of distraction, is precisely when anxious minds have the space to race. Rumination, worry, and catastrophic thinking are typically at their worst in the dark.

Anxiety also maintains insomnia through hyperarousal — the nervous system remains in a state of threat activation that is incompatible with the parasympathetic shift required for sleep onset.

Treatment approaches need to address both the sleep difficulties and the underlying anxiety. See our article on anxiety treatment in Australia for more on evidence-based approaches to anxiety.

Sleep and PTSD

PTSD is associated with severe sleep disturbance, including nightmares, hypervigilance at sleep onset, avoidance of sleep (because of nightmares or fear of losing control during sleep), and fragmented sleep architecture.

Imagery Rehearsal Therapy (IRT) is a specific psychological treatment for trauma-related nightmares with a growing evidence base. EMDR and trauma-focused CBT also address sleep as part of comprehensive PTSD treatment.

Sleep Apnea and Mental Health

Obstructive sleep apnea — a breathing disorder in which the upper airway repeatedly collapses during sleep, causing sleep fragmentation and oxygen desaturation — is highly prevalent and significantly underdiagnosed in Australia.

Sleep apnea produces profound fatigue, cognitive impairment, and mood disturbance that can closely mimic depression. It has been found in studies to be a significant contributing factor in treatment-resistant depression — depression that fails to improve with standard interventions because an underlying sleep disorder is not being treated.

Anyone with treatment-resistant depression, loud snoring, or significant unexplained daytime fatigue should be assessed for sleep apnea.

What Doesn’t Work (And Why)

Sleep hygiene alone

Sleep hygiene — the set of environmental and behavioural recommendations for good sleep (regular sleep times, dark/cool room, avoiding screens before bed, limiting caffeine) — is the most commonly offered sleep advice. It is genuinely useful as a foundation. But for established insomnia disorder, sleep hygiene alone produces only modest improvements.

Sleep hygiene addresses the conditions for sleep. It does not address the cognitive and behavioural patterns that are actively maintaining the insomnia.

Sleeping tablets

Benzodiazepines and Z-drugs (zolpidem, zopiclone) are effective for short-term, acute insomnia. As long-term treatments for chronic insomnia, the evidence is unfavourable: they reduce sleep quality over time, carry significant risks of dependence and withdrawal, impair memory and coordination, and do not address the underlying insomnia mechanisms.

Australian clinical guidelines and international consensus increasingly recommend Cognitive Behavioural Therapy for Insomnia (CBT-I) as the first-line treatment for chronic insomnia — ahead of medication.

What Does Work: CBT-I

Cognitive Behavioural Therapy for Insomnia (CBT-I) is a structured psychological programme, typically delivered over 5–8 sessions, that directly addresses the cognitive and behavioural factors maintaining insomnia.

CBT-I is endorsed as the first-line treatment for chronic insomnia by:

• The American Academy of Sleep Medicine
• The European Sleep Research Society
• The Royal Australian and New Zealand College of Psychiatrists
• Australia’s National Health and Medical Research Council

Components of CBT-I

Sleep restriction therapy: Temporarily limiting time in bed to match actual sleep time, then gradually extending it. Counterintuitively, this is among the most effective components — it consolidates fragmented sleep and rebuilds sleep pressure.

Stimulus control: Re-establishing the bed and bedroom as cues for sleep, by limiting activities in bed to sleep and sex, and getting out of bed if awake for more than 20 minutes.

Cognitive restructuring: Identifying and modifying the anxious and catastrophic thoughts about sleep that maintain hyperarousal (e.g., “If I don’t get 8 hours I’ll be useless” → “Sleep is highly variable; I’ve coped on less before”).

Sleep hygiene: As a complement to the above, not as the primary intervention.

Relaxation training: Progressive muscle relaxation, diaphragmatic breathing, and other techniques to reduce physiological arousal at bedtime.

Psychoeducation: Understanding the science of sleep — sleep drive, circadian rhythms, normal sleep variation — reduces catastrophic interpretation of normal sleep patterns.

How to Access CBT-I in Australia

CBT-I can be delivered by a psychologist who is trained in the approach. It is eligible for Medicare rebates with a Mental Health Care Plan from a GP.

Digital CBT-I programmes (such as Sleepio, which has an Australian evidence base) are also available and effective for some people — particularly as a first step or for those with milder presentations.

If your sleep difficulties are significantly affecting your mental health, raising it with your GP is the right starting point. They can assess for contributing factors (including sleep apnea), rule out other medical causes, and refer you to a psychologist with a Mental Health Care Plan.

Frequently Asked Questions

How are sleep and mental health connected?

The relationship runs in both directions. Poor sleep impairs emotional regulation and thinking and raises the risk of depression and anxiety, while mental health conditions disrupt sleep, for example through early morning waking in depression or a racing mind in anxiety. This creates a cycle where poor sleep worsens mental health and worse mental health further disrupts sleep, each feeding the other.

What is CBT-I and does it work?

CBT-I, Cognitive Behavioural Therapy for Insomnia, is a structured psychological program, usually over five to eight sessions, that addresses the cognitive and behavioural factors maintaining insomnia. Components include sleep restriction, stimulus control, cognitive restructuring, relaxation and psychoeducation. It is endorsed as the first-line treatment for chronic insomnia by major sleep and psychiatric bodies, ahead of medication, and is eligible for Medicare rebates with a Mental Health Care Plan.

Why don’t sleeping tablets fix insomnia?

Benzodiazepines and Z-drugs can help short-term, acute insomnia, but as long-term treatments for chronic insomnia the evidence is unfavourable. They tend to reduce sleep quality over time, carry risks of dependence and withdrawal, impair memory and coordination, and do not address the underlying mechanisms maintaining insomnia. Australian and international guidelines increasingly recommend CBT-I as the first-line approach instead.

Is sleep hygiene enough to fix insomnia?

Sleep hygiene, such as regular sleep times, a dark cool room, limiting screens and caffeine, is a useful foundation, but for established insomnia disorder it produces only modest improvements on its own. It addresses the conditions for sleep but not the cognitive and behavioural patterns actively maintaining insomnia, such as conditioned arousal and anxiety about sleep, which CBT-I targets directly.

Can poor sleep cause depression?

Chronic sleep insufficiency is associated with an increased risk of depression and anxiety, and sleep disturbance is among the most consistent symptoms of depression. Importantly, research shows that treating insomnia in people with co-occurring depression significantly improves depression outcomes, even when delivered separately. This suggests sleep is an active treatment target rather than just a symptom to wait out.

Related reading

• How to sleep better: science-backed tips
• Insomnia and sleep support
• Anxiety treatment services

About the author: Bülent Ada is the Principal Psychologist and Founding Director of Mind Health Associates in Parramatta, Sydney. With over 20 years of clinical experience, Bülent integrates sleep assessment and evidence-based sleep treatment into psychological care for clients with anxiety, depression, trauma, and burnout. Learn more about Bülent.

This article is for informational purposes only and is not a substitute for professional medical or mental health advice. Persistent sleep difficulties should be assessed by a qualified health professional.

Ready to take the next step? Mind Health Associates offers evidence-based treatment for sleep disorders and mental health in Parramatta and via telehealth across Australia. Contact us to enquire about appointments.