How sleep affects your mental health

Published August 2025 | 5 min read
Expert contributor: Dr Ben Bullock, Senior Lecturer and Researcher in the Department of Psychological Sciences and the Centre for Mental Health and Brain Sciences, Swinburne University
Words by Alana Wulff

Find out why poor sleep can affect your mental wellbeing and how simple changes to your routine can help you sleep well and feel better.

There’s nothing quite like the fog and fatigue that follow a sleepless night. You may be easily irritated, feel hungrier than usual, have trouble focusing or find it hard to motivate yourself. This is because sleepless nights can disrupt connections in our brain, making it harder to control our thoughts and feelings, says Dr Ben Bullock, Senior Lecturer and Researcher in the Department of Psychological Sciences and the Centre for Mental Health and Brain Sciences at Swinburne University.

“We blame being cranky on a lack of sleep, but the mechanism we’re talking about is that disconnect between the front part of the brain and the deep emotion centres of the brain,” explains Dr Bullock.

This interference makes us less equipped to control our emotions. “This is where most people see the effects of sleeplessness – they become more emotional because they don’t have the same amount or level of emotional regulation as usual.”

How to stop stress disrupting your sleep

Emotional upheaval can further interrupt your sleep by leaving you feeling anxious or depressed, which can impact the quality of your sleep. “It’s a vicious cycle, because if you’re anxious and you can’t get to sleep, that lack of sleep leads to more anxiety,” says Dr Bullock.

To put an end to this cycle and maintain good sleep hygiene, he suggests treating sleep as a core pillar of your health. “If we’re talking about living well in terms of diet and exercise, sleep is probably the one that gets the least attention,” he says. “We think about eating well even if we don't do it all the time, and we talk about exercising even if we don't do it all the time – but quite often we ignore sleep.”

To make your sleep a priority, start with the basics. “Stick to regular routines in terms of preparing for bed and aim to get up at the same time each morning,” advises Dr Bullock. “It might feel boring, especially if you want to stay up and watch that show or read that book, but having a regular routine is a good way to regulate your circadian system.”
 

How light affects your sleep

The circadian system – a 24-hour biological system we all have – is informed by light, which makes access to natural light an important part of our sleep routine. “We’re really starting to see the importance of natural light and daylight,” explains Dr Bullock. “By the same token, light in the morning is kind of like a clock setter, which sets your body clock up for the day.”

He says the earlier you’re exposed to natural light in the morning, the more likely you are to feel tired at night when it’s darker. Researchers have even found exposure to natural light before waking can improve morning alertness and reduce sleepiness. “Light is really important and it’s becoming more well known,” says Dr Bullock. “Research has found that those of us who are more easily disturbed, and have a more disrupted light system, do have more health and mental health problems.”

The world’s largest study on light exposure and its impact on mental health to date found people who get plenty of natural light during the day lower their risk of depression by 20%. Similar effects are shown among people with psychiatric disorders like anxiety, bipolar and post-traumatic stress disorder.

Practical tips to help you sleep well

While a lack of sleep can leave you feeling anxious about how little sleep you’ve had, Dr Bullock recommends trying not to worry. “Worrying about sleep causes anxiety, which can impact your sleep,” he says. “Try to trust in the process and remember you have this in-built rhythm – we are a species that sleeps at night – and eventually you will fall asleep.”

If your sleep disruptions or issues continue for a long time and there’s no obvious reason for them, Dr Bullock suggests seeking medical advice from your GP. “Tell them you’re not sleeping, and you don’t know why,” he says.

If your sleep issues are taking a toll on your mental wellbeing, eligible members^* can get a free annual HealthyMinds Check-in with a psychologist – giving you tailored support and, depending on your needs, directing you to a GP for a mental health treatment plan and Medicare-subsidised sessions or appropriate support programs and resources.

Eligible HCF members^{^} can also get a free 12-month subscription to the Sleepfit app, which can help you identify sleep issues, recommend improvements and give you access to personalised tools.

If you’re looking for simple changes you can make tonight to help you fall asleep faster, Dr Bullock suggests following the usual sleep tips, like dimming the lights at night and avoiding blue light before bed, as this affects the onset of sleep hormones. Recent research has revealed that light at night, in particular, disrupts the circadian rhythm by altering the natural light–dark cycle.

Studies also show exercise has a positive impact on sleep. If you need some motivation, the HCF Healthful app gives you access to a personalised Health Score, evidence-based health programs, real-time health and wellbeing tracking, goal setting and a 24/7 digital coach⁺.

Importantly, Dr Bullock recommends avoiding caffeine late in the day. “Have all your caffeine in the morning, because it's in your system for six to eight hours,” he says.

Caffeine isn’t the only drink to be wary of. Curbing your alcohol consumption where possible may help in the long term, particularly if you’re using it to fall asleep. “Yes, it makes you feel drowsy, but alcohol stops you from getting that really deep, restorative sleep,” says Dr Bullock. “If you’re using alcohol to manage anxiety and sleep, you should consider tapering this off over time.”

Better sleep starts here

Need some help getting a good night’s rest? Thanks to our partnership with Sleepfit Solutions, eligible HCF members^{^} can get a free 12-month subscription to the Sleepfit app, designed to improve sleep and overall wellbeing.