Sleep and Mood
Poor sleep and low mood often occur together, and this link is well supported by scientific research. Many people notice that when they sleep poorly, emotions feel harder to manage and stressors feel heavier than usual. Sleep difficulties such as insomnia do more than create fatigue. They influence the brain systems involved in emotional regulation, motivation, and cognitive clarity.
Research consistently demonstrates that inadequate sleep or insomnia increases the likelihood of experiencing low mood. People who live with chronic insomnia show higher rates of depression, more emotional reactivity, reduced tolerance of stress, and greater difficulty concentrating. Suboptimal sleep also disrupts circadian rhythms, which support hormonal balance, daytime energy, and emotional stability.
This connection was the focus of recent research led by PhD candidate Vanika Lall at The University of Western Australia, in collaboration with supervisors Dr Melissa Ree, Clinical Associate Professor and Director of Sleep Matters, and Professor Romola Bucks, a leading academic in sleep and cognition. The study investigated how improving sleep can ease depressive symptoms. We get a little academic in this post, as we dig into not just whether a treatment works, but how it works. The findings provide compelling evidence that sleep treatment deserves a more central place in mental health care.
What Did the Study Do?
The study by Lall and colleagues adds important clarity to the sleep and mood relationship. 127 adult participants with both depressive disorders (average age around 39, about 61% women) engaged in cognitive behavioural therapy for low mood. The researchers measured how improvements in their self-reported sleep related to improvements in depressed mood following the CBT program. Importantly, this study also looked at whether this relationship was due to changes in negative thinking and/or changes in behavioural activation. UWA Profiles and Research Repository
This new research found that improving insomnia symptoms improves mood through two key pathways: cutting down repetitive negative thinking (RNT: worry and rumination) and boosting behavioural activation (BA: how engaged and active we are during the day).
Key Findings
- The sleep mood connection
While better sleep and better mood were linked, the direct link between them vanished once reductions in repetitive negative thinking and increases in behavioural activation were accounted for. In other words, the mood boost comes because sleep helps reduce negative thinking and increases engagement, not simply because the sleep was better. - Repetitive Negative Thinking (RNT)
Sleep improvement was associated with reductions in rumination and worry, those endless loops of negative thoughts that often disrupt both sleep and emotional health. - Behavioural Activation (BA)
Improved sleep seemed to pave the way for more engagement in positive or goal-directed behaviours, making it easier to get out of bed, approach tasks, and reconnect with life.
Why This Matters
Improved sleep appears to help turn the volume down on worries and supports people to engage better in their life, two very powerful interventions for low mood and depression. Interventions that treat poor sleep, such as CBT for insomnia (CBT-I) should be considered as important when treating depression. Addressing worry and rumination aswell as increasing BA early in treatment may also amplify mood benefits.
Looking Ahead
The findings are groundwork rather than the final word. Future studies should gather data across time points to confirm causal flow, should look at interventions that focus on sleep difficulties rather than mood, and use richer sleep assessments. Look out for Vanika’s follow-up research, which goes on to do just this.
If you are experiencing persistent insomnia or feel that sleep difficulties are affecting your mood, daily functioning, or recovery from depression, support is available. Sleep Matters is a team of clinical psychologists who specialise in evidence based assessment and treatment of insomnia, circadian rhythm issues, and other sleep concerns. Many people find that once sleep improves, their energy, motivation, and emotional resilience also shift in a positive direction.
Our clinicians are here to help you move toward more restful nights and brighter days.
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