Why sleep matters: the emotional toll of insufficient sleep

Psychologists have long suspected that when we don’t get enough sleep, we become less happy, more anxious, and more prone to stress, and potentially even at higher risk for conditions like depression; recent research has proved their suspicions were correct! Let’s dive into how lack of sleep affects your mood and mind.

One of the most immediate effects of sleep deprivation is a change in mood, which is usually for the worse; you probably notice that you’re more short-tempered, easily frustrated, or feel “down” after even just one night of poor sleep. In a 2023 meta-analysis, University of Houston researchers reviewed more than 150 studies from 50 years to confirm that losing sleep makes people less emotionally resilient; it makes us unhappy, increases anxiety, and challenges our emotional function.¹

Even mild sleep loss, such as going to bed an hour or two late or having fragmented sleep for a night, had measurable impacts on mood. Throughout all of the studies, participants consistently reported higher levels of irritability, tension, and worry after nights of poor sleep. How can one night’s sleep have such a huge impact? According to several brain imaging studies, lack of sleep makes our brains’ emotional centers more reactive but our frontal lobe (which helps with impulse control and emotional regulation) less active. Basically, one night of poor sleep leads to exaggerated emotional responses like snapping at your partner or losing patience with your children. Now imagine how several nights of poor sleep in a row might impact your emotions and life!

There is a vicious cycle created by the strong link between sleep and mental health: poor sleep can cause or worsen mental health issues, and mental health issues can disturb sleep. We’ve already looked at the impact of just a single night of poor sleep; now let’s look at the long-term effects of habitually short sleep. A recently published meta-analysis completed by Ningbo Medical Center LiHuiLi Hospital, Henan Normal University, and Liaocheng Second People’s Hospital Internal Medicine reviewed more than 50 studies over 25 years; researchers concluded that individuals with insomnia are 10 times more likely to have clinically significant depression and 17 times more likely to have anxiety. That same analysis showed that people who have trouble sleeping are twice as likely to develop depression when compared with good sleepers.² Of course, sleep loss isn’t the only cause, but it’s a major contributing factor.

The good news is that improving your sleep can improve your mood! The analysis included an encouraging finding: when people with poor sleep got help to improve their sleep quality (such as therapy for insomnia or changing their poor sleep habits for better), their anxiety and depression symptoms significantly decreased. Treating sleep problems can be a tool for improving mental health!

When we don’t get enough rest, we find it difficult to regulate our emotions. You might cry more easily or feel hopeless about challenges that wouldn’t usually faze you. Essentially, sleep is our mental recovery time. During our deep and REM sleep stages, our brains process emotional experiences and resets our emotional stability. If that process is cut short, we lose some of our natural capacity to buffer our emotions. When we regularly shortchange our sleep, we are less effective at handling our own stress and emotions.

It doesn’t just impact how we feel internally, either – it affects how we relate to those around us. Without adequate sleep, our capacity to empathize and be patient significantly deteriorates, which can strain our relationships.³ Small annoyances with a partner, family member, or colleague can quickly escalate into conflicts (now imagine if both parties are sleep-deprived!). In a recent experiment performed at the University of California, Berkeley, researchers found that after a single sleepless night, subjects were less able to recognize others’ emotions and had diminished activity in brain regions associated with empathy.³ This means that, if you haven’t had adequate sleep, you might miss that your friend is upset or misinterpret someone’s neutral comment as a snide remark – this can set the stage for misunderstandings and strained relationships.