Why a Lack of Sleep Makes You Anxious

A poor night’s rest can cause your brain to overreact

Photo: Kinga Cichewicz/Unsplash

Some consequences of a bad night’s sleep are obvious — fatigue, difficulty concentrating, a yearning for bed. But some other effects, such as a weaker drive to be social the next day, are frequently overlooked because they’re unexpected or misunderstood. In a study published late last year, a team of scientists from the University of California, Berkeley focused their attention on another hidden problem of limited sleep: anxiety.

It turns out there is a close relationship between how long people sleep and how they experience the world. The longer people go without sleep, the more distressed they begin to feel. Sleep disturbances are also a common symptom of major mood disorders such as depression. Improving sleep quality is an early target for many approaches to therapy, because when people sleep better, they feel better.

It could be that sadness and worry are simply consequences of feeling tired, but it could also be that there are direct links between sleep and mood regulation systems in the brain. To answer this question, the Berkeley researchers surveyed people’s anxiety levels both after a normal night of sleep and after a second night of total sleep deprivation. In addition, they recorded each person’s brain activity while they watched videos that made them uncomfortable (for example, witnessing a young child cry).

As expected, people felt more anxious when they were deprived of sleep than when they were allowed to sleep. When the researchers looked inside people’s heads with a brain scanner, they found that a brain area known as the medial prefrontal cortex — an area linked to emotional control — reduced its activity when people were sleep deprived. More specifically, this area of the brain was less active in response to the stress caused by watching uncomfortable videos. This suggests that a sleep-deprived brain is less able to control its reaction to momentarily stressful events.

Feelings of stress and anxiety after a bad night’s sleep appear to be driven by a weakened emotional control system in the brain.