How a lack of sleep can cause intrusive thoughts (2025)

© Shutterstock

Mental illness and intrusive thoughts - For some time now, mental illness has been associated with intrusive thoughts and the uncomfortable and distracting emotions that go with them.

© Shutterstock

Clear link - Indeed, studies have shown a clear link between debilitating intrusive thoughts and mental illnesses, such as depression and post-traumatic stress disorder (PTSD).

© Shutterstock

Intrusive thoughts and sleep deprivation - Intrusive thoughts, in turn, have been linked with sleep deprivation. Studies show that someone who is well rested can generally suppress a negative memory quite quickly.

© Shutterstock

Insomnia -

Someone who struggles with insomnia, on the other hand, may find it difficult to suppress the same memory and it may continue to bother them for a long time.

© Shutterstock

Missing piece of the puzzle -

Until recently, scientists were puzzled as to why exactly sleep deprivation contributes to intrusive thoughts, i.e. what is actually going on in the brain?

© Shutterstock

Finding answers -

Thanks to a recent study published in the journal Proceedings of the National Academy of Sciences USA, we now have more insights.

© Shutterstock

Aim of the study - The aim of the study was to determine whether the brain's right dorsolateral prefrontal cortex (rDLPFC) is negatively impacted by intrusive thoughts.

© Shutterstock

The rDLPFC -

As previous studies have shown, the rDLPFC is responsible for suppressing the retrieval process of memories. The retrieval itself happens in a different part of the brain: the hippocampus.

© Shutterstock

The hypothesis -

The researchers hypothesized that not getting enough sleep inhibits the ability of the rDLPFC to suppress unwanted memories, and therefore contributes to intrusive thoughts.

© Shutterstock

Testing the hypothesis -

In order to test their hypothesis, the researchers recruited a group of 85 students and trained them to associate neutral faces with specific images, some of which were negative, such as a car crash.

© Shutterstock

Creating connections -

The aim was for the students to create a mental connection between the faces and the images, so that when they were shown the face in isolation, an automatic memory retrieval process would occur.

© Shutterstock

Two groups -

The students were then divided into two groups. The first group was made to stay up all night, while the other group was sent to sleep in a lab.

© Shutterstock

Monitoring -

The sleeping students were monitored for how much time they spent in rapid-eye-movement (REM) sleep and non-REM sleep.

© Shutterstock

In the morning -

In the morning, all the participants were shown images of the faces they had seen in training, and they were asked either to think about the associated memory or repress it.

© Shutterstock

fMRI imaging -

Throughout the task, researchers used a functional magnetic resonance imaging (fMRI) scanner to measure the students' brain activity.

© Shutterstock

The results -

The fMRI results confirmed the team's hypothesis: compared with the students who had slept, those who stayed up all night had significantly lower rDLPFC activity when they were asked to suppress intrusive thoughts.

© Shutterstock

Elevated hippocampus activity -

In fact, activity in their hippocampus was shown to be elevated, most likely because the rDLPFC was not managing to shut down the retrieval process.

© Shutterstock

Important to note -

According to Scott Cairney, one of the researchers on the study, these findings do not suggest that sleep deprivation causes a general decline in brain activity.

© Shutterstock

What the results suggest -

Rather, the results suggest that not getting enough sleep can negatively affect specific parts of the brain that are involved in executive function.

© Shutterstock

Other findings -

Another interesting finding of the study was related to the participants who had slept through the night.

© Shutterstock

The importance of REM sleep - The data shows that there was a positive correlation between the amount of time the participants spent in REM sleep and the level of rDLPFC activity, specifically when it came to the memory suppression task.

© Shutterstock

Interesting finding - According to the team, this is particularly interesting since many mental health disorders that are associated with intrusive thoughts, such as depression and PTSD, are also associated with disturbed REM sleep.

© Shutterstock

Expert opinions -

Various experts in the field have taken time to give their thoughts on the findings of the study. One such expert is Zara Bergstrom, a cognitive psychologist at the University of Kent in England.

© Shutterstock

"Intriguing" results - According to Bergstrom, the results of the study are "intriguing," and they seem to suggest that REM sleep plays a key role in the process of maintaining adequate memory control.

© Shutterstock

Important caveat -

However, she also adds that in order to determine whether REM sleep has a causal role in controlling memories and thoughts, we will need further research that manipulates sleep directly.

© Shutterstock

Implications for therapy -

According to Maria Wimber, a cognitive neuroscientist at the University of Glasgow, the study results may also have the potential to inform therapeutic approaches.

© Shutterstock

Enhancing REM sleep -

According to Wimber, treatments that enhance REM sleep could become part of the therapy for disorders that are associated with intrusive thoughts, such as PTSD.

© Shutterstock

Treating acute trauma -

The same interventions may even be used for acute trauma as a possible preventative measure to make sure that upsetting memories and flashbacks never emerge in the first place.

Sources: (Scientific American)

See also: How much of our brains do we actually use?

© Shutterstock