Using non-invasive techniques to manipulate our emotions, it might be possible to curtail the screaming horrors that plague our sleep.

A study conducted on 36 patients diagnosed with a nightmare disorder showed that a combination of two simple therapies reduced the frequency of their bad dreams.

Scientists invited the volunteers to rewrite their most frequent nightmares in a positive light and then playing sound associated with positive experiences as they slept.

"There is a relationship between the types of emotions experienced in dreams and our emotional well-being," says psychiatrist Lampros Perogamvros of the Geneva University Hospitals and the University of Geneva in Switzerland.

"Based on this observation, we had the idea that we could help people by manipulating emotions in their dreams. In this study, we show that we can reduce the number of emotionally very strong and very negative dreams in patients suffering from nightmares."

Many people suffer from nightmares, which aren't always a simple case of a few bad dreams. Nightmares are also associated with poor-quality sleep, which in turn is linked with a whole plethora of other health issues.

Poor sleep can also increase anxiety, which in turn can result in insomnia and nightmares. Recent studies have shown that nightmares and sleep disturbances have seen an uptick during the ongoing global SARS-CoV-2 pandemic.

Given that we don't really understand why, or even how, our brain creates dreams while we sleep, treating chronic nightmares is something of a challenge.

One non-invasive method is imagery rehearsal therapy, in which patients rewrite their most harrowing and frequent nightmares to give them a happy ending. Then, they "rehearse" telling themselves that rewritten story, trying to overwrite the nightmare.

This method can reduce the frequency and severity of nightmares, but the treatment is not effective for all patients.

In 2010 scientists found that playing sounds that people have been trained to associate with a certain stimulus, while those people are sleeping, aids in boosting the memory of that stimulus. This has been named targeted memory reactivation (TMR), and Perogamvros and colleagues wanted to find out if it could improve the effectiveness of imagery rehearsal therapy (IRT).

After having the study's participants complete a dream and sleep diary for two weeks, the volunteers were all given a single IRT session. At this point, half of the group underwent a TMR session, creating a link between a positive version of their nightmares and a sound.

The other half served as a control group, imagining a less horrific version of a nightmare without being exposed to positive sounds.

Both groups received a sleep headphone headband that would play the sound – the piano chord C69 – while they were sleeping, every 10 seconds during REM sleep when nightmares were most likely to occur.

The groups were evaluated after two weeks of additional diary entries, and then again after three months without any sort of treatment.

At the start of the study, the control group had, on average, 2.58 nightmares per week, and the TMR group had an average of 2.94 weekly nightmares. By the end of the study, the control group was down to 1.02 weekly nightmares, while the TMR group had dropped to just 0.19. Even more promising, the TMR group reported an increase in happy dreams.

At the three-month follow-up, nightmares had risen slightly in both groups, to 1.48 and 0.33 per week respectively. However, that is still an impressive reduction in the frequency of nightmares, the researchers said, suggesting that using TMR to support IRT results in a more effective treatment.

"We were positively surprised by how well the participants respected and tolerated the study procedures, for example performing imagery rehearsal therapy every day and wearing the sleep headband during the night," Perogamvros says.

"We observed a fast decrease of nightmares, together with dreams becoming emotionally more positive. For us, researchers and clinicians, these findings are very promising both for the study of emotional processing during sleep and for the development of new therapies."

The team's research has been published in Current Biology.