The position you sleep in can have an effect on the amount of sleep you get because sleeping in the wrong position could leave you more prone to nightmares.

A study published in 2016 in the journal Sleep and Hypnosis found that people who sleep on their left side run a 41% chance of having nightmares because left-side sleepers put more stress on their hearts, while only 15% of people who slept on their right side had them. The Sleep and Hypnosis journal study also found high school students who slept on their stomachs had more empowering dreams.

A study in the National Library of Medicine found that patients who slept on their left side showed changes in their heart activity, which is an indicator of stress. This is because the heart is more likely to shift very slightly to the left and right in this position. Participants who slept on their right side showed almost no changes in heart activity. This is unlikely to cause health issues if you don’t have pre-existing heart problems, but if you have heart disease or are at risk of heart failure, the change in heart activity could lead to discomfort.

Sleeping on your back can also lead to nightmares — especially people who experience breathing problems while asleep… they are more likely to bounce from deep sleep to light sleep and experience anxious or disturbing dreams, common in people with obstructive sleep apnea (OSA). For individuals with OSA, it’s common for the degree of apnea to be worse during supine (back) sleep compared to lateral (side) or prone (stomach) sleeping positions.

In people with OSA, the airway can partially collapse, resulting in a decrease in oxygen and increase in carbon dioxide levels in the body. These fluctuations can trigger the fight-or-flight response, causing stress or feelings of suffocation. This can contribute to disturbing dreams or nightmares.

So changing your sleeping position could influence the kind of dream you have. The best sleep position is a position that is optimal for healthy breathing and potentially better for your dreams! However, warding off nightmares isn’t just about sleep position. The most important factor is comfort.