Previous studies have found that many people worldwide have difficulty getting quality sleep. In the United States, around 56% of people are estimated to have a sleep disorder, compared to about 31% in Western Europe.

One potential factor contributing to poor sleep is nightmares. Research indicates that approximately 85% of adults experience at least one nightmare each year, while around 5% suffer from them frequently.

Nightmares can have various causes. They are often linked to mental health conditions like post-traumatic stress disorder (PTSD), anxiety, and stress.

Additionally, certain medications, as well as the use of alcohol and illegal drugs, can trigger nightmares. Eating close to bedtime may also increase the likelihood of having them.

“Sleep disturbances affect a huge proportion of the general population; one large survey found that 30-40% of individuals will have a clinically significant sleep disorder in their lifetime,” Tore Nielsen, PhD, professor in the Faculty of Medicine, the Department of Psychiatry and Addiction at the Université de Montréal in Canada, and director of the Dream & Nightmare Lab in the Center for Advanced Research in Sleep Medicine at the Montréal North Island Integrated University Health and Social Services Centre (CIUSSS NIM), told Medical News Today.

“We have effective treatments for some, but by no means all, of these disorders. So, any intervention that can help improve sleep contributes to the overall national battle against poor sleep,” Nielsen said.

Nielsen, the lead author of a recent study published in Frontiers in Psychology, found that consuming excessive amounts of dairy—particularly among those who are lactose intolerant—may contribute to nightmares and disrupted sleep.

The researchers analysed data comparing food intolerances with reports of sleep problems and nightmares. They found that lactose intolerance was linked to digestive issues, poor sleep quality, and an increased occurrence of nightmares.