Some say that a person’s dreams are a window to their subconscious, painting an imaginary picture of the happiness, struggles, celebrations, and turmoil that one experiences during their daily life. While interpretations of dreams tend to be arguable, and highly subjective, a new study finds that kids who have nightmares may be victims of bullying.

The research, presented at the annual meeting of the Pediatric Academic Societies in Vancouver, B.C., shows that although a child may be in the dark about the altercations they experience in school, they are still suffering on the inside. “Nightmares are relatively common in childhood, while night terrors occur in up to 10 percent of children,” said lead author Dr. Suzet Tanya Leyera, a research fellow at the University of Warwick, in a press release. “If either occurs frequently or over a prolonged time period, they may indicate that a child/adolescent has or is being bullies by peers. These arousals in sleep may indicate significant distress for the child.”

The findings provide new insight into a childhood development issue that often goes unnoticed. Although staying quiet about a bully might avoid certain consequences, it often has unforeseen consequences for the victim’s own health. Besides sending over 90,000 kids to the emergency room each year, study after study has shown that bullying affects a child’s physical and cognitive functioning as much as 40 years later in life — these effects emerge in the form of a higher chance of smoking, depression, anxiety, ADHD, and overall mental health deficits.

For their study, the researchers looked at data on over 6,400 children who were part of the Avon Longitudinal Study of Parents and Children — which monitors child development and health through follow-up interviews. At ages 8 and 10, the children were interviewed about bullying, and at 12 years old, they were asked about nightmares, night terrors, sleep walking, and other kinds of parasomnia.

Nightmares were the most common, occurring among 24.2 percent of the kids, while 9.3 percent of them experienced night terrors, and 12.6 slept walked. Overall, 36 percent of kids had some kind of parasomnia. Next, the researchers compared rates of bullying at 8 years old to those of parasomnias at 12, finding that victims, and those who were both victims and bullies, were most likely to have nightmares.

“Our findings indicate that being bullied is a significant stress/trauma that leads to increased risk of sleep arousal problems, such as nightmares or night terrors,” said Dr. Dieter Wolke, a professor of developmental psychology and individual differences at the university, in the release. “It is an easily identifiable indicator that something scary is being processed during the night.”

By being aware of these sleep disturbances, parents can get a clue into their children’s psychological wellbeing, Wolke said. In doing so, they can then open up a discussion about the goings on at school. In addition to that, the Department of Health & Human Services also advises parents to teach kids how to deal with bullying — through humor or firmly telling a bully to “stop” — as well as through participation in activities the child is passionate about (where they can meet people with similar interests).

Source: Leyera et al. Can Bullying Become a Nightmare? At the Pediatric Academic Societies Annual Meeting. 2014.