A new study suggests that symptoms of depression and insomnia are the strongest predictors of having frequent nightmares.

Results show that 3.9% of participants reported having frequent nightmares during the previous 30 days, including 4.8% of women and 2.9% of men. Frequent nightmares were reported by 28.4% of participants with severe depressive symptoms and 17.1% of those with frequent insomnia. Further analysis that adjusted for potential confounders found that the strongest independent risk factors for nightmares were insomnia, exhaustion, and the depressive symptom of “negative attitude toward self.”

“Our study shows a clear connection between well-being and nightmares,” says lead author Nils Sandman, a researcher in the Centre for Cognitive Neuroscience at the University of Turku in Finland, in a release. “This is most evident in the connection between nightmares and depression, but also apparent in many other analyses involving nightmares and questions measuring life satisfaction and health.”

Study results are published in the April issue of the journal Sleep.

The American Academy of Sleep Medicine reports that nightmares are vivid, realistic, and disturbing dreams typically involving threats to survival or security, which often evoke emotions of anxiety, fear, or terror. A nightmare disorder may occur when repeated nightmares cause distress or impairment in social or occupational functioning.

The study was a joint effort of the University of Turku and the Finnish National Institute of Health and Welfare. Sandman and the research team analyzed data from two independent cross-sectional surveys of the Finnish general adult population conducted in 2007 and 2012. Participants were 13,922 adults between 25 and 74 years of age; 53% were women. The surveys involved a questionnaire that was mailed to the participants and a health examination at the local primary healthcare center, where the completed questionnaire was returned and checked by a nurse. Occasional nightmares in the past 30 days were reported by more than 45% of participants, and 50.6% reported no nightmares at all.

Sandman notes that the cross-sectional study did not allow for an examination of causality. However, he suggested that the results do raise intriguing possibilities worth investigating in the future.

“It might be possible that nightmares could function as early indicators of onset of depression and therefore have previously untapped diagnostic value,” he says. “Also, because nightmares, insomnia, and depression often appear together, would it be possible to treat all of these problems with an intervention directed solely toward nightmares?”

Financial support for the study was provided by the Jenny and Antti Wihuri Foundation, Finnish National Doctoral Programme of Psychology, Sigrid Juselius Foundation, University of Helsinki, Turku Institute for Advanced Studies, and Academy of Finland.