Nightmares are more common in people who sleep longer

Nightmares are more common in people who sleep more than nine hours a night, according to British researchers, who also identified other factors. So, if you have too many bad dreams, set your alarm clock earlier.

Nobody likes to have nightmares. Especially since these bad dreams can prevent you from enjoying a night of restful sleep. Nightmares are common after a traumatic or stressful event (death of a loved one, exams...), and in people suffering from a post-traumatic shock (attack, war, violence...). But many people have nightmares from time to time and about 5% of the population would have them every week.

Psychiatric disorders are associated with a higher frequency of bad dreams. For example, half of the people with borderline personality disorder have nightmares and at least 10% of schizophrenics have bad dreams. In addition, nightmares are correlated with psychological distress, self-harm and suicidal behaviors.

But what factors contribute to bad dreams? To answer this question, researchers at Oxford University in the United Kingdom conducted a study of nightmares in the general population. The team recruited 846 people through advertisements in the media and databases of candidates for sleep studies. Participants completed an online survey.

For example, they were asked to indicate the number and severity of nightmares experienced in the previous two weeks. They also answered questions about their lives: recent divorce, tendency to worry, amount of sleep, alcohol consumption. The results are presented in the journal Social Psychiatry and Psychiatric Epidemiology.

Worry and long sleep promote nightmares

Not surprisingly, worrying about the future was related to the risk of bad dreams and their severity. It was actually the main factor associated with nightmares. Indeed, if we brood over our worries when we go to bed, this feeds negative elements into our dreams, hence the greater number of bad dreams. Because dreams are often a reflection of experiences during the day. A vicious circle can be established: daily worries feed the nightmares which amplify the worries the next day, etc.

The team also found a statistically weaker relationship between nightmare frequency and sleeping more than nine hours per night. One hypothesis is that sleeping longer increases the time spent in REM sleep, the phase of sleep where dreams are most frequent. This phenomenon could be combined with worry: people who have nightmares tend to have disturbed sleep, which increases their worry and makes them sleep more the rest of the week, and they still have bad dreams.

Physical exercise did not appear to be associated with nightmare risk, nor did alcohol, which may seem surprising. Hallucinogenic experiences and paranoia were, however, associated with bad dreams.

The researchers therefore advise people who sleep more than nine hours and have a lot of nightmares to force themselves to sleep less.

Interested in similar topics? You may also be interested in this article: Can sleep deprivation kill - is it really worth going to bed later?