Regular nightmares in childhood may be a sign of looming psychological problems, according to researchers.
A new study published in the journal Sleep claims that while most children experience nightmares, those who have regular bad dreams may be at greater risk of developing psychotic disorders as adults.
Children who have night terrors - a particularly vivid form of nightmare in which the dreamer can experience hallucinations and paralysis - may also be more susceptible, say the authors.
In the study, 6,800 children were monitored up to the age of 12 by researchers from the University of Warwick.
Parents were asked about the sleep patterns of their children, and at the end of the study subjects were assessed for psychotic experiences such as hallucinations, delusions, and the belief that their thoughts were being controlled.
Children with one bout of recurrent nightmares were 16 times more likely to develop psychotic symptoms, while children who had more than one bout were 56 times more likely.
Children who had regular night terrors were twice as likely as those with regular nightmares to develop the symptoms.
Researcher Prof Dieter Wolke told the BBC: "Nightmares are relatively common, as are night terrors, it is quite normal, but if they persist then there may be something more serious about it."
It is still not clear what the exact connection between nightmares and psychotic states is.
Some experts believe that traumatic events early in a child's life might trigger both nightmares and psychosis.
Others believe that neurological flaws may play a role.
Lucie Russell, the Director of Campaigns at YoungMinds, said the study showed nightmares could be used to anticipate later psychological problems.
"This is a very important study because anything that we can do to promote early identification of signs of mental illness is vital to help the thousands of children that suffer.
"Early intervention is crucial to help avoid children suffering entrenched mental illness when they reach adulthood."