"Regular nightmares in childhood may be an early warning sign of psychotic disorders," BBC News reports. While many children have the occasional nightmare, a history of regular nightmares could be the sign of something more serious, the news reports.
The study in question followed more than 6,000 UK children and found that those whose mothers reported them as having regular nightmares over at least one period up to age nine were significantly more likely to report having had a "psychotic experience" at age 12.
While the news reports may be understandably worrying for parents, it is worth bearing in mind that the findings need to be confirmed in further studies.
Also, the findings don't suggest that having regular nightmares definitely mean your child will have psychotic experiences. In addition, reporting a single psychotic experience at age 12 would not mean that a child definitely had a psychotic disorder such as schizophrenia, or would go on to develop one later on.
The authors note that it is not possible to say whether nightmares are directly causing the increase in risk of psychotic experiences. This means that it is not clear whether stopping the nightmares (if this were possible) will have an effect on risk of these experiences.
Psychosis - reducing the risk
Psychosis may be caused by general medical conditions, mental health (psychological) conditions, or substance use (alcohol or drugs). It may not always be possible to prevent psychosis, but one way to reduce the risk is to avoid substance use, such as recreational drug use.
For example, research has shown regular cannabis users are 40% more likely to develop a psychotic illness, such as schizophrenia, than people who do not use the drug.
People who regularly use "skunk" (the herbal type of cannabis specifically grown for its increased strength) are thought most at risk.
Where did the story come from?
The study was carried out by researchers from King's College London and other research centres in the UK. It was funded by the UK Medical Research Council, Wellcome Trust, University of Bristol, and Economic and Social Research Council. The study was published in the peer-reviewed medical journal Sleep.
The BBC News headline "Childhood nightmares may point to looming health issues" is unnecessarily frightening for parents. The figures quoted in the BBC News about the risk associated with nightmares ("a three-and-a-half times" increase in risk), comes from an analysis that cannot tell us whether the sleep problems or psychotic experience came first. And therefore it cannot tell us which might be contributing to the other.
The Mail Online provides a better summary of the results in its story.
What kind of research was this?
This was a prospective cohort study looking at the possibility of a link between sleep disorders and later psychotic experiences in childhood. This is the most appropriate study design for assessing this question.
The research was part of an ongoing birth cohort study called the Avon Longitudinal Study of Parents and Children (ALSPAC). This ongoing study looks at factors that determine a person's health from childhood onwards.
This is the most appropriate study design for assessing this question. The researchers also carried out some cross-sectional analyses, but these cannot tell us which factor came first, and therefore which might be influencing the other.
Therefore, these analyses cannot answer the question of whether frequent nightmares might increase psychosis risk or whether psychotic experiences might increase risk of nightmares.
What did the research involve?
The researchers assessed whether the children had any problems with sleep (such as difficulty getting to sleep, nightmares, night terrors, or sleepwalking) between the ages of two-and-a-half and nine years, and at age 12. They also assessed whether the children had experienced psychotic experiences at age 12. They then analysed whether children with sleep problems were more likely to report psychotic experiences.
The study aimed to recruit all pregnant women living in the Avon region who were due to give birth between April 1st 1991 and the end of 1992. They recruited 14,775 women who gave birth to a live baby.
The mothers completed questionnaires about their and their child's health and development from the time of recruitment. Sleep problems were assessed in six postal questionnaires sent at intervals between the ages of two and a half and nine years, and in a standard face to face interview when the child was aged 12 years.
The questionnaires asked the mother if their child experienced regular problems going to sleep, nightmares, or sleep walking. The interview asked the child whether they had nightmares, or someone had told them they had shown signs of night terrors or sleep walking in the past six months. If they answered yes, they were asked more questions to gain further information.
At age 12, the children also had a face to face semi structured interview to find out whether they had any psychotic experiences. These experiences could be:
- Hallucinations: seeing or hearing something that wasn't there
- Delusions: for example feeling spied on, persecuted, that their thoughts were being read, or having delusions of grandeur
- Thought interference: feeling that someone was inserting thoughts into their mind or removing thoughts, or that other people could hear their thoughts
These types of experiences can be symptoms of serious mental health conditions such as schizophrenia, or can be triggered by physical illnesses or substance use.
The current study included the 6,796 children whose mothers had completed at least three questionnaires about sleep problems up to the age of nine, as well as the child interview about psychotic experiences at age 12 years.
The researchers then looked at whether children with sleep problems were more likely to report psychotic experiences. They took into account factors that might influence this association (confounders), including:
- family adversity during the pregnancy
- child IQ
- evidence of neurological problems
- mental health diagnoses (made at age seven)
- behavioural problems
What were the basic results?
According to the mothers' reports, between the ages of two-and-a-half and nine years, about three-quarters of children experienced at least some nightmares. About a fifth of children (20.7%) had regular nightmares reported in one time point in this period; 17% had regular nightmares reported at two time points, and 37% had regular nightmares reported at three or more time points.
At age 12, 36.2% reported at least one sleep problem (nightmares, night terrors, or sleep walking). At this age, 4.7% of children reported having had a psychotic experience that was judged not to be related to fever or substance use, and was not experienced when the child was falling asleep or waking up.
Children who were reported as experiencing regular nightmares at one time point between the ages of two-and-a-half and nine years, had higher increased odds of reporting psychotic experiences at age 12 than those who never had regular nightmares (odds ratio (OR) 1.16, 95% confidence interval (CI) 1.00 to 1.35).
The more persistent the nightmares were, the greater the increase in the odds. For example, those who were reported as having regular nightmares in at least three time periods between the ages of two and a half and nine years had a 56% increase in odds of a psychotic experience (OR 1.56).
Problems getting to sleep, or night waking between the ages of two and a half and nine years were not associated with psychotic experiences at age 12.
Children who reported any sleeping problems at the age of 12 (nightmares, night terrors, or sleep problems) were also at higher odds of reporting psychotic experiences than those without these problems (OR 3.62, 95% CI 2.57 to 5.11).
How did the researchers interpret the results?
The researchers conclude that nightmares and night terrors in childhood, but not other sleeping problems, are associated with reporting psychotic experiences at age 12 years.
The study has found that children who have regular nightmares between the ages of two-and-a-half and nine were more likely to report a psychotic experience (for example a hallucination or delusion) at age 12. While the study was relatively large and well designed, it does have limitations. As with all research findings, they ideally need to be confirmed by other studies.
Parents reading this article should not become unduly distressed by thinking that their child's nightmares mean they will develop psychosis later on in life. Firstly, while a lot of children experienced nightmares at some point up to the age of nine (almost three-quarters), very few reported having had a psychotic experience at age 12 (about one in twenty).
In addition, a single psychotic experience at age 12 would not mean that the child had a diagnosis of a psychotic disorder, or guarantee that they would go on to develop psychosis later on.
Thankfully, psychosis is uncommon, affecting around one in 100 people, and mostly at ages 15 or over. Cases among children under the age of 15 are rare.
Finally, as the authors themselves note, it is not possible to say whether nightmares are directly causing the increase in risk of psychotic experiences.
There are some other points to note:
- Although BBC News reports that night terrors were mostly experienced between the ages of three and seven years, night terrors in this study were only specifically assessed at age 12. At younger ages the researchers only asked about nightmares, problems getting to sleep, and night waking.
- The analyses of the link between sleep problems at age 12 (such as night terrors) and psychotic experiences at the same age is cross-sectional, and therefore it is not possible to say which factor came first - the sleep problem or the psychotic experience.
- The figure from these analyses (3.5 times increase in risk) is much higher than the increase in risk of having a psychotic experience age 12 after having nightmares from age two and a half to nine years which was only 16%.
- The study relies on mothers' reports of children's sleep problems up to the age of nine years and did not delve into the frequency or severity of sleep problems. It is possible that this may lead to some inaccuracies - for example, some children with sleep problems may be missed.
- Although the researchers tried to take into account some factors that may have influenced results (potential confounders), others may also be having an effect, such as total amount of sleep a child had.
Read more about common sleep problems in children.
If you child is experiencing persistent sleep problems then ask your GP for advice.
"Regular nightmares in childhood may be an early warning sign of psychotic disorders," BBC News reports. While many children have the occasional nightmare, a history of regular nightmares could be the sign of something more serious.
Links to Headlines
Childhood nightmares may point to looming health issues. BBC News, March 1 2014
Children who have lots of nightmares at risk of suffering hallucinations and psychosis as teenagers. Mail Online, March 2 2014
Childhood nightmares 'increase risk' of health problems. ITV News, March 1 2014
Children who have nightmares at greater risk of psychosis in later life. Daily Mirror, March 1 2014
Links to Science
Fisher HL, Lereya ST, Thompson A, et al. Childhood Parasomnias and Psychotic Experiences at Age 12 Years in a United Kingdom Birth Cohort. Sleep. Published online March 1 2014