Lunar phase and stroke-like symptoms

Behind the Headlines

Tuesday August 19 2008

Belief that the moon affects the human mind is persistent

“The full moon may cause people to suffer symptoms similar to those of a stroke”, the Daily Express reports. It says that on nights with a full moon, the number of people treated for “mystery numbness and coordination loss” rises significantly. A study found that about 129 of 7,200 people (2%) admitted to a stroke unit over a 14-year period had medically unexplained stroke symptoms (MUSS). When the researchers compared occurrence of MUSS to lunar patterns, they found that they peaked during the full moon.

The study looked for an association between the lunar cycle and admissions for stroke and MUSS. The moon has long been associated with changes in human mood and behaviour, and the findings here may confirm that MUSS has a ‘psychiatric’ component. However, studies of this type cannot prove a causal relationship and more research is needed to establish what is happening. In the meantime, awareness that during the full moon MUSS may occur more commonly in women under 65 years, along with appropriate investigations, may speed up accurate diagnosis and help avoid unnecessary emergency treatments. Anyone who believes they are having stroke symptoms should seek immediate care and dial 999, regardless of the lunar phase.

Where did the story come from?

Dr Faheem Ahmad and colleagues from the University of Glasgow Medical School carried out the study. No sources of funding are mentioned. The study was published in the (peer-reviewed) Journal of Psychosomatic Research.

What kind of scientific study was this?

This was a cross-sectional analysis of data from a case series, of more than 7,200 patients admitted to a stroke unit over 15 years.

There is a persistent belief that the phases of the moon have an influence on human health and behaviour, though the evidence for this seems inconclusive. In this study, the researchers were interested in exploring whether lunar phases have any effect on cerebrovascular disease, but in particular on the numbers of people presenting with a stroke and those presenting with MUSS. A diagnosis of MUSS is made if there is no sign of organic disease and comprehensive investigations are negative. It is usually considered to be a ‘psychiatric’ condition rather than ‘medical’ and the researchers theory was that admissions would increase on full moon days.

To investigate this, they conducted a case series study, analysing records of all admissions to the Western Infirmary Acute Stroke Unit between January 1993 and September 2006. People are admitted to this unit when they present with a suspected stroke, and undergo investigations (clinical, biochemical and radiological) to confirm their diagnosis. The researchers divided the lunar month into recognised quarters: new moon, first quarter, full moon and last quarter. They then assessed whether the phase of the moon had any effect on the number of people admitted for MUSS. They also looked at whether there was a link between admissions and season and whether significant dates such as Friday the 13th and Halloween had any effect. In a later step, they analysed the genders separately and also considered the patterns in people under 65 years and those over 65 years.

What were the results of the study?

The researchers reported that during the 167 lunar cycles that occurred during their study period, some 7,219 people were admitted to the stroke unit. Of these, 6,845 had a diagnosis of stroke while 129 had a first presentation of MUSS.

No association was found between the phases of the moon and a diagnosis of stroke. However, there was an association between admission for MUSS and the full moon. About 36% of MUSS (47 diagnoses out of 129), occurred when there was a full moon – more than the 25% expected in this quarter of the lunar cycle (p=0.023). MUSS was also linked with season, with more admissions during autumn and winter. Neither MUSS nor stroke were linked to ‘culturally significant dates’, Halloween or Friday the 13th). Women and patients under 65 years experienced more MUSS.

What interpretations did the researchers draw from these results?

These results, suggest the researchers ‘add credence to the concept of lunar stimuli influencing human health behaviours’. They go on to say that they believe their data is robust and that the link between MUSS and phases of the moon is a true one.

What does the NHS Knowledge Service make of this study?

This case series study suggests that medically unexplained stroke symptoms (MUSS) – considered to be ‘psychiatric’ rather than ‘medical’ – may be linked to the phases of the moon. The researchers mention some possible psychological and biological explanations for the link, such as variations in gravitational pull, but say that ‘the underlying mechanism remains elusive’. Some points of significance:

  • The researchers assessed the psychological association further by looking at the culturally significant dates Halloween and Friday the 13th, but were unable to find a relationship with these days. However, these were annual, rather than monthly events and no cases of MUSS occurred on these days, so this may have been a chance negative finding.
  • Studies of this design (i.e. cross sectional), cannot prove causation. The researchers acknowledge this and call for further work to corroborate their findings, in particular through prospective studies that could go some way to identifying the physical and psychological determinants of MUSS.
  • The researchers acknowledge that some patients who were labelled as having MUSS may have had an undetected underlying organic disease. If this were the case, the association with MUSS would have been reduced.

These findings will be of interest to the scientific and medical communities. The moon has long been associated with human emotion and mood, though the evidence for this is inconclusive. This study suggests there may be a link between the lunar cycle and admissions for MUSS.

The researchers suggest that the findings could aid in staff training and service planning and they report that thrombolytic therapy is often given mistakenly to MUSS patients. The researchers suggest that an awareness that during the full moon MUSS may occur more commonly in women under 65 years may speed up accurate diagnosis and help avoid unnecessary emergency treatments. Given that MUSS is only diagnosed when other reasons cannot be found for the symptoms, perhaps of more importance is the accurate diagnosis with imaging of anyone presenting with stroke symptoms. Investigations should aim to identify people who really need treatment.

It is crucial that anybody experiencing stroke symptoms seeks immediate medical attention, as the sooner that treatment is given, the better the chances of a good recovery.

Analysis by Bazian

Edited by NHS Choices

Links to the headlines

Fake stroke effect linked to full moon. Daily Express, August 19 2008

Links to the science

Ahmad F, Quinn TJ, Dawson J, and Walters M. A link between lunar phase and medically unexplained stroke symptoms: An unearthly influence? Journal of Psychosomatic Research 2008; 65: 131-133

Further readingWardlaw JM, del Zoppo G, Yamaguchi T, Berge E. Thrombolysis for acute ischaemic stroke. Cochrane Database Syst Rev 2003, Issue 3


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