Night­mares could be caused by too much sleep­ing, says study

More than nine hours of shut-eye dou­bles your risk of hav­ing a bad dream

The Star Early Edition - - NEWS - DAILY MAIL

IN OUR in­creas­ingly hec­tic lives, the chance to have a lie-in is a dream come true for many of us.

But sleep­ing for too long can ac­tu­ally cause night­mares, research sug­gests.

More than nine hours of shut-eye dou­bles your risk of hav­ing a bad dream com­pared to get­ting six hours, an Ox­ford Univer­sity study found.

The sci­en­tists said this is be­cause night­mares oc­cur dur­ing the rapid eye move­ment (REM) stage – a type of sleep that oc­curs in in­ter­vals dur­ing the sleep cy­cle – and so if you spend longer asleep you will go through more stages of REM.

The re­searchers sug­gested cut­ting down on sleep if you ex­pe­ri­ence a lot of night­mares – with seven to nine hours the op­ti­mum amount.

One of the study’s au­thors, Dr Bry­ony Sheaves, a research clin­i­cal psy­chol­o­gist at Ox­ford’s Sleep and Cir­ca­dian Neu­ro­science In­sti­tute, said: “The longer that we sleep, the more rapid eye move­ment (dream­ing sleep) we get. This means that the op­por­tu­nity for night­mares to oc­cur is greater.

“Some peo­ple may have no­ticed they have more dreams on days that they sleep in. If you are par­tic­u­larly prone to night­mares, this may be plac­ing you at a greater like­li­hood of hav­ing one.”

On the pop­u­lar the­ory that eat­ing cheese be­fore bed can give you bad dreams, Sheaves said: “Rather bor­ingly, no study that I have read has ac­tu­ally tested this.

“But I think it shows that peo­ple are fas­ci­nated about why we have night­mares.”

One in 20 peo­ple have a night­mare ev­ery week. Dur­ing the night, we spend much of the time in a deep, restora­tive sleep – also called nonREM sleep – when breath­ing is slower and mus­cles relaxed.

This is in­ter­spersed with in­ter­vals of REM, which oc­cur around ev­ery 90 min­utes, dur­ing which your eyes move rapidly un­der your eye­lids and you have spikes in brain ac­tiv­ity as you dream. REM in­ter­vals be­come longer later in the night, dom­i­nat­ing the sec­ond half of your sleep pe­riod.

The team ques­tioned 846 peo­ple aged 18 to 77. It found 45% had suf­fered at least one night­mare in the pre­vi­ous fort­night.

They ex­am­ined what af­fects the fre­quency of night­mares, look­ing at sleep du­ra­tion, al­co­hol con­sump­tion, ex­er­cise lev­els, worry, paranoia, hal­lu­ci­na­tions and de­per­son­al­i­sa­tion, a kind of psy­cho­log­i­cal shut­down caused by ex­pe­ri­enc­ing trauma.

Sleep du­ra­tion was the sec­ond big­gest risk fac­tor after wor­ry­ing. It is be­lieved the repet­i­tive thoughts trig­gered by anx­i­ety ‘feed’ neg­a­tive dream con­tent.

Paranoia, hal­lu­ci­na­tions and de­per­son­al­i­sa­tion were also found to be po­ten­tial trig­gers for bad dreams. But al­co­hol and a lack of ex­er­cise were found to have no ef­fect.

The re­sults were ad­justed to re­flect the dif­fer­ences in peo­ple’s stress lev­els and ex­pe­ri­ences of trauma.

The study, pub­lished in the jour­nal So­cial Psy­chi­a­try and Psy­chi­atric Epi­demi­ol­ogy, states: “We pre­dict that sta­bil­i­sa­tion of the sleep win­dow might thus lead to a re­duc­tion in night­mare oc­cur­rence for those with longer sleep du­ra­tions.”

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