Sleep problems and schizophrenia may have common roots, raising hopes that the devastating mental disorder could be improved by helping patients overcome insomnia.
In a new study monitoring the sleep and circadian rhythms of people with schizophrenia, researchers found many more sleep problems in the schizophrenia patients versus mentally healthy controls. Combined with other research linking a schizophrenia-related gene with sleep-wake cycles in mice, the findings suggest that sleep and schizophrenia are more closely intertwined than ever realized, study researcher Russell Foster told LiveScience.
"We've been thinking of sleep disruption as one of the genetic, developmental and environmental contributors to the development of these appalling conditions," said Foster, who is a circadian and visual neuroscientist at the University of Oxford.
Sleep and schizophrenia
Clinicians have long recognized that schizophrenia and disturbed sleep go hand-in-hand — about 80 percent of schizophrenia patients have sleep problems, Foster said. But these problems have usually been dismissed as a medication side effect or as the result of social isolation and unemployment in people with the disorder. [10 Stigmatized Health Disorders]
"That didn't make too much sense to me," Foster said.
Many mental disorders come with a side of sleep problems, including depression and bipolar disorder, Foster and his colleagues realized. And intriguingly, genes linked to circadian rhythm — the neural and biological system that attunes our sleep-wake cycles to dark and light — may play a role in some of these disorders. A gene called SNAP25, for example, is known to be important in the circadian system. SNAP25 abnormalities have also been linked to schizophrenia.
Studying sleep
In order to take a systematic look at the circadian rhythms of people with schizophrenia, Foster and his colleagues recruited 20 people with the disease and instructed them to wear movement-detecting wristwatches for six weeks. The amount of motion detected can be analyzed to determine whether the person is asleep or awake, given the vastly different movement patterns between the two states.
The patients also filled out questionnaires and kept daily diaries of their sleep and activities. All of the patients were taking medication to control their symptoms, and they had all been stable on that medication for at least three months. Finally, the patients gave 48 hours work of urine samples to be tested for melatonin, a hormone that regulates sleep (melatonin makes a person sleepy).
For comparison, the researchers asked another 21 mentally healthy but unemployed adults to wear the same watches and keep the same records as the people with schizophrenia. Unemployed people were chosen because the patients with schizophrenia were all unemployed, and employment can alter sleep patterns by forcing people to get up with an alarm clock.
The insomnia of schizophrenia
A comparison between the two groups revealed that while unemployed people keep fairly regular sleep hours, every person with schizophrenia in the sample had a sleep problem.
"What became very clear is that they are massively and completely disrupted," Foster said.
This disruption did not follow a common pattern. Some people with schizophrenia went to bed late and got up late, with their melatonin release patterns delayed by several hours compared with healthy counterparts. Others would get up later and later every day, their circadian rhythms "drifting" through time. The most severely affected showed no normal 24-hour sleep-wake pattern at all. They'd alternate sleep and activity throughout the day and night. [Are You Getting Enough Sleep? (Infographic)]
The results weren't the result of unemployment, because the unemployed-but-healthy group did not show them. Nor could they be linked to any specific medication or dosage level, Foster said.
These results, published in the April issue of the British Journal of Psychiatry, mesh with another recent study by Foster's team, this one published in January in the journal Current Biology. In that study, the researchers examined the sleep-wake behaviors of mice with a SNAP25 gene mutation mimicking schizophrenia.
"Quite amazingly those mice show a [sleep] pattern which is just like the patients with schizophrenia," Foster said.
In mice, the problem arises in broken communication between the cells in the brain that set the body's "clock" and the neurons that then go on to match the body's physiology to that clock. If the same is true of humans with schizophrenia, Foster said, it's possible that by easing sleep troubles, you could also decrease schizophrenia symptoms. This could be done with light therapy, melatonin treatment or even cognitive-behavioral therapy, a kind of talk therapy that helps patients change behaviors such as when and how they fall asleep.
"We want to look at individuals with full-blown conditions, bipolar, psychosis, schizophrenia, to try to develop therapies which will stabilize sleep-wake," Foster said. "And at the same time look precisely at the impact we're having on their physiology."
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