Out of the blue? How the colour of light could be used to treat mental illness | Medical research
AAt first glance, the psychiatric ward in Trondheim looks a lot like any other unit caring for patients in acute mental distress. But as night falls, filters come down on the windows and the lights transform into a soft amber glow. By removing blue wavelengths that interfere with the body’s internal clock, doctors are testing an unusual idea here: The very design of the room could become a form of treatment.
Light is the primary signal regulating the body’s circadian rhythm – the approximately 24-hour biological clock that governs sleep and many other bodily processes. Growing evidence links circadian disruption to conditions such as depression, cardiovascular disease, and dementia, and disruptions in sleep-wake cycles are a long-recognized feature of mental illness, particularly bipolar disorder.
“More and more anecdotal and experimental evidence suggests that bipolar people are very sensitive to light, which may be unhelpful to them in terms of seasonal mood swings and manic relapses with the lengthening days in spring,” said Professor Daniel Smith, a psychiatrist at the University of Edinburgh who runs the UK Circadian Mental Health Network and was not involved in the study.
“The general idea is that exposure to evening light, in particular, delays the clock phase, suppresses melatonin, and because of that, people fall asleep later and probably don’t sleep as well,” he said. Poor sleep can then destabilize daily patterns of rest and activity, which, in vulnerable individuals, can trigger mood episodes.
For this reason, there is growing interest in using light to stabilize people’s bodily rhythms and, therefore, improve their symptoms – although relatively few large clinical studies have tested this idea.
When doctors in Trondheim began planning a new psychiatric unit, it offered a rare opportunity to test the idea in practice. The team installed a dynamic lighting system and automated shades designed to remove blue wavelengths from the service in the evening.
“Many patients with severe mental illness suffer from circadian disruption and we wanted to see if we could do something by changing the lighting system,” said Håvard Kallestad, a researcher and consultant psychologist at St Olavs Hospital and the Norwegian University of Science and Technology, who led the research.
The unit was divided into two identical halves with the same layout, staff and facilities. The only difference was the evening light environment. In one room, the lighting changes from 6 p.m. to suppress blue wavelengths – the type to which the circadian system is most sensitive – while blinds and filters block similar light from windows and screens. In the other, patients benefit from standard hospital lighting.
A previous study showed that healthy volunteers staying in the ward had changes in melatonin secretion, sleep patterns and alertness.
The team has now tested the approach in 476 patients admitted to short-term psychiatric intensive care suffering from psychosis, mania, severe depression and suicidal thoughts. Half were assigned to serve with blue-depleted lighting and the other half to standard lighting.
The research, presented at a recent meeting of the International Society for Bipolar Disorders and published in PLOS Medicine, found that although overall length of stay was similar – typically three or four days – patients treated in the circadian-friendly ward had greater clinical improvement and less aggressive behavior.
Kallestad said: “We found that there was an additional gain to being in this blue light environment in terms of the number of patients who were in a mild disease state upon discharge and the level of improvement that patients had upon admission.
“Just by modifying the light spectrum, we can improve the quality of treatment, and we have observed this in particular with aggressive behavior. »
Aggression and agitation are common challenges in acute psychiatric wards, where studies suggest that the occurrence of aggressive behavior varies between 8% and 76% of cases, posing risks to both patients and staff.
Smith said: “I think the discovery of aggression alone is really important, because it makes it a little easier to deal with these people. »
Professor Derk-Jan Dijk, a sleep and circadian researcher at the University of Surrey, who was not involved in the study, said one of the most interesting aspects was that the intervention was embedded within the service itself. “The burden on participants is virtually zero: they do not need to sit in front of a light box or wear anti-blue glasses.”
Such approaches could be implemented at scale by designing indoor environments better suited to human biology, he added. “They confirm that the effects of light on the brain are not limited to the biological clock or sleep. They also influence mood and alertness.”
Researchers are also studying whether circadian lighting could benefit people beyond psychiatric wards. The UK’s National Institute for Health and Care Research has appealed for funding for trials to see if it could help ‘reset’ the internal clocks of people living in care homes and reduce dementia-related behavioral problems.
Professor Anthony Gordon, Director of the NIHR Health Technology Assessment Program, said: “This is about whether we can use light therapy to reduce anxiety, improve sleep and provide a cost-effective, drug-free way to improve quality of life in residential care settings across the country. »
Professor Colleen McClung, a neuroscientist at the University of Pittsburgh who last month published a study on circadian rhythms in psychiatric disorders, said such approaches could become increasingly personalized: “For example, if someone has delayed circadian rhythms, light therapy in the morning will advance the rhythms. If a person’s rhythms are advanced, light therapy in the afternoon or evening could be beneficial.”
Wearable devices that track sleep and activity patterns could help identify these individual differences and guide treatment, she said.
