Heading into Daylight Savings Time here in the Northeast, we are facing the darker, shorter days of winter. For many people that also means a dip in mood. And for a sub-group of those folks, the loss of daylight hours can trigger a depressive episode, which goes beyond a sad mood to include symptoms such as low energy, impaired concentration, trouble enjoying things, and hopelessness. This is referred to as Seasonal Affective Disorder (SAD).
In addition to therapy and antidepressants, we also use light therapy to treat and manage seasonal depression. This means sitting in front of a specialized light box, usually for 30 minutes in the mornings, starting in September and continuing into the Spring. Light therapy provides significant relief for people who live with SAD especially when it works to prevent the onset of an episode.
Light therapy works by re-setting peoples circadian rhythms our 24-hour internal clocks that respond to light and dark in the environment. The clock is triggered when receptor cells in the back of the eye send light/dark signals to the brain, which then sets off cascades of responses that drive our sleep/wake cycles and energy variations through the day.
People living with depression or bipolar disorder typically experience powerful disruptions to their circadian rhythms. During a depressive episode people often have a terrible time getting to sleep at night and staying awake during the day. Energy is set to low all the time. In bipolar disorder, during a manic episode, the energy is set to high at all times. During a manic episode, they feel no need to sleep they just keep going like the Energizer Bunny. Helping someone with mania get some sleep is a key step to shutting down the over-charged mood cycle.
Knowing the benefits of light therapy on depression, researchers have wondered whether dark therapy could calm mania. Could mimicking darkness help someone in a manic episode get better sleep, which would reduce their manic symptoms? In 2005, a researcher studied the effect of 14 hours of darkness per day on patients in the hospital with mania. The results were dramatically positive sleep was much better compared to a control group. However, enforcing 14 hours per day of darkness was clearly not tolerable for patients.
Since then, scientists have discovered a receptor in the retina (back of the eye) that they think of as a daylight receptor. It responds to a limited wavelength of light blue light in particular. When blue light hits this receptor, it sends signals to the brains master clock which then communicates the time to be awake message to the rest of the brain and the body. When this light is absent, the master clock signals the brain and body that the time to rest and sleep has arrived.
Knowing about this receptor has led to the creation of blue-light-blocking lenses, which prevent blue light from reaching the daylight receptor, so that the master clock stops signaling the brain that its time to wake up. Essentially these glasses create virtual darkness, which delivers nearly the same benefits as keeping people in the dark for 14 hours a day without the drawbacks of actually doing so.
Now, researchers in Norway have published a paper looking at the effects of virtual darkness on the sleep of people in a manic episode. (Henriksen, T. E. G., Grnli, J., Assmus, J., Fasmer, O. B., Schoeyen, H., Leskauskaite, I., Lund, A. (2020) Blue-blocking glasses as additive treatment for mania: Effects on actigraphy-derived sleep parameters. Journal of Sleep Research, 29(5). https://doi.org/10.1111/jsr.12984.) It was a small study, including twenty people who were hospitalized with mania. They divided patients into two groups. One group wore blue-light-blocking (BB) glasses from 6 PM to 8 AM, for seven nights, while the other group (the control group) wore clear glasses during that time. They removed the glasses only when they were in bed for sleep, with the lights out.
The results were encouraging. By the fifth night, the group in the BB group experienced more sleep time while in bed and more restful (less active) sleep than did those in the control group. The BB group also needed less sleep medication than did the people in the control group. The difference was noticeable and happened relatively quickly. More hours of darkness helped people in a manic episode sleep more efficiently and more soundly.
More studies need to be done on larger groups of people, and many more questions need to be explored, but the idea and the initial results are intriguing. Treating mania typically relies on powerful medications, which this would not replace, but can dark therapy play a role in helping symptoms resolve more quickly? Could it help people with bipolar disorder re-route or mitigate a potential manic episode if they use them as soon as they notice any sleep changes? Does it help us think about how to design living and sleep spaces for psychiatric inpatients experiencing manic symptoms?
For now, those of us living in four-season locations are heading into actual darkness for many more hours of our day. Looks like we have scientific explanations for feeling so tired as the days get shorter, especially until we adjust to the time change. For us, its not too soon to bring on the holiday lights! But those whose mania is commonly triggered by the holidays may hope for a pair of blue-light blockers in their stockings, instead.