The surprising type of light that can change the way we feel

Loading

For the new study, Cain and co-author Malisa Burge exposed 35 participants to light that was the same brightness, but either blue-enriched on blue-depleted while they reflected on whether positive or negative words, such as whether they were a “good”, “terrible” or “unloved” person. Two weeks later, the participants, whose average age was 20, repeated the exercise under the other type of light.

When they were under light with more blue wavelengths in it, they could reject the negative words more easily than when they were under the blue-depleted light.

“They could shut down negative thoughts more easily,” Cain says. “The amount of blue in a light actually changed how people thought of themselves.”

Blue light is important for our health in various ways and helps to strengthen our internal clocks. “We just need to get it in the day, and the best way to do that is to go out and get natural light,” Cain says. “There’s tons of blue light in outdoor light.”

The issue is that blue light and brightly lit environments at night suppress melatonin production and can disrupt our circadian rhythm. This can have serious implications not only for the quality of our sleep but for our health, making us more vulnerable to chronic diseases such as diabetes and affecting our lifespan by up to five years.

He adds that the study “goes a long way” in explaining our relationship with light, why we are so tied to our screens and want brightly lit indoor and outdoor environments at night: “It makes us more positive about ourselves!”

It’s a short-term gain for long-term pain.

“It ultimately makes us unhealthy because we are drawn like moths to a flame on an unconscious level because it makes us happier and more positive,” Cain says. “And so without knowing it consciously, we’re consuming this light at night which then disrupts our clocks and disrupts our sleep and makes us more likely to have long-term mental health problems.”

Loading

And the more disrupted our sleep, the worse our mood and the stronger the drive to feel better: “It’s this kind of downward spiral.”

Christopher Gordon, professor of sleep health at Woolcock Institute of Medical Research, says the study contributes to a larger body of work trying to understand how light can help with a spectrum of mental health issues, from emotional regulation to clinical depression.

“You could potentially put these [blue] lights into LEDs which can go into offices and [the] home environment and provide therapeutic light,” he says. “I think in the future, light will be used as a health intervention, but it will be a specific spectral type of lighting.”

As the sun goes down, our lights should be dimmed and red, where possible, as the cells in our eyes aren’t “excited by red light”. This allows our bodies to wind down and prepare for sleep.

But we have to consciously go against our biological draw towards brighter lights, blue screen lights and the hit they provide.

“If you just do what feels ‘natural’, it’s going to be doing this unnatural thing of seeking light,” Cain says. “Because in our natural history, all light we could get was good light. Now that is not the case because we have control of our lighting environments, and we have light-emitting devices.

“Even though it makes you feel good in the moment, it’s not a good long-term solution to feeling better.”

Make the most of your health, relationships, fitness and nutrition with our Live Well newsletter. Get it in your inbox every Monday.