Making light of depression…
Friday, November 24, 2023.
Here are some amazing new findings that may help you better manage your depression right now…
How humans are exposed to light over the day and night can increase depression risk by 30% — and decrease it by 20%.
People exposed to high amounts of light at night are at a 30 percent higher risk of depression, research finds.
Those who get high amounts of light during the day, though, have a 20% lower chance of depression.
While most people are aware that excess light at night can be damaging, fewer know about the benefits of daytime exposure to light.
How the study was conducted
The study included data from almost 87,000 humans which clearly underscored the health impact of light exposure on cognitive functioning.
Dr. Sean Cain, study co-author, emphasized the significance of their findings:
“Our findings will have a potentially huge societal impact.
Once people understand that their light exposure patterns have a powerful influence on their mental health, they can take some simple steps to optimize their well-being.
It’s about getting bright light in the day and darkness at night.”
The study used data from the UK Biobank, which is a massive database of health information. The researchers carefully recorded each study subjects’ exposure to light, as well as their sleep hygiene, and overall mental and physical health.
The results revealed that many psychiatric disorders were linked to light exposure.
In a breaking study recently published in Scientific Reports, Prof. Cain and his team carefully studied the effect of modern home lighting environments, and especially how they affected sleep.
The value of this study was it’s care in design.
For example, study subjects wore an individual light meter – called a spectrophotometer – that was developed with engineer Vineetha Kalavally, a co-author on the study, from the Monash University Malaysia campus.
It was a small clip-on device that can be worn on the upper body. It measures all wavelengths of light.
Most critically, it accurately measures how our body’s circadian clock perceives the light currently experienced.
This innovative wearable device measures the specific negative impacts of evening light exposure on a study subject’s circadian clock and sleep hygiene, including reduced production of the sleep-promoting hormone melatonin.
Will we someday be wearing light-measuring pins like these?
“We think eventually the device will be used in the treatment of depression, and sleep disorders, and basically feeding back to people this non-conscious information about what kind of light they’re in….
“It’s almost like a third eye, so it tells you something that you’re not consciously aware of, because this photoreceptor system, it’s very ancient; it feeds into old, subcortical areas of the brain,” Prof. Cain explained.
Nearly half of the homes in the study had unhealthy enough light to suppress melatonin production by a whopping 50%! But the study also found that the effect of artificial light on individuals varied greatly – by as much as 50-fold – and was difficult to predict.
Dr. Phillips and Prof. Cain were just awarded an ARC Discovery Project grant to investigate how these individual differences in sensitivity to light affect shift workers.
The problem of night light…
A human’s risk of developing bipolar disorder, anxiety, or even self-harm were all linked to increased exposure to light at night by the researchers in this study.
Light has an upside during the day. Light exposure during the day is a good thing, it measurably decreases the risk of psychosis.
Dr. Cain discussed the implication of these findings for different humand settings and lifestyles::
“And our findings were consistent when accounting for shiftwork, sleep, urban versus rural living and cardio-metabolic health.”
The confusion of light and time…
“Yin and yang is all about the balance of light and darkness, and it’s important,” Prof. Cain says. “That’s how we organise our physiology.”
Artificial light disrupts this rhythm, disturbing our sleep and affecting our health. “We’re confusing this system, and having more chronic illness as a result,” he says.
The problem of progress vs. human evolution…
“We now live in this kind of twilight zone,” Prof. Cain says. “When we evolved, it was very bright in the day, with quick transitions between darkness and light.
But now we live indoors, so we’re not out in bright daylight so much. And at night, we’re not in darkness anymore.
We’re living in that in-between region, between darkness and light now. And that’s where you see the big inter-individual differences.”
On nights when humans had increased exposure to light in the evening, they were also found to have more trouble getting to sleep, the study found.
The problem of blue light
Blue light is particularly disruptive to our circadian rhythms.
“So while we’ve been doing the right thing for the environment by changing to energy-efficient lights, we’ve likely been having a negative impact on our sleep, mood and general heath. In time, we may find that those negative effects were much more costly than the energy savings.” said Dr. Phillips.
Let’s talk choosing lighting ecology. Choose LED lights that are yellow and warm, instead of cool and blue for example. Or another option is installing dimmer switches to decrease the volume of light in the house before bedtime.
Watching movies on a TV screen on a dim setting, rather than a bright computer on your lap, can also curb the damaging effect of their blue light emissions.
“If you look at all of human evolutionary history as a 24-hour day, we’ve had control of our lights for the last 77 seconds of that day,” Prof. Cain explained. “We did not evolve to control the light, and our bodies don’t expect light at the wrong times. And when they get it, the whole system of these clocks in our bodies gets messed-up, and we’re all a little bit more tired, a little bit more miserable.”
The problem with the lighting revolution…
“While we’ve been doing the right thing for the environment by changing to energy-efficient lights, we’ve likely been having a negative impact on our sleep, mood and general health.”
“Once you disrupt these rhythms, you can have countless chronic, negative health effects,” he says.
“Your weaknesses will start to be exposed. So, if you’re someone who is more likely to develop cardiovascular disease, that might show up. If you’re more likely to have diabetes or metabolic disease, they will show up. In animal models, and even in humans, you can create essentially almost any chronic disease by disrupting sleep and circadian rhythms.”
Wow! Researchers discovered that even the practice of daylight saving time disrupts the natural rhythm, and can have health consequences.
“It artificially moves us away from the natural light-dark cycle,” explained study co-author Dr. Phillips says. “There are some interesting studies on people who live on the eastern versus the western side of time zones, which is similar to living in standard versus daylight saving time. People on the western edge of time zones have more health problems.”
Modern industrialised societies have created an environment for which humans were not designed…
During most of human evolution we were outside, and consequently exposed to high levels of light during the day and once inside, exposed to very low levels of light at night.
The brain has become comfortable with this cycle, and naturally functions best in this particular protocol.
Unfortunately, the contrast between day and night has become more blurred, which confuses our bodies, Dr. Cain observed:
“Humans today challenge this biology, spending around 90% of the day indoors under electric lighting which is too dim during the day and too bright at night compared to natural light and dark cycles.
It is confusing our bodies and making us unwell.”
The advice for mental health is straightforward: when the sun is out, get as much as you healthily can, after it goes down keep your environment as dark as you possibly can.
Let’s let science light our way.
Be well, stay kind, and Godspeed!
RESEARCH:
Burns, A.C., Windred, D.P., Rutter, M.K. et al. Day and night light exposure are associated with psychiatric disorders: an objective light study in >85,000 people. Nat. Mental Health 1, 853–862 (2023). https://doi.org/10.1038/s44220-023-00135-8
