When it comes to reviewing the literature, it is very apparent that mental health disorders are more often than not tied to poor sleep quality and a disrupted circadian rhythm.
Our circadian rhythms are tied to light and dark cycles which means that the wrong type of light at the wrong time of day or night can disrupt our circadian rhythms and negatively impact our sleep.
Exposure to artificial blue and green light in the 400-550nm range after sunset tells our brains to suppress melatonin which makes it very difficult to get good quality restorative sleep.
A healthy sleep cycle according to Harvard Health is one that lasts 90 minutes and goes through light, REM and deep phases. These phases will then release the appropriate levels of neurotransmitters needed for mental wellbeing (1)
Lack of natural light exposure is also disrupting our circadian rhythms as we are missing out on important light messages to the brain through non-visual receptors in the eye called ipRGCs and melanopsin. Sunlight also releasees serotonin and dopamine which helps elevate mood and help us sleep later in the evening. Minimising sun exposure either consciously or sub-consciously combined with increasing our time spent under artificial light is disrupting our body clocks, wrecking our sleep and leading to steep rises in mental illness across the world.
Attention Deficit Hyperactive Disorder (ADHD)
According to the CDC in 2015 one in ten children between the ages of 5-17 are now diagnosed with ADHD (2).
Numerous studies have been released that show that a disrupted circadian rhythm and poor sleep often go hand in hand with ADHD sufferers. This has also been seen in studies that show poor sleep can mimic symptoms of ADHD in normal children. Lack of sleep in normal children often results in poor attention span and lack of focus the next day. It is also very clear in the literature that poor sleep can intensify symptoms of ADHD but on the flip side improving their sleep and circadian rhythms can improve their disorder (3).
Studies have been carried out with children with ADHA by getting them to wear blue light blocking glasses in the evenings before bed. The results showed a statistically significant decrease in anxiety and improved sleep quality. They also went to bed earlier when wearing the blue light blocking glasses (4).
This type of study shows that sleep and disrupted circadian rhythms have a huge role to play in children with ADHD. A disrupted circadian clock and poor sleep is tied to exposure to sleep blue and green light after, lack of sunlight during the day and overexposure to blue light during the day from artificial sources.
Anxiety and Depression
Studies using different methods and populations estimate that 65% to 90% of adult patients with major depression, and about 90% of children with this disorder, experience some kind of sleep problem (5)
Anxiety and depression are on the rise and we are seeing even more cases in children. Mental Health America states a 37% increase of reported mood disorder symptoms among young people over a 9-year period (6).
Blue light exposure is linked to mood disorders which include disruption of brain plasticity, neurotransmission, hormone secretion and gene expression.
Lack of sleep caused by exposure of blue light after dark had been shown in studies to mess up the cortisol cycle. Cortisol is meant to be highest in the mornings and lowest at night. But disrupted sleep and circadian ryhthms can reverse this cycle which can then increase your susceptibility to anxiety, stress or depression (7).
Anxiety and depression can be regulated through correct circadian cycles of dopamine and serotonin. Sunlight increases these two neurotransmitters which means that missing out on morning sunlight could be increasing your risk of anxiety and depression. Being inside at the office or at home exposing yourself to artificial blue light disrupts your sleep but missing out on sunlight at the same time is as detrimental to your mental health.
Serotonin also has another function which is to react with tryptophan in the gut later in the evening. Then in the absence of blue and green light it creates melatonin which helps us sleep and also is a potent antioxidant needed to help clear waste products from our body and also fight inflammation. Higher levels of inflammation have been linked to metabolic and neurological diseases.
Harvard Health has also shown that you are four times more likely to develop depression if you have a sleep issue. They have also shown that people who are depressed almost always have a sleep issue.
Seasonal Affective Disorder (S.A.D)
S.A.D is personified by feelings of low mood in winter months. Incidences of S.A.D can be correlated to long periods of no sun exposure which is why its typically common in winter months.
During these months we are often exposed to even more artificial blue light as days shorten and we stay inside due to the cold weather. This is a double whammy on our mental health as we are disrupting our body clocks through excess exposure to artificial light but also missing out of sunlight which we know is essential for elevated mood, improved mental wellbeing and better sleep.
The best two ways to counteract the negative effects of S.A.D is to get sunlight during the day. It does not matter if it’s cold or cloudy, just being outside during the day allowing your skin and eyes to absorb natural light which is enough to increase dopamine and serotonin production. The second way is to then allow these neurotransmitters to do their job post sunset by blocking blue and green light from artificial sources. Wearing 100% blue/green light blocking glasses is a great way to improve sleep and reduce symptoms of S.A.D.
Blue light from S.A.D lamps have been shown in the literature to improve mood. However, this is an unnatural short term fix that if administered over long periods could lead to circadian disruption, poor sleep and eventually other related mental health issues such as those described in this article.
It is hard in the Northern Hemisphere to get outside during winter months. Daylight savings and the reduction in actual day time means we often arrive at work when its dark, work under artificial light all day and then return home after sunset. Its important that if this sounds like your winter days Monday to Friday you get outside for natural light breaks whenever you can.
Thank you so much for reading all the way through this article. Mental health is on the rise and we need to ensure we fight against it. Many people will need your support as we head into the Northern Hemisphere winter so make sure you offer compassion, love and words of positivity to them to help them during these hard time.
- CDC, 2015. Percentage of Children Aged 5–17 Years with Diagnosed Attention Deficit/Hyperactivity Disorder (ADHD). Morbidity and Mortality Weekly Report (MMWR). October 16, 2015 / 64(40);1156.
- Cortese, S., 2015. Sleep and ADHD: What We Know and What We Do Not Know. Sleep Medicine, 16(1), pp.5-6.