In the largest study ever conducted on the mental health impacts of light exposure, researchers have found that artificial light elevates the risk for psychiatric disorders.
The investigation involved nearly 87,000 participants and was led by Professor Sean Cain of the Monash School of Psychological Sciences.
“Circadian rhythm disturbance is a common feature of many psychiatric disorders. Light is the primary input to the circadian clock, with daytime light strengthening rhythms and night-time light disrupting them,” wrote the study authors.
“Therefore, habitual light exposure may represent an environmental risk factor for susceptibility to psychiatric disorders.”
The comprehensive research demonstrates that artificial light exposure, particularly at night, is linked with a greater chance of conditions such as anxiety, bipolar disorder, PTSD, and an increased risk of self-harm.
The study also revealed a 30% increase in the risk of depression for individuals with high nighttime light exposure.
Conversely, the study also sheds light on the positive effects of substantial daytime light exposure.
The findings suggest that ample daylight exposure can reduce the risk of depression by 20 percent, and is also associated with a diminished risk of other mental health issues.
In other words, exposure to daylight is a simple, non-medicinal way to help protect yourself from mental health challenges.
“Our findings will have a potentially huge societal impact,” said Professor Cain. “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 wellbeing. It’s about getting bright light in the day and darkness at night.”
The research was focused on 86,772 participants from the UK Biobank.
Among the data collected from these individuals, the experts analyzed their exposure to light, sleep patterns, levels of physical activity, and mental health status.
It is crucial to note that the observed impact of nighttime light exposure on mental health remained consistent across various demographics and was not influenced by physical activity levels, season, or employment status.
“Our findings were consistent when accounting for shiftwork, sleep, urban versus rural living and cardio-metabolic health.”
Professor Cain pointed out the disjunction between modern human lifestyles and our biological systems, suggesting that contemporary living conditions might be detrimental to our mental health.
He noted that human brains evolved under conditions of bright daylight exposure followed by almost complete darkness at night.
“Humans today challenge this biology, spending around 90 percent 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 study is published in the journal Nature Mental Health.
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