The largest study on light exposure that examines its impact on mental health found that excessive exposure at night increases the risk for psychiatric disorders such as anxiety, bipolar and post-traumatic stress disorder (PTSD) severity as well as self-harm.
The study, led by Sean Cain, from the Monash School of Psychological Sciences, found that when people are exposed to high amounts of light at night, the risk of depression increases by 30%. Similar patterns of results were seen for self-harm behaviour, psychosis, bipolar disorder, generalised anxiety disorder, and PTSD, a press statement by Monash University explains. Furthermore, the study, involving 87,700 participants, showed that more exposure to daytime light could be a non-pharmacological means for reducing psychosis risk.
These findings show that the simple lifestyle change of avoiding light at night and seeking brighter light during the day could be effective in reducing serious mental health issues. “Once people understand that their light exposure patterns have a powerful influence on their mental health, they can take some simple steps to optimise their wellbeing. It’s about getting bright light in the day and darkness at night,” Cain said in the press statement. The findings were published in the journal Nature Mental Health.
Cain noted that today people are spending most of their day indoors under electric lighting which is too dim during the day and too bright at night instead of natural light and dark cycles. “It is confusing our bodies and making us unwell,” he added.
This study reiterates the findings of a 2020 study by the University of Michigan, which showed that morning light therapy can be used as an effective treatment method for depression and has been effective in reducing symptoms of chronic pain. However, evening light can suppress melatonin and become a health issue over time.
Both studies suggest that it’s important to understand the positive and negative impacts of exposure to light. Maintaining work and sleep schedules to avoid excessive exposure to artificial light at night and taking time out daily to soak in the morning light could go a long way in keeping health risks at bay.