People exposed to light at night (artificial lighting) are at increased risk of psychiatric disorders such as anxiety, bipolar disorder, and post-traumatic stress disorder, as well as self-harm. In contrast, people who receive natural daylight benefit from a non-pharmacological process to reduce the risk of psychosis. These are the main conclusions of a study carried out with the participation of 87,000 people, the largest in this field of research to date. The results of this work led by experts from the Turner Institute of Mental and Brain Health at Monsah University, in Melbourne (Australia), have been published in the journal Nature Mental Health.
The figures presented in this pioneering research are truly remarkable. Thus, in people exposed to large amounts of light during the night the risk of depression increased by 30%, while those who were exposed to large amounts of light during the day reduced their risk of depression by 20%. The authors indicate that the negative effects of exposure to artificial lighting were observed in similar proportions for self-injurious behavior, psychosis, bipolar disorder, generalized anxiety disorder, and post-traumatic stress disorder.
Monsah University states, in a release note on the results of this study, that “these findings indicate that the simple practice of avoiding light at night and seeking brighter light during the day could be an effective, non-pharmacological means.” to reduce serious mental health problems.
Sean W. Cain, associate professor at Monash University and lead author of the study, believes that “once people understand that their light exposure patterns have a powerful influence on their mental health, they can take some simple steps to optimize your well being”. “It is about obtaining bright light during the day and darkness during the night. Our findings will have a potentially enormous social impact,” says Professor Cain in statements released by his university.
The study is based on the clinical data of 86,772 people, participants – with confidential identity – of the United Kingdom Biobank. Medical records were examined to determine the study subjects’ light exposure, sleep, physical activity, and mental health. The results are extrapolated based on various demographic factors, physical activity, season and employment. The average age of the participants was 62.4 years and 57% of the total analyzed were women.
“And our findings were consistent when taking into account shift work, sleep, urban versus rural living, and cardiometabolic health,” says the study’s lead author.
Humans in modern, industrialized times have literally turned our biological systems upside down. According to Associate Professor Cain, our brains evolved to function best in bright light during the day and almost no light at night.
“Today, humans defy this biology and spend about 90% of the day indoors under electric lighting that is too dim during the day and too bright at night compared to natural light-dark cycles. This it confuses our bodies and makes us feel bad,” says the lead author of the study.
