Largest study ever on light exposure proves impact on mental health

The world’s largest study on light exposure and its impact on mental health, with nearly 87,000 participants, found that increased exposure to light at night increases the risk of psychiatric disorders such as anxiety, the severity of bipolar disorder and PTSD, and self-harm. Importantly, the study also found that increased daytime light exposure may act as a non-pharmacological way to reduce the risk of psychosis.

In people exposed to large amounts of light at night, the risk of depression increased by 30%, while those exposed to large amounts of light during the day reduced their risk of depression by 20%. Similar results were observed for self-harming behaviors, psychosis, bipolar disorder, generalized anxiety disorder, and PTSD. 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 way to reduce serious mental health problems.

The study, led by Associate Professor Sean Cain, from the Monash School of Psychological Sciences and the Turner Institute for Brain and Mental Health in Melbourne, Australia, is published today in the journal Natural mental health.

“Our findings will have a potentially huge societal impact,” said Associate Professor Cain. “Once people understand that their patterns of light exposure have a powerful influence on their mental health, they can take some simple steps to optimize their well-being. It’s all about getting bright light during the day and darkness at night.”

All 86,772 study participants came from the UK Biobank and were screened for their light exposure, sleep, physical activity and mental health. Associate Professor Cain said the impact of nighttime light exposure was also independent of demographics, physical activity, season and employment.

“And our results were consistent when accounting for shift work, sleep, urban versus rural living, and cardio-metabolic health,” he said.

Humans in modern and industrialized times have literally disrupted our biological systems. According to Associate Professor Cain, our brains evolved to work best with bright light during the day and then with almost no light at night.

“Humans today are challenging this biology, spending approximately 90% of the day indoors under electric lighting that is too dim during the day and too bright at night compared to natural light and light cycles. “darkness. It disrupts our bodies and makes us sick,” he said. said.