A link has been made between exposure to light and its effect on mental health - and the findings have the potential for huge impacts on society.

A study at Monash University involving a huge 87000 participants found increased exposure to light at night increases a person’s risk for psychiatric disorders such as anxiety, bipolar and PTSD severity as well as self-harm. 

It seems, as humans in modern, industrialised times, we have literally turned our biological systems upside down.

 But there is an easy fix, as the study also found that increasing exposure to daytime light can act as a non-pharmacological means for reducing psychosis risk.

The findings were published in the journal, Nature Mental Health, last week and research led by Associate Professor Sean Cain from the Monash School of Psychological Sciences.

“Our findings will have a potentially huge societal impact,” said Associate 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 optimise their wellbeing. It’s about getting bright light in the day and darkness at night.”

Professor Cain said findings were consistent when accounting for shiftwork, sleep, urban versus rural living and cardio-metabolic health. According to Associate Professor Cain, our brains evolved to work best with bright light in the day and then with almost no light at night.

 In those exposed to high amounts of light at night, the risk of depression increased by 30 per cent – while those who were exposed to high amounts of light during the day reduced their risk of depression by 20 per cent. Similar patterns of results were seen for self-harm behaviour, psychosis, bipolar disorder, Generalised Anxiety Disorder, and PTSD.  

Associate Professor Cain said the impact of night light exposure was also independent of demographic, physical activity, season and employment. According to Associate Professor Cain, our brains evolved to work best with bright light in the day and then with almost no light at night.

“Humans today challenge this biology, spending around 90 per cent 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,” he said.