A recent study has added some academic heft to the adage that a sunny disposition is the best medicine to treat anxiety and depression.

Researchers at Monash University in Melbourne have found that people who get more light during the day and less at night are less likely to suffer from mental health issues.

People have, historically, lived by the sun’s rise and fall. The nights were lit only by the moon. But now, we – not just youngsters but a lot of older adults too – are spending time inside lit by the blue glow of computer screens.

Humans in modern, industrialised times have literally turned their biological systems upside down. According to study leader 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% 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.

The Monash study, involving nearly 87,000 participants, found increased exposure to light at night increased a person’s risk for psychiatric disorders such as anxiety, bipolar, and post-traumatic stress disorder (PTSD) severity as well as self-harm.

However, increasing exposure to daytime light can act like a non-pharmacological means for reducing psychosis risk.

In those exposed to high amounts of light at night, the risk of depression increased by 30% – while those who were exposed to high amounts of light during the day reduced their risk of depression by 20%.

Similar patterns of results were seen for self-harm behaviour, psychosis, bipolar disorder, generalised anxiety disorder, and PTSD.

The findings indicate that avoiding light at night and seeking brighter light during the day could be an effective, non-pharmacological means of reducing serious mental health issues.

Associate Professor Sean Cain said the findings could have a potentially “huge societal impact”.

“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,” he said.

There are good reasons to believe light is a key to better mental health. Exposure to light sets our circadian clock. If that clock is set wrong, we are at risk of a range of diseases.

It is known that people who work at night and sleep during the day face a much higher risk of mental and physical illness, for example.

“We know disruptions to circadian rhythms cause disruption to mental health measures,” Michael Berk, director of Deakin University’s Institute for Mental and Physical Health and Clinical Translation told the Sydney Morning Herald.

“We know if you want to trigger an episode of bipolar, the very best way to do that is muck with the circadian clock.”

The important message is to get as much light – taking precautions, of course, against sunburn – as possible during the day and as little as possible at night.

Work outside as much as possible and avoid light – particularly blue light – at night.

Related reading: Monash News, SMH