There's fresh insight into the link between bright light and mental health with research revealing modern lifestyles are confusing our bodies and making us sick.

A study of almost 87,000 people published in peer-reviewed journal Nature Mental Health found being exposed to light at night increases a person's risk of psychiatric disorders.

It increased the likelihood of depression by 30 per cent, while also driving up the likelihood of anxiety, bipolar, PTSD severity and self-harm.

In contrast, being exposed to bright light during the day decreased the risk of depression by 20 per cent.

The findings could have a major impact as people can take simple steps to help their wellbeing, according to the study's lead author Sean Cain from Monash University and the Turner Institute for Brain and Mental Health.

"Our findings were consistent when accounting for shiftwork, sleep, urban versus rural living and cardio-metabolic health," he explained.

The study analysed information from 86,772 people who are part of the UK Biobank and the results were also consistent across demographics and seasons.

Human brains evolved to work best with bright lights during the day but modern lifestyles had affected that, Associate Professor Cain said.

"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," he said.

"It is confusing our bodies and making us unwell."

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