Shining bright light on "night owls" can help alleviate their depression, local university researchers have found in the world's first such study.

Bright light therapy can help adjust patients' biological clocks, doubling their chances of recovering from depression without any adverse side effects, they found.

The team pointed out that about one in five depressed patients are "night owls" who are more likely to commit suicide and do not respond well to conventional treatments.

The Chinese University and University of Hong Kong recruited 93 patients with an average age of 13.7 years who suffered moderate to severe depression and slept from 2am to 10am.

The participants were divided into two groups. Bright lights mimicking outdoor light was shone at one group for 30 minutes a day for five weeks, with the starting time gradually getting earlier over the period, while dimmer lights were used in the control group.

Some 67.4 percent of patients who underwent bright light therapy improved their depressive symptoms in around two weeks, compared to 46.7 percent in the control group.

"There are two possible mechanisms. One, they shifted their circadian rhythm. The other is the direct effect of bright light therapy to the biological mechanism of depression - for example, affecting the brain stem nucleus or changing their serotonin balance," said professor Wing Yun-kwok, chairman of the department of psychiatry at CUHK.

Researchers encouraged members of the public to maintain a regular sleep cycle - by exposing themselves to sunlight in the morning and avoiding excessive use of electronic devices in the evening - to reduce the risk of depression.

Meanwhile, a survey by the Mental Health Association of Hong Kong found that a record-high number of people showed symptoms of depression.

Its biennial survey showed that 23 percent of the interviewees suffered from borderline depression, marking a 5 percentage point increase compared to its survey from 2018.

Some 8.4 percent of respondents fell into the clinical depression category - a 1.7 percentage point increase.

Women and those aged between 18 and 44 fared worse, while those with lower incomes and education levels also felt more pressured amid the pandemic.

The association suggested the public adopt a lifestyle that prioritizes exercise and sleep more and utilizes social media to stay in touch with families and friends. They should also seek professional help, as the survey found only 10 percent of respondents did so.

carine.chow@singtaonewscorp.com

WingYun-kwok, center, said light therapy could shift patients' circadian rhythm and improve depression.

Light therapy plays brightening role