This is a randomized placebo-controlled trial to examine the efficacy of two-week bright light therapy for patients with post-COVID-19 fatigue.

This randomized placebo-controlled trial aims to evaluate the efficacy of BLT in reducing fatigue symptoms after COVID-19 infection. The second aim of the study is to explore the effects of BLT on insomnia, depression and anxiety symptoms.

Method: Each eligible participant will be randomized to either i) bright light therapy (BLT) or ii) dim red light (placebo) treatment for 30-minutes daily at their habitual wake time for a total of two weeks. Participants will be evaluated at baseline, 2nd (end of treatment), and 4th week (post-treatment 2-week) for fatigue and other symptoms.

Inclusion Criteria:

• Age 18 or above
• Capable to give informed consent
• COVID-19 infection confirmed by PCR test or a Rapid Antigen Test (RAT) with onset of at least three months
• Reports new onset or exacerbation of fatigue after onset of COVID-19 and lasted for over two months
• Scoring 7 or above for the item "worst level of fatigue during the last 24 hours" in the Brief Fatigue Inventory

Exclusion Criteria:

• A current or past history of bipolar disorder, schizophrenia, neurodevelopmental disorder, organic mental disorder; intellectual disabilities or substance use disorder.
• Presence of contraindications to bright light therapy: for example, history of light induced migraine/ epilepsy; current use of photosensitizing medications; presence of eye disease: e.g. retinal blindness, severe cataract, glaucoma.
• Significant medical condition/ hearing impairment/ speech deficit leading to incapability of completing clinical interview.
• Regular shift-workers
• Trans-meridian flight in the past 3 months and during the study
• Currently receiving any structured psychotherapy
• Self-reported untreated sleep disorders (e.g. severe insomnia, obstructive sleep apnea, restless leg syndrome), psychiatric illness (e.g. depression), or medical conditions associated with fatigue (e.g. anemia, heart failure, autoimmune disorders)
• Enrolment in another clinical trial of an investigational medicinal product or device.

The subjects will be explained that the study aims to test the efficacy of two different modalities of light treatments for fatigue including white light and red light, without mentioning which one is the placebo.