Light therapy, also called phototherapy or bright light therapy, is a treatment involving exposure to artificial light at controlled wavelengths and time points to treat a variety of medical and non-medical conditions. Most studied for Seasonal Affective Disorder (SAD), circadian rhythm sleep disorders, and other forms of depression, light therapy emulates the beneficial properties of natural sunlight.Light therapy is beneficial for various health conditions, including: Seasonal affective disorder (SAD) Depression and anxiety disorders Sleep disorders, such as insomnia Travel related jetlag Skin conditions, such as psoriasis and eczema Chronic pain, such as fibromyalgia What is light therapy and how does it work? The human body has a natural response to light, which helps regulate our sleep-wake cycle, mood, and overall well-being. Light therapy works by mimicking natural sunlight and stimulating the production of specific hormones and neurotransmitters in the brain. This imitation of sunlight is key in helping to set or reset our body's natural clock, which can improve mood-related issues.One example is the hormone melatonin, which helps regulate our circadian rhythms. Exposure to light, especially blue light, can - in the evening hours and at night - suppress the production of melatonin, in addition to making us more alert and energized. This is why it is often used to treat SAD or other forms of depression.Moreover, light therapy can also affect the production of serotonin, a neurotransmitter responsible for regulating mood (Serotonin is a precursor of Melatonin). Serotonin levels tend to be lower during the winter months when there is less sunlight, leading to symptoms of depression and anxiety. By increasing serotonin levels through light therapy, individuals may experience improved mood and reduced symptoms of depression. Types of Light Therapy There are different types of light therapy, each utilizing a specific wavelength or color of light. The most common types include UV, red, blue, and infrared light therapy. The different types of light therapies work by targeting specific cells or tissues in the body. For example, UV light therapy targets skin cells, while red and infrared light therapies target blood vessels and muscle tissue. UV Light Therapy UV (ultraviolet) light therapy uses ultraviolet rays to treat skin conditions such as psoriasis, vitiligo, and eczema. This type of light therapy works by slowing down the growth of skin cells and reducing inflammation. It is typically administered in a controlled medical setting using special lamps or light boxes. Red Light Therapy Red light therapy, also known as low-level laser therapy (LLLT), uses red or near-infrared light to promote healing and reduce pain and inflammation. It has been found effective in treating skin conditions, such as acne and rosacea, as well as reducing joint pain caused by conditions like arthritis. Red light therapy can be administered through specialized devices or in a clinical setting. Blue Light Therapy Blue light therapy is primarily used to treat circadian related issues (e.g. sleep, energy levels, digestion, etc.) as well as skin conditions such as acne. Circadian effects are elicited by directing light into the eyes, activating melanopsin in the photosensitive retinal ganglion cells responsible for non-image-forming visual functions. Moreover, these functions facilitate hormone secretion, synchronize circadian rhythms, and impact cognitive and affective processes. The skin condition treatment works by killing the bacteria that cause acne and reducing inflammation. This type of light therapy can be administered through special lamps or handheld devices. Infrared Light Therapy Infrared light therapy utilizes infrared rays to penetrate deep into the skin, providing relief for muscle and joint pain. It is also used to promote healing in wounds and injuries. This type is often administered through specialized devices or in a clinical setting. How does light therapy work? Light therapy operates on the principle of photobiomodulation, a process where light exposure stimulates cellular and tissue activity which sets off a series of biochemical reactions. As cells are exposed to light, they absorb photons and convert their energy into a form they can use to carry out vital functions, such as tissue repair and the production of collagen. This therapy has been shown to help support the production of adenosine triphosphate (ATP), the energy currency of the cell, thereby enhancing cellular metabolism and accelerating the healing and regeneration of tissues. In terms of circadian rhythm regulation, light therapy plays a crucial role by influencing the body’s internal biological clocks that dictate our sleep-wake patterns and energy levels. The timing of light exposure is key: morning light therapy can suppress the production of melatonin, the hormone that signals the duration of darkness to our body, and which can help promote alertness during the day. In contrast, dimming lights in the evening can help maintain melatonin levels, supporting the process of synchronization of our bodily rhythms. Additionally, light therapy has been found to increase serotonin production, a neurotransmitter associated with mood and well-being (Serotonin is a biosynthetic precursor of melatonin). This is particularly beneficial during winter months when daylight is limited, helping to alleviate symptoms associated with Seasonal Affective Disorder (SAD). Who is light therapy good for? Individuals with Seasonal Affective Disorder (SAD): Light therapy is a well-established treatment for SAD, a type of depression that occurs at a specific time of year, usually in the winter when daylight hours are shorter. Time of day of light exposure is of utmost importance to help treat SAD, because light at the wrong time of day can worsen SAD. People with Certain Sleep Disorders: Those with circadian rhythm sleep disorders, such as delayed sleep phase disorder, can benefit from light therapy. It helps to adjust their internal body clock to desired (often socially driven) times of wake and sleep. The time of day of light exposure is of utmost importance to help treat circadian rhythm and sleep disorders because light at the wrong time of day can worsen a disorder.  Patients with Non-seasonal Depression: Emerging studies suggest that the treatment may also be effective for non-seasonal depression, potentially helping to improve mood and well-being in individuals with major depressive disorder. Time of day of light exposure is of utmost importance to help treat depression, because light at the wrong time of day can worsen a depression. Individuals with Certain Skin Conditions: Conditions like psoriasis, eczema, and vitiligo have been treated with UV light therapy, which can help to slow down cell growth and reduce inflammation. People with Jet Lag or Shift Work Disorder: This treatment can help adjust the body’s internal clock for those who travel frequently across time zones or work irregular hours, improving sleep and alertness.  It’s important to note that while the method can be beneficial for these conditions, it should be used under the guidance of a healthcare professional to ensure it is appropriate for the individual’s specific health needs and to manage any potential side effects. To date, there is no off-the-shelf solution and any intervention using light in the context of shift- and night work is advised to be accompanied and supervised by a professional chronobiologist and expert on the non-visual effects of light in humans. Time of day of light exposure is of utmost importance to help treat related disorders, because light at the wrong time of day can worsen a disorder. Risks and side effects While light therapy is generally considered safe, it is not without potential risks and side effects. Awareness and proper management of these can help ensure a safe and effective treatment experience. Potential skin reactions Some individuals may experience skin reactions to light therapy specifically to UV and IR light therapy. Those with sensitive skin or conditions like lupus that can be exacerbated by light are especially prone to reaction. Reactions can include redness, irritation, or rash. UV-light therapy, used for conditions like psoriasis, carries a risk of skin burning similar to sunburn if not correctly monitored. Eye strain or damage: The eyes are particularly sensitive to light. Exposure to intense or prolonged light, especially very strong and unregulated UV blue light, can lead to eye strain. In some cases, without proper eye protection, there is a risk of damage to the retina. It is crucial to use light therapy devices that filter out UV light and to follow guidelines on duration and intensity of exposure. Precautions to take To mitigate risks, several precautions are recommended: Use light therapy devices that comply with safety standards and are recommended by health professionals. Start with shorter sessions and gradually increase duration under professional guidance. If using light therapy for skin conditions, apply sunscreen or other protective barriers as advised by a healthcare provider. Individuals with a history of skin cancer or retinal diseases should consult with a healthcare provider before beginning light therapy. Do not look directly into the light sources. Wear eye protection if recommended, especially for those with pre-existing eye conditions or when using light boxes that emit UV rays.   Devices and equipment for light therapy Light boxes UV (ultraviolet) light therapy uses ultraviolet rays to treat skin conditions such as psoriasis, vitiligo, and eczema. This type of light therapy works by slowing down the growth of skin cells and reducing inflammation. It is typically administered in a controlled medical setting using special lamps or light boxes. Dawn simulators Another type of popular light therapy device is a dawn simulator. This device works by gradually increasing the amount of light in a room, mimicking the sunrise. It is commonly used to help regulate ease of waking up . Light therapy wearables Wearable light therapy devices, such as eye masks or glasses, are also becoming more popular, especially as they provide freedom of movement and typically shorter sessions with equivalent effectiveness as light boxes. These devices use LED lights to target specific areas of the body, and can be used for adjustment of internal body clocks, energy levels, minimizing jet lag and improving mental performance. It is advised to precheck whether the device of choice has been subjected to scientific studies to validate its effectiveness. How to choose the right device Identify your needs Determine the primary purpose of the light therapy. Consider consulting a health specialist on this topic. Different conditions require specific types of light therapy, such as bright light for mood disorders. Quality and safety Prioritize devices that are certified for safety and effectiveness. Look for ones that filter out harmful UV rays and have a proven track record of reliability. Size and portability Consider how you will use the device. If you travel frequently, a compact, portable model might be ideal. When crossing time zones during travel, please be aware that time points of light exposure need to be adjusted accordingly. A major contributor to the effectiveness of any light intervention is time of day with respect to the time of our body clocks and not the clocks on walls, on our wrists or our smartphones. For home use, a larger, stationary device could be more suitable. Features Evaluate the features of the device, such as adjustable light intensity, timers, personalized programs and the type of light emitted. These features can enhance the effectiveness and convenience of the therapy. User reviews Research user reviews to gauge the effectiveness and usability of the device. Real-world experiences can provide valuable insights into the device’s performance. Warranty and support A good warranty and responsive customer support are indicators of the manufacturer’s confidence in their product and their commitment to customer satisfaction. They also ensure you have assistance if issues arise. Conclusion Light therapy stands out as a versatile tool in managing various health issues, from mood disorders like SAD to sleep and circadian rhythm disturbances. Its role in syncing our internal clocks and improving overall wellness is significant. However, it’s important to remember that light therapy, while beneficial, is not a one-size-fits-all solution. Each individual’s needs and health conditions are unique. Therefore, consulting with healthcare professionals before embarking on a light therapy journey is crucial. They can provide tailored advice, ensuring that the therapy aligns with your specific health requirements and lifestyle. Alternatively, look for the device that provides personalized advice either via consultancy or software (e.g. App).

Written by Alex

Alex is an AYO Co-Founder with over a decade of experience in Circadian Health. His background includes technology, health and fitness, and marketing.