Red Light Therapy and Depression
Red and infrared light is being recognized for a number of different treatment applications, from helping with wound healing to decreasing pain and inflammation. One area where red light therapy is starting to gain traction is in the treatment of mental health conditions, in particular, depression.
While on first blush, it may seem fanciful that shining a red light on the skull would have any impact on mood, research is clearly showing that different frequencies of red and infrared light have robust physiological effects.
The Effects of Red Light Therapy on the Brain
Red light therapy has numerous beneficial effects on brain tissues, including (Wang 2024):
- Increasing blood flow
- Decreasing inflammation
- Improving brain cell survival, i.e. decreasing apoptosis or programmed cell death
- Encouraging new brain cell formation
- Increasing growth factors
- Improving lymphatic drainage
- Activating DNA transcription
- Supporting antioxidant production
- Stimulating energy production
- Increasing new blood vessel formation
- Regulating calcium ions
Increasing Blood Flow to the Brain
The brain is only 2% of our body weight, yet it consumes approximately 15% of the overall blood supply (Tameem 2013). In depression, areas of the brain often have a decreased blood flow, especially in older patients (Taylor 2014). By improving blood flow, the brain centers that have not been receiving adequate oxygen and nutrients can be better supported, improving overall function. Red light therapy has been shown to improve blood flow. A small study in veterans with traumatic brain injury found that two-thirds of participants had improved blood flow when exposed to red and near infrared light that was pulsed at different frequencies for 20 minutes three times per week (Hipskind 2019).
Decreasing Inflammation
A study in rats showed decreased inflammation in the brain after a heart attack with the application of red light therapy (Wang 2020). Other animal studies show decreased brain inflammation after stroke (Lee 2017).
Increasing Brain Cell Survival
Apoptosis is the technical term for when cells go through a biochemical process that results in their death. An animal study in spinal cord injury showed increased brain cell survival with red light exposure (Hu 2020).
Encouraging New Brain Cell Formation
Studies in mice after a traumatic brain injury have found that near infrared light exposure increases the development of new brain cell formation (Vatansever 2013). A separate study in mice found that near infrared light pulsed at 40 Hz promoted brain stem cell formation and decreased anxiety behaviors (Qi 2024).
Increasing Brain Cell Growth Factors
Growth factors, like brain-derived neurotrophic factor (BDNF), act like fertilizer for brain cells, encouraging their growth. Red light therapy has been shown to increase brain cell growth factors like BDNF. In a rat model of depression, near infra-red light exposure has been shown to improve depressive behaviors and increase the growth factor BDNF levels in the brain (Zheng 2023).
Improving Lymphatic Drainage
A study in a mouse model of Alzheimer’s disease found that infrared light stimulation was able to improve dementia symptoms and appeared to work, at least partially, through increased lymphatic drainage of the brain (Semyachkina 2021). The drainage point is around the bridge of the nose, suggesting that intranasal or frontal light stimulation might work best to enhance lymphatic drainage of the brain.
Activating DNA transcription, Supporting Antioxidant and Energy Production
The DNA is the master blueprint for all of the proteins produced throughout the body. Production of these proteins is regulated through multiple pathways. Near infrared light therapy has been shown to increase DNA transcription. The proteins that were increased were involved with energy production and anti-inflammatory effects (Eells 2004).
Increasing New Blood Vessel Formation
The official medical term for new blood vessel production is angiogenesis. Animal studies of recent wounds have found that light stimulation, including red light, increases new blood vessel formation (Dungel 2014). The increased production of new blood vessels enhanced the healing process.
Regulating Calcium Ions
Calcium ions are important for relaying cellular signals throughout the brain and body. Red light has been shown to increase the calcium levels inside nerve cells which can increase their chances of firing or sending a signal (Golovynska 2021).
All of these effects are potentially relevant for why red and infrared light may have therapeutic potential in the treatment of depression.
Clinical Studies of Red and Infrared Light for Depression
One of the initial pilot studies explored treatment of the frontal brain region with near infrared light applied to the forehead for four minutes in a single session (Schiffer 2009). The ten patients were then followed for four weeks. At two weeks post treatment, two-thirds of them had achieved remission of depression and anxiety. However, by four weeks, symptoms were strongly trending back towards baseline, indicating the effects from a single treatment were transitory.
A small double-blind, crossover, proof-of-concept trial where patients received near-infrared light applied to the forehead for six sessions or placebo also found benefits (Cassano 2015). On average, depression symptom severity was reduced 35% with the applications of near-infrared light in the four patients. Although again, after treatment discontinuation, symptoms reemerged.
The same research group performed a double-blind study that included 21 patients (Cassano 2018). They found that infrared light exposure had medium to large effects sizes for reducing depressive symptoms. Considering that antidepressants have a small effect size, the results deserve further replication in larger clinical trials.
A double-blind study in college students struggling with anxiety and depression also reported significant benefits (Kerppers 2020). In the study, light treatments were quite short, under two minutes in duration, and were applied daily for one month. Even with the short treatment, there were some significant reductions in symptoms for the students.
In 2022, researchers attempted to treat depression with very low level infra-red light exposure. The trial failed to show benefits and the researchers concluded that the benefits appear to occur with higher level exposures for longer periods of time with an increased number of sessions (Iosifescu 2022). One of the most recent trials treated 11 patients with major depressive disorder for 14 days with near-infrared light over the left forehead region (Hao 2024). The patients had decreased depression severity that was still significant after two months.
While a meta-analysis from 2022 didn’t find the benefits of infrared therapy outweighing placebo, the variance in protocols, including the intensity and duration of treatments could easily have been confounding the results (Cho 2023).
Conclusion
Considering the potential safety of red and infra-red light therapy for treating depression and the relative poor performance of current antidepressants, red light therapy deserves further attention. Currently, the optimal light frequencies, intensity of light, duration of exposure and number of sessions for optimal response is unknown. With numerous patients not finding relief with standard antidepressant treatments, hopefully more research on red light therapy can prove that light may be a viable approach for helping to reduce depressive symptoms.
