Phototherapy is effective. But for whom does it work? Basic overview of the light therapy benefits in depression, sleep problems, dementia and more.

How does phototherapy work?

When the light of a specific frequency and intensity from the Sun or a therapy light reaches your eye, the cells of the retina send signals to the brain. Once these signals reach the internal brain clock, it starts releasing substances such as hypocretin, dopamine, serotonin and noradrenaline. These molecules affect our mood, arousal and sleep-wake pattern, for which the effects propagate throughout the whole body.

This mechanism was developed during evolution to adapt our bodies and actions to the rhythms of day and night as well as seasons of the year. Our ancestors benefited from the light which readily increased their activity in long summer days (perfect for hunting and gathering) while leaving them passive in winters, thus saving energy. In a civilized society, however, we do not enjoy being drowsy and demotivated when not exposed to the sunshine. Therefore, modern medicine exploits this system by producing similar light that enable our brains to obtain the boost of signals from the retina that it needs in order to function optimally.

What are the benefits?

“Lethargics are to be laid in the light, and exposed to the rays of the sun, for the disease is gloom.” – Aretaeus of Cappadocia

Light therapy for depression and other mood disorders

In mood disorders, the tradition of phototherapy goes back to the ancient civilizations. Even in modern medicine, we have been using bright light to treat depression for nearly half a century. There is adequate scientific evidence granting bright light therapy formal recommendations from leading professional institutions such as the American Psychology Association as well as positive evaluations from the Cochrane Reviews.

Phototherapy is known to be particularly efficient in (major) depression, seasonal affective disorder and bipolar disorder:

According to its lower estimates, the effects of bright light therapy in depression are medium: roughly twice as high when compared to various self-help techniques and courses and half the effect than psychotherapy or medication produce.

According to higher estimates, the treatment effects are large: about four times higher than self-help methods and comparable to those of psychotherapy and medication.

Especially with bipolar or severe depression it is important to note that bright light therapy is there to give you an extra kick, not to replace necessary medication. Similarly, phototherapy works well with what we consider the golden standard in the realm of mental health: psychotherapy. Again, psychotherapy with bright light is better than single therapy on its own.

Light therapy for insomnia and other sleep problems

With light being responsible for keeping our daily rhythm aligned with the day and night, it is natural that bright light therapy also treats poor sleep. Along with decades of clinical experience, we have hundreds of scientific articles, reviews and analyses demonstrating that bright light therapy is an effective treatment for numerous sleep problems.

But do you know how many different sleep disorders currently exist? It is impossible for one remedy to heal everything. The effectiveness of phototherapy varies from large effects in circadian disorders and true insomnia to zero effect in narcolepsy or apnea. For details, see our overview of different sleep disorders and review of the most recent meta-analytical study on phototherapy in sleep problems.

Light therapy for Parkinson’s disease and dementia

Besides many positive results of light therapy for depression in the elderly, there is intensive research scrutinising its effects on symptoms of brain diseases related to aging.

In the case of Parkinson’s disease, the findings are convincing. Although we still have much to learn, the most recent summary of evidence shows that in the studies we have so far, light therapy helped Parkinsonian patients not only with depressions and anxieties, but also with motor problems, including tremors and imbalance. Although the effect on motor problems is not yet thoroughly researched, thus any conclusions on this topic would be speculative, the entirety of the data we have collected thus far indicates that bright light therapy is likely to be effective for, at the vera least, the non-motor symptoms.

For Alzheimer’s disease, the newest scientific analysis from 2018 finds light therapy to be a “promising intervention.” Light therapy appears beneficial for demented patients suffering from sleep problems or depression. Once again, there may be additional benefits, but with the data we have in 2019, any conclusion about that would be speculative.

Emerging applications: from anxiety to obesity

Knowing the effects of bright light on brain activation and benefits in depressive and sleep disorders, scientists are researching where else the lamp-shine has potential to improve our physical and mental health, the results of which are striking:

Research on cancer patients and survivors implies that light therapy may help them with fatigue, besides sleep and depression problems . Considering the evidence of general effects of phototherapy on mood and arousal mechanisms, not to mention the positive results of direct clinical studies, there is little room for doubt. However, at the current knowledge threshold, it is too early for final conclusion.

. Considering the evidence of general effects of phototherapy on mood and arousal mechanisms, not to mention the positive results of direct clinical studies, there is little room for doubt. However, at the current knowledge threshold, it is too early for final conclusion. Research on various mental struggles, from anorexia to ADHD, suggests that people suffering from these conditions might find some relief from light therapy too .

. With a growing understanding of civilization diseases, such as obesity or high risks of dementia and cardiovascular disease, we are also finding links between our guts and our circadian rhythms. Obesity and cholesterol levels seem to depend partly on the patterns of our arousal, which itself strongly depends on exposure to light. In recent years, phototherapy has been successfully used to help reduce obesity. Another study linked light to stress and anxiety. By manipulating our inner rhythms, light therapy may affect our body as a whole. Nevertheless, any practical recommendations remain speculative in this area.

Limits of the bright light therapy

There are no major adverse side effects of phototherapy. However, knowing the benefits, make sure to also understand that the the bright light remedy is not omnipotent, just as nothing else is, especially in the world of mental health (except for love, maybe). Therefore, it is important to understand that the thousands of studies proving bright light therapy effective are related to specific conditions.

Even when treating problems where the bright light is the most effective, such as depressive disorders and sleep problems, the results are not guaranteed. We all differ – and so do our problems, their causes and their solutions. Whether an individual is going to get cured or rarely a certainty, no matter whether we discuss medication, psychotherapy or bright light. In the case of phototherapy, success of failure of the treatment depends largely on genes and neurochemistry related to light perception and processing, in addition to the individual mix of social, psychological and biological causes behind your condition.

Thousands of neuroscientists and psychologists who participate in research and development of better lamps don’t develop new treatments to make you ignore the well-documented effects of existing methods. We encourage you to find a professional, licenced psychotherapist. Your local or national association of psychotherapists surely has a list of providers to recommend. You may also check our article on possibilities of online psychotherapy – but as long as you can, opt for the real, human therapy in your town, because that is what is most researched.

Please, do not forget about other means of treatment, dazzled by the light of lamps!

Where to continue?

To learn more about the specific disorders, the research devoted to them and treatment guidelines, see our sections on depression, seasonal affective disorder, bipolar disorder, sleep problems, dementias and Parkinson´s, anxious disorders and pain and fatigue.

To understand the neurobiological underpinnings of the light therapy, check our Science behind chapters.

To see the clinical validation of the bright light therapy, check our overview of recent meta-analyses.

Finally, you can learn more about the context of other therapies and practical information.

…or simply select the topic of your interest: