As daylight hours dwindle, a significant portion of the population experiences a corresponding dip in mood adn energy levels. following a year marked by reduced sunshine across France – with some regions reporting dozens of fewer daylight hours – experts are focusing on accessible interventions to combat these effects. This article explores the science behind light therapy, a recognized treatment for conditions like Seasonal affective Disorder and other disruptions to the body’s natural circadian rhythm, and offers guidance on how to safely and effectively utilize it this winter.
2024 saw a significant lack of sunshine across France. Some regions experienced several dozen fewer hours of sunlight compared to seasonal norms. This decrease in light directly impacts our bodies, which rely on the day-night cycle to regulate many biological functions. Understanding these impacts is crucial for maintaining well-being during the darker months.
This seemingly minor disruption can significantly affect mood, alertness, and sleep. Light therapy has emerged as a recognized therapeutic tool for certain winter-related conditions, designed to counteract this lack of light stimulation.
Why Does Lack of Light Make Us Feel Tired?
Table of Contents
The mechanism is straightforward: less light equals fewer signals to our internal clock.
Light, captured by specialized cells in the retina, normally sends a clear message to the brain: it’s daytime, wake up, activate energy mode. In winter, especially when outdoor brightness decreases, this stimulation becomes insufficient.
Consequences include:
For some individuals, this seasonal vulnerability can develop into Seasonal Affective Disorder (SAD), with symptoms consistently appearing in the fall or winter.
How Does Light Therapy Reset the Internal Clock?
Light therapy involves exposure to very intense artificial light (often 10,000 lux, equivalent to a bright spring morning) to replicate the biological effects of natural light.
This light quickly reduces melatonin, a hormone that promotes drowsiness, and simultaneously stimulates serotonin, essential for improving mood and energy levels.
Additionally, specialized cells in the retina capture this brightness and transmit signals to our internal clock, helping to restore a regular circadian rhythm.
For Which Conditions Is Light Therapy Truly Effective?
Seasonal Affective Disorder (SAD)
Light therapy has proven most effective in treating Seasonal Affective Disorder (SAD). Those affected often describe depressive symptoms, including overwhelming fatigue, a need for more sleep, decreased motivation, and a persistent sadness that gradually worsens—only to lift with the return of spring.
Clinical studies demonstrate that light therapy is a first-line treatment for SAD, often alleviating fatigue, loss of interest, low mood, and excessive sleepiness.
Light therapy also plays a role in sleep disorders where the internal clock is out of sync. This includes cases where sleep is delayed (Delayed Sleep Phase Syndrome), when shift work disrupts the day-night cycle, or when long-distance travel interferes with adjusting to a new time zone.
In these situations, targeted light exposure can resynchronize the sleep-wake cycle. By sending a clear signal to the brain, light advances the biological clock and helps the body regain a stable rhythm.
Winter Fatigue and Low Energy
Even without a diagnosed psychiatric condition, winter fatigue is a common experience as days shorten. Individuals may feel sluggish, lack motivation, and find it difficult to get going in the morning.
This lack of energy isn’t just a feeling. Reduced light disrupts signals sent to the brain indicating the start of the day, delaying the activation of wakefulness mechanisms.
Without sufficient stimulation, the body remains in a state of semi-sluggishness, leading to decreased motivation, reduced concentration, and a general feeling of being out of sync. This phenomenon, common in winter, is primarily due to a light deficiency that disrupts our internal clock and impacts daily energy levels.
Light Therapy and Certain Dementias?
Light therapy is also gaining attention in more sensitive areas, such as Parkinson’s disease and certain forms of dementia. Preliminary research suggests that structured light exposure may help stabilize sleep-wake cycles, often severely disrupted in these patients.
Some results also show a reduction in agitation later in the day, a common phenomenon known as “sundowning,” which significantly impacts the daily lives of older adults and their caregivers.
However, these advances remain cautious, and studies conducted so far involve small participant groups and sometimes very different protocols. The observed effects are encouraging but not strong enough to be incorporated into official recommendations. Currently, this is a promising area of research rather than a validated routine clinical practice.
How to Benefit from Light Therapy This Winter?
Light Therapy: What Intensity Should You Choose?
Intensity is crucial in light therapy. Studies demonstrating its effectiveness almost all rely on exposure to 10,000 lux, a value corresponding to a bright spring morning. By comparison, a standard indoor room offers only 300 to 500 lux, far too little to affect the biological clock.
Below this level, the session must be extended to achieve the same effect. For example, a lamp delivering 5,000 lux often requires 45 minutes to an hour of exposure, compared to 30 minutes for 10,000 lux. The important factor isn’t just the displayed power, but also the lamp’s ability to maintain a stable intensity at the recommended distance.
What is the Best Time of Day?
Timing is almost as important as intensity. Light therapy is most effective in the morning, ideally within the first hour of waking. This is when the biological clock is most receptive and light can advance the circadian rhythm.
A session too late in the day may reduce the effect—or even have the opposite result: further delay sleep onset. Therefore, morning use remains the golden rule. For individuals with particularly delayed sleep onset, practitioners recommend exposure immediately upon waking, before any other activity.
How Long Should Exposure Last?
Duration depends directly on intensity. With a lamp offering 10,000 lux, recommendations generally range from 20 to 30 minutes per day. Below this, exposure must be extended to ensure a real impact on melatonin secretion and serotonin stimulation.
Consistency is also essential. A single session has limited effect. To allow the body to adjust, focus on daily exposure for several consecutive days, then maintain the rhythm during the darkest weeks of winter.
Light Therapy: How to Position Yourself?
You don’t need to, and shouldn’t, stare directly at the light. The important thing is that the lamp remains in your field of vision, slightly above eye level, as if the light were coming from a window. The ideal distance varies depending on the model, but is often between 30 and 50 centimeters.
During the session, you can read, have breakfast, or work. The goal is to integrate exposure into a daily routine without unnecessary constraints.
Which Lamp Should You Buy?
Not all lamps are created equal, and some only have the name “light therapy.” Several criteria must be present:
- CE medical certification, guaranteeing safety and compliance,
- absence of UV rays, to protect the eyes and skin,
- a sufficiently large light surface for even exposure,
- an intensity actually measured at the recommended use distance.
In practice, it’s best to avoid lamps that are too small, fanciful models, or uncertified devices, which don’t guarantee sufficient light output.
GOOD TO KNOW
Morning light not only regulates melatonin, it also helps reset the natural cycle of body temperature, a key marker of our internal clock. By slightly advancing this thermal rhythm (which drops at night and rises during the day), light therapy helps stabilize sleep and energy.
Subscribe to our newsletter
Ma Santé
