blue light effects
Excessive blue light can negatively affect mental health

Blue light can affect mental health by interfering with the way our brain regulates mood, emotions and sleep. The lift in our spirits in response to a sunny day with bright blue skies is an obvious beneficial effect of light on our mood. This effect is primarily from blue light, the color with the highest energy in the visible color spectrum.

The ill effects of blue light are less obvious. Blue light exposure close to bedtime can disrupt the sleep/wake cycle (circadian rhythm), and affect hormone secretion, nerve signaling (neurotransmission) and the brain's ability to adapt (plasticity) to changing situations. Excessive blue light can cause sleep and mood disorders, leading to depression.

What is blue light?

Blue light is one of the colors in the visible color spectrum that combine to form white light. Each color in the light spectrum has a different wavelength, frequency and energy level. Violet light has the shortest wavelength in the visible color spectrum at around 400 nanometers (nm) while red is at the other end of the spectrum at 700 nm wavelength.

Blue light is a high energy, high frequency light with short wavelengths between 450 and 495 nm. Sunlight is the primary source of blue light during the day, but fluorescent lights and light-emitting diodes (LED) also emit blue light. Electronic devices such as television, smartphones, computers and tablets have LEDs that emit blue light ranging from 400 nm to 490 nm.

Visible blue light is different from the blue light therapy that uses ultraviolet (UV) rays to treat certain skin conditions such as psoriasis. Harmful effects of UV rays on eyes and skin are relatively well-known, and people routinely protect themselves from UV ray exposure, but the ill effects of visible blue light are less apparent and often overlooked.

What does blue light do to your brain?

Light is one of the most important environmental factors that influence our brain. Among all colors in the spectrum, blue light has the greatest response from our brains. Light or absence of it plays a major role in maintaining a normal circadian rhythm, which is a process by which our brain regulates biological processes and behaviors that are important for good health.

The brain produces different hormones to keep us bright and energetic during the day and to help us sleep during the night. This 24-hour cycle of our internal clocks is known as circadian rhythm. Light plays an important role in sending signals to the brain to release the right kind of hormones depending on the time of day and the needs of our body.

In the morning, blue light signals the brain to lower the level of melatonin, the hormone that regulates the body’s circadian rhythm and energy metabolism. The drop in melatonin is the signal for hormones such as serotonin which raise our energy. In the evening, the fading light signals the brain to raise the melatonin levels, improving our night time sleep.

Why is blue light harmful?

Prolonged exposure to blue light from LED screens causes digital eye strain, with symptoms such as blurred vision, dry eyes, irritation and stinging or burning of eyes. There is no conclusive evidence so far of blue light causing any eye disease, however. Children and teenagers appear to be more susceptible to the effects of blue light than adults.

Before the invention of artificial light, sunlight was the main source of blue light, and our circadian rhythm was in synchrony with the 24-hour solar day. Today, we have bright lights that provide us security in the night and help us run essential services such as hospitals through the night. We also constantly use many LED-lit electronic devices which emit strong blue light.

While night lights and electronic devices improve our lives in many ways, they also may disrupt our circadian rhythm. Disruption of circadian rhythm not only affects melatonin and sleep patterns, but it also causes imbalance in the levels of other hormones such as dopamine and serotonin which regulate our mood and emotions, resulting in mood disorders and depression.


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What are the benefits of blue light?

Exposure to blue light for at least an hour in the morning, particularly from sunlight, helps raise our alertness and energy levels during the day. Blue light therapy is an effective treatment for seasonal affective disorder (SAD), a form of depression.

SAD most often occurs in the fall and winter months in people living in the far northern and southern latitudes, where daylight hours are short during these months. An hour of exposure to blue-light-emitting lamps in the morning has been found to suppress the melatonin levels and improve SAD depression symptoms.

Blue light therapy can also be useful in treating other conditions such as:

How do you limit exposure to blue light?

The following are some steps you can take to limit blue light exposure:

  • Limit your screen time by putting away your devices two to three hours before bedtime.
  • If you are a night shift worker and cannot avoid blue light, try wearing blue light glasses which block some of the blue light.
  • Reduce the screen brightness in your device or use night light mode, if available.
  • Use a dim red light if you do use a night light when sleeping.
  • Expose yourself to plenty of sunlight, especially in the mornings.

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Medically Reviewed on 4/26/2021