Blue Light Can Lead to the Blues

Medically Reviewed by Whitney Seltman, OD on October 07, 2020

Too much screen time could be taking a toll on your mental health.

That’s because your smartphone, tablet, laptop, and TV all give off blue light. So do fluorescent and LED (light-emitting diode) light bulbs.

While evidence is growing that shows blue light can be helpful during the day, nighttime exposure has been linked to health issues like sleeplessness and mood disorders. Here’s what you need to know.

What Is Blue Light?

It’s one of several colors in the visible light spectrum. The others are:

  • Red
  • Orange
  • Yellow
  • Green
  • Blue
  • Indigo
  • Violet

You may know them by the acronym ROY G BIV. Together, they make the white light you see when the sun -- the main source of blue light -- is shining. 

How Blue Light May Affect Your Mental Health

Scientists think nighttime exposure to blue light throws off your circadian rhythm, or sleep/wake cycle. This could lead to symptoms of depression. That’s because your circadian rhythm plays a role in several brain and behavioral processes, like neurotransmission and hormone secretion.

The risks are higher if you spend time on digital devices or get exposed to other sources of blue light after the sun goes down. An animal study found mice exposed to dim light in the evening for 4 weeks showed higher rates of depressive symptoms than mice exposed to the normal light-dark cycle.

Blue light also slows or stops your body’s release of melatonin, the hormone that regulates sleep. In one study, participants using an e-reader at bedtime took longer to fall sleep and reported feeling groggy the next morning. Another study showed just 2 hours of blue light exposure in the evening can impact the release of melatonin. Trouble sleeping is one of the most common symptoms of mood disorders like depression and anxiety. Your risk for a mood disorder is higher anytime you’re not getting enough sleep.

Show Sources


Harvard Medical School: “Blue Light has a Dark Side.”

Translational Psychiatry: “Timing of light exposure affects mood and brain circuits.”

Mental Health America: “How Blue Light Affects Mental Health.”

Chronobiology International: “Systematic review of light exposure impact on human circadian rhythm.”

Proceedings of the National Academy of Sciences: “Evening use of light-emitting eReaders negatively affects sleep, circadian timing, and next-morning alertness.”

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