Does a Solar Eclipse Have Effects on the Brain?

This post was edited by Mike Battista, Director of Science and Research at Creyos (formerly Cambridge Brain Sciences).

On Monday, April 8, 2024 many people across North America will be able to experience a total solar eclipse. The solar eclipse will cross through Canada, the United States, and Mexico. For those in the affected regions, darkness will fall in the middle of the afternoon. It’s an amazing sight to see—with the right safety precautions. 

A solar eclipse inspires a sense of awe, and many questions, including:

• What effects does a solar eclipse have on the brain?

• How does an eclipse affect human behavior, mood, emotions?

• Does it affect the day-night cycle in animals and people?

• How do you safely view a solar eclipse?

In this article, we’ll explore the effects of solar eclipse on the brain, including potential psychological effects. First, we'll cover the basics.

What is a Solar Eclipse?

A solar eclipse occurs when the moon passes between the Earth and the sun, obscuring all or part of the sun's light from reaching Earth. Visually, from our position on Earth, solar eclipses give the appearance that the moon covers the sun's surface, either partially or completely. This phenomenon can only happen when the moon, sun, and Earth are aligned in a straight line, with the moon casting a shadow on Earth's surface.

How Often Do Solar Eclipses Occur?

The frequency of solar eclipses depends on the type. Of course, not everyone will be able to experience solar eclipses whenever they happen, as they occur over particular parts of the world, and sometimes over the oceans or remote places.

• Partial Solar Eclipse: Partial solar eclipses are the most common type of solar eclipse. On average, they occur about two to four times per year somewhere on Earth.

• Total Solar Eclipse: Total solar eclipses are less common than partial eclipses. They occur about once every 18 months somewhere on Earth's surface, but the path of totality (where the total eclipse is visible) is narrow and can vary in location for each eclipse.

• Annular Eclipse: Annular solar eclipse is less common than total eclipses. They occur when the moon is too far from Earth to completely cover the sun's disk, resulting in a ring of sunlight around the moon's silhouette. Annular eclipse occurs about once every 1-2 years.

In preparation for experiencing an eclipse, you might be wondering what effects it could have on the brain, including psychological effects on mood and emotions. Let's dive in.

The Brain’s Response to a Solar Eclipse

Does a solar eclipse have an effect on the human brain? We explored this question in response to two mechanisms of human cognition: sleep and visual processing.

Sleep

When it comes to potential impacts on sleep and cognitive performance, here's what we know. Humans change across the day-night cycle, operating on a circadian rhythm. Early risers and night owls have patterns of cognitive performance that vary according to the time of day. Hormone levels and body temperature also go up and down in predictable daily rhythms. When the human circadian rhythm is disrupted (e.g. by travel, job requirements, or drugs), effects can include health problems, trouble sleeping, and big changes to mood.

But is a solar eclipse enough to interrupt our circadian rhythm or cause noticeable effects in humans? No, not really. There are no known physical effects, according to the NASA website.

Vision

The eyes are an anatomical extension of the brain, synaptically connected to the visual cortex. Since the eyes play an essential function in visual processing, you'll want to avoid potential damage caused by the sun.

Solar retinopathy is an uncommon condition that can result from looking at the sun directly, such as during an eclipse. It can cause mild-to-moderate visual acuity deficit. Fortunately, the effects are generally temporary, and people who have experienced this condition tended to recovery within 3–6 months after the inciting event.

Impact of Solar Eclipses on Mood and Emotions

In NASA's FAQ about the potential ways solar eclipses have an effect on humans, they do mention that psychological effects are real. A sense of awe can accompany the direct observation of the movement of celestial bodies that we all depend on, yet rarely think about.

Awe does have an affect the brain. In one fMRI study, scientific researchers asked participants to watch awe-inspiring nature scenes. They observed that brain activity in participants' default mode network (DMN) was dampened, suggesting that they experienced less rumination and self awareness, and conversely more engagement and immersion in the activity. Dampened DMN activity is also associated with experiences like flow state.

All that to say: a little awe may be good for the brain.

There are also many cultural stories and myths about solar eclipses that can shape a person's emotional experience of an eclipse event. Some of these stories take a tone of warning or suggest that eclipses are an omen.

The effects here may have more to do with psychology than the phenomenon itself. Humans tend to remember things that align with our expectations—that's what confirmation bias is after all. So because watching an eclipse can evoke a heightened sense of meaning, people may tend to remember what happens, for better or worse, in the days or weeks following.

Addressing Mental Health or Mood Changes

For those searching for an explanation for significant mental health or mood changes, especially lasting concerns, there may be other explanations to investigate. (Because beyond a temporary sense of awe, solar eclipses are not known to have lasting effects on emotions, mood, or mental health.)

Cognitive assessments and mental health screeners are some of the tools that healthcare providers can use to gather data rich insights on baseline cognitive performance and any significant changes.

Are you a healthcare provider? Learn more about Creyos Health.

Safety Precautions for Viewing Solar Eclipses

Viewing an eclipse can be a thrilling experience, but it requires some preparation and safety precautions, starting with proper eye protection.

There are a few ways to safely view a solar eclipse, including:

• Wearing solar eclipse glasses

• Using a telescope or binoculars with solar filters

• Viewing the effects indirectly, such as with a pinhole projector

When using direct methods of viewing, it's important to protect your eyes during all stages of a solar eclipse, including the partial phases leading up to totality (in the case of a total solar eclipse) and any other phase where the sun is partially obscured by the moon. Additionally, if you're using indirect viewing methods like pinhole projectors or solar telescopes, you should still avoid looking directly at the sun.

Viewing the sun directly can damage the eyes. Never use regular sunglasses, smoked glass, or homemade filters, as they do not provide adequate protection.

By following these safety precautions, you can enjoy the awe-inspiring spectacle of a solar eclipse.

Final Thoughts: Enjoy the Next Eclipse Event

The total eclipse is sure to be an amazing event. Be sure to take the necessary safety precautions to protect your eyes—in other words, get your solar eclipse glasses ready!