News / Health

Night Time Light Exposure Linked to Depression

Jessica Berman
A new study suggests that exposure to bright lights in the evening hours may increase the risk of depression and learning difficulties.

According to researchers at The Johns Hopkins University in Baltimore, steady exposure to bright lights at night produced signs of depression and learning disabilities in a group of laboratory mice.

It is well known that day and night rhythms can affect human metabolism, including psychological functions.  Biologist Samer Hattar says this is a condition known as seasonal affective disorder, or SAD, where some people become depressed during the winter season when days grow shorter.  SAD is often treated successfully by having patients spend time in front of special lamps called light boxes, whose full spectrum bulbs simulate natural daylight.

Hattar’s team also believes depression and learning deficits can set in for so-called "night owls" -- people who stay up very late and -- because they tend to sleep in late -- do not see much morning light.

That is a reaction the researchers saw in their study of mice exposed to a cycle of three-and-a-half hours of light followed by three-and-a-half hours of darkness.  Hattar says the cycle did not deprive the mice of sleep, just altered their wake-sleep cycle.

“So, we think that light at the wrong time of the day is very similar to what patients with seasonal affective disorder experience when they have shorter day length.  Although the two cycles look completely different, we think they ..converge somehow at the same function of depression and learning deficit,” Hattar said.

The nighttime light phenomenon seems to occur in people, or in the mouse study, rodents that were not exposed to much light during the day.  In humans, the researchers hypothesize it switches the light-dark cycle, causing changes in mood and learning.  For example, in the study, mice exposed to too much light at night had trouble learning and remembering tasks compared to normal mice.

The phenomenon might occur when people who are not exposed to much light at work during the day get home and switch on bright, mood-altering light sources such as iPads, data phones, large screen televisions or lamps with high wattage light bulbs.

Hattar says it appears that special cells in the eye, called intrinsically photosensitive retinal ganglion cells, become activated by this bright nighttime light, during what should be a period of downtime, stimulating the brain’s center for mood, memory and learning.

Investigators saw the mood changes in mice that were exposed to the unusual day-night cycle. Mice on a normal cycle were more energetic.
 
Hattar says the depressed mice did not have as much energy and drank little sugar water prepared for the rodents, behavior that investigators improved with a well-known antidepressant.

“By showing that they could reverse them with antidepressant drugs that work in humans, like we did in the paper by giving the animals Prozac,” Hattar said.

Hattar recommends that people who work in an office all day take a walk while it is still light out when they get home and dim the lights in their homes as much as possible - while still being able to see or read - to avoid depression caused by too much nighttime light exposure.

A paper on the effects of nighttime light on mood is published in the journal Nature.

You May Like

Mali's Female Basketball Players Rebound After Islamist Occupation

Islamist extremists ruled northern Mali for most of 2012, imposing strict Sharia law, and now some 18 months later, the region is slowly getting back on its feet More

Video Vietnamese Staging Chinese Product Boycott After Oil Rig Spat

Many Chinese-made products go unsold, for now, with numerous Vietnamese consumers still angry over recent dispute More

Koreas Mark 61st Anniversary of War Armistice

Muted observances on both sides of heavily-armed Demilitarized Zone that separates two decades-long enemies More

Featured Videos

Your JavaScript is turned off or you have an old version of Adobe's Flash Player. Get the latest Flash player.
Students in Business for Themselvesi
X
Mike O'Sullivan
July 26, 2014 11:04 AM
They're only high school students, but they are making accessories for shoes, fabricating backpacks and doing product photography - all through their own businesses. It's the result of a partnership between a non-profit organization that teaches entrepreneurship and their schools. VOA's Mike O'Sullivan and Deyane Moses met the budding entrepreneurs near Los Angeles.
Video

Video Students in Business for Themselves

They're only high school students, but they are making accessories for shoes, fabricating backpacks and doing product photography - all through their own businesses. It's the result of a partnership between a non-profit organization that teaches entrepreneurship and their schools. VOA's Mike O'Sullivan and Deyane Moses met the budding entrepreneurs near Los Angeles.
Video

Video Astronauts Train in Underwater Lab

In the world’s only underwater laboratory, four U.S. astronauts train for a planned visit to an asteroid. The lab - called Aquarius- is located five kilometers off Key Largo, in southern Florida. Living in close quarters and making excursions only into the surrounding ocean, they try to simulate the daily routine of a crew that will someday travel to collect samples of a rock orbiting far away from earth. VOA’s George Putic has more.
Video

Video Not Even Monks Spared From Thailand’s Junta-Backed Morality Push

With Thailand’s military government firmly in control after May’s bloodless coup, authorities are carrying out plans they say are aimed at restoring discipline, morality and patriotism to all Thais. The measures include a crackdown on illegal gambling, education reforms to promote students’ moral development, and a new 24-hour phone hotline for citizens to report misbehaving monks. Steve Sandford reports from Bangkok.
Video

Video Virtual Program Teaches Farming Skills

In a fast-changing world beset by unpredictable climate conditions, farmers cannot afford to ignore new technology. Researchers in Australia are developing an online virtual world program to share information about climate change and more sustainable farming techniques for sugar cane growers. As VOA's Zlatica Hoke reports, the idea is to create a wider support network for farmers.
Video

Video Airline Expert: Missile will Show Signature on Debris

The debris field from Malaysia Airlines Flight 17 is spread over a 21-kilometer radius in eastern Ukraine. It is expected to take investigators months to sort through the airplane pieces to learn about the missile that brought down the jetliner and who fired it. VOAs Carolyn Presutti explains how this work will be done.
Video

Video Treatment for Childhood Epilepsy Heats up Medical Marijuana Debate

In the United States, marijuana is classed as an illegal drug by the federal government. But nearly half the states have legalized it, to some degree. Proponents say some strains of marijuana might have exceptional health benefits, for treating pain or inflammation in chronic conditions such as cancer, multiple sclerosis and epilepsy. Shelley Schlender reports on a strain of medical marijuana developed in Colorado that is reputed to reduce seizures in childhood epilepsy
Video

Video Airbus Adds Metal 3D Printed Parts to New Jets

By the end of this year, European aircraft manufacturing consortium Airbus plans to deliver the first of its new, extra-wide-body passenger jets, the A350-XWB. Among other technological innovations, the new plane will also incorporate metal parts made in a 3-D printer. VOA's George Putic has more.
Video

Video AIDS Conference Welcomes Exciting Developments in HIV Treatment, Prevention

Significant strides have been made in recent years toward the treatment and prevention of HIV, the virus that causes AIDS. This year, at the International AIDS Conference, the AIDS community welcomed progress on a new pill that may prevent transmission of the deadly virus. VOA’s Anita Powell reports from Melbourne, Australia.
Video

Video IAEA: Iran Turns its Enriched Uranium Into Less Harmful Form

Iran has converted its stockpiles of enriched uranium into a less dangerous form that is more difficult to use for nuclear weapons, according to the United Nations’ Atomic Energy Agency. The move complies with an interim deal reached with Western powers on Iran's nuclear program last year, in exchange for easing of sanctions. Henry Ridgwell reports for VOA from London.

AppleAndroid