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

US, China Have Dueling Definitions of Cybersecurity

Analysts say attribution or or proving that a particular individual or government is responsible for a hack, is a daunting task More

Snowden: I'd Go to Prison to Return to US

Former NSA contractor says he has not received a formal plea-deal offer from US officials, who consider him to be a traitor More

Goodbye Pocahontas: Photos Reveal Today's Real Native Americans

Weary of stereotypes, photographer Matika Wilbur is determined to reshape the public's perception of her people More

Featured Videos

Your JavaScript is turned off or you have an old version of Adobe's Flash Player. Get the latest Flash player.
Russia’s Syria Involvement Raising Concerns in Europei
Luis Ramirez
October 02, 2015 4:45 PM
European nations are joining the United States in demanding that Russia stop targeting opposition groups other than the Islamic State militants as Russian warplanes continue to conduct raids in Syria. The demand came in a statement from Britain, France, Germany, Qatar, Saudi Arabia, Turkey and the United States Friday. VOA Europe correspondent Luis Ramirez reports.

Video Russia’s Syria Involvement Raising Concerns in Europe

European nations are joining the United States in demanding that Russia stop targeting opposition groups other than the Islamic State militants as Russian warplanes continue to conduct raids in Syria. The demand came in a statement from Britain, France, Germany, Qatar, Saudi Arabia, Turkey and the United States Friday. VOA Europe correspondent Luis Ramirez reports.

Video First Self-Driving Truck Debuts on European Highways

The first automated semi-trailer truck started its maiden voyage Friday, Oct. 2, on a European highway. The Daimler truck called 'Actros' is the first potentially mass-produced truck whose driver will be required only to monitor the situation, similar to the role of an airline captain while the plane is in autopilot mode. VOA’s George Putic reports.

Video Nano-tech Filter Cleans Dirty Water

Access to clean water is a problem for hundreds of millions of people around the world. Now, a scientist and chemical engineer in Tanzania (in East Africa) is working to change that by creating an innovative water filter that makes dirty water safe. VOA’s Deborah Block has the story.

Video Demand Rising for Organic Produce in Cambodia

In Cambodia, where rice has long been the main cash crop, farmers are being encouraged to turn to vegetables to satisfy the growing demand for locally produced organic farm products. Daniel de Carteret has more from Phnom Penh.

Video Migrant Influx Costs Europe, But Economy Could Benefit

The influx of hundreds of thousands of refugees and migrants is testing Europe’s ability to respond – especially in the poorer Balkan states. But some analysts argue that Europe will benefit by welcoming the huge numbers of young people – many of them well educated and willing to work. Henry Ridgwell reports from London.

Video Botanists Grow Furniture, with Pruning Shears

For something a bit out of the ordinary to furnish your home, why not consider wooden chairs, crafted by nature, with a little help from some British botanists with an eye for design. VOA’s Jessica Berman reports.

Video New Fabric Helps Fight Dust-Related Allergies

Many people around the world suffer from dust-related allergies, caused mainly by tiny mites that live in bed linen. Polish scientists report they have successfully tested a fabric that is impenetrable to the microscopic creatures. VOA’s George Putic has more.

Video Burkina Faso's Economy Deeply Affected by Political Turmoil

Political turmoil in Burkina Faso over the past year has taken a toll on the economy. The transitional government is reporting nearly $70 million in losses in the ten days that followed a short-lived coup by members of the presidential guard earlier this month. The crisis shut businesses and workers went on strike. With elections on the horizon, Emilie Iob reports on what a return to political stability can do for the country's economic recovery.

Video Fleeing Violence, Some Syrians Find Refuge in Irbil

As Syrians continue to flee their country’s unrest to seek new lives in safer places, VOA Persian Service reporter Shepol Abbassi visited Irbil, where a number Syrians have taken refuge. During the religious holidy of Eid al-Adha, the city largely shut down, as temperatures soared. Amy Katz narrates his report.

Video Nigeria’s Wecyclers Work for Reusable Future in Lagos

The streets and lagoons of Africa's largest city - Lagos, Nigeria - are often clogged with trash, almost none of which gets recycled. One company is trying to change that. Chris Stein reports for VOA from Lagos.

Video Sketch Artist Helps Catch Criminals, Gives a Face to Deceased

Police often face the problem of trying to find a crime suspect based on general descriptions that could fit hundreds of people in the vicinity of the crime. In these cases, an artist can use information from witnesses to sketch a likeness that police can show the public via newspapers and television. But, as VOA’s Greg Flakus reports from Houston, such sketches can also help bring back faces of the dead.

Video Thailand Set to Build China-like Internet Firewall

Thai authorities are planning to tighten control over the Internet, creating a single international access point so they can better monitor content. VOA Correspondent Steve Herman reports from Bangkok on what is being called Thailand’s own "Great Firewall."

Video Croatian Town’s War History Evokes Empathy for Migrants

As thousands of Afghanistan, Iraqi and Syrian migrants pass through Croatia, locals are reminded of their own experiences with war and refugees in the 1990s. VOA's Daniel Schearf reports from the town of Vukovar, where wartime scars still are visible today.

Video Long Drought Affecting California’s Sequoias

California is suffering under a historic four-year drought and scientists say even the state's famed sequoia trees are feeling the pain. The National Park Service has started detailed research to see how it can help the oldest living things on earth survive. VOA’s George Putic reports.

VOA Blogs