Read Norman Rosenthal’s original 1984 paper describing SAD

SAD 101 from the folks at NIMH—where the condition was first identified

Norman Rosenthal led the team at the National Institute of Mental Health that first identified and described seasonal affective disorder in 1984. This 101 from NIMH explores the basics of the condition, from who develops it to how it is treated.

Norman Rosenthal’s struggle with SAD inspired him to understand it

The South African doctor migrated to New York City in the 1970s. During his first winter there, he noticed the shorter days had a significant impact on his mood compared to those in his hometown of Johannesburg, South Africa, which is much closer to the equator. After three years of this seasonal mood shift, he decided to focus his studies. Hear him speak in this quick narration.

One theory claims the retinae of SAD patients may fail to adjust to less light in winter

Most people’s eyes become more sensitive to light in the winter months, but some do not. This failure to adjust causes ripple effects on those individuals’ biological clocks. This Ted-ED video provides a clear, brief, narrative explanation of the condition in six minutes.

10 percent of SAD cases occur in the summer

Despite its significantly lower incidence, summer-risk SAD is as significant as its winter counterpart. Rather than being prompted by less light, the summer version is typically spurred by high temperatures, strong light, distinct summer time social pressures (appearing in a bathing suit, for example), and pollen. Common treatments include keeping cool and prioritizing sleep.

An engineer tracked his moods for decades and helped researchers identify SAD

Civil engineer Herb Kern had bipolar and would record his moods dating back to 1967. He noticed the seasons were a major factor in the increase and severity of his episodes. By reaching out to researchers at the National Institute of Mental Health, Kern became the first human to confirm increased melatonin levels during winter and to receive bright light therapy.

Roughly 10% of the world has SSAD—SAD’s milder, nonclinical cousin

Subsyndromal affective disorder is diagnosed when someone exhibits two of the nine major criteria for depression (but not more than five) as a result of seasonal changes. While it is milder than primary SAD, SSAD is still significant and impacts millions.

SAD disrupts melatonin secretion, producing it longer in the morning

The hormone is secreted from the pineal gland in the brain and is key to the timing of sleep. However, the substance does not generate sleep itself. With seasonal affective disorder, the body misperceives the photoperiod—the time with light—and the cycle of sleeping and waking gets off-phase, leading to issues with circadian rhythms.

The design of a psychiatric ward in Norway aims to integrate more circadian rhythm-friendly lights as part of its treatment protocols for conditions including psychosis, severe depression, and more.

Winter-risk SAD is more likely in regions above 40 degrees latitude north

Using latitude, depression prevalence, and populations of women and those aged 18-30, this map shows the risk of experiencing seasonal affective disorder during the winter. Researchers weighted latitude most (50%) and demographics least (5% each for women and young adults). Overall risk is not a useful predictor of prognosis for an individual.

Bright light therapy involves basking in 10,000 lux of light for 30 minutes each morning

Nothing is better than going outside and soaking up real sunlight. However, this is harder in winter, especially in very cold and cloudy regions. SAD lamps are designed to project 10,000 lux—a unit of illuminance, or how much light actually hits a surface (rather than how much is produced, like watts). This video discusses product options and practical considerations.

SAD uniquely affects people with attention-deficit hyperactivity disorder

Those with ADHD—chronic issues with attention and executive function—are primed for SAD. Many are disproportionately evening chronotypes (more awake in the evening), have a delayed sleep phase, and have low sensitivity to light in the morning. This podcast explores the overlap between these two groups.

JJ Schildkraut theorized depression is linked to brain chemical imbalances—in 1965

Schildkraut was one of the first to put forward this idea, which stemmed from lab animal research. A decade later, researchers published the first landmark paper on fluoxetine—better known by trade name Prozac—which increases serotonin levels in the brain.

A 1974 Science News article proclaimed that within a decade, light therapy would be on par with traditional drugs.

Light therapy was widely used as a medical treatment for various maladies in the early 1900s before it was replaced by antibiotics.

Bupropion is the only antidepressant approved for the preventive treatment of SAD

Clinical trials showed a 44% reduction in risk for recurrence of SAD for those who took the drug compared to a placebo group. Bupropion is a norepinephrine–dopamine reuptake inhibitor, which increases dopamine (other common antidepressants, known as selective serotonin reuptake inhibitors, sometimes can suppress dopamine, but not always).

Lack of sunlight during Arctic winters can fuel a winter slump and a circadian disconnect.

Women are four times as likely to be diagnosed with seasonal depression

This prevalence trend mirrors the broader incidence of depression among women and is well-documented. Researchers suggest the disparity stems from differences in hormones, social role expectations, coping mechanisms, and more. Men may also present with depression differently, and seek help less.

See photos of ultraviolet light therapy, widely administered in the early 1900s, particularly among children with skin diseases, tuberculosis, rickets, and more.

See how antidepressants—used by roughly 1 in 10 Americans—were discovered.

Chronobiologists study the effect of time on biological cycles

Circadian rhythms were first observed in the 1700s, when French astronomer Jean-Jacques D'Ortous de Mairan put a plant in a dark room and watched it still respond to day and night cycles, setting off further studies about specific light-dark biological cycles, an area of inquiry that continues today with the human "clock proteins" at the molecular level.

The science of spring fever

Researchers have confirmed what people have sensed for ages: Our emotions during the springtime can go a little wild. This piece breaks down the impact of the seasonal transition on our bodies and prescribes a few ways to mitigate the effects.

Circadian rhythm disruption can influence various mental health disorders

This 2020 research overview surveys the relationship between disrupted circadian clocks and disorders including schizophrenia, anxiety, and bipolar disorder. It incorporates findings and therapeutic approaches drawing from human night shift studies and jet lag studies alongside animal research.

High-powered red light therapy—delivered directly to nerve fibers via a fiber optic needle—has been used in recent experimental research to suppress pain.

Artificial lighting and modern practices like working late are linked with sleep shifts

An analysis of five adults participating in a German reality program that tasked them with living in a Stone-Age-like settlement for 2.5 months, provided some insights into how modern conditions may have shifted our circadian rhythms. The participants slept about 90 minutes more under these conditions, and went to bed earlier and rose earlier, raising questions about how circadian rhythms, sleep, and sleep quality are affected by modern lifestyles.

This 1440 Original video dives into what the science says about phototherapy and its various potential applications.

Animals get SAD—especially those in zoos, like pandas

Giant pandas in locations outside their evolved latitudinal range (from southeast Asia to northern regions around Beijing) exhibit more sluggish behavior, even when they were born there. Researchers have observed that similar sensitivities to "photoperiods" (or time with light) impacts many animals, including birds, insects, and our pets. (Nautilus imposes a metered paywall.)

Studies suggest when you sleep is as important as how much you get.

The side effects of falling back and springing forward

Daylight saving time can interfere with a person’s sleep schedule, but it also has been linked to increased rates of depression, heart attack, stroke, cancer, and car accidents. UT Southwestern’s Dr. Joseph Takahashi explains why the time change is bad for your brain and health.

There is a template for how to live a better, healthier day, and it includes a digital sunset

Science suggests that early-morning exercise, later-morning peak work or social time, consistent exercise, and a "digital sunset"—starting to turn down the lights in the evening and avoid screens—are important for circadian health.

Emulating Earth’s light-dark cycle is important for astronaut health and safety

Astronauts aboard the International Space Station experience 16 daily sunrises, but scientists have learned to try to promote circadian rhythms by phasing through several light settings aboard the ISS to improve astronauts’ sleep and productivity.

View historical records of solar observations and discoveries, from telescopes in the early 1600s revealing sunspots to NASA's Parker Solar Probe photographing the sun from within its outer corona in 2025.

Daylight Saving Time is linked to a rise in heart attacks and strokes

Losing an hour of sleep with seasonal time changes is not good for our health and it’s linked to risks for the first couple days of Daylight Saving Time, including a short-term rise in heart attacks and strokes. Scientists theorize these elevated risks are linked to the disruption to the body’s circadian rhythm.

Studying the circadian clock of a tiny swimming polar creature may help forecast polar ecosystem health

A 2025 study found that Antarctic krill, a food chain staple in the Southern Ocean, have an internal biological clock that helps regulate its swimming patterns and helps the tiny shrimp-like animals adapt to daily and seasonal environmental changes. Better understanding of how the clock and light cues interact may help scientists understand how well the species will respond to pronounced climate change in the polar region.

The science of springtime, 101

Dive into the basics on springtime including the astronomy that brings it about, natural signs of spring's arrival, and some of the cultural approaches to the season.

Some data shows cold showers can help with depression

An icy water exposure can lead to the release of norepinephrine, cortisol, dopamine, and other stress hormones that are beneficial, among other potential effects. Some data shows that this type of exposure can help combat depression symptoms among some patients, but more research is still needed. (Some users may encounter a paywall.)

Daylight saving time, explained

Daylight saving time is supposed to help—but does it? Dive into the history, science, and consequences of this biannual aspect of American life (unless you're from Arizona or Hawaii).

Red light therapy—a treatment harnessing a specific form of energy that penetrates the top layers of skin—is marketed for skincare and wellness, but has its roots in NASA plant growth research.

Temperature and certain medications can also affect your circadian rhythms

Although light and dark have the largest influence on circadian rhythms, temperature, stress, and certain medications are among the factors that also play a role. Persistent trouble sleeping or staying asleep may signal it’s time to see your doctor to get a better sleep-wake schedule.

An overview of modern clinical research on LSD

Researchers have determined that LSD, taken in a medical setting, decreases anxiety related to "life-threatening disease," reduces brain reactivity to fearful faces, increases the meaning and emotional response derived from music, and more. No complications of LSD administration have been observed in medical settings, though acute adverse effects, including exhaustion, nausea, and difficulty concentrating.

Parasites have circadian rhythms, too

Researchers are working to unravel how circadian rhythms of parasites and their hosts affect one another. They’re investigating how to potentially target and disrupt those clocks for disease treatments.

The body's sleep-wake cycle is one of its many circadian rhythms

The body's sleep-wake cycle is one of its many circadian rhythms, which are behaviors or biological processes that exhibit 24-hour patterns. These rhythms are deeply impacted by light exposure, food availability, and much more, meaning where you live impacts your sleep.

Psychiatrist Bruce Greyson created a scale to identify and rate NDEs

Researcher Bruce Greyson is one of the world’s leading experts on near-death experiences. This article explores what the field of NDE research has learned over the last five decades, discusses the difficulties of studying such a controversial topic, and outlines what we’ve ruled out as the cause of these events.

How depression affects the brain

Treatment for depression has historically hinged on the theory that the condition was caused by underactive or abnormal neurotransmitters, specifically serotonin and norepinephrine. This four-minute video by Yale Medicine details how these neurotransmitters didn't explain the symptoms of depression but, two other neurotransmitters involved in regulating mood and emotion did. GABA and glutamate, some of the brain's most plentiful neurotransmitters, may possibly be the source of depressive symptoms.

Most things you would get tested for at the doctor’s office are influenced by circadian rhythm

In this video, a Salk Institute Researcher offers daily habit tips focused on aligning with your circadian rhythms. She notes heart rate and blood pressure are highest in the afternoon, for example, and there’s a triglyceride peak in the morning. Generally, she says, it’s a good idea to schedule your doctor’s checkups at the same time of day each year so there’s consistency across your data.

Autism spectrum disorder, defined in 2013, was previously categorized as numerous disorders.

American medical organizations rescind recognition of diagnosis cited in police custody deaths

American medical organizations have rescinded their recognition of a syndrome whose theory stemmed from discredited research. This article explores the history and implications of "excited delirium syndrome," a medical condition that can reportedly...

LSD-like drugs may inspire new antidepressants

LSD and psilocybin have shown promise as antidepressants. Using a virtual library of similar chemical compounds, researchers determined via animal studies that two molecules inspired by LSD have antidepressant effects without any associated hallucinogenic experience. These molecules were found to be 40 times more potent than the common antidepressant fluoxetine, also known as Prozac, with antidepressant effects lasting up to 21 days.

Mixed reality technologies may help treat depression

A study led by a team from Stanford University showed that MR can help people with depression by providing pathways to engage in activities such as digital board games and dancing. Participants saw reduced symptoms of depression that made their overall treatment plans more successful.

Depression changes the brain, causing distinct structural alterations visible on brain scans, but effective treatment can eventually make a depressed brain resemble a healthy one.

LSD fueled a countercultural movement before evolving into a potential therapeutic

As the use of recreational psychedelics became common, authorities were quick to claim LSD had lasting adverse effects, criminalizing the drug and halting scientific study for decades. Over time, LSD's reputation shifted from a potential source of enlightenment to a dangerous drug that could dim a person's future, and back to a possible therapeutic compound.