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

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.

Its predictability distinguishes SAD from other forms of depression

Most major depression is "stochastic"—brought on without a clear trigger. SAD—also known as major depression with a seasonal component—is unique in that its onset is predictable. Many of those affected can predict its occurrence accurately within a range of three weeks. This podcast explores this unusual feature of SAD, among other expert takes.

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.

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.

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.

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.

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.

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.

Having five of nine key symptoms constitutes a major depression

Before professional standards were adopted, practitioners used varying criteria to diagnose mental health disorders. By the 1970s, more objective lists were organized, culminating in this list of polythetic criteria—a list of symptoms where no single criterion is required, but a minimum number must be present.

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).

Roughly 1 in 125 people have autism spectrum disorder globally

The disorder has been increasingly diagnosed as its definition has grown broader and as clinicians have become more adept at identifying it—with some estimates suggesting the figures are much higher. These figures include people across the spectrum, some of whom live mostly independent lives, while others require life-long care and assistance.

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.

Bipolar disorder, which is characterized by extreme mood swings, affects nearly 3% of the US population

There are two types of this disorder. Bipolar 1 features a significant manic episode—abnormally elevated mood and frantic energy—followed by repeated depression, while Bipolar 2 vacillates between depressive episodes and hypomania, a milder form of mania, but not a full mania. Listen to this podcast as experts explain the condition.

Anhedonia, which means 'without pleasure' in Greek, is typical in major depressive disorder

This common symptom—a flat affect—results in previously enjoyable hobbies no longer bringing pleasure. People with anhedonia may also avoid social situations because they anticipate they'll bring no joy, not because of anxiety or fear.

Gene expression patterns are similar between ASD, schizophrenia, and bipolar disorder

Postmortem brain tissue analysis suggests there are genetic and epigenetic similarities between individuals with autism, schizophrenia and bipolar disorder. All three conditions appeared to have activation of genes in astrocytes and suppression of specific genes that function at the junction between neurons, called synapses. (Some users may encounter a paywall.)

Prolonged Grief Disorder has certain recognizable risk factors

This official diagnosis is characterized by intense, daily symptoms of grief a year after the loss of a loved one among adults and faster—around at least six months—for kids and teens. Factors that put people at increased risk of this disorder include being single, attachment anxiety, violent or unnatural death, low education, low income, and multiple losses, among others.

Learn the differences between mild cognitive impairment and age-associated memory loss

Mild cognitive impairment is a condition in which people experience more thinking and memory problems than expected for their age. It's often associated with depression and anxiety. Daily routines, writing things down, and healthy lifestyle choices can help cope with the condition, but there's no cure. The condition elevates the risk of developing dementia and Alzheimer's.

People with schizophrenia typically die 9 years earlier than the general population

The syndrome, which affects roughly 1 in 233 adults, is often associated with other serious health issues, including cardiovascular, metabolic, and infectious diseases, which may contribute to early deaths. The side effects of long-term antipsychotic medications also may influence the mortality timing—weight gain, for example, is a common side effect of the drugs and can contribute to cardiovascular issues.

About 12.5% of US adults experience a phobia in their lifetime, a diagnosis that hinges on the intense fear interfering with daily life and persisting for at least six months.

What is space sickness?

Mix motion sickness minus gravity with a host of other variables, and you’ve got a recipe for space adaptation syndrome. It can hit anyone, even astronauts who escaped the issue previously. This article details the history and science behind space sickness.

Social Security supports retirees, the disabled, and survivors

The Social Security Administration is responsible for more than just retirement benefits. Outside of the more well-known use case of retirement benefits, the SSA is also responsible for disability, family, and survivor benefits, supplemental security income, and more.

The rare but deadly time bomb lurking after a measles infection

Subacute sclerosing panencephalitis, also known as Dawson disease, is a progressive and fatal neurodegenerative condition caused by a dormant measles infection. Typically, patients recover from measles normally, with the symptoms of SSPE only appearing years or even decades later. The incidence rate in unvaccinated pediatric patients is estimated to be around one in 1,300.

Carrier screening enables individuals without symptoms to see if they carry a gene for disease

Some conditions are autosomal recessive—meaning a person may carry a gene for that condition, but not have symptoms. Cystic fibrosis, sickle cell disease, and Tay-Sachs disease are examples of autosomal recessive diseases in which a person must inherit two copies of a nonfunctioning gene—one from each parent—to develop disease.

Fear or disgust related to clusters of holes and cracks, called trypophobia, may stem from evolutionary processes to help us avoid pathogens

This type of extreme reaction to harmless holes, dots, cracks, and seed collections can be debilitating for those who have it, but it is not an officially recognized disorder in the DSM-5.

Influenza infects up to a billion people worldwide each year

The World Health Organization estimates that seasonal influenza causes about 1B cases annually, including 3 to 5M severe illnesses and between 290,000 to 650,000 deaths.

1 in 5 American adults report daily loneliness

Twenty percent of US adults said they felt lonely "a lot of the day yesterday" in Gallup polling conducted in 2024. The survey was conducted with more than 6,000 adults who took part in a web survey.

The hormonal disorder PCOS was renamed PMOS in 2026, a move designed to improve care and research by shifting the focus to the hormonal causes of this condition that affects 1 in 8 women.

Alzheimer's can lead to brain shrinkage, with an average of around 2% of volume reduction per year

Studies suggest when you sleep is as important as how much you get, and syncing with your circadian rhythms may lead to less fatigue and improved long-term health outcomes

In 2026, Finland was named the world's happiest country for the ninth consecutive year based on its wealth, social safety network, and high life expectancy, among other factors.

Use this calculator to find the dollar value of your mental load, from meal planning to coordinating after-school care for your children.

Up to a million Girl Scouts sell about 200 million cookie boxes every spring, generating $800 million, largely because refusing a child is frowned upon

20,000 letters to the advice columnist 'Dear Abby' provide insight into prevailing sex, religion, and LGBTQ fears, anxieties, and concerns from the 1950s onward.

Poison ivy can cause rashes year-round since all parts of the plant contain urushiol, the oil that triggers our allergic response.

'Silent' fireworks have gained more interest in recent years as a quieter celebratory option.

All rainbows are 'raincircles' caused by water droplets separating white sunlight into a spectrum of colors, but Earth's surface blocks the bottom half of the circle from our line of sight.

Three Ebola species are responsible for most large outbreaks of the disease, yet the only approved Ebola vaccine is known to work against just one of them.

Discover the catastrophic consequences of a failure of the US electrical grid—something that is more likely than many Americans think.

An investigation suggests a Scottish island became awash in forever chemicals via seafoam and seaspray—raising questions about what that means for the safety of other coastal areas.

Browse a detailed visual analysis of over 200,000 similes—comparisons that often use 'like' or 'as'—from popular fiction to see how frequently writers the same idiomatic expressions.

Crows are believed to have intelligence on par with a seven-year-old child and demonstrate complex behaviors, from problem-solving with tools to recognizing human faces.

Salvador Dalí believed he was his own dead brother, who had died nine months before he was born

The Great Salt Lake's distinct dual coloration results from high-salinity organisms that only live in the northern portion and produce a purple protein.

Explore the known asteroids, comets, and spacecraft involved in asteroid studies within our solar system with 'Eyes on Asteroids,' a 3D visualization from NASA.

In 1939, baseball star Lou Gehrig delivered his inspirational 'Luckiest Man' speech after retiring due to the health condition that now bears his name.

While atoms are normally made of protons, neutrons, and electrons, exotic ones have been built with antimatter—alternate versions of normal matter that live for fractions of a second and are about a billion times as rare.

El Niño, Spanish for 'the boy,' was named after Jesus Christ because the phenomenon resembled the weather changes observed around Christmastime.

A 2019 Facebook event called on attendees to "Storm Area 51, They Can't Stop All of Us," resulting in countless memes, the creation of a music festival, and eventually the arrests of those who did try to approach the area.

Sunflowers have long been a symbol of nuclear disarmament because they can extract large amounts of radioactive cesium from soil.

The Nasdaq's 'Magnificent 7' companies are responsible for roughly 40% of the Nasdaq 100 index's gains, while the remaining 93 companies account for the other 60%.