December 14, 2021 - Reduced sunlight can cause a drop in serotonin that may trigger depression. Melatonin levels. The change in season can disrupt the balance of the body's level of melatonin, which plays a role in sleep patterns and mood.

It happens during certain seasons of the year, most often fall or winter. It is thought that shorter days and less daylight may set off a chemical change in the brain leading to symptoms of depression.

1 week ago - Seasonal affective disorder (SAD, colloquially referred to as seasonal depression) is a mood disorder subset in which people who typically have normal mental health throughout most of the year exhibit depressive symptoms at the same time each year. It is commonly, but not always, associated ...

Most research to date has investigated potential causes of winter-pattern SAD because it is more common and easier to study. As a result, less is known about summer-pattern SAD, and more research is needed. Studies indicate that people with SAD, especially winter-pattern SAD, have reduced levels of the brain chemical serotonin, which helps regulate mood. Research also suggests that sunlight affects levels of molecules that help maintain normal serotonin levels.

Seasonal affective disorder or SAD is a type of depression experienced by some people during the winter months, when there is less natural sunlight.

August 9, 2025 - That said, these levels decline in winter both for people who experience symptoms of seasonal affective disorder and those who don’t. The common cause is reduced outdoor daylight exposure.

People with seasonal affective disorder have difficulty regulating the neurotransmitter serotonin, a neurotransmitter believed to be responsible for balancing mood [2]. In one study, people with SAD had 5% more SERT, a protein that assists with serotonin transport, in the winter months than in summer [2]. SERT transports serotonin from the synaptic cleft to the presynaptic neuron, so higher SERT levels lead to lower serotonin activity, thus causing depression [2]. Throughout the summer, sunlight generally keeps SERT levels naturally low [2]. But as sunlight diminishes in the fall, a corresponding decrease in serotonin activity also occurs.

July 14, 2025 - Seasonal depression, or seasonal affective disorder (SAD), is a form of depression triggered by the change of seasons.

October 16, 2024 - While the exact cause is unknown, it may be linked to the reduced amount of sunlight affecting the natural chemicals like serotonin and melatonin in your body that determine mood and energy levels and regulate sleep.

SAD is thought to be linked to the lack of sunlight, which can disrupt the body's internal circadian rhythm and lead to decreased levels of serotonin, a brain chemical that affects mood.

November 23, 2023 - “In seasonal affective disorder, neurotransmitter levels become unbalanced. This imbalance affects how you respond to light-dark changes, especially in the fall.” · The cause of summer SAD is less clear, but may be in part due to low vitamin D.

Abnormal regulation of circadian rhythms likely contribute to an individual's inability to match his or her circadian rhythms to changes in seasons, resulting in changes in sleep, mood, and behavior as daylight hours change.

SAD has been linked to changes in the brain prompted by shorter daylight hours and less sunlight in winter. As seasons change, people experience a shift in their biological internal clock or circadian rhythm that can cause them to be out of ...

The exact cause of SAD isn't clear, but some kids' and teens' brains react differently to fewer hours of daylight. Daylight affects two chemicals in the brain: serotonin and melatonin.

March 25, 2025 - Biology plays a critical role in shaping how individuals respond to seasonal changes. Genetics: Research suggests that genetic predisposition may influence a person’s susceptibility to SAD. A family history of depression or mood disorders can increase the likelihood of experiencing symptoms. Hormonal Influence: As sunlight exposure decreases, the body produces more melatonin and less serotonin, affecting sleep patterns and emotional regulation.

April 20, 2024 - The condition is linked to neurotransmitters like dopamine, norepinephrine, and glutamate, although the exact pathophysiology is unclear.[1][12] Disruptions in the body's circadian rhythm due to reduced sunlight exposure during fall and winter are thought to be involved in the onset of winter-onset ...

Seasonal affective disorder is a type of depression that occurs during the same season each year. Researchers think that SAD is caused by changes in the level of exposure to sunlight. Light therapy is the main treatment for SAD.

October 31, 2025 - When the days grow shorter and temperatures drop, millions of people find themselves grappling with the “winter blues.” This is known as seasonal affective disorder, which is a form of depression that follows a seasonal pattern. Emerging primarily during the fall and winter months when sunlight exposure decreases and clocks fall back, seasonal affective disorder can take a toll on a person’s daily life.

Lack of light may upset your "biological clock," which controls your sleep-wake pattern and other circadian rhythms. Lack of light may also cause problems with serotonin, a brain chemical that affects mood. Seasonal affective disorder (SAD) can come and go at about the same time each year.

October 9, 2020 - Seasonal affective disorder (SAD) is a type of depression linked to reduced sunlight exposure, particularly during winter, which can disrupt the body’s circadian rhythm and chemical balance.