Shorter Days and Darker Afternoons May Trigger Depression

As daylight hours decrease with the approach of winter, people vulnerable to seasonal depression may experience changes in their mood, energy levels and mental well-being.

Millions of people worldwide are estimated to experience seasonal affective disorder (SAD), a form of depression that typically begins in autumn and improves during spring or summer. Reduced daylight, particularly darker afternoons following the return to standard time, can trigger symptoms.

A milder form, known as subsyndromal SAD, is also recognised by medical experts, while seasonal depression during summer remains less understood.

Dr Norman Rosenthal, who led the National Institutes of Health (NIH) research team that first described the disorder in 1984, coined the term seasonal affective disorder. He said the acronym's simplicity and memorability helped it gain widespread recognition.

Scientists Investigate Possible Causes

Researchers have yet to identify a single cause of SAD. According to the NIH, the condition affects significantly more women than men.

Its symptoms resemble those of depression and may include persistent feelings of hopelessness and pessimism, along with difficulties in concentration, memory and decision-making.

Scientists are investigating how specialised cells in the eyes respond to blue wavelengths of light and send signals to the brain that influence mood and alertness.

Sunlight contains substantial amounts of blue light. When these cells detect it, they activate the brain's alertness centres, helping people feel more awake and potentially improving their mood.

Kathryn Roecklein, a researcher at the University of Pittsburgh, studied how people with and without SAD respond to blue light. Her research found that people with SAD were generally less sensitive to blue light, particularly during winter, suggesting a possible link between reduced light sensitivity and seasonal depression.

Light Therapy Can Ease Winter Depression

Bright-light therapy has proved effective for many people with SAD, said Dr Paul Desan of Yale University's Winter Depression Research Clinic.

The treatment generally involves sitting in front of a specially designed bright-light device for about 30 minutes each morning. Research supports using devices that provide around 10,000 lux of light, approximately 20 times brighter than ordinary indoor lighting.

Desan said the therapy could also benefit people experiencing milder forms of winter-related low mood.

Such devices cost between $50 and more than $400. However, some products marketed for SAD may not provide sufficient brightness to be effective, he cautioned.

Yale has tested different products and published recommendations, while the nonprofit Center for Environmental Therapeutics also offers a consumer guide to choosing suitable light devices.

People diagnosed with SAD may consult their health insurance providers to determine whether the cost of light therapy equipment is covered.

Therapy and Medication Also Offer Relief

Antidepressant medication and light therapy are among the first-line treatments for SAD. Doctors also recommend maintaining a regular sleep schedule and spending time outdoors, even on cloudy days.

Although light therapy can be effective, its benefits may diminish after treatment is discontinued.

Research has also shown that cognitive behavioural therapy (CBT), a form of talk therapy, can produce longer-lasting benefits, said Kelly Rohan, a researcher at the University of Vermont.

CBT involves working with a therapist to identify and change unhelpful patterns of thinking.

Rohan said therapy can also help people gradually resume enjoyable activities and overcome the tendency to withdraw during winter.

Planning simple activities, such as meeting a friend for coffee or spending time outdoors, can help people remain socially active and improve their mood.