An annual pattern of winter depression and melancholy, better known as seasonal affective disorder (SAD), suggests a strong relationship between mood and the amount of light during the day.
Simply put, less exposure to light can lower your mood.
Winter depression is common, but about 10 million Americans are affected by a long-term depression called seasonal affective disorder each year. In addition to depressed mood, symptoms include anxiety, low self-esteem, prolonged sleep, constant cravings for carbohydrates, and reduced physical activity levels.
I am a nutritional neuroscientist whose research focuses on the effects of diet and lifestyle factors on mood and brain function, including mental distress, resilience, and motivation.
Through research, I learned that seasonal affective disorder can happen to anyone. However, people with a history of mood disorders are at increased risk. Young adults of all ages and women are particularly susceptible.
Why Seasonal Depression Occurs
When daylight saving time ends each fall, a one-hour reverse shift reduces the amount of light most people receive in their 24-hour cycle. As the days get shorter, people may experience general moodiness and long-term depression associated with less time in the sun.
This is caused by deviations between sleep and wake cycles, meal schedules, and other daily activities. Research shows that this mismatch may be associated with mental health disorders such as anxiety and depression.
Our sleep-wake cycles are controlled by the circadian rhythm, a body clock that is regulated by light and darkness. Like a normal clock, it resets approximately every 24 hours and controls metabolism, growth, and hormone release.
When our brain receives a limited signal of sunlight, it releases melatonin, a sleep-supporting hormone, even though there are still a few hours left before our usual bedtime. It can affect how much energy you have, when and how much you eat. This process, called neuronal plasticity, involves the growth and organization of neural networks. This is crucial for brain repair, maintenance, and overall function.
You can readjust your circadian rhythm to better match your new light-dark schedule. This means getting in the sun as soon as possible after waking up, which means getting your sleep, exercise and eating routines more in sync with your pre-time change routines. Eventually, you can gradually transition to your new schedule.
Close relationship between serotonin and melatonin
Serotonin is a chemical messenger in the brain and plays an important role in regulating several functions such as mood, appetite and circadian rhythms.Serotonin is also converted to melatonin at lower light intensities. As mentioned earlier, melatonin is the hormone that regulates the sleep-wake cycle and signals to the brain that it’s time for sleep.
Less exposure to sunlight during the winter causes it to get dark earlier in the evening, which results in the conversion of serotonin to melatonin.As a result, this premature release of melatonin causes disruption of the sleep-wake cycle. For people with seasonal affective disorder, this causes moodiness, daytime sleepiness, and loss of appetite regulation, usually leading to unhealthy snacking. Because of its close relationship to , we often crave foods rich in simple sugars, such as sweets.
Strategies for fighting the winter blues
In winter, most people leave work when it gets dark. For this reason, light therapy is usually recommended for those who experience seasonal affective disorder or who have short periods of seasonal funk.
This can be as simple as turning on the light immediately after waking up. Get at least an hour of natural light early in the morning. Preferably, do this about an hour after your normal wake-up time, when your circadian clock is most sensitive to light. This is the same in the morning, regardless of when you wake up. Light therapy boxes that reproduce outdoor light are effective for people living in northern latitudes where the sun rarely shines in winter.
Avoiding coffee, tea, and heavy meals before bed can also improve sleep quality. Increases serotonin production and supports regulation of circadian rhythms. A balanced diet of complex carbs and healthy proteins supports steady serotonin and melatonin production, and practicing downtime before bed can help reduce stress.
By taking these small steps, you can adjust your circadian rhythm faster. For millions of people with mood disorders, it could literally mean happier times in their darkest days.
