I’m learning about North Texas weather and the seasons here. While my midwestern friends are talking about snow and ice, I was in short sleeves yesterday sweeping pine needles off my driveway. Regardless of the latitude though, we all can sense the onset of winter. There’s more darkness – as our days shorten we’re more likely to leave for work in the dark and drive home after work in the dark. We know intuitively that this cycle of light and dark happens every year – why does it catch us off guard? What’s triggering the regret and sadness as winter comes? Darkness and night are often associated with fear of the unknown and unseen.
Seasonal Affective Disorder (SAD) is a type of depression which affects half a million people in the USA every winter, with a peak incidence in December, January and February. Three out of four SAD people are women and the main age of onset is between 18 and 30 years of age. It is rare to develop SAD within 30 degrees of the equator and it can occur in either the northern or southern hemisphere. Now we’re starting to understand more about the reason for these “winter blues”.
Buried in the base of the brain is the pineal gland, which produces a hormone or chemical messenger called melatonin. In the animal kingdom, the pineal gland controls circadian rhythms such as when to sleep, when to wake, when to migrate, when to hibernate, when to build a nest and become pregnant or lay eggs. Now there is data to show that melatonin plays a role in temperature regulation, the function of the immune system and even the onset of sexual maturity in the animal kingdom.
But what of humans? Prior to 50 years ago, the pineal gland was thought to be a vestigial or remnant organ without significant function. (Similar to the appendix attached to the large intestine – although we’re starting to appreciate the role of the appendix in “re-seeding” the GI tract with beneficial bacteria after antibiotics are used.) Research has shown that melatonin is synthesized in our bodies from the neurotransmitter serotonin and that the levels of melatonin rise with the onset of darkness while the serotonin levels drop at night as it is turned into melatonin. Daylight is perceived by the retina in the back of our eyes, which sends a message to the pineal gland and “shuts down” melatonin production until the darkness returns. Because of this research, many people have used melatonin supplements to help with sleep patterns; the problem with this approach is that melatonin probably doesn’t cause the sleep cycle to “turn on” as much as it plays a part in inhibiting the brain’s urge to be awake. In other words, perhaps the reason why not everyone benefits from using the supplement for improving sleep is that some other hormonal imbalance is causing the wakefulness.
As you can imagine, there is a lot of interest in understanding the human side of the pineal gland and melatonin story. For instance, we know that melatonin levels are high in children from ages 4 to 7 and then levels decline overall – presumably to allow puberty to begin to develop. In addition, studies in mice show that the immune system is up regulated in the presence of melatonin while antibody production is reduced if the pineal gland is removed. We don’t know how this plays out in our own immune function.
So what does this mean for people with SAD? The solutions will be different for everyone. One option is to increase the amount of daylight or full-spectrum light you’re exposed to in a day. Open the blinds and curtains, install skylights, and arrange your schedule to be outside in midday. Some companies sell full-spectrum lights to turn on for a period of time before or after daylight ends. Another option is to “migrate” south with the birds and spend the winter in sunnier climates.
Pay attention to the quality and quantity of food in your diet. Although it is harder to find fresh locally grown organic produce in the winter, perhaps you have frozen or canned some of your bountiful harvest and can turn to nourishing whole grains and soups and stews. Experiment with root vegetables and cold weather crops. Exercise daily. Bundle up if necessary and enjoy the lacey ice branches and the quiet snowscapes. Or commit to the gym and listen to a book on tape or that jazz CD you just bought as you work out.
Most of all, appreciate the changes in the light/dark cycle. Pay attention to the change in the darkness. The Winter Solstice on December 21st signals the gradual shift back to longer days. The return of the sun. (And in my religious tradition, the birth of the son.) The gift of light that we can appreciate in any context every year.