by Amelia Douglass
Winter can be a wonderful time of year; magical snowy landscapes, crackling fires, tasty warming beverages and time to spend with family and friends. However, all these festivities are accompanied by significantly shorter days and thus less sunlight than in the summer. As an example, many places in the continental United States experience between 14 and 16 hours of sunlight in summer and only 8 to 9 hours in winter. Less sunlight facilitates some of the experiences we all love about winter such as cuddling up by a roaring fire while reading a good book. However, you might not know that lack of light in the winter has been linked to feelings of depression, low energy and motivation, sluggishness, as well as changes in appetite and weight. It’s estimated that approximately 20% of people experience some of these symptoms during the winter months. This is a large percentage of people, so how and why does this occur?
Recent scientific research has shown that changes in light directly affects parts of the brain that regulate mood. Scientists working with mice have found that a special type of cell in the retina detect light levels and communicate with parts of the brain that regulate mood. When the mice were exposed to shorter days than normal, they developed depression-like symptoms. Astonishingly when these special light-detecting cells were removed, the depression-like symptoms were absent. Similarly, another study in humans supported these findings. The scientists put study subjects inside an MRI machine in order to measure activity in different parts of their brains. Excitingly, they found that exposure to varying light levels caused changes in different parts of the brain known to directly affect emotions and mood. The researchers think that these regions receive information about light directly from the eye, just like in the mouse study.
So, these studies show a convincing link between light and mood. But why would this be the case? Why should lack of light make us feel depressed and conversely, why do we need light to be happy? The short answer is that we don’t know yet! One possible explanation relates to the fact that humans are diurnal, meaning we are active during the day and less so at night. Darkness instructs our body to go inside, prepare for sleep and preserve energy for the next day. In winter, most of us are still awake and active even when the sun has set. This means we are battling against our brain’s ‘default mode’ which is trying to make us slow down and get ready for sleep. Thus, we may feel a bit more sluggish and less motivated than usual.
Fortunately, there are some things we can all to do improve our mood during winter such as spending time outside during the daytime, exercising and doing things that we enjoy! If you find that you are really struggling with your mood over the winter months, don’t be afraid to go and speak to a doctor about how you’re feeling.