In the early 1980s, a researcher at the National Institute of Mental Health (NIMH) named Norman E. Rosenthal noticed that he would grow depressed, each year without fail, at the onset of winter. A sober, scientific individual – he set out to systematically describe and report on this odd, familiar depression that seemed to ebb and flow with the seasons. And although industry experts were initially skeptical of the condition’s existence, Dr. Rosenthal’s work struck a personal chord with many other researchers – many of whom privately struggled with precisely what Rosenthal described, not just their patients – prompting further research into the subject.
The condition, now known as Seasonal Affective Disorder, and appropriately-abbreviated “SAD,” is a well-known feature of life in colder climates. It’s known among clinicians as one of the most common factors implicated in major depressive disorder, which means that SAD is not a separate disorder but a specific type of depression – one characterized by a recurring, seasonal pattern, with symptoms lasting about 4 to 5 months per year, and receding upon the changing seasons. Most people who experience SAD have also experienced at least one other episode of major depression in their lives, and the two are closely related.
It’s best thought of in terms of susceptibility and triggers. Specific individuals are born with different brain chemistry, making them naturally prone to depressive moods. And SAD statistics overlap precisely with those of other forms of depression. It occurs more commonly in women than men and occurs more often in people with pre-existing mental health conditions – especially bipolar type-II, ADHD, and eating disorders. It also seems to have a genetic component, as SAD is more common in people who have relatives with mental illnesses.
But climate remains the best, most-obvious predictive feature. In Florida, about 1.5% of the population reports seasonal mood changes. While in Alaska, a full 10% of the population reports struggling with SAD.
But like depression as a whole, we don’t fully understand the disorder. Research suggests that the culprit is dysfunction within two chemical systems – serotonin and melatonin. The former chemical is responsible for mood regulation, and our body relies on sunlight to create the precursor molecules, or building blocks, of serotonin. The latter is a hormone produced inside the body which regulates our circadian rhythm – again, a function of how much sunlight we get. So, the prevailing theory is that decreased sunlight reduces serotonin and boosts melatonin production, throwing our daily rhythms out of whack. As a result, affected individuals cannot adjust to the dramatic seasonal changes in the length of their day – sleeping longer, eating the wrong food at the wrong times, and falling into a self-perpetuating cycle of insomnia.
But where does this leave us? Fortunately, as with other forms of depression, treatments are available for SAD. In a separate post, I’ll cover some of the typical ways we address depression, as well as SAD-specific tips for beating the Winter Blues.