Happiness is found in the contrast, they say. But what about sadness? And to sharpen the point even further, when it comes to seasonal affective disorder — that energy-draining condition that rolls around three months out of the year — what about depression?

Since its initial description in 1984, seasonal affective disorder (SAD, fittingly) has spawned a wealth of research into what makes us feel the way we do. Five years after Dr. Norman E. Rosenthal helped make the discovery, he and his research team stumbled upon a lesser publicized condition. Suddenly, people weren’t just hibernating in the winter and blooming in the spring and summer months. Once the heat hit, so did their depression.

A Very Different Mechanism

For Rosenthal, currently a professor of clinical psychiatry at Georgetown University, the sheer absence or presence of light began to seem like a weaker argument for why these disorders cropped up. “Inherent in the timing of the disorder is something in the causes of the disorder,” he told Medical Daily. For example, darkness has been shown time and again to predict the severity of the winter variety of SAD. But during the summer months, when light is abundant, some people report equal levels of illness.

“The fact summer depression is happening in the summer suggests there’s a very different pathophysiology — a very different mechanism at work — that is inducing symptoms.”

Unfortunately, as Rosenthal points out, in the field of summer depression research there is a surplus of observation and a shortage of explanation, a lot of what without much why. One theory speculates a combination of increased light and heat is what’s causing the depressive symptoms, which, it should be noted, are markedly different from winter SAD. People with summer depression grow agitated and sleepless, unlike their late-sleeping peers in winter who are easily exhausted.

The statistics are light when it comes to prevalence, but most estimates find five percent of the total population suffers during the dark winter months. Summer depression occurs among roughly one percent of the population. But don’t ask these people about the root cause of their depression, Rosenthal says. You won’t learn very much.

“When people are very distressed they don’t become very poetic. They don’t say ‘to feel sharper than a serpent’s tooth,” he said. “They say ‘I feel terrible and it sucks.’”

How To Treat

That’s not to say his patients haven’t offered helpful insights. Rosenthal recalls one patient who felt the effects one evening driving home, when the sun was low on the horizon. “The sun cut through me like a knife,” the patient told him, “and caused me to feel depressed.” Descriptions like these are common, much in the way winter SAD patients mull over the darkness with a sense of empty that is in a way claustrophobic.

More than two decades of research have confirmed geography plays a role. People in New Hampshire are significantly more likely to feel the effects of winter SAD than summer SAD because their climate shifts most dramatically during the winter months. In hotter climates further toward the equator, the summer months are the ones to brave. What comes as a welcome break in chilly New Hampshire is an oppressive heat wave in Texas. The seasons may be the same, but the temperatures — both relative and absolute — vary widely.

Treating each disorder also comes with unique challenges. Rosenthal concedes that antidepressants will rear their head eventually, but the two paths leading to pharmaceuticals wind and undulate without intersection. Winter SAD sufferers, for instance, often are encouraged to buy a light therapy box, which sits on a desktop and mimics the sun’s natural rays, along with spending ample time outside, when the sun is still shining.

Summer SAD gets an entirely different treatment regimen. These patients are prone to lose weight, not gain it, and they’re often guilty of sleeping too little, not too much. Doctors will suggest oral doses of melatonin, a hormone secreted in the brain as a natural sleep aid, and rising early in the morning — two ways to reset the body’s circadian rhythms, which may be disrupted due to prolonged daylight. For Rosenthal, the ongoing intrigue lies in the diversity of what’s been successful.

“Some respond to the cold, some respond to the dark — dark glasses, keeping in dark rooms — some respond to the burst of light early in the morning… What I guess is interesting to me about that is even among people with summer depression, you’re probably dealing with a mixed group with different causes to them,” he said. “They’re not all cut out of one mold.”

And that could be the key point. Depression is a recognized pattern of behavior and brain chemistry, but it’s also a complex mixture of environmental, social, and biological components. Painting a dresser bright yellow or cranking the air conditioning to full blast may work in each particular case, but that’s as far as the prescription can go — at least until science, as it always strives to, learns a little bit more. Here’s to the sweet relief of March and October.