New research into the connection between weather and moods has started to chip away at old myths as well as uncover some potentially powerful treatments for the winter blues.
The first myth to die is the idea that everyone feels bad when the weather gets foul. It turns out that most people might fall into one of four categories when it comes to their moods and weather, say researchers who have studied more than 2,000 Germans by way of daily questionnaires about their moods and other happenings in their lives.
"We saw differences and we actually categorized people according to their differences," said Jaap Denissen of Humboldt University in Berlin. He and his colleagues have submitted their latest work, an expansion of an earlier study, to the journal Emotion.
The four categories Denissen and his team identified are 1) those people who are unaffected by the weather or seasons, 2) people who love summer, 3) people who hate summer and 4) people who love rain.
"We could clearly label these types," Denissen told Discovery News.
They also found that children tend to be the same types as their mothers. However, they do not know yet if the categories have any genetic basis or are learned. Sorting that out would take a lot more research, he said, including the study of large numbers of identical twins to see if they respond to weather and season in sync or differently.
The large numbers are always needed, Denissen explained, because that's the only way to sort out and isolate meaningful causes and effects relating to moods. Making the same correlation on an individual basis is impractical because it is difficult to sort out what variable -- like exercise, sleep, social activities and free time -- in one person's life is influencing what mood. With thousands of people, however, patterns start to emerge.
One underlying cause of some season and weather-related depression that is neither genetic or learned could be vitamin D deficiency. In recent years there has been a surge of research connecting vitamin D deficiencies with all sorts of health effects -- particularly in less sunny seasons.
"There is a seasonal variation and that's well documented," said Sue Penckofer, a professor at Loyola University Chicago, referring to vitamin D deficiencies in the Unites States Penckofer has been investigating the role of vitamin D deficiencies in the onset and severity of symptoms of diabetes and other diseases. Those symptoms, which include fatigue, can be helped with a little more vitamin D (although not too much, since vitamin D is toxic in large quantities).
Vitamin D is found in fish and specially enriched dairy products. It's also produced in human skin when it's exposed to sunlight, hence the seasonal connection. In northern climates vitamin D deficiencies are not uncommon in the winters, Penckofer explained, especially among darker skinned individuals.
Skin pigment blocks sunlight from entering the skin to make vitamin D, which is probably why African American women have been shown to suffer from lower vitamin D levels than other women, she said.
Fortunately it's possible to supplement vitamin D in diets, which has shown mood-enhancing results in individuals Penckofer has worked with.
"What I can say for a fact is that we have seen people reporting that they feel better and don't feel as tired" when they are supplementing their vitamin D, Penckofer said. "One lady said 'I feel like the Energizer bunny.'"
Although vitamin D is not a panacea for all seasonal moodiness, it's certainly another factor to consider in the ongoing battle to sort out how we are affected by the world around us.
"We just want to give people insights into what drives their moods," agreed Denissen.