11/04/2011 08:51 am ET Updated Jan 04, 2012

Seasonal Affective Disorder: When Are We Saddest?

As we slowly progress from the bright, burnished days of fall to the cold of the winter, it's no surprise that our moods start getting darker too.

Just exactly why weather affects us so severely, though, is still a matter of controversy. Some scientists say that the culprit is serotonin -- the chemical that makes us happy -- which controlled by the amount of light we receive. When there's a lack of light, serotonin converts into melatonin, which controls our sleep. Consequently, come winter, we become sadder and sleepier.

But researchers based in Norway have found that in Scandinavian countries, seasonal affective disorder affects people during spring and summer, but not as much during the winter months, thereby calling into question the light-brain-chemical theory.

HuffPost blogger and SAD pioneer Dr. Norman Rosenthal suggests making a plan to cope with the brutal winter months. "Compensate for the lack of sunlight. Find a room in your house where you get sunlight, and spend time in it. Get out and exercise. Enjoy the extra hour of sunlight in the morning," he says. We're also less resilient and more likely to be affected by stress so Dr. Rosenthal suggests finding time to meditate.

But when, as a collective population, are we likely to be saddest? While no official data exists, there are times of the year that are well-known for their depression-inducing qualities. Take a look.