The ‘SAD’ case of seasonal affective disorder

Most people undergo some alteration in their overall mood or behaviour with the changing seasons. We usually ascribe it to the short days and deep freeze of “the winter blahs,” the season most often to blame. But, for as much as six per cent of the population, those seasonal shifts in their emotional weather are a serious problem, affecting energy levels, sleep, eating patterns and mood. In extreme cases, the changes are so overwhelming people are driven to suicide.

Seasonal affective disorder (SAD) may be the culprit. People in their 20s to their 40s are most susceptible, but SAD can also affect children and the elderly. It’s four times more prevalent among women than men, at least up until menopause, when the numbers level off. (SAD may be affected by the cyclical secretion of the female sex hormones estrogen and progesterone.)

In his 1993 book Winter Blues — Seasonal Affective Disorder: What It Is and How to Overcome It, Dr. Norman E. Rosenthal suggests one underlying cause of SAD — in addition to predisposing factors, such as stress — may be a disregulation of melatonin. Melatonin is a hormone produced by the pineal gland, a pea-sized structure tucked undneath the brain.

Each night, like clockwork, the pineal releases melatonin into the bloodstream in minute quantities until dawn. The secretion of melatonin signals the duration of darkness, and thus serves as an important seasonal time cue in animals. Thus, SAD may ultimately result from light deprivation, a theory that seems to be borne out by a number of observations. Geographic prevalence studies, for example, have shown the farther north you go, the more incidence of SAD you’ll find. In Mexico, south Texas and Florida, the prevalence of SAD is only 1.4 per cent, while across the northern United States and southern Canadian provinces, the figure leaps to 10.2 per cent.

Another confirming factor is the experience of people who develop symptoms of SAD with the setting of the sun, a condition known as “Hesperian depression,” after the Greek name for the evening star, Hesperus. And, most important, there is the proof inherent in the fact that most people suffering from SAD can be effectively treated with light therapy (though some people also respond to psychotherapeutic techniques or antidepressant medications).

Light therapy quite simply consists of sitting in front of a light source — such as a fluorescent lamp — at an appropriate distance with your eyes open. It’s not necessary to stare continuously at the light, Rosenthal writes, “though it may be helpful — and quite safe — to do so from time to time. The fact that light therapy works even if you do not stare directly at the light source suggests that the entire retina takes part in the response to light therapy and not just the central (and most visually sensitive) area. The peripheral part of your retina, which you use for spotting things in the periphery of your field of vision, is rich in receptors able to trap light. These receptors may be important for mediating light’s antidepressant effects.”

Rosenthal suggests seeking medical help under any of the three following circumstances: If your functioning is significantly impaired (you have difficulty concentrating or completing simple tasks, trouble motivating yourself to go to work, etc.); you experience significant depression (sadness, crying spells, excessively negative, pessimistic or guilty thoughts, feelings of worthlessness, etc.); or your physical functioning (sleep, eating patterns) is markedly disturbed during the winter.