Humors, seasons and depression

Around 2500 BC, ancient Greek and Ayurvedic physicians first described how humors body fluids such as bile or blood were related to a persons wellbeing and mood. Thousands of years later in the second century AD, the concept was firmly entrenched in medicine, and physicians such as Galen wrote detailed descriptions on how these humors related to the seasons. In the past 20 years, modern science has confirmed that seasons do affect mood. Scientists now believe there could be a relationship between the humor, yellow bile, and depression.

Seasonal affective disorder (SAD)

In 1984, Dr Norman Rosenthal and his team at the National Institute of Mental Health, USA, described a condition they termed seasonal affective disorder, or SAD. Dr Rosenthal observed there was a link between the decreased hours of sunlight during winter and the occurrence of depression. Most people are aware of the winter blues where tiredness, difficulty in getting out of bed and weight gain become common as autumn turns into winter. But for some individuals these blues can become so exaggerated they pose a serious health problem.

Typical symptoms associated with SAD include a decrease in physical activity, sometimes with almost any effort seeming too much. Associated with this diminished activity is an increase in time spent asleep, a condition called hypersomnia. Often there is an increased craving for high-energy carbohydrate foods, such as cakes. As a result, weight gain is often reported in SAD sufferers. However, its not the physical symptoms of SAD that are the most debilitating. Common mood changes include depression, anxiety and irritability. These, in turn, can lead to poor concentration, breakdowns in relationships, troubles in the workplace, loss of libido and increased susceptibility to infection. In fact, irritability associated with SAD can be so extreme it may be partly responsible for the increased incidence of child abuse during winter months.

Risk factors for SAD

What makes certain people susceptible to SAD? Without doubt, the most important factor is the persons inherent body chemistry; that is, how their brain chemistry responds to decreases in light. Next come the external factors.

The further you live from the equator, the more likely you are to suffer from the condition, because winters have fewer daylight hours. In fact, any condition that reduces exposure to light during winter increases the likelihood of SAD for example, extended periods of cloud cover and working in an office for long hours. Typical fluorescent office lighting cannot substitute for sunlight. It has even been reported that some individuals who work long hours inside office buildings with few windows may experience symptoms all year round.

Who develops SAD? Surprisingly, the vast majority (70 to 80 per cent) are women, with most developing the condition for the first time in their thirties. Cases of childhood SAD can also occur. Based on two major epidemiological studies in Italy and Switzerland, it appears that around 9-10 per cent of the population is affected by SAD to varying degrees. However, for every individual with full-blown SAD, there are many more with milder winter blues, which can nevertheless still impact on a persons quality of life.