Frequently Asked Questions
How many people are affected by SAD?
Up to half the people surveyed by the BBC said they felt like hibernating in the winter.
Other studies have shown that up to half a million Britons are affected by SAD.
How bright is a Summer's day?
It depends what time of day it is, how sunny it is, and how near the equator you are. Taking all these factors into account, it varies between 40,000 lux and 100,000 lux.
What is the minimum recommended dose for light therapy?
General opinion is that for light therapy to work it has to be a minimum of 2,500 lux.
What are the symptoms of S.A.D.?
The symptoms of Seasonal Affective Disorder (SAD) are
A tendency to want to oversleep in the morning, often resulting in actual oversleeping in the morning and difficulty in getting to work on time.
Fatigue, in the form of general tiredness and lack of interest in activities in general.
Depression, not necessarily clinical depression, but a general feel of gloom brought on by the gloomy days of winter.
Cravings for carbohydrates and sweet foods, which can be explained by the way animals build up their reserves of fat to see them through the winter.
How does the Body Clock Work?
The body clock is controlled by the Suprachiasmaticnuclei (SCN), a master control which is triggered by light sensitive ganglian cells in the retinas of the eyes.
What is Melatonin?
Melatonin is a hormone whose chemical name is 5-methoxy-N-acetyltryptamine.
This controls the complicated body clock which tells us we should be sleeping at night, waking during the day, sleeping longer in the winter than in the summer, etc.
What is Seratonin?
Seratonin is a neurotransmitter, which controls our general mood and behaviour, in the context of SAD, it regulates how good or bad we are feeling.
What are Circadian Rhythms?
Circadian Rhythms are the basic body clock cycles, which tell us when we should sleep (usually when it is dark), when to wake up (usually when it is light), and when we are at our most active (in the Summer) and our least active (in the Winter)
Does everyone suffer from SAD?
No, it is virtually unknown in people living within 30 degrees of the equator, so it is certainly related to the amount of sunlight we receive.
About 10% of the population of Northern Europe suffer from at least mild symptoms of SAD.