SEASONAL AFFECTIVE DISORDER (SAD)

Seasonal affective disorder ( SAD ) was only defined as a psychiatric disorder in 1986 when Norman Rosenthal and his colleagues published the first paper suggesting that the seasons were important in the development of depressive illness in certain individuals (1) although Hippocrates had hinted at this some 2000 years before. “Whoever should want to study medicine … should consider the seasons of the year” he wrote in 400BC.

We all know that a sunny day makes us feel brighter but it is only recently that we have discovered why. When ultra violet light strikes the back of the eye is causes the release of the brain chemical, serotonin. This is the neurotransmitter that makes us feel warm, happy and content and is the chemical that is increased by drugs like prozac. Advertisers have used the term “ sunshine” to help sell goods for a long time as we associate bright sunshine with happiness and contentment. The opposite effect is that darkness reduces the serotonin level and causes the release of melatonin the natural brain chemical which makes us sleepy.

In our caveman days we lived mainly in equatorial countries where these brain chemicals were developed to aid our survival. Darkness was a time to sleep and we have developed a system whereby our brain releases a sleep inducing chemical in response to darkness. Studies are currently looking at the usefulness of melatonin in sleep disturbances.
It makes sense that this should work and it is much more natural than using drugs to induce sleep. Our physiological design appears to be suited to equatorial countries with the high incidence of depression in more northern countries such as Scandinavia, due in part to the lack of sunshine.

Some people are acutely sensitive to the drop in serotonin which occurs in the winter. About 2% of the UK population have SAD but up to 10% are affected to a lesser degree. In fact we are all affected to some degree. I know as a GP that in the dark miserable days of winter I will be busier than in summer. This is in part due to the drop in mood that these conditions produce which will lower the threshold for wanting to see a doctor.

The treatment of choice for SAD is exposure to a “light box” which emits a bright light without harmful ultraviolet rays.  Exposure to light boxes for as little as 20 minutes daily can significantly improve mood in those with SAD. Most researchers recommend 30 minutes daily exposed to a 10,000 lux light source.

A very interesting recent finding is that exposure to bright lights can help those with non seasonal affective disorder or ordinary depression , producing an improvement equal to that of anti depressant drugs. For those seeking alternatives to pharmaceutical treatments for depression may well want to consider this especially as the improvement came after one week, not the usual 3 – 4 weeks of drug therapy. Care must be taken for anyone with bipolar disorder or manic depression as light therapy could initiate a manic phase of the illness.
Light therapy has also been used in pre menstrual syndrome (PMS) to great effect and has a potential use in chronic fatigue syndrome due to the disturbance in circadian rhythms that occurs in this condition.

Light alarm clocks are also becoming popular where a slowly increasing light source wakes the user naturally. This is how our ancestors were awoken and is another demonstration that using natural methods can be more effective than conventional drugs. Light boxes can be obtained from reputable suppliers both online and in the high street. Full spectrum lighting is also available where conventional light sources are converted to be therapeutic by the use of full spectrum light bulbs. We will offer advice on the optimal use of light boxes in The Essential Health Clinic in Glasgow in the near future.
 
1. Seasonal Affective Disorder in children and adolescents
AU Rosenthal NE, Carpenter CJ, James SP, Parry BL, Rogers SL, Wehr TA.
SO American Journal of Psychiatry. 1986 Mar;143(3):356-8

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