Seasonal Affective Disorder

Effect of sunlight and season on serotonin turnover in the brain
Lancet. 2002 Dec 7;360(9348):1840-2
Alterations in monoaminergic neurotransmission in the brain are thought to underlie seasonal variations in mood, behaviour, and affective disorders… We showed that turnover of serotonin by the brain was lowest in winter (p=0.013). Moreover, the rate of production of serotonin by the brain was directly related to the prevailing duration of bright sunlight (r=0.294, p=0.010), and rose rapidly with increased luminosity. Our findings are further evidence for the notion that changes in release of serotonin by the brain underlie mood seasonality and seasonal affective disorder.

This is the first definitive proof that bright light increases serotonin levels. The study was based in Melbourne, Australia (which is famous for having very changeable weather) and it even showed variations on a day-to-day basis.

Beginning to see the light

Arch Gen Psychiatry. 1998 Oct;55(10):861-2
The evidence is in that light is an active neurobiological agent... Light therapy is easy to administer in outpatient settings, lacks major side effects, and, importantly, is cost-effective.

This issue of the Archives (probably the most widely respected journal in the field) was largely given over to light treatment.

Serotonin in the spotlight (letter)
Nature. 1997 Jan 9;385:123
AB "Here we report new data ... which raise the possibility that light can significantly modify the processing of serotonergic signals by the mammalian brain. ... suggests new mechanisms that may underlie the beneficial effects of artificial light therapy in circadian timing and mood disorders ... - changes which could have important implications for the use of light as a 'drug' to alter neurochemical activity in the brain."

SAD, the NIMH follow-up study (over 9 years)
Am J Psychiatry. 1996 Aug;153(8):1028-1036
A 9 year study of 59 patients showed that 44% continued to use lights after 9 years, 19% stopped because they did not need to use them any longer. 70% used lights over 2 or more years. A further 19% stopped because of inconvenience (using the 2500 lux 2 hour treatment time). For each winter more patients used lights than used antidepressant medication.

Abnormal behavioural and hormonal responses to m-CPP in SAD
Psychiatry Res. 1994 May;52(2):181-197
SAD sufferers and non-sufferers were randomly assigned bright light treatment for 3 weeks, then randomly assigned infusions of a placebo or m-CPP (a post-synaptic serotonin (5HT) agonist). SAD sufferers who had not received light treatment exhibited "activation-euphoria", all other candidates did not show these changes. The hypothesis of deficient serotonergic transmission in SAD, leading to supersensitive postsynaptic serotonin receptors is borne out in the replicated abnormal behavioural responses to m-CPP. Light appears to reverse this abnormality, perhaps by increasing serotonergic transmission.

Opthalmological profile of 71 SAD patients
SLTBR Abstracts. 1993 June
No test of central retinal function showed any abnormality over 5 years of the study.

This was a placebo-controlled test and gives a possible insight into the underlying cause of SAD.

Effects of different light wavelengths in SAD
Am J Psychiatry. 1991 April;148(4):509-511
14 SAD patients were assigned to red or green light treatment for one week in a crossover design. Despite patients' similar expectations for the antidepressant effect of red and green lights, green light has an efficacy similar to white light, whereas red light resembles placebo in other studies. This study supports the hypothesis that the response to light therapy is mediated by biological rather than psychological/placebo factors.

This was a placebo-controlled trial, showing that the effect of light therapy is not psychosomatic.

Effects of light treatment upon mood and melatonin in patients with SAD
University of London Institute of Psychiatry Psychological Medicine. 1989 Aug
19;(3):585-590
Comparison of artificial daylight and red light treatments on 10 patients (aged 30-73 years) with SAD showed a superior effect from artificial daylight, suggesting that light treatment for SAD achieves more than a placebo effect.

This was one of the first placebo-controlled trials.

Fighting the Winter Blues with bright light
Psychology Today. 1989 Jan/Feb;18-21
The authors review the major studies, symptoms and treatments of SAD. They highlight the convenience and effectiveness of artificial light therapy.

Treating chronobiologic sleep and mood disorders with bright light
Psychiatric Annals. 1987 Oct;17(10):664-9
One of the most promising non-pharmacological treatment of psychiatric disorders is bright light. The article discusses how bright light and other factors affect human circadian disorders. It supports the hypothesis that winter depression is the result of delayed circadian rhythms with respect to sleep.

Seasonal Affective Disorder in children and adolescents
American Journal of Psychiatry. 1986 Mar;143(3):356-8
The authors studied seven children with symptoms of SAD. During the winter months the children regularly experienced irritability, fatigue, school difficulties, sadness, and sleep changes as well as other symptoms of SAD found in adults. An open trial of bright environmental light reversed many of these symptoms and improved mood and social functioning in the winter months.

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