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Seasonal affective disorder: beating the blues

John Eagles
MB ChB MPhil MRCPsych
Consultant Psychiatrist
Royal Cornhill Hospital

The influence of the seasons on human wellbeing, and on our mood in particular, was recognised by Hippocrates and Aristotle. Not until 1984, however, was seasonal affective disorder (SAD) - of which winter depression is the most common presentation - established as a respectable diagnostic entity.(1) Clinical researchers described 29 patients who experienced recurrent seasonal depressions and reported the beneficial effects on 11 patients of bright artificial light. Some remain sceptical of the diagnosis, but scepticism appears to be receding as evidence accrues on the epidemiology and biology of winter depression and its response to treatment.
It is an interesting paradigm to think of winter depression as a form of attenuated hibernation, which may have conferred evolutionary advantages upon our cave-dwelling ancestors. The hormone melatonin almost certainly mediates seasonal changes in our sleep-wake cycle and, in SAD, sufferers experience circadian phase delay: that is, they are hypersomnolent in the morning and often livelier in the evening, as in those experiencing jet lag after flying west to east. This circadian phase-shift in SAD is thought to underlie the effectiveness of morning light therapy.

Symptoms of SAD
The hallmark of winter depression is recurrent annual episodes that start in the autumn or winter and remit in the spring. Some clinicians regard complete summer remission as an important diagnostic criterion; certainly, in my experience, people who report normality in the summer (even to the extent of slight overactivity, exuberance and extraversion) tend to respond better to winter treatment. As in nonseasonal depression, sufferers experience low mood (often worse in the morning), anergia, low libido, anxiety, irritability and social withdrawal. The following symptoms, however, tend not to occur in nonseasonal depression but to characterise the presentation of SAD in winter:

  • Hypersomnia.
  • Daytime somnolence, peaking in late afternoon.
  • Increased appetite, often for carbohydrates and chocolate.
  • Weight gain.

Two UK community studies (in Aberdeen and north Wales), both using similarly tight diagnostic criteria, found prevalence rates for SAD in the adult population of 3.5% and 2.4% respectively.(2,3) These figures probably represent the clinically significant end of a spectrum of symptom severity. Most people in the UK will experience to a degree some of the winter symptoms, notably lower mood and energy, increased sleep requirement and dietary changes. For most, no treatment is merited, but at the more clinically severe end of the spectrum it becomes more contentious as to whether the disorder should be recognised and "medicalised".
While SAD exists (and can be treated successfully), in children its prevalence increases significantly at puberty, notably among girls, so that there is quite a marked preponderance of female adult sufferers. This does not endure into old age, probably indicating that aetiology is partly linked to female reproductive hormones.
After screening many patients in primary care, our research group compared SAD sufferers with controls who experienced little or no seasonal change in well-being. The SAD patients were heavy users of healthcare services, having more consultations, tests, prescriptions and specialist referrals.(4) They presented with and were investigated and treated for a wide variety of somatic complaints. The diagnosis of SAD had rarely been considered in these patients, probably because of the frequency of somatised presentations, which are known to obscure diagnoses of affective disorders. Along with this "somatising camouflage", however, the typical recurring symptoms of SAD can, one hopes, be elicited; successful diagnosis and treatment is a rewarding enterprise.

Making the diagnosis and helping the patient to make sense of his or her symptoms are the first steps in successful management. Low mood, inactivity, weight gain and social withdrawal conspire to generate vicious circles of worsening symptoms.
Improvement in any of these areas should cause "knock-on" improvement in others. It is helpful to remind sufferers that winter depression is recurrent, but transient, and to advise them to focus on the shortest day as a psychological winning post, whereafter the days are again lengthening. For mildly affected people, self-help should be advised, and the most important elements during autumn and winter are:

  • Regular exposure to natural daylight.
  • Remaining physically active.

Regular walks outside combine these two elements.

For more severely affected people, the above measures should be coupled with antidepressants and/or light therapy; a recent meta-analysis of research studies confirmed the efficacy of light therapy in seasonal and nonseasonal depression (see Box 1).(5)

Patient preference, including availability and convenience, may influence the choice between antidepressants and light therapy.
Otherwise, it is logical to start with an antidepressant when "nonseasonal" symptoms (eg, weight loss, early morning wakening) predominate, and with light therapy when symptoms of hypersomnia, carbohydrate craving and weight gain are present.


  1. Rosenthal NE, Sack DA, Gillin JC, et al. Seasonal affective disorder: a description of the syndrome and preliminary findings with light therapy. Arch Gen Psychiatry 1984;41:72-80.
  2. Eagles JM, Wileman SM, Cameron IM, et al. Seasonal affective disorder among primary care attenders and a community sample in Aberdeen. Br J Psychiatry 1999;175:472-5.
  3. Michalak EE, Wilkinson C, Dowrick C, et al. Seasonal affective disorder: prevalence, detection and current treatment in north Wales. Br J Psychiatry 2001;179:1-4.
  4. Eagles JM, Howie FL, Cameron IM, et al. Use of health care services in seasonal affective disorder. Br J Psychiatry 2002;180:449-54.
  5. Golden RN, Gaynes BN, Ekstrom RD, et al. The efficacy of light therapy in the treatment of mood disorders: a review and meta-analysis of the evidence. Am J Psychiatry 2005;162:656-62.
  6. Avery DH, Eder DN, Bolte MA, et al. Dawn simulation and bright light in the treatment of SAD: a controlled study. Biol Psychiatry 2001;50:205-16.

SAD Association
PO Box 989 Steyning
BN44 3HG