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SAD is now an accepted clinical condition but still underdiagnosed in primary care ­ Mr Pavan Mallikarjun and Professor Femi Oyebode advise on how it presents and how to treat it

Seasonal affective disorder (SAD) is a well-described subtype of depression characterised by depressions occurring regularly in autumn and winter, alternating with non-depressed periods in spring and summer.

There was initial scepticism about its existence but it is now well accepted as a clinical condition and is in the DSM IV (Diagnostic and Statistical Manual of Mental Disorders, fourth edition) published by the American Psychiatric Association as depressive disorder, seasonal type 2.

Research in primary care has identified that SAD, although common, is often underdiagnosed or misdiagnosed1.


The symptoms of SAD typically begin in autumn or winter and peak between December and February. Untreated cases generally resolve during spring and summer. In summer, up to a third of individuals may experience a reversal of their symptoms and experience symptoms of mild hypomania.

The cardinal feature of patients with SAD as described by Rosenthal et a · 2 is the apparent sensitivity to changes in season and latitude at approximately the same time every year.

The clinical picture includes symptoms typical of depression, including low mood, decreased activity, decreased libido, anxiety, irritability and impairment of social and occupational functioning.

Unlike the non-seasonal type of depression, there is no diurnal variation. More than three-quarters of SAD sufferers may also have atypical symptoms of depression including increased appetite and weight, carbohydrate and chocolate craving, increased duration of sleep (despite feeling the sleep to be of poor quality), and daytime drowsiness, particularly during late afternoons.

The depressive episodes are usually mild to moderate, though it can be severe enough to warrant hospitalisation in a small proportion of patients. The depressive episodes are seldom severe enough to require absences from work, though the symptoms tend to disrupt productivity due to decreased concentration and motivation.

It is well known that people with even mild depressive episodes are at risk of suicide, and there should be careful monitoring for emerging suicidal thoughts in this group of patients. The diagnosis of SAD needs to be reserved for individuals experiencing a depressive episode with symptoms severe enough to impair their social and or occupational functioning.

Rosenthal and the DSM IV criteria require two consecutive years in which the depressive episodes developed in autumn or winter, and remitted the following spring or summer, without the occurrence of non-seasonal depressive episodes in the same period.

The WHO's diagnostic criteria for research are more stringent in that it requires three consecutive years.


Prevalence estimates for SAD vary from 0 to 10 per cent and despite methodological inconsistencies of the studies, SAD appears to be a common disorder in the general population.

The onset of SAD typically occurs between ages 20 and 30 and as with other mood disorders there is a female preponderance.

Recent negative life events, poor social support and being non-native have been associated with SAD. The available evidence indicates that those who migrate to higher latitudes are more prone to develop SAD.

The course of the illness appears to be variable, with fewer than half the initially diagnosed SAD patients retaining the seasonal pattern to their illness and the rest developing a non-seasonal pattern to their illness. In a small proportion of the patients the illness had completely remitted.


Strategies for the management of SAD include light therapy, antidepressant medication, exercise and psychotherapy.

The treatment modality to be used depends on the severity and symptomatology of the disorder and patient preference. Simply spending more time outdoors and exercising regularly in the winter may help those with milder symptoms.

However, in patients experiencing moderate to severe forms of SAD or who have social or occupational disruption, other forms of treatment need to be considered.

·Light therapy

Light therapy or phototherapy involves exposure to artificial light. Bright light therapy is recommended as first-line treatment for winter SAD.

There is considerable research evidence for treatment of SAD with light therapy using a light box. Features associated with good response to light therapy include hypersomnia, increased appetite, weight gain and complete remission of symptoms in summer.

A meta-analysis of randomised controlled trials of light therapy in SAD has found that, measured by the responder analysis, the number needed to treat is in the four to five range3 which is a good indication for the efficacy for light therapy treatment.

The box above details how to use light therapy.


There is a paucity of clinical trials on the use of antidepressants in SAD. The tricyclics being sedative are generally avoided in this group of patients. There is evidence for some of the SSRIs, particularly sertraline4 and fluoxetine5. Hesselman et al in an open trial reported the efficacy of mirtazepine6.

In patients who are non-responsive to light therapy or prefer other treatment, SSRIs are the treatment of first choice.

The duration of treatment is usually six months after recovery of symptoms. Further RCTs are required to establish the safety and efficacy of antidepressant medication.


There is evidence that physical exercise either used alone or in combination with light therapy is beneficial. It is also beneficial to receive as much sunlight as possible while indoors, in brightly lit surroundings at the workplace, and at home spending as much time as possible near windows facing the sun.

Taking a winter holiday in sunny climes is desirable but may not be practical for many.

Behaviour and cognitive behaviour therapies may have a role, though this needs more research before being advocated.

How to use light therapy

Light therapy involves the patient sitting facing the light of 2500 lux for two hours or light of 10000lux for 30 minutes each morning for the period of time needed to reduce symptoms and induce remission.

Light therapy should preferably be started in the mornings to maximise treatment response, but can carried out at other times in the day. It is best avoided after 8pm because of the risk of insomnia.

Light boxes are preferred. Evidence for light visors and light simulation clocks is lacking.

Patients need to be sitting 2-3ft away from a light box, usually on a table, allowing the light to shine directly through the eyes.They can carry out normal activities such as reading, working, eating and so on while stationary in front of the box.

Side-effects include headaches, eyestrain, nausea, insomnia and agitation, but these are generally minor and transient. Response to therapy occurs within a week and not later than three weeks. It is recommended that light therapy be used throughout winter and to resume treatment the following autumn, either in advance or with onset of mild symptoms.


1 Michalak EE et al. Seasonal affective disorder: prevalence, detection and current treatment in North Wales.

Br J Psychiatr 2001;179:31-4

2 Rosenthal NE et al. Seasonal affective disorder: a description of the syndrome and preliminary findings with light therapy.

Arch Gen Psychiatr 1984;41:72-80

3 Thompson C. Evidence-based treatment in seasonal affective disorder: practice and research (eds T Partonen and

A Magnusson). Oxford University Press, 2001. Pp 151-8

4 Moscovitch A et al. A placebo-controlled study of sertraline in the treatment of outpatients with seasonal affective disorder. Psychopharmacology 2004;171:390-7

5 Lam RW et al. Mulitcenter, placebo-controlled study of fluoxetine in seasonal affective disorder. Am J Psychiatr 1995;152:1765-70

6 Hesselman B et al. Mirtazapine in seasonal affective disorder (SAD): a preliminary report. Human Psychopharmacology 1999;14:59-62

Useful websites

A registered charity informing public and professionals about SAD

Society for Light Treatment and Biological Rhythms

Rosenthal's website provides the public with an opportunity to

take an online test for SAD

Useful books

·The Little SAD Book. SAD Association: Steyning, 1999

·Seasonal affective disorder: practice and research. Partonen and Magnusson (eds). Oxford University Press: Oxford, 2001

·Winter blues ­ seasonal affective disorder: What it is and how to overcome it. Rosenthal NE. Guildford Press: New York, 1998

Pavan Mallikarjun is senior house officer

Femi Oyebode is professor and head of department, department of psychiatry,

Queen Elizabeth Psychiatric Hospital, University of Birmingham

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