Seasonal affective disorder (SAD) is a mood disorder characterised by depressive episodes that occur with seasonal light variation. It is thought that it is underdiagnosed in general practice. The condition affects women more than men and commonly presents in patients in their thirties. It affects approximately 7 per cent of the UK population.
SAD is caused by the reduced light exposure during the shortened days of winter. Current theories behind its underlying mechanisms have not been confirmed but include changes in circadian rhythms, melatonin production and lack of serotonin.
Symptoms commonly begin in September and continue until April, with January and February being the worst months.
For patients with SAD it can be a serious, disabling illness affecting relationships and quality of life.
A less severe form of the condition is subsyndromal SAD or 'winter blues'. While the symptoms of subsyndromal SAD are milder, it remains debilitating and has a higher incidence, with approximately 17 per cent of the population affected.
SAD should be considered in any patient presenting with episodes of depression that have a seasonal pattern. The DSM-IV diagnoses the disorder when depressive cycles occur for at least two consecutive years during autumn and winter with full remission in spring and summer.
It notes that atypical symptoms may or may not be present. Screening tools, such as questionnaires used for depression or the specific 'seasonal pattern assessment questionnaire', can be used to help identify patients with the disorder.
Typical depressive symptoms include low mood, tearfulness, negative thoughts, poor motivation, hopelessness and lack of enjoyment. Cognitive dysfunction is also common causing problems with concentrating and poor memory. Anxiety, reduced libido and social isolation can also exist.
Atypical features include oversleeping. This presents as difficulty rising in the morning or increased sleeping during the day. As the days shorten energy levels may also reduce causing lethargy. Patients may over-eat, gaining weight as a consequence, or develop eating disorders, such as bulimia.
Often harmful coping mechanisms can surface with the use of drugs or alcohol. Physical symptoms, such as headache, palpitations and generalised aches and pains, may also present. As in other depressive disorders suicide can be a complication, so GPs should make sure to assess suicidal risk. Any underlying organic disorders, such as hypothyroidism, should be ruled out.
Once SAD has been diagnosed, the patient should be reassured about their diagnosis and be given a full explanation about the disorder.
Give the patient advice about the treatment options and information about the support services available.
Simple advice about getting more exposure to daylight is effective. Advise the patient to work in bright conditions, increase their time outdoors and to get plenty of exercise outdoors.
Healthy eating and relaxation techniques may also help. If appropriate, encourage the patient to consider a holiday in a sunnier climate.
Patients should be advised to seek support from friends and family. Referral for psychotherapy or cognitive behavioural therapy may also be of benefit.
Light therapy has been shown to reduce the severity of depressive symptoms more than placebo for SAD and helps two thirds of patients.
It is recommended that patients sit for 30-60 minutes a day, preferably in the morning, just under a metre away from a bright light source that is approximately 2,500-10,000 lux.
A normal light bulb is about 250 lux and a bright summer's day is 100,000 lux.
The greater the lux the less exposure time required. It is recommended that light units designed specifically for SAD are used. Unfortunately these units cannot be obtained on the NHS.
However, companies that sell them often allow free trial periods before purchasing.
It can take several weeks before the benefits are seen. If there is no response after six weeks, further advice should be sought.
Antidepressants may be useful. They are recommended if there has been a lack of response to light therapy or if there are signs of major depression.
SAD can seriously affect a patient's quality of life.
GPs should be aware of the condition during winter months and consider screening for it, especially if atypical depressive symptoms are present.
Once diagnosed, patient education can be given and advance plans can be made for future winter seasons to ensure symptoms are reduced.
- Dr Taylor-Walker is a locum GP in Leicestershire
1. The Seasonal Affective Disorder Association www.sada.org.uk