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  1. Drug and Therapeutics Bulletin
  1. 1Drug and Therapeutics Bulletin Editorial Office, London WC1H 9JR
  1. dtb{at}bmjgroup.com

    Low mood associated with a certain season (usually winter) is very common. For example, in the UK, up to 6% of adults have “recurrent major depressive episodes with seasonal pattern”, commonly known as seasonal affective disorder (SAD).1 2 3 People with SAD consult in primary care more often than age- and gender-matched control groups; patients also receive more prescriptions and are referred more often to secondary care.4 Around 6-35% of patients require hospitalisation for SAD at some point.5 Here we discuss the management of adults with SAD, and in particular light therapy.

    About SAD

    SAD involves symptoms typical for depression (eg, lowered mood, energy loss, fatigue) and also atypical symptoms (eg, hypersomnia, increased appetite and eating, carbohydrate craving, weight gain).1 2 6 Some specialists have questioned the value of considering “SAD” as a separate diagnostic category from non-seasonal depression;7 and of note it is classified as a subset of recurrent major depressive or bipolar disorder rather than as a separate category by both the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV; see box 1) and the World Health Organization’s International Statistical Classification of Diseases and Related Health Problems (ICD-10).1 8

    Box 1 DSM-IV criteria for “with seasonal pattern” within recurrent major depressive disorder or major depressive episodes in bipolar disorder1

    • Regular temporal relationship between the onset of major depressive episodes and a particular time of the year (eg, fall [autumn] or winter)

    • Full remissions (or a change from depression to mania or hypomania) at a characteristic time of year (eg, spring)

    • In the last two years, two major depressive episodes that demonstrate the seasonal relationship and no non-seasonal episodes

    • Seasonal episodes substantially outnumber non-seasonal episodes that may have occurred over the individual’s lifetime

    What causes SAD?

    Evidence suggests that SAD has a genetic element, with genes affecting serotonin metabolism (which has a seasonal pattern) being implicated in seasonal mood variations.9 10 Melatonin, a hormone secreted by the …

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