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Seasonal variation in antidepressant prescriptions, environmental light and web queries for seasonal affective disorder

  • Thomas Lansdall-Welfare (a1), Stafford Lightman (a2) and Nello Cristianini (a3)

The state of an individual's mental health depends on many factors. Determination of the importance of any particular factor within a population needs access to unbiased data. We used publicly available data-sets to investigate, at a population level, how surrogates of mental health covary with light exposure. We found strong seasonal patterns of antidepressant prescriptions, which show stronger correlations with day length than levels of solar energy. Levels of depression in a population can therefore be determined by proxy indicators such as web query logs. Furthermore, these proxies for depression correlate with day length rather than solar energy.

Declaration of interest


Corresponding author
Correspondence: Nello Cristianini, Intelligent Systems Laboratory, Merchant Venturers Building, University of Bristol, Bristol BS8 1UB, UK. Email:
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The British Journal of Psychiatry
  • ISSN: 0007-1250
  • EISSN: 1472-1465
  • URL: /core/journals/the-british-journal-of-psychiatry
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Seasonal variation in antidepressant prescriptions, environmental light and web queries for seasonal affective disorder

  • Thomas Lansdall-Welfare (a1), Stafford Lightman (a2) and Nello Cristianini (a3)
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