RESEARCH SUMMARY DETAIL

Cold Summer Weather May Increase Likelihood of Depression

Author's Title: Cold Summer Weather, Constrained Restoration, and the Use of Antidepressants in Sweden
Author(s) Name: Terry Hartig, Ralph Catalano, and Michael Ong
Year of Publication: 2007
Search Related Keywords: Gender Influence  Influence of Time  Outdoor Space  Quality of Life and Well Being  Stress 

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Design Issue
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This study examined the relationship between cold summer weather and the distribution of antidepressants in Sweden to determine whether restrained access to restorative settings (e.g., nature) is related to symptoms of depression.


  • Previous studies investigated the positive health benefits of participating in restorative activities (e.g., vacations or outdoor activities) rather than the potential negative effects of restrained access to restorative settings resulting from cold summer weather.
  • Findings from previous studies (e.g., Hammen, 2005; Rosenthal et al., 1984; Turner & Lloyd, 2004; Williamson, 2000) suggest that depression and distribution of antidepressants (selective serotonin reuptake inhibitors; SSRIs) may be related to deprivation of restorative activities during summer months.
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Design Criteria
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Author Identified:
  • Understand that limited access to restorative environments may have a negative impact on mental health.

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Key Concepts
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  • Antidepressants were prescribed more frequently to men and women in the colder Julys than in the warmer Julys from 1991 to 1998. On average, a 1º C increase in temperature (from the lowest temperature reported) during the month of July yielded a reduction in the number of adult Swedish women taking antidepressants by 0.2159 per thousand. This effect was greater in women than men.
  • Many workers in Sweden take paid vacations from work during the month of July versus the months of June or August, suggesting that the increased outdoor experiences may explain the relationship between temperature and antidepressant use during the month of July.
  • Alternative explanations for increased distribution of SSRIs during cool July months in Sweden include people receiving extra medication in case of vacationing or increased stress in parents caused by the presence of their children in the household during the summer months.
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Research Method
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  • Monthly dispensed drugs in the antidepressant category NO6AB (SSRIs only) in the World Health Organization’s (WHO) Anatomical Therapeutic Classification system was the dependent variable. Amount of SSRIs distributed monthly in Sweden from January 1991 to December 1998 (based on a 4% sample from 1991 to 1996 and all prescriptions from 1996 to 1998) for all ages were collected from the sole provider of depression medications in Sweden based on units of defined daily doses (DDD; assumed average maintenance dose per day for a drug used for its main indication in adults) per thousand people.
  • mean monthly temperatures for June, July, and August were the independent variables. mean monthly temperatures were determined based on mean high and low temperatures and daily readings (3 collection times per day; 7.00, 13.00, and 19.00) from weather stations (19) located near population centers. Average monthly temperatures for each of the 12 months throughout the course of the study were also included.
  • descriptive statistics and autoregressive, integrated, and moving average time-series modeling was used to analyze the data.
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Limitations
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  • The generalizability of the findings may be limited to people who are experiencing depression.
  • The diagnoses for the use of SSRIs distributed in this study are unknown and may have affected the generalizability of the findings.
  • The cause of increased dispensation of DDD is unknown and may have been due to either new prescriptions or increases in prior dosages.
  • Time that passed between the time of prescriptions and actual mood changes were not accounted for.
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Commentary
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Tables and graphs of the data were included. Future research investigating mental health problems other than depression caused by cold summer months; examining the effects of consecutive cold months during the summer; examining whether there is a delay between the cold months and a person’s health responses; and involving other weather conditions in other geographical locations were recommended.



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Adapted From
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Author(s): Terry Hartig, Institute for Housing and Urban Research, Uppsala University, Gävle, Sweden, Ralph Catalano, School of Public Health, University of California, Berkeley; and Michael Ong, Division of General Internal Medicine and Health Services Research, University of California, Los Angeles
Article Title: Cold Summer Weather, Constrained Restoration, and the Use of Antidepressants in Sweden
Publisher: Elsevier
Publication: Journal of Environmental Psychology
Publication Type: Refereed Journal
Date of Publication: 2007
ISSN: 0272-4944
Volume: 27
Issue: 2
Pages: 107-116