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Sunshine, temperature and suicidal behavior in patients treated with antidepressants: an explorative nested case control study.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Neuroscience.
Norwegian Institute of Public Health, Oslo, Norway.
Center for Pharmacoepidemiology, Department of Medicine Solna, Karolinska University Hospital, Karolinska Institutet, Stockholm, Sweden.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Neuroscience.
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

Background

The association of suicide and suicide attempts with climatic factors has been investigated in the past with contradicting results.

Objective

Our aim in this article is to explore if different exposure windows for sunshine or temperature are associated with increased suicidal behavior, measured by suicide and attempted suicide, among people starting an antidepressant treatment.

Methods

By using Swedish registers and daily data about temperature and sunshine duration, we explored the association of sunshine and temperature and suicidal behavior in two exposure windows in patients treated with antidepressants between July 2007 and December 2011. From a source population of 784 792 patients, 307 completed and 1674 attempted suicides were included as cases in the conditional logistic regression analyses, while controlling for potential confounders, including season, as well as temperature and hours of sunshine when these variables were not the main exposure variable. Ten controls were matched to each case using risk-set sampling. In stratified case control analyses by season, age, and sex were conducted using regression models with interaction terms.

Results

There was no overall association between temperature or sunshine with suicidal behavior. However, in stratified analyses, a statistically significant effect modification between age and average daily temperature/sunshine during the last four weeks was discovered for the outcome of suicide attempt (p=0.001 and 0.017 respectively). Amongst older patients (65+) an increase of one hour in the average daily sunshine during the last four weeks was associated with an 8% increase in the rate of suicide attempt. In the same age group, an increase of one degree Celsius in the average daily temperature during the weeks 1-4 was associated with a 3% increase in the rate of suicide attempt.

Conclusions

Despite the absence of an overall association between sunshine and temperature and suicidal behavior, our results point to a possible effect modification by age, with higher risk of suicide attempts found only in the older age groups.

Keyword [en]
suicide, season, sunshine, temperature, antidepressants
National Category
Natural Sciences
Research subject
Psychiatry
Identifiers
URN: urn:nbn:se:uu:diva-330905OAI: oai:DiVA.org:uu-330905DiVA: diva2:1149321
Available from: 2017-10-15 Created: 2017-10-15 Last updated: 2017-10-15
In thesis
1. Suicide Seasonality: Theoretical and Clinical Implications
Open this publication in new window or tab >>Suicide Seasonality: Theoretical and Clinical Implications
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Background: Although suicide seasonality has been well-documented, surprisingly little is known about its underlying mechanisms.

Methods: In this thesis, data from three Swedish registers (Cause of Death Register, National Patient Register, Prescribed Drugs Register) and data from the Swedish Meteorological and Hydrological Institute were used.

In Study I, the amplitude of suicide seasonality was estimated in completed suicides in 1992-2003 in individuals with different antidepressant medications or without antidepressants.

In Study II, monthly suicide and sunshine data from 1992-2003 were used to examine the association between suicide and sunshine in groups with and without antidepressants.

In Study III, the relationship between season of initiation of antidepressant treatment and the risk of suicidal behavior was explored in patients with a new treatment episode with antidepressant medication.

In Study IV, the complex association between sunshine, temperature and suicidal behavior was investigated in patients with a new treatment episode with an antidepressant in two exposure windows (1-4 and 5-8 weeks) before the event.

Findings: Study I: Higher suicide seasonality was found in individuals treated with selective serotonin reuptake inhibitors (SSRIs) compared with those given a different antidepressant treatment or those without any antidepressant treatment.

Study II: In individuals treated with SSRIs, there was a positive association between sunshine and suicide, with the association stronger in men treated with SSRIs compared with men treated with other antidepressants. An effect modification by age was observed.

Study III: The elderly (65+) had a higher risk of suicide when initiating antidepressant treatment in summer and a higher risk of suicide attempt when starting antidepressant therapy in spring and summer. Younger patients (0-24) demonstrated a higher risk of suicide attempt when treatment was initiated in autumn.

Study IV: In the elderly (65+), a harmful association was observed between the risk of suicide attempt and the average daily temperature during the four weeks before the suicide attempt, as well as with average daily sunshine during both exposure windows (1-4 and 5-8 weeks) before the suicide attempt.

Significance: Our results provide epidemiological support for the role of the serotonergic system in seasonality of suicide in which both medication and climate may be involved.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2017. 74 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 1383
Keyword
suicide, season, antidepressants, sunshine, temperature
National Category
Neurosciences
Research subject
Psychiatry
Identifiers
urn:nbn:se:uu:diva-330907 (URN)978-91-513-0108-2 (ISBN)
Public defence
2017-12-07, Gunnesalen, Ing 10, Akademiska sjukhuset, Uppsala, 13:00 (Swedish)
Opponent
Supervisors
Available from: 2017-11-16 Created: 2017-10-15 Last updated: 2017-11-16

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