title: Seasonal variation in suicidal behavior with prescription opioid medication.
abstract: BACKGROUND
  Suicide attempts by self-poisoning utilizing prescription opioids account for more than half of prescription drug abuse and misuse emergency calls received by poison centers. Additionally seasonal suicidal behavior using other means is a commonly replicated finding. We hypothesized seasonal behavior would exist in individuals using opioid medication as a suicide means, and that this pattern would change at different latitudes in the United States.
  
  
  METHODS
  We used a harmonic regression strategy to investigate sinusoidal seasonal variations of suicidal behavior utilizing prescription opioids, and to contrast changes in seasonal behavior by latitude within the United States. Further, we investigated associations between suicide frequency utilizing opioid medication and frequency of dispensed opioid prescriptions.
  
  
  RESULTS
  Seasonal patterns were identified; overall, all harmonic terms were significant (p<0.05). Interaction terms of harmonic by latitude and harmonic by gender also were significant (p<0.05). After stratification, females had significant harmonic terms at all latitudes. A changing peak time period with latitude also was observed, such that the peak appeared later at more southern latitudes. Additionally, increased dispensed prescriptions rates per population were associated with increased suicidal behavior utilizing prescription opioids.
  
  
  CONCLUSIONS
  This study has limitations due to its ecological nature and to missing data that may inform our understanding of suicide risk factors, such as marital status and socio-economic status.
  
  
  CONCLUSIONS
  Suicidal behavior with prescription opioids follows a seasonal pattern that changes with latitude within the United States. Further, increased accessibility may contribute to increased suicidal attempt rates utilizing prescription opioids.
authors.affiliation: Rocky Mountain Poison and Drug Center, Denver Health and Hospital Authority, 777 Bannock St., MC 0180, Denver, CO 80204, United States; University of Colorado Denver School of Medicine, United States. Electronic address: jackdavis.epi@gmail.com.
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: Davis
authors.affiliation: University of Colorado Denver School of Medicine, Medical Scientist Training Program, United States.
authors.forename: Veronica B
authors.initials: VB
authors.lastname: Searles
authors.affiliation: Rocky Mountain Poison and Drug Center, Denver Health and Hospital Authority, 777 Bannock St., MC 0180, Denver, CO 80204, United States.
authors.forename: S Geoff
authors.initials: SG
authors.lastname: Severtson
authors.affiliation: Rocky Mountain Poison and Drug Center, Denver Health and Hospital Authority, 777 Bannock St., MC 0180, Denver, CO 80204, United States; University of Colorado Denver School of Medicine, United States.
authors.forename: Richard C
authors.initials: RC
authors.lastname: Dart
authors.affiliation: Rocky Mountain Poison and Drug Center, Denver Health and Hospital Authority, 777 Bannock St., MC 0180, Denver, CO 80204, United States.
authors.forename: Becki
authors.initials: B
authors.lastname: Bucher-Bartelson
mesh_terms: D000328:Adult; D000701:Analgesics, Opioid / Q000009:adverse effects*; D011307:Drug Prescriptions; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012307:Risk Factors; D012621:Seasons; D013405:Suicide / Q000523:psychology*; D013406:Suicide, Attempted; D014481:United States
chemical_list: D000701:Analgesics, Opioid
keywords: Accessibility; Prescription opioids; Seasonality; Suicide attempts