title: Reference periods in retrospective behavioral self-report: A qualitative investigation.
abstract: BACKGROUND
  Self-report questions in substance use research and clinical screening often ask individuals to reflect on behaviors, symptoms, or events over a specified time period. However, there are different ways of phrasing conceptually similar time frames (eg, past year vs. past 12 months).
  
  
  METHODS
  We conducted focused, abbreviated cognitive interviews with a sample of community health center patients (N = 50) to learn how they perceived and interpreted questions with alternative phrasing of similar time frames (past year vs. past 12 months; past month vs. past 30 days; past week vs. past 7 days).
  
  
  RESULTS
  Most participants perceived the alternative time frames as identical. However, 28% suggested that the "past year" and "past 12 months" phrasings would elicit different responses by evoking distinct time periods and/or calling for different levels of recall precision. Different start and end dates for "past year" and "past 12 months" were reported by 20% of the sample. There were fewer discrepancies for shorter time frames.
  
  
  CONCLUSIONS
  Use of "past 12 months" rather than "past year" as a time frame in self-report questions could yield more precise responses for a substantial minority of adult respondents.
  
  
  CONCLUSIONS
  Subtle differences in wording of conceptually similar time frames can affect the interpretation of self-report questions and the precision of responses.
authors.affiliation: Friends Research Institute, Baltimore, Maryland.
authors.forename: Jan
authors.initials: J
authors.lastname: Gryczynski
authors.affiliation: Friends Research Institute, Baltimore, Maryland.
authors.forename: Courtney
authors.initials: C
authors.lastname: Nordeck
authors.affiliation: Friends Research Institute, Baltimore, Maryland.
authors.forename: Shannon Gwin
authors.initials: SG
authors.lastname: Mitchell
authors.affiliation: University of Maryland, College Park, Maryland.
authors.forename: Kevin E
authors.initials: KE
authors.lastname: O'Grady
authors.affiliation: New York University, New York, New York.
authors.forename: Jennifer
authors.initials: J
authors.lastname: McNeely
authors.affiliation: Duke University, Durham, North Carolina.
authors.forename: Li-Tzy
authors.initials: LT
authors.lastname: Wu
authors.affiliation: Friends Research Institute, Baltimore, Maryland.
authors.forename: Robert P
authors.initials: RP
authors.lastname: Schwartz
mesh_terms: D006801:Humans; D011939:Mental Recall; D012189:Retrospective Studies; D057566:Self Report; D019966:Substance-Related Disorders / Q000523:psychology*; D013998:Time Perception