title: Crack cocaine trajectories among users in a midwestern American city.
abstract: OBJECTIVE
  Although crack cocaine first appeared in cities in the United States in the mid-1980s, little is known about its use over long periods of time. This study identified crack cocaine user groups on the basis of long-term trajectories.
  
  
  METHODS
  Following a natural history approach, data were collected periodically from 1996 to 2005. Group-based modeling assessed the probability of a crack smoker becoming abstinent during the observation period.
  
  
  METHODS
  A targeted sampling plan guided the recruitment of a community sample of crack cocaine users in Dayton, Ohio.
  
  
  METHODS
  Crack smokers (n = 430) 18 years or older whose urine tested positive for cocaine metabolites at the baseline interview.
  
  
  METHODS
  Interviewer-administered and audio computer self-administered, structured questionnaires were used to collect data on a range of variables, including frequency of crack use. Abstinence was defined as not having used crack for at least 6 consecutive months during the study.
  
  
  RESULTS
  Three trajectory-based groups were identified: (1) No Change, characterized by a very low probability of abstinence; (2) Some Change, characterized by a low to moderate probability of abstinence; and (3) Dramatic Change, characterized by a high probability of abstinence. African Americans and men were significantly less likely to become abstinent. For the majority of the people (63.6%), crack use was uninterrupted by extended periods of abstinence during the study.
  
  
  CONCLUSIONS
  Crack cocaine use that persists for a decade or longer may well be the norm for a large proportion of people who have experience with the drug.
authors.affiliation: Center for Interventions, Treatment and Addictions Research, Wright State University Boonshoft School of Medicine, Dayton, OH 45435, USA. russel.falck@wright.edu
authors.forename: Russel S
authors.initials: RS
authors.lastname: Falck
authors.forename: Jichuan
authors.initials: J
authors.lastname: Wang
authors.forename: Robert G
authors.initials: RG
authors.lastname: Carlson
mesh_terms: D000328:Adult; D019970:Cocaine-Related Disorders / Q000453:epidemiology*; D016578:Crack Cocaine; D005260:Female; D006801:Humans; D013287:Illicit Drugs; D008297:Male; D009820:Ohio / Q000453:epidemiology; D015995:Prevalence; D012307:Risk Factors; D012309:Risk-Taking; D012959:Socioeconomic Factors; D011795:Surveys and Questionnaires; D013997:Time Factors
chemical_list: D016578:Crack Cocaine; D013287:Illicit Drugs