title: Trends in registered medical marijuana participation across 13 US states and District of Columbia.
abstract: BACKGROUND
  Medical marijuana (MMJ) laws and policies have evolved rapidly over the past decade in the United States. Public health concerns over the impact of these laws might be influenced by the degree of MMJ participation, but little is known about changes to this population over time. Trends in registered MMJ participation are described for 13 states in the US and District of Columbia (DC) since 2001.
  
  
  METHODS
  Numbers of MMJ participants were obtained from state MMJ patient registries. A subset of states reported differences by sex and age. Prevalence of MMJ participation per 1000 was calculated. Data from California and Washington were not available.
  
  
  RESULTS
  MMJ participation was relatively low and flat from 2001 to 2008 (i.e., less than 5 per 1000 adults). Participation rose sharply in Colorado, Montana, and Michigan in 2009-2010, but not for other states. High rates can currently be found in Colorado, Oregon, and Montana (i.e., 15-30 per 1000) with the national average around 7.6 per 1000 adults. Two-thirds of participants are male, but sex differences may be decreasing over time. Less than 1% of MMJ registrants are under 18, but this segment is growing in Colorado and Oregon. Participants tend to be older (50s), but Colorado and Arizona have larger proportions of young adult (21-30) registrants.
  
  
  CONCLUSIONS
  Participation in MMJ programs varies considerably by state and within states over time. Trends are discussed within the context of federal and state policies, and the availability of marijuana via dispensaries.
authors.affiliation: Department of Mental Health, Johns Hopkins Bloomberg School of Public Health, 624 North Broadway, 8th Floor, Baltimore, MD 21205, United States. Electronic address: bfairma3@jhu.edu.
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Fairman
mesh_terms: D000328:Adult; D000368:Aged; D004219:District of Columbia; D005260:Female; D006801:Humans; D008297:Male; D064086:Medical Marijuana / Q000600:supply & distribution; D008875:Middle Aged; D010358:Patient Participation / Q000639:trends*; D015995:Prevalence; D012042:Registries; D012727:Sex Characteristics; D014481:United States; D055815:Young Adult
chemical_list: D064086:Medical Marijuana
keywords: Adolescents; Legalization; Marijuana; Medical; Sex differences; Trends