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Motor Vehicle Injury – Alcohol-Impaired Driving: Maintaining Current Minimum Legal Drinking Age (MLDA) Laws


What the CPSTF Found

About The Systematic Review

The CPSTF finding is based on evidence from a systematic review of 33 studies (search period 1966 - 2000).

The review was conducted on behalf of the CPSTF by scientists from CDC’s Division of Unintentional Injury Prevention with input from a team of specialists in systematic review methods and experts in research, practice and policy related to motor vehicle injury prevention.


As of February 2017, all 50 states had set their minimum legal drinking age laws at 21. Some states allow youth to consume alcohol in certain situations, for example during religious ceremonies or when parents give permission.

Summary of Results

More details about study results are available in the published evidence review pdf icon [PDF - 2.29 MB].

The systematic review included 33 studies.

  • Most of the studies assessed the effects of changes in the MLDA from ages 18 to 21 or vice versa.
    • Effects of raising the MLDA: crash-related outcomes decreased by a median of 16% (14 studies; 1 study evaluating fatal crashes among 16-17 year olds was not included in the summary effect measures)
    • Effects of lowering the MLDA: crash-related outcomes increased by median of 10% (9 studies)
    • Estimated effect of raising the MLDA by 3 years (from 18 to 21) from regression-based studies: crash-related outcomes decreased by a median of 12% (9 studies)
  • Effects were stable over follow-up times ranging from 7 months to 9 years.

Summary of Economic Evidence

An economic review of this intervention did not find any relevant studies.


  • Results should be applicable to all drivers 18–20 years of age.
  • Results are based on studies from the United States, Australia, and Canada. They may not apply to countries with different alcohol consumption or driving patterns.

Evidence Gaps

CPSTF identified several areas that have limited information. Additional research and evaluation could help answer the following questions and fill remaining gaps in the evidence base. (What are evidence gaps?)

  • How do variations in enforcement levels influence the effectiveness of MLDA laws?
  • What are the independent effects of publicity on the effectiveness of MLDA laws?
  • Does public compliance with new laws change in a predictable manner over time?
  • How do interventions to reduce alcohol-impaired driving interact with each other (e.g., 0.08% BAC laws and administrative license revocation)?
  • What effects do these interventions have on long-term changes in social norms about drinking and driving?
  • Are interventions equally effective in rural and urban settings?
  • Are interventions equally effective when applied to populations with different baseline levels of alcohol-impaired driving?
  • Do MLDA laws reduce other forms of alcohol-related injury?
  • What are the cost-benefit, cost utility, and cost-effectiveness of interventions to reduce alcohol impaired driving?
  • What role can community coalitions play in maintaining MLDA laws?

Study Characteristics

  • Studies were conducted in the United States, Australia, and Canada.
  • Most studies in the review assessed the effect of changes in the minimum legal drinking age from 18 to 21 years or vice versa.
  • Included studies reported the following outcomes: fatal injury crashes or crash fatalities; fatal and nonfatal injury crashes; or other crash types.


Zaza S, Sleet DA, Elder RW, Shults RA, Dellinger A, Thompson RS. Response to letter to the editor. American Journal of Preventive Medicine. 2002;22:330-1.

Sleet DA. Evidence based injury prevention: guidance for community action. In: Australian Third National Conference on Injury Prevention and Control. Australian Third National Conference on Injury Prevention and Control. Brisbane, Queensland, Australia; 1999.