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  • Capacity is the ability to understand the nature and effect of one’s acts
    • May have capacity in one moment and lack capacity in another
  • Main question to consider is "does the patient have the ability to understand the nature and effect of his or her acts in a specific moment in time?"
  • Mini mental status exam (MMSE) score <19 is correlated with lack of capacity
  • Patients who lack capacity may not make their own medical decisions.


  • Must have all four criterion to achieve capacity[1]
  • Criterion 1 - communicate a choice
    • Clearly demonstrate preference for a treatment option
    • Reversals of choice due to altered mental status or psychiatric disease suggests lack of capacity
  • Criterion 2 - understand relevant information
    • Grasp fundamental understanding of information communicated by physician
    • Must understand condition, purpose of treatment, benefits/risks of treatment, and alternatives
  • Criterion 3 - appreciate situation and its consequences
    • Acknowledge medical condition (no denial, delusions)
    • No acknowledgement termed "lack of insight"
      • "What do you believe is wrong with your health now?"
      • "Do you believe that you will need treatment to make your health better?"
      • "What do you believe will happen if you are not treated?"
      • "Why do you think doctors recommend this treatment?"
  • Criterion 4 - reason about treatment options
    • Demonstrate rational processing of relevant information communicated by physician
      • "What makes treatment 1 better than treatment 2?"
      • "How did you decide to accept or reject recommended treatments?"

See Also


  1. Appelbaum PS. N Engl J Med 2007;357:1834-40