Definitions of abnormality

• Statistical infrequency


  A person's trait, thinking or behaviour is considered to be an indication of abnormality if it is found to be numerically (statistically) rare
• The statistical approach is the most useful when dealing with characteristics that can be reliably measured
• Average IQ is 100
• 68% of people have an IQ in the range from 85-115
• Only 2.5% of people score below 70
• Scoring below 70 is unusual and may lead to a diagnosis of intellectual disability disorder
• Weaknesses of statistical infrequency

  • Some unusual characteristics can be positive (e.g. very high IQ)
  • Some common behaviours are not desirable (e.g. depression)
  • It is hard to determine where to draw the line between common and statistically infrequent behaviour
• Deviation from social norms


  If a person behaves in a way that is different from what most of society do and does not follow the standards set by society, they are considered abnormal
• Weaknesses of deviation from social norms

  • Social norms change over time (e.g. homosexuality)
  • Social norms are dependent on culture (e.g. hearing voices)
• Failure to function adequately


  When behaviour interferes with daily routines, then it is considered abnormal
• Strengths of failure to function adequately

  • Recognises the patient's perspective
• Weaknesses of failure to function adequately

  • There are exceptions where maladaptive behaviour is not abnormal due to specific circumstances (e.g. Gandhi's hunger strike)
• Deviation from ideal mental health

  Jahoda (1958) identified 6 characteristics which she believed promoted psychological health. Anyone unable to show these quantities, she thought indicated abnormality and would be vulnerable to mental disorder
• Characteristics of ideal mental health

  • Positive attitude towards self
  • Accurate perception of reality
  • Resistance to stress
  • Personal autonomy
  • Mastering the environment
  • Self-actualisation
• Strengths of deviation from ideal mental health


  • Offers a comprehensive criteria for assessing mental health
• Weaknesses of deviation from ideal mental health

  • Difficult to meet all criteria (setting an unrealistically high standard)
  • Culturally relative (based on western ideas of individuality)