Defining Abnormality

Defining abnormal behaviour is difficult. None of the following are sufficient (or even necessary) to define abnormal behaviour. They help to clarify, but do not solve the problem.

Statistical Infrequency

  • The characteristics of the majority are considered normal


  • Not all unusual behaviour is considered abnormal - gifted people are not made 'average'.

Violation of Social Norms

  • Some deviations from the norm are considered normal, others not.


  • These acceptable deviations modify over time (e.g. homosexuality was a mental illness until 1973)
  • Social acceptability differs between cultures (e.g. auditory hallucinations are acceptable in some cultures).

Causing Distress

  • Abnormal behaviour could distress the individual


  • However distress is part of every day life
    • Trauma
  • Some disorders do not cause distress
    • Mania

Causes Impairment

  • Impairment to an individual's ability to function (socially, occupationally, personal functioning) could be considered abnormal


  • Mentally-able people can be diagnosed as having a mental disorder
    • Asperger's Disorder