What is Mental Illness? #2
PART 2 Underpinning the attempts to categorise and classify mental illness are 4 broad approaches… 1.Deviation from statistical norms (statistical infrequency) This is based on the notion that abnormal thought and behaviour are pretty rare in the general population. The scores of most human characteristics and behaviours, when measured, tend to fall fairly evenly about the mean, giving the bell curve of normal distribution. Eg: there are a lot of people who are ‘averagely’ tall or aggressive whereas very few people are very small or highly aggressive. Thus, there are as many people/scores above the mean as below it in a normal distribution. The further you travel from the mean, the fewer people/scores there are in the population. In a normal distribution – see graphic above – the majority of individuals are clustered around the mean. In a normal distribution the scores of 95.5% of the population will fall within 2 standard deviations from the mean. Scores beyond 2 standard deviations are considered statistically infrequent and, therefore, abnormal. Thus, thoughts and behaviours which occur in 4.5% or less of the population can be considered abnormal. As a way of defining what is meant by mental illness, this approach works well for… Read More
