Deviation from statistical norms
Deviation from statistical norms occurs when behaviour, emotions or thought processes differ statistically from the majority; it is measurable and quantifiable. Normal statistical behaviour is identified as two standard deviations on either sidbe of the mean in a normal distribution curve, so abnormal behaviour would be approximately 2% of the population on either side of the curve. For example, IQ of 70 and 140.
Deviation from social norms
In any society there are standards of acceptable behaviour that are set by the social group. These are social norms (known as unwritten rules) include morals as well as expectations about how people should think. Deviation from social norms occurs in the sense of deviant behaviour and thoughts; when behaviour is anti social or undesirable. For example, sexual and gender identity disorders which includes paedophilia.
Failure to function adequately
Failure to function adequately when individuals experience considerable suffering and distress and a general inability to cope with everyday activities. Rosenhan and Seligman (1989) identified observer discomfort which is behaviour that causes distress or discomfort to others e.g. Swearing and unpredictability which is behaviour that is unpredictable and sometimes uncontrolled e.g. Laughing at inappropriate times. For example, depression which leads to apathy or despair.
Deviation from ideal mental health
Deviation form ideal mental health when individuals experience considerable suffering and distress and a general inability to cope with everyday activities. Johada (1958) identified personal growth and self actualisation as factors of being normal. Not having these factors would indicate abnormality. E.g. Depression leads to apathy and despair.