It must consider more than just statistical frequency, it should also take in to account social norms, differences among people and lifestyle ‘trends’ or patterns. Also, if behaviour has negative effects on the person or people, it could be considered abnormal. A further point to consider is personal distress i.e. someone who has consistent, severe depressive feelings or a person who has an extreme, irrational fear causing anxiety, these cases would be classed as neuroses: a form of abnormality. In summary, there are many factors which need to be taken in to account when diagnosing what is
