Reliability of diagnosis dysfunctional behaviour is always been controversial. There are several reliability issues in diagnosis of dysfunctional behaviour.
One of the reliability issues that can be discussed about diagnosis of dysfunctional behaviour is the issue of subjectivity involved. Subjectivity refers to a situation or method where interpretation varies from person to person. Diagnosis of dysfunctional behaviour is based on often qualitative and subjective criteria. Same symptoms can be interpreted differently by different psychiatrists. For example, Rosenhan and Seligman’s criteria for deciding abnormal behaviour have subjectivity in the way you interpret abnormality. One of the characteristics highlighted by Rosenhan and Seligman is maladaptiveness and it is characterised by behaviour that prevent people from achieving goal and having fulfilling relationship. A vast majority of people have problem with achieving goals, having fulfilling relationship, yet we cannot classify them as maladaptive. How much of the problem can qualify somebody to maladaptive is subjective. Since subjectivity leads to individual interpretation, it is fair to expect different psychiatrists might give different diagnosis of the same case. Different interpretation and diagnosis means inconsistency in diagnosis. Therefore, it can be concluded that diagnosis of dysfunctional behaviour is lowered by subjectivity involved. However, since mental illnesses do not have objective blood or urine tests, there will be some amount of subjectivity and psychiatrists are working hard to reduce subjectivity as much as possible by making things as explicit.
Another reliability issues that can be discussed in the context of diagnosis of bags dysfunctional behaviour is the issue of bias. Bias occurs when people interpret things from certain stereotypical position. The extent of bias of the psychiatrist will influence the kind of diagnosis given. For example, it is clearly evident in the study of Ford and Widiger that when same clinical case is given with male or female gender identified or gender specified, psychiatrists showed gender bias in diagnosing those cases. If the gender specified was female, Histronic personality disorder was more likely diagnosis. On the other hand, if the gender specified was male, antisocial personality disorder was more likely diagnosis. Bias brings subjectivity in diagnosis and therefore reduces reliability. However, as long as human judgement is involved in any diagnosis. It is very difficult to avoid bias. Therefore, it can be concluded that the reliability of diagnosis of dysfunctional behaviour is seriously affected.
Another reliability issue that can be discussed in the context of diagnosis of dysfunctional behaviour is the issue of quantification. More precisely, we can quantify things, more likely, we could have reliable measures. For example, in physical illnesses blood test and precisely quantify the number of haemoglobin cells in blood. On the other hand diagnosis of dysfunctional behaviour involves often qualitative things or vaguely quantitative. It is very difficult to quantify things like worry or anxiety. Testing of the characteristics like worry or anxiety is often done using rating scale or checklist. Rating scale and checklist have their own reliability issues. However, psychologists argue that psychiatric diagnostics is developing and not as robust as diagnosis of physical disorder. In conclusion, it can be said that problem of quantification negatively affects reliability of diagnosis of dysfunctional behaviour.