In 1952, the American Psychiatric Association published the first Diagnostic and Statistical Manual of Mental Disorders (APA, 1952). The goal was to provide psychiatrists with a standardized set of definitions and descriptions of psychiatric diagnoses, as well as statistical information to facilitate diagnosis and further research. The intention was to unify the field, facilitate communication among clinicians, and to promote research in order to improve our understanding of mental illness and treatment. Over the subsequent decades, the DSM has undergone many revisions. The most recent revision, DSM-5, was published in 2013. Each successive revision reflected the level of technical knowledge available at that time. These revisions also reflected the prevailing view of mental illnesses held by the mental health profession and society at large. For a more detailed history of the various revisions of DSM please return to the section entitled, "The history of the current diagnostic system."
Making the distinction between similar but different disorders can be difficult at times. When someone meets the criteria for several different diagnoses at the same time it is called "co-occurrence of diagnoses." The frequency of co-occurring disorders is quite high (Oldham et al., 1995). Robert Cloninger notes that nearly every personality disorder can be reliably paired with at least one other disorder (Cloninger, 2007). For instance, you may recall that Avoidant Personality Disorder is characterized by a profound sense of inferiority which leads to the avoidance of social situations for fear of embarrassment or humiliation. It is not difficult to see how this same person could meet the criteria for Social Phobia; a specific type of anxiety disorder. Let's look at some of these commonly co-occurring diagnoses a little more closely.