The chapter outlines diagnostic practices with DSM-5 and ICD-11, practical steps of conducting a diagnostic interview, and to conduct a Mental State Examination.

Valid diagnostic standards are important for both the treatment and scientific study of SUD. Primary features of SUD are uncontrolled compulsive drug use, and harmful consequences of drug use. The DSM-5, a successor to the DSM-IV, lists diagnostic criteria for SUD, and its use is the standard for diagnosis of the disorder. Physiological withdrawal symptoms are only 1 of 11 possible criteria, so are neither necessary nor sufficient for a positive diagnosis. Differences among individuals in gender, psychiatric disorders, and other factors can influence the diagnosis of SUD. Less severe cases may be difficult to distinguish from heavy but non-pathological use of drugs, including alcohol. Screening tests cannot provide a diagnosis, but can identify individuals whose drug use warrants a full diagnostic interview. For those with an SUD, the diagnostic interview can be the initial phase of treatment by establishing a therapeutic relationship with a mental health professional. A skilled clinician can often counteract the denial and defensiveness that can prevent an accurate diagnosis of SUD.