A Psychological Diagnosis is a classification or labeling of a client's stated and perceived difficulties following a formal assessment by a psychologist or trained professional. To make a psychological diagnosis, the psychologist uses the diagnostic guidelines and criteria set down by the Diagnostic and Statistical Manual of Mental Disorders (DSM).
The possible diagnoses cover a broad range of physical mental disorders (i.e.traumatic brain injury or schizophrenia), personality disorders (essentially dysfunctional coping styles), psychological disorders (i.e. depression, obsessive-compulsive disorder, etc.), developmental disorders, addictions, and a wide range of other conditions. Giving a client a psychological diagnosis is necessary, partly for treatment planning and partly because insurance companies and other clinical funding sources require a "label" for statistical and other purposes.