Schizophrenia - Diagnostic Interviewing

Schizophrenia, which is considered the most severe psychiatric disorder, is characterized by many impairments, such as psychosis and apathy, cognitive deficits and comorbid symptoms, as well as disrupted functioning and behavioral problems. Diagnostic interviewing is the "gold standard" for establishing a psychiatric diagnosis. In this section, we review diagnostic interviewing strategies for what are currently considered to be the characteristic symptoms of schizophrenia, recognizing that diagnostic criteria may change (as they have in the past).

Current classifications - hence, diagnostic criteria - of schizophrenia are based primarily on the work of Kraepelin, who focused on the deteriorating course of the illness (which he termed dementia praecox), and Bleuler, who emphasized the core symptoms of the disorder as difficulties in thinking consistently and concisely (loose associations); restriction in range of emotional expression, and emotional expression that is incongruent with the content of speech or thought (flat and inappropriate affect, respectively); loss of goal-directed behavior (ambivalence); and retreat into an inner world (autism).

The two current major classification systems in psychiatry, the Diagnostic and Statistical Manual of Mental Disorders (DSM; American Psychiatric Association, 2000) and the International Classification of Diseases (ICD; World Health Organization, 1992) both specify that the diagnosis of schizophrenia is based on the presence of characteristic symptoms, the absence of others, and psychosocial difficulties that persist over a significant period of time. Symptoms must be present in the absence of general medical or so-called "organic" conditions (e.g., substance abuse, neurological disorders such as Huntington's disease, and more) that could lead to a similar clinical presentation.

The characteristic symptoms of schizophrenia are divided into positive and negative symptoms, although cognitive impairments and perhaps some comorbid symptoms may be core deficits of schizophrenia as well (American Psychiatric Association, 2000).

Positive symptoms refer to the presence of perceptual experiences, thoughts, and behaviors that are ordinarily absent in individuals without a psychiatric illness. The typical positive symptoms are hallucinations (primarily hearing, but also tactile feelings, seeing, tasting, or smelling in the absence of environmental stimuli), delusions (false or patently absurd beliefs that are not shared by others in the person's environment), and disorganization of thought and behavior (disconnected thoughts and strange or apparently purposeless behavior).

Some positive symptoms are considered highly specific, such as first-rank symptoms (e.g., delusions of thought insertion and auditory hallucinations with a running commentary), and perhaps even pathognomonic (i.e., inappropriate affect). For many people with schizophrenia, positive symptoms fluctuate in their intensity over time and are episodic in nature, with approximately 20–40% experiencing persistent positive symptoms (Curson, Patel, Liddle, & Barnes, 1988). Of note is that the term psychosis usually addresses delusions and hallucinations (Rudnick, 1997).