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).
Negative symptoms are the opposite of positive symptoms, in that they are defined by the absence of behaviors, cognitions, and emotions ordinarily present in persons without psychiatric disorders. Common examples of negative symptoms include flat affect, avolition (lack of motivation to perform tasks), and alogia (diminished amount or content of speech). All of these negative symptoms are relatively common in schizophrenia, and they tend to be stable over time. Furthermore, negative symptoms have a particularly disruptive impact on the ability of people with schizophrenia to engage and to function socially, and to sustain independent living.
The diagnosis of schizophrenia, according to DSM-IV-TR (American Psychiatric Association, 2000), which is the most current diagnostic system in psychiatry, requires the following criteria: (a) two or more characteristic symptoms, each present for a significant portion of time during a 1-month period (or less if successfully treated); (b) social/occupational dysfunction; (c) persistence of the disturbance for at least 6 months, of which at least 1 month must fully meet criterion a (active-phase symptoms). The other criteria exclude other psychiatric disorders, particularly schizoaffective disorder, mood disorders, substance use disorders, general medical condition, and pervasive developmental disorders (unless delusions and hallucinations exist, in which case schizophrenia can be diagnosed in conjunction with pervasive developmental disorders). There are various subtypes of schizophrenia (i.e., paranoid, disorganized, catatonic, undifferentiated, and residual [American Psychiatric Association, 2000]), but their validity is not well established, and a patient can present with more than one of them over time.
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