Schizophrenia is a clinical diagnosis you can make if typical symptoms are present long enough and are severe enough in the absence of other causative factors (i.e., drug use, medical illness, or other psychiatric disorders).
Schizophrenia can be reliably diagnosed using criteria-based diagnostic schemes (e.g., DSM-IV or ICD-10).
Typical symptoms of schizophrenia are psychosis and negative symptoms, but other symptom domains (cognition, affect, catatonia) need to be assessed as well. Use a rating scale to track symptom severity over time.
Psychosis by longitudinal symptom review is key for a diagnosis of schizophrenia, but not if the patient is psychotic in your office.
Madness is tonic and invigorating. It makes the sane more sane. The only ones who are unable to profit by it are the insane.”
—Henry Miller, American writer, 1891-1980
The syndrome of schizophrenia, as described in the previous chapter, can be reliably diagnosed using well-established criteria such as those developed by the American Psychiatric Association or the World Health Organization (Table 8.1). These diagnostic criteria represent a consensus among experts and identify narrowly defined, core schizophrenia.
Your diagnosis of the schizophrenia syndrome is made clinically; the name (or label) that you give your patient’s disease is based on criteria for classification (of which there are competing schemes). Yet the clinical phenomena are much richer than the diagnostic criteria, so avoid resorting to “checklist psychiatry” in which all you know about the disease is a limited list of symptoms that you check off your clipboard (Freudenreich et al., 2004).
TABLE 8.1. Key Diagnostic Features of Schizophrenia (according to DSM-IVa)
6 months of illness (including prodrome); 1 month of acute symptoms
Functional decline
Required
a This list is based on the fourth edition of the American Psychiatric Association’s Diagnostic and Statistical Manual, DSM-IV. Other diagnostic schemes differ in the criteria required for a diagnosis of schizophrenia. For example, the World Health Organization’s 10th edition of the International Classification of Diseases, ICD-10, requires only 1 month of acute symptoms and no functional decline.
DIAGNOSING SCHIZOPHRENIA FOR THE FIRST TIME
All psychiatric disorders are diagnosed by typical symptoms and a typical course only after “organic” causes have been ruled out. I do not like to call schizophrenia a “diagnosis of exclusion,” as this often implies “by default”; schizophrenia is still diagnosed positively, only if typical signs and symptoms and a typical course are present.
KEY POINT
Psychosis does not equal schizophrenia: There are many etiologies of psychosis, with schizophrenia merely one diagnostic possibility. A differential diagnosis to exclude other reasons for psychosis is necessary.
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KEY POINT
