u psychotic symptoms that occur only during periods of mood disturbance. In the United States-United Kingdom Diagnostic Project, Cooper and colleagues (14) reported that, in the New York sample, mood disorders—particularly mania with psychotic features—were frequently diagnosed as schizophrenia. An abrupt onset of symptoms and a predominance of affective symptoms usually distinguish bipolar mood disorder with psychotic features from schizophrenia (7). However, some patients diagnosed with bipolar disorder may continually display low-level psychotic symptoms. Patients with mania may have a wide variety of psychotic symptoms, such as hallucinations, paranoid delusions, and formal thought disorder. Flight of ideas occurring during a manic episode may be confused with a chronic formal thought disorder, but this rarely occurs without other symptoms of mania, such as euphoria, decreased need for sleep, and hyperactivity. Patients with schizophrenia may sleep poorly and have episodes of hyperactivity, but these symptoms are usually secondary to delusions and hallucinations, rather than to euphoria, grandiosity, and hyperactivity of mania.
Patients with major depressive episodes may also experience hallucinations and/or delusions, which are usually mood-congruent (i.e., consistent with depressive themes of guilt, worthlessness, etc.). Sometimes mood-incongruent delusions may occur in the context of a major depressive episode, but more typical symptoms of depression should precede them to distinguish the presence of an affective source. When patients with depression experience hallucinations, they are typically of shorter duration and fragmented, and occur within the context of predominantly affective symptoms. In this group of patients, the clinician may have difficulty establishing whether the affective symptoms preceded psychotic symptoms or vice versa. In such circumstances, more information can be gathered, often from members of a patient's family, before the final diagnosis is determined, and often an extended period of observation and/or empirical treatment is needed to lend further diagnostic clarity.
On the other hand, individuals with schizophrenia may also experience depression (15). These episodes generally occur along with other symptoms of schizophrenia and within the context of an otherwise typical symptom pattern for schizophrenia (16). Wassink and associates (17) found that in a group of carefully diagnosed and well-characterized patients with recent-onset schizophrenia, the majority had at least one depressive symptom and more than one-third met DSM-III-R criteria
u for a major depressive disorder. To further complicate things, depressive symptoms of social withdrawal, lack of interest, and psychomotor retardation may resemble the negative symptoms of schizophrenia. If available, a careful history will reveal whether these symptoms occur in the context of a typical depressive illness or with other symptoms such as poor appetite, terminal insomnia, and self-reproach. Furthermore, further history may reveal whether the depressed (sad) mood did or did not precede marked withdrawal, lack of interest, and psychomotor retardation.
Delusional disorder (formerly paranoid disorder) has been shown to be relatively uncommon in clinical settings (18); however, it is frequently confused with schizophrenia. Of the subtypes of delusional disorder, the persecutory type is the most common. Delusional disorder, persecutory subtype, is often difficult to distinguish from paranoid schizophrenia (19). However, in delusional disorder, only a single, well-encapsulated, nonbizarre (i.e., plausible in the sense that the imagined events could conceivably occur) delusional system is present. The diagnosis of delusional disorder does not include hallucinations, disorganized behavior, or negative symptoms, as in typical schizophrenia, and the delusions should not be fragmented. In general, the age of onset of delusional disorder is later than for schizophrenia (often over the age of 50 years) and there is usually less impairment in occupational and social functioning.
Brief reactive psychosis is a disturbance that has a sudden onset of positive psychotic symptoms (i.e., hallucinations, delusions, disorganized speech, or grossly disorganized or catatonic behavior) that last for at least 1 day but less than a month. The individual with a brief reactive psychosis eventually has a full return to the premorbid level of functioning. It should not be confused with schizophrenia, except in cases in which a coherent history cannot be obtained (12). Brief reactive psychosis may be mistaken for schizophrenia when the patient has a pre-existing personality disorder that bears some similarities to the prodrome of schizophrenia. However, since patients with schizophrenia are usually psychotic for many months before coming to treatment, this is usually not a problem in most clinical settings. For new, acute-onset cases of schizophrenia, this differential diagnosis can be difficult until additional time passes and the course of the illness becomes clear.
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