OBJECTIVE - This study determined the sources and frequency of diagnostic uncertainty for patients with chronic psychosis and active cocaine abuse or dependence and assessed the usefulness of prospective follow-up in clarifying diagnosis.
METHODS - A total of 165 male patients with chronic psychoses and cocaine abuse or dependence on inpatient units of a Veterans Affairs medical center were evaluated using the Structured Clinical Interview for DSM-III-R (SCID-R), urine tests, hospital records, and interviews with collateral sources. An algorithm allowing key SCID-R items and diagnostic criteria to be designated as provisionally met or uncertain was applied, resulting in a provisional diagnosis and a list of alternate diagnoses. The assessment was repeated 18 months later in an attempt to resolve diagnostic uncertainty.
RESULTS - In 30 cases (18 percent), initial assessment produced a definitive diagnosis, including 21 cases of schizophrenia, six of schizoaffective disorder, and three of psychostimulant-induced psychotic disorder. In the other 135 cases, a definitive diagnosis could not be reached because of one or more sources of diagnostic uncertainty, including insufficient periods of abstinence (78 percent), poor memory (24 percent), and inconsistent reporting (20 percent). Reassessment at 18 months led to definitive diagnoses in 12 additional cases.
CONCLUSIONS - It was frequently difficult to distinguish schizophrenia from chronic substance-induced psychoses. Rather than concluding prematurely that psychotic symptoms are, or are not, substance induced, clinicians should initiate treatment of both psychosis and the substance use disorder in uncertain cases. The persistence or resolution of psychosis during abstinence and additional history from the stabilized patient or collateral sources may clarify the diagnosis.