Thought disorder can precede psychosis by years and, in some cases, help predict its outcome.
A prospective study of patients with new-onset psychosis found high rates of thought disorder, regardless of the patients’ underlying mental illness. After 20 years of follow-up, thought disorder had remitted significantly more in bipolar patients than in patients with schizophrenia or schizoaffective disorder.
"Positive symptoms seemed to fade away over time and were less prominent [by 20 years’ follow-up] in all groups," Dr. James A. Wilcox and his colleagues reported in the August issue of Comprehensive Psychiatry. "By contrast, the more negative symptoms seemed to persist in schizophrenia and were less relenting overall."
Dr. Wilcox of the University of Arizona and his coauthors followed 188 patients with new-onset psychosis for 20 years, In all, 68 had been diagnosed with schizophrenia, 60 with schizoaffective disorder, and 60 with bipolar disorder in the manic state. All of the patients provided a detailed personal history and were evaluated with the Brief Psychiatric Rating Scale (BPRS) and the Scale for the Assessment of Thought, Language, and Communication (TLC). Patients were reinterviewed at 10 and 20 years after initial presentation (Compr. Psychiatry 2012;53:674-8).
The initial BPRS evaluation indicated that all patients were severely or extremely ill, with a mean score of 86 for those with schizophrenia, 81 for those with schizoaffective disorder, and 78 for those with bipolar disorder. The baseline mean TLC scores were 33, 32, and 29, respectively.
At the 10-year follow-up, the authors were able to reassess 86% of the cohort. "We found that levels of thought disorder remained significantly higher in patients with schizophrenia than in all other groups," they noted. In contrast, "levels of thought disorder dropped considerably in patients with schizoaffective disorder and very significantly in subjects with bipolar disorder."
The mean TLC score at that evaluation was 23 for those with schizophrenia, 20 for those with schizoaffective disorder, and only 3 for those with bipolar disorder. The mean BPRS scores reflected a similar trend: They remained high for the schizophrenia and schizoaffective groups (70 and 68, respectively), and were significantly lower for those with bipolar disorder (38).
The authors evaluated 79% of the cohort at 20 years. Both the schizophrenia and schizoaffective groups still had "prominent" rates of thought disorder. The mean TLC score was 19 for those with schizophrenia and 18 for those with schizoaffective disorder. In contrast, the bipolar group had a mean TLC score of 5.
The BPRS showed a similar pattern, with still-elevated mean scores in the schizophrenia and schizoaffective groups (65 and 63, respectively), compared with a mean score of 23 for the bipolar group.
The negative thought disorders of poverty of thought and poverty of content were highly predictive of later BPRS scores, and of the long-term outcomes of employment and hospitalization.
"We feel comfortable reporting that the symptoms normally assessed as ‘negative thought disorder’ are strong predictors of poor clinical outcome over the life span of many people," the authors noted.
Limitations of the study included the fairly small number of subjects enrolled and the inability of the investigators to ensure that interviewers were blind to the diagnoses.
Still, the findings show that gathering data early in the course of illness can help doctors understand the evolution of psychotic symptoms over time. "We urge continued study of unique symptoms such as thought disorder to help guide and understand the developing features of severe psychiatric disease states," the investigators wrote.
The National Institute of Mental Health and the CHOPE Endowment paid for the study. The authors had no relevant disclosures.