Comparing clinical and neurocognitive features of the schizophrenia prodrome to the bipolar prodrome

Abstract

Background: There is an increased interest in early intervention strategies for severe mental disorders with hopes of mitigating the emergence and impact of the illness. Individuals at clinical high-risk (CHR) for schizophrenia have been primarily identified by the presence of attenuated positive symptoms. Although bipolar disorder and schizophrenia may have overlapping etiologies, few studies have investigated the potential prodrome in bipolar disorder. We sought to determine if there is a prodrome to bipolar disorder and if clinical or neurocognitive measures could distinguish between the bipolar and schizophrenia prodromes.

Methods: We examined subjects who were initially identified as CHR for schizophrenia during the prodromal phase of the illness and followed them prospectively. Unexpectedly, eight subjects developed bipolar disorder. Baseline data from subjects who eventually developed bipolar disorder (pre-BP; N=8), schizophrenia or a psychotic disorder (pre-SZ; N=24) and a non-converter comparison group (NCC; N=115) were compared.

Results: The pre-BP and pre-SZ groups did not differ on attenuated positive symptom severity, global measures of functioning or on the global neurocognitive score. Compared to NCC individuals, both pre-BP and pre-SZ patients reported more severe attenuated positive symptoms and were more likely to be on antipsychotic medication at baseline. The pre-SZ group had a significantly lower current IQ and was significantly more impaired than the NCC group on the overall neurocognitive score.

Conclusions: This study provides preliminary support for a bipolar prodrome, which may be indistinguishable from the schizophrenia prodrome based on clinical and neurocognitive measures currently used in high-risk schizophrenia programs.