Replication of the abnormal niacin response in first episode psychosis measured using laser Doppler flowmeter

Introduction

Impaired sensitivity of the skin flush response to niacin is found in approximately 30% of patients with schizophrenia. Although the niacin response abnormality (NRA) may serve as a useful endophenotype for schizophrenia, few studies have directly replicated NRA in patients with first-episode psychosis (FEP).

Methods

In total, 204 patients with FEP, 16 with psychotic mood disorder (PMD), and 68 healthy controls (HC) were included. The log₁₀(EC₅₀) values represent the concentration of methyl nicotinate required to elicit a half-maximal blood flow (MBF) response, and the MBF value was calculated. The NRA was defined as having log₁₀(EC₅₀) molar value above the 90% and an MBF value below the 60% of those in the HC group.

Results

In total, 13.7% of the FEP, 12.5% of the PMD, and 7.4% of the HC group met the definition of NRA. Significant differences were found in the log₁₀(EC₅₀) values between the FEP and HC groups (p = .014) and in the MBF between the FEP and PMD groups (p = .011). Patients with FEP and NRA had more severe negative symptoms than those with a normal niacin response.

Discussion

These data represent the NRA in patients with FEP, defining a small subgroup of patients with early-phase psychosis possessing a clinically significant phospholipid-signaling defect.