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11-03-2010 | Mental health | Article

Psychiatric disorders vary in underlying serotonin pathology

Abstract

Free abstract

MedWire News: Patients with bipolar disorder and schizophrenia display a diminished loudness dependence of the auditory evoked potential (LDAEP) relative to mentally healthy controls, study results show.

In contrast patients with major depressive disorder and those with anxiety disorders had a similar LDAEP to that of controls. The researchers say these disparities in strengths of LDAEP suggest differences in underlying serotonin-related pathology in these various psychiatric disorders.

“The LDAEP indicates the increase or decrease in amplitude of the N1/P2 component in response to an increase in stimulus intensity and has been identified as a correlate of central nervous serotonergic activity,” explain Seung-Hwan Lee (Inje University, Ilsan Paik Hospital Goyang, South Korea) and colleagues.

Thus a weak LDAEP reflects high serotonergic neurotransmission, and vice versa.

Studies have shown a significantly diminished LDAEP in schizophrenia, indicating higher serotonergic activity in these patients in line with the serotonin hypothesis of schizophrenia. The role of serotonin pathology in other psychiatric disorders is, however, less clear.

Lee et al assessed LDAEP in 123 patients with major depressive disorder, 37 with bipolar disorder, 46 with schizophrenia, 37 with panic disorder (PD), 31 with generalized anxiety disorder (GAD), and 28 with post-traumatic stress disorder (PTSD), as well as 55 mentally healthy controls.

Participants were assessed in a sound-attenuated room and electroencephalography (EEG) data were recorded from 64 scalp electrodes. Auditory stimulation comprised 1000 stimuli with an interstimulus interval that was randomly assigned between 500 and 900 milliseconds (ms). Tones of 1000 Hertz and 80-ms duration were presented at five intensities: 55, 65, 75, 85, and 95 decibels.

The researchers found that LDAEP was significantly stronger in healthy controls and in patients with major depressive disorder than in patients with either bipolar disorder or schizophrenia.

LDAEP did not differ significantly between patients with major depressive disorder and healthy control subjects, or between healthy control subjects and patients with anxiety disorder, including PD, GAD, and PTSD.

Lee et al conclude: “Major psychiatric disorders exhibit different strengths of LDAEP according to their serotonin-related pathology.

“Measurement of the LDAEP appears to be a clinically useful tool, providing information regarding the pathophysiology underlying major psychiatric disorders.”

The research is published in the journal Progress in Neuro-Psychopharmacology and Biological Psychiatry.

MedWire (www.medwire-news.md) is an independent clinical news service provided by Current Medicine Group, a trading division of Springer Healthcare Limited. © Springer Healthcare Ltd; 2010

By Andrew Czyzewski

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