Rationale: The loudness dependence of the auditory evoked potential (LDAEP) has been proposed as a potential biological marker of central serotonergic activity. This study aimed to test the hypothesis that the LDAEP can be used to predict the response to escitalopram in patients with GAD.
Method: Twenty-five patients with GAD were recruited. Scores on the Hamilton Anxiety Rating Scale (HAM-A), Clinical Global Impression-Severity Scale (CGI-S), and Beck Anxiety Inventory (BAI) were evaluated. To evaluate the LDAEP, the auditory event-related potential was measured before beginning medication. Peak-to-peak N1/P2 amplitudes and current source densities were calculated at five stimulus intensities, and the LDAEP was calculated as the linear-regression slope. The current source densities of the evoked potentials were analyzed by standardized low-resolution brain electromagnetic tomography (sLORETA). The loudness dependence of the current densities (sLORETA-LDAEP) was also calculated.
Results: The pretreatment LDAEPs of all patients were positively correlated with the CGI-S response rates at 4 and 8 weeks, and with the HAM-A and BAI response rates at 8 weeks. The sLORETA-LDAEPs were positively correlated with the HAM-A response rates after 8 weeks of treatment. The HAM-A and CGI response rates at 8 weeks were higher in patients with a strong pretreatment LDAEP than in those with a weak LDAEP.
Conclusions: The present study revealed that GAD patients with a favorable response to escitalopram treatment are characterized by a stronger pretreatment LDAEP. Measurement of the LDAEP appears to provide useful clinical information for predicting treatment responses in patients with GAD.