Clinical characteristics associated with different strengths of loudness dependence of auditory evoked potentials (LDAEP) in major depressive disorder

Loudness dependence of auditory evoked potentials (LDAEP), also called as intensity dependence of auditory evoked potentials (IDAP), has been proposed as a potential marker for central serotonergic tone and has been noticed for its possible clinical implications in depression. However, its distributions in major depressive disorder (MDD) and factors affecting it are largely unknown. In this study, we examined its distribution and relationships with various demographic and clinical variables in MDD patients. In 143 MDD patients, the LDAEP was measured using five intensities of auditory stimulus. The influences of ten independent variables (age, gender, education years, marital status, psychiatric family history, age of onset, suicide attempt history, depression severity, later augmentation of mood stabilizer, and smoking status) on the LDAEP strength were examined using univariate analyses and data mining method. The mean (±S.D.) LDAEP was 0.90 (±0.73) μV/10. dB (-0.78-3.83 μV/10. dB). Female gender, smoking, and being married were consistently associated with a weaker LDAEP. In the pathway model, sequential combination of being male, living alone, and older age predicted the strongest LDAEP, whereas female gender, older age, and smoking predicted the weakest LDAEP. These variables need to be considered when interpreting the LDAEP.