Sex difference in the loudness dependence auditory evoked potential and depressive symptoms

The central serotonergic system is involved in the pathophysiology of a number of psychiatric disorders including depression, anxiety disorders, eating disorders and personality disorders. Development of a valid noninvasive markers of central brain serotonin will aid in identifying psychiatric patients as well as ‘‘at-risk’’ population with a serotonergic dysfunction. Recently, the loudness dependence auditory-evoked potential (LDAEP) has been suggested as a possible noninvasive electrophysiological marker of central serotonin function, as reduced serotonergic activity is thought to increase the slope of the LDAEP function. Thus, in order to determine whether depressive symptoms are related to serotonin function within a nonclinical population, the present study obtained measures of both depression and LDAEP slopes from 16 male and 25 female healthy undergraduate volunteers. Serotonin was measured as the intensity dependence of the auditory-evoked N1/P2 component at Cz. Depressive symptoms during the week before testing were measured from the same participants using the CES-D depression scale. Correlation analysis was employed to determine whether the depression score was related to the measure of serotonin function (LDAEP). Data show that N1/P2 slopes is correlated with depression scores in females (trend level) and inversely with depression scores in males. This suggests that depression was related to low levels of serotonin in females, and high level of serotonin in males. This result is consistent with the N1/P2 literature for females, but inconsistent for males. These discrepant results highlight the need to account for sex in serotonin/depression research