The loudness dependency of the auditory evoked N1/P2-component as a predictor of the acute SSRI response in depression

Rationale A serotonergic dysfunction is supposed to play a pathogenetic role in depression, but there is it considerable number of non-responders in the acute treatment of depression with serotonergic agents like SSRI. Thus, an indicator of central serotonergic activity could lead to a more specific pharmacological treatment of depression. In animal and human data there is a growing amount of evidence that a strong loudness dependency of late auditory evoked potentials (LDAEP) is an indicator of low serotonergic activity and vice versa. Objective: In 29 depressive inpatients (DSM-LII-R diagnosis 296.x in 28 patients, 300.4 in one patient), the hypothesis was tested that a strong LDAEP prior to treatment can predict a better clinical outcome under SSRI treatment over 4 weeks. Results: Patients with a strong pre-treatment LDAEP had a significantly greater decrease of depressive symptoms (Hamilton Scale for Depression) after 4 weeks than patients with a flat LDAEP. Significantly more responders fell into the group with a high LDAEP. Contrary to what might be expected, a second recording in a subsample of 19 patients after 4 weeks of treatment failed to show changes in the LDAEP. Conclusion: Our finding confirms the hypothesis, that a strong LDAEP, indicating a low serotonergic activity, is related to a favorable response to acute SSRI treatment ill depression. The LDAEP is a promising tool for the prediction of response to serotonin agonists in depression and it seems to be of clinical importance.