Background: Major depressive disorder, for some, follows a chronic relapsing course. However, no reliable marker has been established that allows the identification of this sub-group of patients. Preliminary findings suggest that baseline startle magnitude may be such a marker. This study evaluated whether differences in baseline startle magnitude during remission could prospectively predict depressive symptomatology and recurrence.
Methods: A group of previously depressed individuals (n=25), who were in full remission at the time of testing, had their startle reflex measured via surface EMG electrodes on the left orbicularis oculi muscle. These people were then followed-up 2 years later and their depressive symptomatology during the intervening period was assessed using the psychiatric ratings scale of the Longitudinal Interval Follow-up Evaluation (LIFE; [Keller, M.B., Lavori, P.W., Friedman, B., Nielsen, E., Endicott, J., McDonald-Scott, P., et al. (1987). The Longitudinal Interval Follow-up Evaluation. A comprehensive method for assessing outcome in prospective longitudinal studies. Arch. Gen. Psychiatry, 44(6), 540-548]) and incidents of recurrence assessed using the Structured Clinical Interview for DSM-IV (SCID-I/P; [First, M.B., Spitzer, R.L., Gibbon, M., & Williams, J.B.W. (2001). Structured clinical interview for axis 1 DSM-IV disorders. New York: New York State Psychiatric Institute]).
Results: It was found that a relatively attenuated startle response at initial assessment was strongly predictive of both depressive symptomatology and those who would experience relapse.
Limitations: This study has a relatively small sample size that limits the degree to which a thorough co-variant analysis can be conducted and also makes the analysis of gender-based difference impracticable. Additionally, as no healthy control group is included, we report a relative rather than absolute attenuation of startle to be indicative of symptom severity and recurrence proclivity.
Conclusions: These preliminary findings suggest that an attenuated startle response may have utility as an endophenotypic marker of risk for recurrence of Major Depression and residual sub-syndromal symptomatology. Such a marker may facilitate the early identification and treatment of those most at risk of recurrent Major Depression.