The Relationship between Suicide Ideation and Parasuicide: An Electrophysiological Investigation using the Loudness Dependence of Auditory Evoked Potential

Angelika Marsic


The loudness dependence of the auditory evoked potential (LDAEP) has been proposed as a promising valid and a non-invasive indicator of behaviorally relevant central 5-HT functioning. There is limited research on the utility of the LDAEP in discriminating individuals who engage in various degrees of suicidal behavior. The primary purpose of the present study was to examine if the LDAEP, as a measure of central serotonergic functioning, can be useful in distinguishing groups of individuals who: (a) solely experience suicidal ideation (SI group); (b) experience suicidal ideation and have engaged in deliberate self-harm acts (SH group); and (c) individuals with no history of suicidal ideation or deliberate self-harm behavior (control group). I was also interested in observing whether the nature of individuals' suicidal behavior (i.e., cognitive versus cognitive and behavioral) would differentiate individuals' performance on Self-Aggression Paradigm (behavioral measure of self-aggression; SAP) and Suicide-Implicit Association Test (reaction-time based measure of implicit cognitive associations with death/suicide; S-IAT). Forty-eight participants consisting of college students and community members were recruited for this study. I predicted that (1) The SH group would exhibit the largest LDAEP slope, followed by the SI group, and finally the Control group; (2) The SH group would obtain the largest mean shock score and would self-select the highest number of "20" shock, followed by the SI group, and finally the Control group; (3) SI and SH groups would obtain a more negative S-IAT index, indicating pro-suicide tendencies, than the Control group; (4) the LDAEP slope would be positively related to the SAP indexes and negatively related to S-IAT index; and (5) the LDAEP would be positively related to the self-report measures of self-harm behavior and aggression, and negatively related to self-report measure of reasons for living. Contrary to expectations, most of our predictions were not supported. Clinical implications and future research directions are discussed.