PS270. The neural correlates of suicidal ideation in healthy subjects

Introduction: There have been multiple explorations for the finding of biological markers of suicide. Some studies indicated the association of neurophysiological markers with suicidal ideation (SI). In previous studies, antidepressant treatment-emergent SI was associated with theta value in midline right frontal region, and pretreatment assessment of frontal quantitative EEG (QEEG) may be associated with worsening SI during antidepressant treatment. However, there is limited understanding for the alteration of EEG theta power as biological marker for SI, not in the course of antidepressant treatment. We examined frontal theta power involvement with SI in healthy subjects Method: Resting QEEG data were recorded from 90 healthy subjects. Subjects who had an experience of suicide attempt, current and/or lifetime Axis I and II psychiatric disorders were excluded. According to Scale for suicidal ideation (SSI), the subjects were divided into two group: high SSI group (n = 33) and low SSI group (n = 57). Individual frontal electrodes (Fp1, Fp2, F7, F3, Fz, F4, F8) and central midline electrodes (FCz, Cz) were examined with absolute power in theta band. Clinical state was assessed using Hospital Anxiety and Depression. Result: We found that theta power in all channels positively correlated with SSI. High SSI group showed higher theta power at Fz, F4, FCz, Cz than low SSI group. No significant differences were found at the other electrodes. Theta power in fronto-central region was significantly increased in high SSI (t = -3.173, p = 0.0029) compared to low SSI Conclusion: QEEG theta power at midline locations could be associated with SI in healthy subjects. Theta activity in fronto-central region may be more reliable region to predict SI than midline right and left frontal region. Further QEEG studies are needed to assess potential of QEEG as biomarker for SI in clinical monitoring. PS271 Characteristics of Adolescents Who Visit the Emergency Department Following Suicide Attempts Yeon-Sik Bang, Seongho Min, Joung-Sook Ahn, Ki-Chang Park, Min-