Project 466565

Major depressive disorder (MDD) affects 11% of Canadians aged 15-24 and the heritability of MDD is estimated to be 40%. Current research aims to identify biological markers of MDD that precede symptom onset in order to predict prognosis. Combined transcranial magnetic stimulation and electroencephalography (TMS-EEG) allows researchers to study brain function by non-invasively stimulating brain regions and then measuring induced activity. Studies have shown that a negative peak in activity forms 100 milliseconds after a TMS pulse (N100) and that youth and adults with MDD have significantly larger N100 peak amplitudes than healthy controls. Despite the high heritability of MDD, the predictive utility of the N100 marker in at-risk youth has not been studied. The proposed research will address this gap by determining the relationship between parental MDD and N100 amplitudes in at-risk youth and the utility of N100 amplitudes to predict MDD onset. It is hypothesized that N100 amplitudes will be associated with parental MDD severity, will serve as a significant predictor of MDD onset, and will be stable in youth who do not develop MDD. A minimum of 80 youth will be recruited from a longitudinal study and will have TMS-EEG data collected at baseline. Parental MDD will be assessed at baseline and youth will complete MDD questionnaires at baseline and 9-month intervals. N100 peak amplitudes will be quantified and correlated with parental MDD scores. The relationship between N100 amplitudes and MDD onset will be investigated using 9- and 18-month follow-up data. Knowledge of family history and presence of brain markers in youth will allow healthcare providers to implement strategies to delay the onset of MDD and reduce the severity of symptoms.