Behavioral and neuroimaging evidence prodromal to major depressive disorder onset in a young adult without personal or family history of psychiatric disorder: Case report.

Background: Subthreshold symptoms of major depressive disorder (MDD) may be underreported due to stigma and/or cognitive impairment associated with this illness. Identifying objective behavioral and neural markers prodromal to MDD onset would help overcome this bias. This case study reports prospective behavioral and neuroimaging evidence prodromal to MDD onset in a young adult without prior personal or family history of psychiatric disorders who was identified during a longitudinal study of mood disorders. Methods: The participant completed the SCID-5 and other assessments of depression as well as the Vividness of Visual Imagery Questionnaire at baseline, 6-month follow-up, and 12-month follow-up. The participant completed the Emotion Intensity Rating task and high-resolution structural images were collected using magnetic resonance imaging (MRI) at baseline and 6-month follow-up. The levels of cortical myelin computed as the T1w/T2w ratio were used in a linear discriminant analysis (LDA) to predict participant's diagnostic status at baseline and 6-months. Results: The participant presented as a healthy control at baseline and 6-month but met criteria for MDD at the 12-month follow-up based on the SCID-5. The participant's visual imagery as well as the ability to correctly recognize neutral faces dramatically reduced from baseline to 6-month follow-up. The LDA classified the participant as an individual with depressive disorders at both baseline and 6-month follow-up despite the absence of either subthreshold or clinical symptoms of depression. Conclusions: While preliminary, the results suggest that the measures of cortical myelin, response to neutral and emotional facial expressions, and vividness of visual imagery could be prodromal to illness onset, whereas clinician-administered or self-reported measures of depression symptoms were uninformative.