In summary, the L3D study will use new PET-MRI brain imaging biomarkers of neurodegeneration in combination with wearable technology to investigate how stress and neural markers of pathological brain aging such as tau protein abnormalities (tauopathy), temporal lobe grey matter loss, white matter and vascular pathology contribute to the pathophysiology of late-life depression. The gene discussed is MAPT; the disease is tauopathy.