There exist already a few studies that have measured changes of brain metabolism pre and post Electroconvulsive Therapy (ECT) by Positron emission tomography (PET) but these were all performed in a small number of patients and used different methodologies. It is therefore not surprising that these investigations provided inconsistent results, as reviewed previously {{23 Schmidt,E.Z. 2008}}.

In patients with treatment-refractory major depressive episodes, the investigators here therefore probed (a) whether changes in cerebral glucose metabolism measured by PET occur after treatment with ECT and (b) whether these correlate with the clinical amelioration of symptoms. To pursue this goal, the investigators assessed clinical effects, neurocognitive function, and brain metabolism using 18F-Fluoro-deoxyglucose (18F-FDG) PET at baseline and at the end of treatment.

Patients with a treatment refractory depression - defined as absent clinical improvement of depressive symptoms after at least two trials with antidepressants from different pharmacologic classes adequate in dose, duration of at least 6 weeks, and compliance {{30 Berlim,M.T. 2007}} - in whom ECT had been intended on clinical grounds were consecutively asked for participation in this study. Patients had to be between 18 and 80 years old and to be physically healthy.

Inclusion Criteria:

• clinical indication for ECT
• treatment refractory depressive episode
• age 18-85 y

Exclusion Criteria:

• addiction as a first diagnosis
• dementia