Antidepressant drugs affect monoamines and neuropeptides in human cerebrospinal fluid (CSF) and in rodent brain. The purpose of this study was to investigate if also electroconvulsive therapy (ECT) affects these compounds in a similar manner in the CSF of depressed patients. Homovanillic acid (HVA), 5-hydroxyindoleacetic acid (5-HIAA), and corticotropin-releasing hormone (CRH)-like immunoreactivity (-LI) and neuropeptide Y (NPY)-LI were determined in CSF in six drug resistant patients with major depression. Lumbar puncture was performed at baseline and after completion of eight ECTs. ECT was associated with an increase in NPY-LI (p=0.009) and a decrease in CRH-LI (p≤0.001). HVA (p=0.003) and 5-HIAA (p=0.002) were significantly increased after the ECT. Findings of NPY increase and CRH decrease were similar to those following chronic treatment with citalopram, indicating that these changes might constitute one of the common underpinnings of antidepressant treatment modalities.