This study describes cerebrospinal fluid (CSF), neuropeptide Y (NPY) and substance P (SP) in patients with a recent suicide attempt and during antidepressant treatment. Seven out of 13 patients received antidepressants. The patients were examined on three separate occasions, i.e. at pre-treatment, followed by every 3 or 4 months. Antidepressant treatment seemed to affect the levels of CSF NPY, which decreased significantly between the second and last lumbar puncture despite no significant changes of clinical scores. When the whole group was taken into consideration, both CSF NPY and SP decreased significantly. At pre-treatment, Brief Scale of Anxiety scores were significantly and negatively correlated to CSF SP and tended to be negatively correlated to CSF NPY. There were also significant positive correlations between CSF NPY and SP during the entire study in the whole group, possibly reflecting an inter-relationship between these neuropeptides.