- Summary. Thirteen patients with DSM-III-R diagnosis of either major depression or bipolar I depression participated in the study. The control group consisted of 10 subjects evaluated for headache or suspected meningitis, none of whom were found to suffer from any organic disease. CSF was withdrawn from all subjects for the measurement of soluble interleukin 2 receptor (sIL-2R). CSF sIL-2R levels were found to be lower in patients as compared to controls (df= 1, 20; F= 84; p< 0.000001).