Depression and CSF Endorphin Fraction I: Seasonal Variation and Higher Levels in Unipolar Than Bipolar Patients

Radioreceptor assay of endorphin Fraction I in the cerebrospinal fluid (CSF) of 92 inpatients suffering from major depression revealed the following: (1) clearly elevated levels as compared to normal control subjects, (2) higher levels in unipolar than in bipolar patients, & (3) seasonal rhythms showing peaks in early fall for unipolar patients & late fall for bipolar patients. The annual pattern observed bears some resemblance to the known seasonal variations of affective disorders & suicide.