Melatonin concentration in human blood and cerebrospinal fluid: relationship to stress

In 35 daytime paired blood and cerebrospinal fluid (CSF) samples from 15 patients, melatonin levels in CSF were undetectable or detectable but not higher than blood levels. During pneumoencephalography in 6 patients, no significant elevation of blood melatonin levels was observed, whereas cortisol concentration increased.