beta-Endorphin hypersecretion in depression: possible cholinergic mechanisms.

Morning plasma concentrations of beta-endorphin immunoreactivity were significantly higher in a group of depressed patients meeting the Research Diagnostic Criteria for Major Depressive disorder or Schizo-affective disorder, depressed, than in age- and sex-matched groups of normal controls and psychiatric patients without affective disorders. Furthermore, physostigmine-stimulated release of beta-endorphin immunoreactivity was also significantly greater in the depressed patients. These results provide the first evidence for elevated plasma concentrations of beta-endorphin in depression and also represent further evidence for cholinergic supersensitivity in depression. These results suggest that elevated plasma concentrations of beta-endorphin and cholinergically stimulated hypothalamic-pituitary beta-endorphin release, might potentially represent biological state or trait markers for depression.