Benzodiazepine suppression of cortisol secretion: a measure of anxiolytic activity?

Clinical studies on spontaneous afternoon cortisol levels in depressed patients revealed that oxazepam given a few hours before blood sampling, may suppress the cortisol levels. This was confirmed in a volunteer study, where oxazepam 30 and 60 mg caused a dose-dependent suppression of the cortisol level only lasting 2 or 3 hours in spite of persisting high oxazepam levels in plasma. Subsequently, a study in 28 depressed patients showed a substantial suppression of afternoon cortisol after oxazepam 45 mg given 2 hrs prior to sampling. It may be postulated that this effect is mediated through GABA-ergic receptors inhibiting the hypothalamic release of corticotropin releasing factor (CRF). This is interesting since CRF may have neurotropic effects related to the behavioral responses to stress, and the inhibitory effect thus may represent a mechanism of action for the anxiolytic effect of benzodiazepines.