Preliminary findings regarding the presence of plasmatic benzodiazepine binding inhibitory activity (BBIA) in 14 psychiatric patients prompted us to investigate it further in larger samples of psychiatric patients (n = 44) and in healthy controls (n = 14). The results have shown that BBIA is present in all the subjects included with statistically significant differences between the patients and controls. The highest concentrations were found in the patients with no difference between anxious or depressed patients, and the lowest in the healthy controls. These findings indicate that BBIA might play a role in the pathophysiology of some manifestations of anxiety.