Loss of the circadian variation of platelet [3H]imipramine binding in delusional compared with non-delusional endogenously depressed patients

Background: The circadian variations of the serotonin reuptake sites were studied in 16 patients meeting DSM-IV criteria for major depression with melancholia, either with (n=8) or without (n=8) psychotic symptomatology. Method: The [3H]imipramine binding sites were measured in platelet samples. Results: While no statistically significant difference was found between the morning (09:00 h) and evening (21:00 h) [3H]imipramine Bmax values in the control group, both the non-delusional and delusional melancholic patients showed higher evening than morning Bmax values, which were only statistically significant in the former. When both diagnostic groups were compared, the delusional patients showed significantly lower [3H]imipramine binding values than the non-delusional patients both in the morning and evening samples. Within the non-delusional depressed patients, those individuals with mood circadian variation, assessed by the 18th item of the HDRS, showed significantly lower Bmax values than those without mood variation. Lowest morning and evening Bmax values were noted in the delusional depressed group without mood variations. Conclusions: These results suggest that delusional depressions might have a different neurobiological substrate with loss of chronobiological rhythms.