[Evaluation of olfactory stimuli by depressed patients]

Anhedonia, a cardinal sign of depression, is discussed to originate from a transmitter dysbalance in the central dopaminergic reward system. This system involves neuroanatomically many structures of the olfactory system. Hence the question arises whether anhedonia can be quantified when depressive patients judge smells hedonically. Sensory evaluation of olfactory stimuli by 16 depressive patients was compared that of an age-matched control group. In the group comparison, mono- and birhinal sensory thresholds as well as judgment of intensity were not significantly different. For four of the eight smells, the hedonic judgements were found to be identical between the group of depressives and controls, with the remaining smells not significantly different. There were no differences in the consistency of ranking of smells. In a longitudinal (test-retest) assessment there were again no differences in intensity, familiarity, and hedonic quality of the smells. The findings suggest that changes in the dopaminergic transmitter balance during the state of depression causing anhedonia affect neither olfactory perception nor the hedonic judgement of smells. Contrary to the clinical picture, anhedonia thus seems not to arise at the level of sensory perception yet but should be considered a more complex construct of disturbed central processing.