The relationship between olfactory and emotional processing is an area of increasing interest in schizophrenia research.

Olfactory identification deficits are well described in schizophrenia while the results for pleasantness ratings remain unclear.

Evaluation of odor identification and hedonic judgment related to severity of negative symptoms and β-endorphin concentration.

Fifty outpatients with schizophrenia were included in the study: 25 with negative symptoms (PN) and 25 without predominant negative symptoms (P). They were compared with 23 healthy individuals. In all study groups University of Pennsylvania Smell Identification Test (UPSIT) and odor hedonic evaluation were performed. Clinical symptoms severity was evaluated using PANSS. Plasma concentrations of β-endorphin were assayed in all participants.

PN made more odor identification errors than controls (P = 0.000) and P sample (P = 0.001). Hedonic judgments of unpleasant odors were significantly more pleasant in PN sample than in P (P = 0.03) and controls (P = 0.041). PN had significantly higher concentration of β-endorphin than P sample (P = 0.014) and controls (P = 0.009). No relationship between β-endorphin concentration and odors identification and odor hedonic judgment was found in both patient samples and controls.

Increased level of β-endorphin is related to predominance of negative symptoms but probably it is not involved in olfactory identification performance and hedonic judgment in schizophrenia. Patients with predominant negative symptoms revealed different pattern of pleasantness rating – they experience unpleasant odors as more pleasant. Alterations in smell identification and hedonic judgment could be differentially expressed in some subtypes of schizophrenia.

The author has not supplied his/her declaration of competing interest.