A Comparative Study Of Odor Identification Deficit In Schizophrenia,Bipolar Disorder And Major Depressive Disorder

BackgroundSchizophrenia is a serious mental disorder that causes a heavy burden on patients,their family members and society.Previous studies aiming at first-episode schizophrenia,chronic schizophrenia and individuals at high risk for schizophrenia have indicated that odor identification ability is a potential trait marker of the schizophrenia-spectrum disorder and is related to negative symptomatology.Patients with early-onset schizophrenia exhibit worse cognitive function and carry a worse prognosis,however,most research has focused on olfactory impairment in patients with adult-onset schizophrenia.Olfactory deficits have been reported in mental disorders other than schizophrenia such as bipolar disorder and major depressive disorder.However,the clinical symptoms of schizophrenia show similarities comparing to bipolar disorder and major depressive disorder,making it difficult to differentiating diagnosis between diseases.PurposesStudy 1:To explore the difference of odor identification ability between patients with early-onset schizophrenia and adult-onset schizophrenia,and investigate the relationship between odor identification ability and negative symptoms.Study 2:To explore the differences of odor identification ability among patients with schizophrenia,bipolar disorder with different mood states and major depressive disorder.Subjects and methodsStudy 1:We recruited two independent samples:40 patients with early-onset schizophrenia and 40 age-and sex-matched healthy controls;as well as 40 patients with adult-onset schizophrenia and 40 age-and sex-matched healthy controls.The University of Pennsylvania Smell Identification Test was administered.The Positive and Negative Syndrome Scale was used to identify clinical symptoms of patients with schizophrenia.The Temporal Pleasure Experience Scale was used to measure the traits of individuals in anticipatory and consummatory experiences of pleasure.The relationship between odor identification ability and negative symptoms was analyzed.Study 2:We recruited 91 patients with schizophrenia,70 patients with manic bipolar disorder,70 patients with depressed bipolar disorder,35 patients with euthymic bipolar disorder,85 patients with major depressive disorder and 47 healthy subjects.The Sniffin’ Sticks test was performed on all subjects,and the Anticipatory and Consummatory Interpersonal Pleasure Scale was used to investigate the relationship between odor identification ability and anhedonia in patients with schizophrenia.Results(1)Patients with early-onset schizophrenia and adult-onset schizophrenia have significantly lower odor identification ability than gender-and age-matched healthy subjects,with more sever impairment in early-onset schizophrenia patients.(2)Odor identification ability of patients with schizophrenia,bipolar disorder with different mood states and major depressive disorder was significantly lower than that of healthy subjects,and the impairment of odor identification ability in patients with schizophrenia was the greatest.(3)Odor identification ability of patients with schizophrenia correlated significantly with anhedonia and negative symptoms.Conclusions(1)Odor identification ability deficit may be a trait marker of schizophrenia,which may shed light onto the early recognition and diagnosis of schizophrenia and the differential diagnosis of mental disorders.(2)Odor identification ability is related to the negative symptoms in patients with schizophrenia,which may provide a new perspective for the treatment of negative symptoms.