Anhedonia in Schizophrenia and Major Depressive Disorder Clinical and Functional MRI Study

Background: Anhedonia, is defined as reduced capacity to gain pleasure from pleasurable experiences, is a key symptom of major depression. Several studies had investigated anhedonia in schizophrenia and major depressive disorder, using different psychometric and radiological assessment tools with controversy results in either severity of anhedonia or radiological findings. The aim of this study was to differentiate the nature of the issue of anhedonia in schizophrenia versus major depressive disorder; from clinical and brain function part of view, and to study different variables in this regard.

Methods: This study was carried on 60 participants who were divided into three groups: Group 1: 20 schizophrenic patients, diagnosed according to DSM-5. The symptoms of schizophrenic patients must include anhedonia as a main symptom, Group 2: 20 patients with major depressive disorder according to DSM-5 criteria, and anhedonia was one of their prominent symptoms, Group 3: 20 control subjects.

Results: Our results revealed statically significant differences between participants as regards age of onset, occupational career. Statically significant differences were found between 3 groups. Most of patients in group 1 lacks the interest for social activities and intimate relationships. Statically significant Difference was found between patients in both groups compared to controls. Striatal activity (mainly caudate) was significantly diminished in group 2 (P value <0.001) and group 1 (P value 0.002) relative to controls. Prefrontal activity (ventromedial area ''vmPFC'' and dorsolateral area ''DLPFC'') was increased significantly in group 2 more than control group (P value 0.034). Group 1 shows significantly decreased activation than controls (P value 0.019). Significant differences were found between group 1 and 2 (P value <0.001). Orbito-frontal activity was increased significantly in depressed patients more than group 1 (P <0.001) and controls (P =0.019).

Conclusions: Anhedonia is a highly disabling symptom in patients with schizophrenia or MDD, associated with poor outcome. Depressed anhedonic patients have higher incidence of suicidal ideas, thoughts, and behavior. Depressed patients showed significant striatal hypoactivation associated with hyper activation of prefrontal and orbitofrontal areas. Schizophrenic patients showed diminished activation at striatal areas and frontal cortex. We fail to find significant correlation between severity of anhedonia in both patient groups and degree of fMRI activation in different brain areas involved in reward processing.