Using the grip strength effort task to measure reward processing dysfunction in schizophrenia and major depressive...

Area of Science:

• Neuroscience
• Psychiatry
• Behavioral Science

Background:

• Anhedonia, a core symptom in disorders like schizophrenia and major depressive disorder, signifies impaired reward processing.
• Objective biomarkers are needed for developing effective treatments for anhedonia.

Purpose of the Study:

• To assess the validity, reliability, and feasibility of the Grip Strength Effort Task (GSET) for measuring reward processing.
• To explore reward processing differences in individuals with schizophrenia (SZ) and major depressive disorder (MDD) compared to healthy controls (HC).

Main Methods:

• The GSET, an effort-based decision-making task, was administered to 37 SZ, 40 MDD, and 59 HC participants across four European sites.
• Participants chose between low-effort/low-reward and high-effort/high-reward options.
• Test-retest reliability and multi-site feasibility were evaluated.

Main Results:

• 19% of participants were 'inflexible responders,' always choosing high-effort trials.
• MDD participants, excluding inflexible responders, showed less willingness to exert effort for high reward than controls.
• Willingness to exert effort for high reward negatively correlated with anhedonia severity across all participants.
• Inflexible responders had higher depressive symptoms and punishment anticipation.

Conclusions:

• The GSET can serve as an objective behavioral biomarker for reward processing dysfunction.
• Further research is required to understand inflexible responding and its impact on task interpretation.
• The GSET demonstrates feasibility for multi-site studies and potential for treatment development in anhedonia.