Clinical and Structural Differences in Delusions Across Diagnoses: A Systematic Review.

Area of Science:

• Neuroscience
• Psychiatry
• Neurology

Background:

• Delusions are fixed, false beliefs impacting various psychiatric and neurodegenerative disorders.
• Understanding delusion heterogeneity may refine diagnostic classifications.
• Structural neuroimaging studies offer insights into the neural underpinnings of delusions.

Approach:

• Systematic review of 28 structural neuroimaging studies.
• Focused on delusions in schizophrenia (SZ), bipolar disorder (BP), Alzheimer's disease (AD), and Parkinson's disease (PD).
• Analyzed gray matter changes and clinical presentations.

Key Points:

• Gray matter reductions associated with delusions were observed in the dorsolateral prefrontal cortex, left claustrum, hippocampus, insula, amygdala, thalamus, superior temporal gyrus, and middle frontal gyrus.
• These findings were present across SZ, BP, AD, and PD, though with significant variability.
• Specific regions showed consistent associations across multiple disorders, e.g., dorsolateral prefrontal cortex (SZ, BP, AD).

Conclusions:

• Findings support, but also expand upon, the dopaminergic hypothesis of psychosis.
• New hypotheses involving belief formation networks and cognitive biases are proposed.
• Standardization of assessments is recommended for future transdiagnostic research on delusions.