This retrospective cohort study will examine shared neural mechanisms of social cognitive deficits in adults with autism spectrum disorder and adults with schizophrenia using existing clinical, behavioral, and neuroimaging data from National Taiwan University Hospital cohort studies. The study will include adults with autism spectrum disorder, adults with schizophrenia, and healthy control participants.

Resting-state functional magnetic resonance imaging (MRI) and structural MRI data will be analyzed to estimate default mode network functional transition indices. These indices will be compared between diagnostic groups and examined in association with social cognitive and psychiatric symptom measures, including the Social Responsiveness Scale (SRS) and the Positive and Negative Syndrome Scale (PANSS) when applicable. No new participants will be recruited, and no intervention will be administered. The study will use previously collected data from 80 adults with autism spectrum disorder, 79 adults with schizophrenia, and 108 healthy controls.

Inclusion Criteria:

• Previously enrolled in one of the source cohort studies approved by the institutional review board of National Taiwan University Hospital.

• Adult participants belonging to one of the following groups:

  1. Autism spectrum disorder group: participants with a clinical diagnosis of autism spectrum disorder according to Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) criteria.
  2. Schizophrenia group: participants with a clinical diagnosis of schizophrenia according to DSM-5 criteria.
  3. Healthy control group: participants without a history of autism spectrum disorder, schizophrenia, or other major psychiatric or neurodevelopmental disorders according to available source cohort records.

• Availability of resting-state functional MRI data acquired under the study MRI protocol.

• For participants in the autism spectrum disorder group, availability of autistic trait or social functioning measures, such as the Social Responsiveness Scale, when used in symptom-association analyses.

• For participants in the schizophrenia group, availability of psychiatric symptom measures, such as the Positive and Negative Syndrome Scale, when used in symptom-association analyses.

Exclusion Criteria:

• Missing or incomplete MRI data.
• Poor-quality MRI data due to severe artifacts, failed preprocessing, failed registration, or incomplete brain coverage.
• Excessive head motion during resting-state fMRI that prevents reliable analysis.
• Missing essential demographic or diagnostic information.
• Missing required clinical or behavioral measures for specific association analyses.
• Healthy controls with documented major psychiatric or neurodevelopmental disorders, if identified in source cohort records.

This retrospective cohort study will use pre-existing clinical, behavioral, and neuroimaging data from adult participants who were previously enrolled in cohort studies conducted at National Taiwan University Hospital. The study population includes adults with autism spectrum disorder, adults with schizophrenia, and healthy control participants. Available data include structural MRI, resting-state functional MRI, and symptom or behavioral assessments relevant to social cognition and psychiatric symptoms, including the Social Responsiveness Scale and the Positive and Negative Syndrome Scale when applicable. No new participants will be prospectively recruited, and no intervention will be administered.