This is an observational study aiming to screen biomarkers associated with the diagnosis and treatment outcomes of severe mental disorders (MDD/major depressive disorder, SZ/schizophrenia, BD/bipolar disorder) through 7T ultra-high-field magnetic resonance multimodal imaging and visual perception assessment, thereby optimizing the objectivity and precision of clinical diagnosis and treatment.

I. Core Research Objectives

1. Clarify the specific changes in visual perception behavior and brain imaging (metabolism, functional connectivity) of patients with severe mental disorders before and after treatment.
2. Establish a biomarker system related to disease diagnosis and treatment outcomes to make up for the limitation of current clinical reliance on phenomenological diagnosis.

II. Study Subjects and Inclusion/Exclusion Criteria

1. Recruitment Scope

   • Patient group: MDD, SZ, and BD patients diagnosed in the Department of Psychiatry, the Second Affiliated Hospital of Zhejiang University School of Medicine.
   • Healthy control group: Healthy individuals without a history of mental illness recruited from the general population.

2. Key Criteria

   • Inclusion: Aged 18-45 years; meeting the Diagnostic and Statistical Manual of Mental Disorders, 5th Edition (DSM-5) diagnostic criteria (for the patient group); no organic brain injury or severe physical illness; signing the informed consent form.
   • Exclusion: Organic brain diseases; severe physical illnesses (e.g., tumors); internal metal implants (e.g., cardiac pacemakers); claustrophobia or inability to tolerate MR examinations; pregnancy, etc.

III. Core Study Procedures

1. All participants will undergo 2 sessions of 7T MRI scans (including MRS, fMRI, and other multimodal sequences), focusing on the MT+ brain region and V1 brain region respectively, with the scan order randomly balanced.
2. During the interval between the two MRI scans, participants will complete visual psychophysical experiments, cognitive function tests (e.g., BDT test), and clinical symptom collection.
3. The study will not interfere with routine clinical treatment and strictly adheres to the ethical standards of the Second Affiliated Hospital of Zhejiang University School of Medicine (Ethical Approval No.: 2025 Lun Shen Yan Di 0603).

IV. Study Significance

1. Provide objective biomarkers for clinical practice to improve the accuracy of diagnosis and the scientificity of treatment effect evaluation for severe mental disorders.
2. Reveal the association mechanism between visual cortex-related brain networks and diseases, laying a theoretical foundation for precision diagnosis and treatment.

Inclusion Criteria:

• Participants aged 18 to 45 years old at the time of enrollment
• Male or female participants
• For patients: A diagnosis of major depressive disorder (MDD), schizophrenia (SZ), or bipolar disorder (BD) based on DSM-5 criteria
• For healthy controls: No history of any mental health disorders
• No current severe medical illnesses or history of brain injury such as encephalitis
• Ability to provide written informed consent by the participant or their guardian

Exclusion Criteria:

• History of head injury or brain diseases such as epilepsy
• Presence of severe physical illnesses such as tumors or thyroid problems
• Presence of metal implants in the body like pacemakers or brain devices
• Fear of enclosed spaces (claustrophobia) or inability to undergo an MRI scan
• Current pregnancy

Patient Group: Recruited from the Department of Psychiatry at The Second Affiliated Hospital of Zhejiang University School of Medicine, consisting of three subgroups: patients with major depressive disorder (MDD), schizophrenia (SZ), and bipolar disorder (BD), all meeting the Diagnostic and Statistical Manual of Mental Disorders, 5th Edition (DSM-5) diagnostic criteria.

Healthy Control (HC) Group: Recruited from the general public, with no history of mental disorder diagnosis.

All participants are aged 18 to 45 years (inclusive), meet the study's inclusion/exclusion criteria (no severe physical illnesses, no organic brain injury, etc.), and will complete non-invasive assessments (7T MRI scans, visual psychophysical experiments, cognitive tests, and clinical symptom evaluations) as required. The patient group receives standard clinical treatment (no study-induced intervention) during the study period.