Laboratory Testing for Mental Health Disorders Evaluation
Laboratory testing for mental health disorders should be targeted and based on clinical presentation rather than routine extensive testing for all patients. 1
Core Laboratory Tests
Basic panel for all patients with mental health concerns:
- Complete blood count (CBC)
- Basic metabolic panel (BMP) or comprehensive metabolic panel (CMP)
- Thyroid function tests (TSH, free T4)
- Urinalysis
- Urine toxicology screen 1
Additional tests to consider:
- Liver function tests
- Pregnancy test (for women of childbearing age)
- Electrocardiogram (ECG), especially if considering medications with QTc prolongation risk 1
Patient-Specific Testing
High-Risk Groups Requiring More Comprehensive Evaluation
| Patient Group | Recommended Laboratory Evaluation |
|---|---|
| Elderly (>65 years) | CMP, CBC, thyroid function tests, urinalysis, B12 levels [1] |
| First-episode psychosis | BMP, CBC, thyroid function tests, urinalysis, toxicology screen [1] |
| Substance use disorders | Urine drug screen, CMP, CBC [1] |
| Disoriented patients | CMP, CBC, thyroid function tests, urinalysis, consider neuroimaging [1] |
| Abnormal vital signs | CMP, CBC, thyroid function tests, urinalysis [1] |
| Medical comorbidities | Targeted testing based on medical history and physical findings [1] |
| On psychotropic medications | Therapeutic drug monitoring, medication-specific monitoring [1] |
Clinical Presentation-Based Testing
- Patients with abnormal vital signs: More extensive workup including electrolytes, CBC, and renal function 2
- Patients with disorientation/confusion: Consider neuroimaging (CT/MRI) 1
- First-episode psychosis: Comprehensive evaluation to rule out medical causes 1
Medical Conditions to Consider
Mental health symptoms can be caused or exacerbated by numerous medical conditions:
- Neurological: Stroke/TIA, CNS hemorrhage/trauma, brain tumors/infections, seizures, neurodegenerative disorders 2
- Metabolic/Endocrine: Hypo/hyperglycemia, electrolyte disturbances (especially hyponatremia), thyroid disorders, adrenal disorders 2
- Other: Medication side effects/interactions, substance intoxication/withdrawal, infections, hypoxia 2
Important Considerations
Thyroid Function Testing
Thyroid abnormalities warrant special attention as they can induce mood, anxiety, psychotic, and cognitive disorders. However, up to one-third of psychiatric patients may demonstrate thyroid function test abnormalities that don't reflect true thyroid disease but rather "non-thyroidal illness" 3. These abnormalities often resolve spontaneously without treatment 3.
Routine vs. Targeted Testing
Multiple studies have found that extensive, routine laboratory testing is unnecessary and should be guided by the patient's clinical evaluation 2. False positive laboratory results are 8 times more frequent than true positives in patients with routine testing 2.
Common Pitfalls
- Overreliance on routine testing: Less than 1 test in 50 ordered routinely results in clinically meaningful findings 1
- Attributing symptoms to psychiatric causes without adequate medical workup: Always consider medical causes of psychiatric symptoms 1
- Delaying treatment unnecessarily: Excessive testing can delay necessary psychiatric treatment 1
- Misinterpreting abnormal thyroid function tests: Psychiatric conditions themselves can cause thyroid test abnormalities that don't reflect true thyroid disease 3, 4
Evidence-Based Approach
The American Academy of Pediatrics and American College of Emergency Physicians recommend a focused medical assessment with targeted laboratory testing rather than routine extensive testing 2. Studies have consistently shown that most clinically significant abnormalities can be predicted by history and physical examination 2.
When laboratory testing is performed, it should be guided by the patient's clinical presentation, age, medical history, and current medications rather than applying a one-size-fits-all battery of tests 1.