Understanding Lab Tests for Depression
Written by Private MD Labs Medical Writing Team • Last Updated: September 8, 2025
Depression is a complex mental health condition that affects millions of people worldwide. While depression is primarily diagnosed through clinical evaluation and psychological assessment, there is no single blood test that can definitively diagnose depression. However, lab testing plays a fundamental role in assessing underlying biological factors that may contribute to depressive symptoms.
Top Recommended Test
Serotonin, Serum
Low levels of serotonin in the serum can be indicative of depression. Serotonin is a key neurotransmitter that regulates mood, and a deficiency can lead to depressive symptoms.
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Why Blood Testing is Important for Depression
Depression involves complex interactions between neurotransmitters, hormones, and nutritional factors. Blood tests can help identify imbalances in these areas that may be contributing to symptoms or affecting treatment response. Testing can also rule out other medical conditions that may present with depression-like symptoms.
Other Relevant Tests
Catecholamines, Fractionated, Plasma (Dopamine)
Depression can be associated with low levels of dopamine, leading to a persistent feeling of sadness, lack of interest, and difficulty concentrating. This test measures dopamine levels to help assess neurotransmitter balance.
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Cortisol, Total
Some studies have found elevated cortisol levels in people with depression, although the relationship is complex and not fully understood. This test helps evaluate stress hormone levels that may be affecting mood.
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Cortisol, AM
Depression has been linked to the dysregulation of the hypothalamic-pituitary-adrenal axis, leading to increased cortisol levels. This condition can be identified by a higher than normal cortisol AM value.
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Folate (Folic Acid)
There is a correlation between low levels of folate and depression. Folate is needed for the production of certain neurotransmitters that affect mood, making this test important for assessing nutritional factors.
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Folate, RBC
Some studies have found an association between low levels of folate and depression. This test provides a more accurate assessment of long-term folate status than serum folate alone.
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Vitamin B12 and Folates
Low levels of folate and B12 have been linked to depression and treatment resistance. This comprehensive test evaluates both nutrients that are essential for neurotransmitter production and brain function.
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Testosterone, Total, Male, IA (MALES ONLY)
Low testosterone levels can also impact mental health. Symptoms include depression, fatigue, and irritability. This test is specifically recommended for male patients experiencing depressive symptoms.
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DHEA (Dehydroepiandrosterone), Unconjugated, LC/MS/MS
Some studies suggest that low DHEA levels could be associated with depression. However, the relationship between DHEA and depression is still not fully understood, but this hormone may play a role in mood regulation.
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Omega 3 and Omega 6 Fatty Acids
Low total Omega-3 levels are associated with increased risk of depression, as Omega-3 fatty acids contribute to the fluidity of the brain's cell membrane and play key roles in brain development and cell signaling.
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Vitamin B5 (Pantothenic Acid)
While not directly causing depression, a deficiency in Vitamin B5 can lead to symptoms such as fatigue and irritability that can contribute to depressive states. However, more research is needed in this area.
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Understanding Your Results
It's important to understand that abnormal results in these tests don't necessarily mean you have depression, nor do normal results rule it out. These tests provide valuable information about biological factors that may be contributing to symptoms or affecting your overall mental health. Your healthcare provider will interpret these results in the context of your symptoms and clinical presentation.
Important Considerations
The information here is for educational purposes only and is not a substitute for professional medical advice. Depression is a serious medical condition that requires proper diagnosis and treatment by qualified healthcare professionals. Always consult with a healthcare provider for diagnosis, treatment, and management of depression.
