Are there lower levels of GDNF in the blood of people with bipolar disorder?
GDNF (glial cell line-derived neurotrophic factor) is a protein that helps nerve cells survive and function. Some studies have looked at whether GDNF levels in the blood are different in people with bipolar disorder compared to healthy people. The answer is not clear-cut: some research finds lower GDNF levels, while other studies find no difference. The evidence is strongest for lower GDNF during manic episodes.
What the research says
A 2024 meta-analysis pooled 13 studies and found that, on average, people with bipolar disorder had lower GDNF levels than healthy controls 3. However, the results varied widely across studies, and the authors noted that high heterogeneity and possible publication bias make the finding unreliable 3. A 2020 study specifically in people with a manic episode found significantly lower GDNF levels compared to controls, even after adjusting for age, BMI, and cortisol 10. In contrast, a 2014 study found no overall difference in GDNF levels between bipolar patients and controls, though it did find a higher GDNF/BDNF ratio during mania 9. A 2026 study in youth with autism found no difference in GDNF levels between those with and without bipolar disorder 11. Overall, the evidence is mixed, but lower GDNF during mania is a consistent finding in some studies.
What to ask your doctor
- What do current GDNF findings mean for my diagnosis or treatment plan?
- Are there any blood tests for bipolar disorder that are clinically useful right now?
- Should I be aware of any lifestyle factors that might affect GDNF levels?
- How do my current medications (like lithium) affect neurotrophic factors?
- Are there any ongoing studies on biomarkers for bipolar disorder that I might join?
This question is drawn from common patient questions about Psychiatry and answered using cited medical research. We do not provide individualized advice.