Biomarker predicts bipolarity in depressed patients

By Eleanor McDermid, Senior medwireNews Reporter

Measuring plasma levels of brain-derived neurotrophic factor (BDNF) in patients with a first episode of depression could help to predict who will go on to develop bipolar disorder, research suggests.

“Finding a reliable and robust biomarker identifying bipolar disorder early during a patient’s first presenting episode of depression is critical”, say study author Yiru Fang (Shanghai Jiao Tong University School of Medicine, China) and colleagues.

It would allow for early intervention, potentially improving outcomes, they note in the British Journal of Psychiatry.

The researchers measured messenger (m)RNA and protein levels of BDNF in the plasma of 164 drug-naive patients with a first episode of depression. The patients were aged 31 years, on average, about a quarter were male and their depressive episode had lasted an average of 2.8 months.

Both BDNF measures were significantly lower in these patients than in 167 mentally healthy controls matched for age and gender. Also, among the patients, the 21 who were diagnosed with bipolar disorder during 3 years of follow-up had significantly lower BDNF mRNA levels than those who retained a diagnosis of major depressive disorder (MDD).

The combination of BDNF mRNA and protein levels was more accurate than mRNA or protein levels alone for distinguishing between patients with bipolar disorder and MDD, with respective areas under the receiver operating characteristic (ROC) curve of 0.80, 0.69 and 0.61 on logistic regression analysis. The findings were similar when patients lost to follow-up were classified as having MDD.

“Despite promising results in our study, earlier reports show that BDNF levels among individuals with mood disorders is far from consistent”, observe Fang et al. They attribute this variability to small sample sizes and medication effects; their study was larger than previous ones and restricted to drug-naive patients, they note.

“These results suggest that BDNF level may be a potential biomarker for bipolar disorder that can be detected in the first depressive episode”, the team concludes.

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