A New Blood Test Could Help Diagnose Depression And Bipolar Disorder


If science has the ability to do anything, modernizing medicine and testing technologies have been one of its greatest achievements. In fact just recently, researchers have found that the levels of nerve growth factor happen to be lower in those with depression or bipolar disorder than in those in what they call healthy controls. This means that doctors might be able to use these ‘levels of the growth factor to monitor the effects of antidepressant treatment.’

For adults, there is a protein known as brain-derived neurotrophic factor (BDNF) which promotes both the growth and survival of nerve cells. This protein also plays a very vital role in memory, learning, and maintaining brain flexibility or “plasticity” as it’s otherwise known.

One form of the protein, which is called mature BDFN (mBDFN), has reduced blood levels when a patient undergoes psychological stress, and these low levels are correlated with depression. But unfortunately, there are no commercially available blood tests available in order to differentiate mBDNF with its antecedent, which is called proBDNF.

Why this matters is because the proBDFN ‘binds to a different receptor and causes inflammation and nerve degeneration.’

Professor Xin-Fu Zhou of the University of South Australia in Adelaide explains, “Growing evidence indicates that inflammation in brain cells is linked with depressive behaviors, and proBDNF seems to activate the immune system. Therefore, we must separate if from mature BDNF to get an accurate reading.”

Professor Zhou and his colleagues did a study in animals where they found that injecting proBDNF into the muscles or brain happens to trigger depressive reactions or behaviors.

In response, Professor Zhou and his team managed to successfully develop a test that measures mBDNF in a much more accurate method. With this new test, in collaboration with the University of Adelaide and Kunming Medical University in Yunnan, China, the group used the new test to demonstrate that individuals that suffer from bipolar disorder or depression have significantly lower levels of mBDNF in their blood compared to the ‘healthy controls.’

The Journal of Psychiatric Research released a paper where the study authors explained how doctors could actually use this test to accurately diagnose these conditions while monitoring the success of their treatment as well.

Professor Zhou shared, “This could be an objective biomarker, in addition to a clinical assessment by a doctor.”


It’s An Antibody-Based Test

An antibody-based test is also known as an “enzyme-linked immunosorbent assay” or ELISA. It uses antibodies, proteins, antigens and glycoproteins to identify the existence of certain proteins in the body.

The research group used the new test on blood samples from a variety of participants that were all in-patients. 90 of them had major depressive disorder (MDD), 15 of them had bipolar disorder, while 96 were healthy controls. The healthy controls were those that had gone to a psychiatric hospital to undergo a general medical examination in a mental health hospital, but were not diagnosed with a severe mental illness.

Meanwhile, they also tested another 14 blood samples from people that have a history of suicide attempts within the past 10 years. These 14 participants have since been living in communities and were said to be of a more stable state of mental health than the 90 that were in-patient.

The results of the test showed that the individuals that have major depression or bipolar disorder had considerably lower levels of mBDNF in their blood as compared to the healthy controls. And to add to that, individuals that were taking antidepressants also had higher levels of mBDNF than those that were not medicated.

Surprisingly, the levels of mBDNF between those who attempted suicide in the past and those classified as healthy controls had no substantial difference. Although notably, the individuals belonging to the attempted suicide group were living outside the hospital at the time of the study and it was not known if they did or did not have symptoms of depression.

The study authors calculate that a diagnostic test based on their assay, ‘with a cutoff point of 12.4 nanograms per milliliter of serum, would have a sensitivity of 82.2% and a specificity of 83.3%.’ And what this means is that their test could possibly miss around 1 in every 5 people that do have depression and rather find 1 in every 5 people without depression to be depressed.

Simultaneously, there were also similar findings in the smaller subgroup that had bipolar disorder.


Using Electroconvulsive Therapy

Professor Zhou and his team plan to investigate whether Electroconvulsive Therapy (ECT) can aid in the restoration of imbalances between mBDNF and proBDNF at a later time. This is because ECT is usually effective in individuals that don’t usually respond to antidepressants or psychotherapy.

According to Professor Zhou, “Mood disorders affect millions of people worldwide. However, about one-third of people with depression and bipolar disorder are resistant to antidepressants or alternative therapies. The reasons are not understood, but it could have something to do with the imbalances between the different forms of BDNF, which we hope to investigate next.”

The study certainly has some limitations, which the authors acknowledge. For one, they had originally wanted to measure the serum levels of proBDNF alongside the serum levels of mBDNF. Yet, due to technical reasons, that wasn’t possible. Because of this, the researchers weren’t able to ascertain whether it was the balance between the two forms of BDNF or their absolute values were the ones that had the most considerable effect.

The team also noted that there were other important variables that could have affected the participants’ levels of mBDNF in their blood, like whether they smoked or what their body max index (BMI) was.

Again, it’s important to note that the study participants that were diagnosed with major depressive disorder were in-patient, meaning they only represent a very small portion of all people diagnosed with MDD. Rather, those in the control group were just going to a mental health hospital for their general medical examinations, and therefore don’t represent the general population of those with MDD.

In the end, the team shares that further studies will be needed to see what the levels of mBDNF in individuals with MDD and living in the community compare to those in the general population. The findings of these further studies can eventually help treat patients diagnosed with depression.