What Is Acetyl-l-Carnitine? Depression Linked to Low Levels of Brain Molecule

Depression could one day be diagnosed with a blood test, according to a study that has found a link between depression and a molecule in the body.

A team of U.S. researchers found patients with major depressive disorder have lower levels of a molecule called acetyl-L-carnitine (LAC) in their blood.

Major depressive disorder, also known as clinical depression, is characterized by a persistent low mood that lasts for at least two weeks. Depression can affect a person's ability to cope with everyday life, making activities such as sleeping, working and eating difficult. Specific forms of depression include postpartum and seasonal affective disorder, according to the National Institute of Mental Health.

LAC plays a number of roles in the brain, from regulating our metabolism and helping to kickstart gene expressions—including one that controls levels of the neurotransmitter glutamate, which is involved in almost everything the organ does.

Depression has been linked to a molecule in the body, a study has found. Getty Images

Researchers tested blood samples from 116 participants, 71 with depression and 45 without. They found levels of LAC were significantly lower in patients with depression when compared with the control group. What's more, patients with very low LAC levels were more likely to have more serious depressive symptoms and to have developed depression earlier in life. There was also a higher chance they had experienced childhood trauma and were resistant to treatments for depression. The results were published in the journal PNAS.

Past studies in mice by the same team hinted at a link between levels of LAC and mood disorders in which supplements were shown to ease depressive symptoms.

Bruce McEwen, a professor of neuroscience and behavior at The Rockefeller University, told Newsweek the study revealed LAC was a potential biomarker for depression. If proved, this could be an important step forward for the diagnosis of the mental illness.

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Currently, patients must report their symptoms—such as persistent sadness or a sensation of emptiness, irritability, feelings of guilt, difficulty concentrating, and thoughts or attempts at suicide—to a clinician. Treatments include psychotherapy, for example, cognitive behavioral therapy, as well as such medications as selective serotonin reuptake inhibitors.

But while the research is a step in the right direction when it comes to diagnosing depression using blood, McEwen said: "It is likely that other biomarkers will be needed to further identify, or narrow down, to create a more specific depression subtype. That is, a combination of biomarkers may be needed rather than one alone."

The research could pave the way for further study into biomarkers, and whether LAC could be used as a treatment for depression.

"Hopefully within the next year or two there will be additional information that may lead to a test," McEwen said.