In a recent study, researchers found that people with depression have low blood levels of a substance called acetyl-L-carnitine.
The substance can be naturally produced in the body. It is also available in drugstores, supermarkets, and health food catalogs as a nutritional supplement.
The finding may help develop new treatments for depression.
The research was done by researchers from Stanford University.
Depression is also called major depressive disorder or clinical depression. It is the most prevalent mood disorder in the United States and the world.
Previous research has shown that the disease affects 8-10% of the general population at any given time, with every fourth person likely to experience the condition over the course of a lifetime.
It’s the No. 1 reason for absenteeism at work, and one of the leading causes of suicide.
Current drug treatments are effective for only about 50% of people with depression.
These drugs have numerous side effects and often decrease long term compliance.
Recent studies have found that in rodent experiments, a deficiency of acetyl-L-carnitine was linked to depression-like behavior.
Oral or intravenous use of acetyl-L-carnitine could reverse the animals’ symptoms and help them have normal behavior.
In those studies, the animals responded to acetyl-L-carnitine supplementation within a few days.
This is much faster than current antidepressants, which typically take two to four weeks to kick in among patients with depression.
Other animal studies suggest that acetyl-L-carnitine plays a special role in the brain.
It may work by preventing the excessive firing of excitatory nerve cells in brain regions called the hippocampus and frontal cortex.
The current study shows for the first time the link between acetyl-L-carnitine levels and depression in humans.
In the study, the team recruited 20- to 70-year-old men and women who had been diagnosed with depression.
These participants went through screening via a detailed questionnaire and clinical assessment, plus blood samples and medical histories.
Twenty-eight of them were judged to have moderate depression, and 43 had severe depression.
The study also included 45 healthy people with the same age ranges and sex.
The team found that depressed patients’ acetyl-L-carnitine blood levels were found to be substantially lower than healthy people.
These effects were true for both men and women, regardless of their age.
Further analysis showed that the lowest levels of the substance were in people whose depression symptoms were most severe, who had treatment-resistance depression, or whose depression started early in life.
In addition, the acetyl-L-carnitine levels were also lower among those patients reporting a childhood history of abuse, neglect, poverty, or exposure to violence.
The findings suggest an important new biomarker of major depressive disorder.
They also point the way to a new class of antidepressants that could be freer of side effects and faster-acting than those in use today.
That may help patients for whom existing treatments don’t work or have stopped working.
But the team cautions that people should not rush to the store to pick up a bottle of acetyl-L-carnitine and self-medicating for depression.
Future work needs to test whether supplementing with that substance could actually improve patients’ symptoms.
This is the first step toward developing that knowledge, which will require large-scale, carefully controlled clinical trials.
The findings are published in the Proceedings of the National Academy of Sciences.
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