In a recent study, Stanford researchers found that people with depression have low blood levels of a substance called acetyl-L-carnitine.
Acetyl-L-carnitine can be naturally produced in the body.
It is also widely available in drugstores, supermarkets, and health food catalogs as a nutritional supplement.
Depression, also called major depressive disorder or clinical depression, is the most prevalent mood disorder in the United States and the world.
It 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.
Worse, current pharmacological treatments are effective for only about 50% of the people for whom they’re prescribed.
And they have numerous side effects, often decreasing long term compliance.
In rodent experiments, a deficiency of acetyl-L-carnitine was linked to depression-like behavior.
Oral or intravenous administration of acetyl-L-carnitine reversed the animals’ symptoms and restored their normal behavior.
In those studies, the animals responded to acetyl-L-carnitine supplementation within a few days.
Current antidepressants, in contrast, typically take two to four weeks to kick in—in animal experiments as well as among patients.
Other animal studies suggest that acetyl-L-carnitine, a crucial mediator of fat metabolism and energy production throughout the body, plays a special role in the brain.
It works at least in part by preventing the excessive firing of excitatory nerve cells in brain regions called the hippocampus and frontal cortex.
Previous research has shown the linked between low levels of acetyl-L-carnitine and depression in animal experiments.
The current study marks the first rigorous indication that the link between acetyl-L-carnitine levels and depression may apply to people, too.
The findings 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.
In the current study, the team recruited 20- to 70-year-old men and women who had been diagnosed with depression.
They had been admitted to either Weill Cornell Medicine or Mount Sinai School of Medicine, both in New York City, for treatment.
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.
In comparing their blood samples with those of 45 demographically matched healthy people, the depressed patients’ acetyl-L-carnitine blood levels were found to be substantially lower.
These findings held true for both men and women, regardless of age.
Further analysis showed that the lowest levels occurred among participants whose symptoms were most severe, whose medical histories indicated they were resistant to previous treatments, or whose onset of the disorder occurred early in life.
Acetyl-L-carnitine levels were also lower among those patients reporting a childhood history of abuse, neglect, poverty, or exposure to violence.
These patients, who collectively account for 25-30% of all people with major depression disorder, are precisely the ones most in need of effective pharmacological interventions.
But the team cautions against rushing to the store to pick up a bottle of acetyl-L-carnitine and self-medicating for depression.
They suggest that they’ve identified an important new biomarker of major depression disorder.
But they didn’t test whether supplementing with that substance could actually improve patients’ symptoms.
What’s the appropriate dose, frequency, duration? They need to answer many questions before proceeding with recommendations, yet.
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.
Source: Stanford University.