The Mechanism of Electroacupuncture for Depression on Basic Research: A Systematic Review

This scientific article represents an important contribution to our understanding of how electroacupuncture can help people who suffer from depression. The study offers a comprehensive view of the biological mechanisms involved in this treatment, drawing on experimental research with laboratory animals conducted over recent years.

Depression is considered one of the leading threats to global public health, affecting not only the nervous system but also potentially causing problems in multiple organs of the human body. Although traditional antidepressant medications are available, many have significant side effects, such as sexual dysfunction, gastrointestinal problems, drowsiness, and even suicidal ideation. This makes the search for safer and more effective therapeutic alternatives necessary.

Electroacupuncture is a technique that combines traditional Chinese acupuncture with controlled electrical stimulation. Unlike conventional acupuncture, in which only needles are inserted at specific points on the body, in electroacupuncture an electrical device is connected to the needles to deliver gentle, controlled electrical currents. Previous clinical studies have already shown that this technique can be as effective as conventional antidepressant medications but with fewer adverse effects and, in some cases, with a faster onset of action.

For this systematic analysis, the investigators followed rigorous scientific guidelines and searched multiple scientific databases, including English- and Chinese-language publications, from inception through December 2019. The aim was to identify all experimental animal studies that investigated how electroacupuncture works in the treatment of depression. After a careful screening of more than a thousand initially identified articles, 28 high-quality studies were selected for detailed analysis.

The analyzed studies primarily used well-established animal models to simulate human depression. The most common model was chronic unpredictable mild stress, in which animals are exposed to different types of stress over several weeks to develop behaviors similar to those seen in human depression. The most frequently used acupoints were two specific points on the animals' heads, equivalent to the Baihui and Yintang points in human clinical practice. Most studies used 2 Hz electrical stimulation, considered a low frequency, although some tested higher frequencies.

The results showed that electroacupuncture produces antidepressant effects through multiple simultaneous biological mechanisms, which explains its therapeutic efficacy. One of the main mechanisms identified involves regulation of the hypothalamic–pituitary–adrenal axis, a fundamental system in the body's stress response. When this system is hyperactive, as occurs in depression, there is excessive production of stress hormones. Electroacupuncture demonstrated the ability to normalize this system, reducing levels of hormones such as cortisol and adrenocorticotropic hormone.

Another important mechanism discovered relates to neuroplasticity — the brain's ability to form new connections and reorganize itself. Depression is associated with the loss of this plasticity, especially in the hippocampus, a brain region crucial for memory and emotional regulation. Electroacupuncture was shown to be able to restore synaptic plasticity in the hippocampus, promoting the formation of new neural connections and increasing the expression of a protein called BDNF (brain-derived neurotrophic factor), essential for neuronal survival and growth.

The study also identified that electroacupuncture acts on neurotransmitter systems, the chemical substances that allow communication between neurons. Specifically, it regulates the levels of serotonin, dopamine, and norepinephrine, neurotransmitters fundamental for mood and emotional well-being. In addition, the technique demonstrated anti-inflammatory capacity, reducing the production of proinflammatory cytokines in the brain, which are elevated in people with depression.

The clinical implications of these findings are significant for both patients and clinicians. For patients, the results suggest that electroacupuncture offers a valid and potentially safer therapeutic alternative to conventional antidepressants. The technique appears to work holistically, acting simultaneously on multiple biological systems that are dysregulated in depression. For clinicians, these data provide a solid scientific basis for considering electroacupuncture as an integral part of depression treatment, whether as monotherapy or in combination with other therapeutic approaches.

It is worth noting that some studies included in the analysis tested the combination of electroacupuncture with low doses of conventional antidepressants, observing synergistic effects that surpassed the results of either treatment alone. This suggests that integrating approaches may be particularly beneficial for some patients.

However, this study has some important limitations that should be considered. First, all the research was conducted in animal models, and although these are valuable for understanding biological mechanisms, direct translation to humans is not always guaranteed. In addition, most of the studies focused on specific mechanisms in isolation, not yet providing a fully integrated view of how all these processes interact simultaneously in the treatment of depression.

Another relevant limitation is that few studies directly compared the mechanisms of action of electroacupuncture with those of conventional antidepressants, which would be valuable for better understanding the differences and similarities between these therapeutic approaches. Future clinical studies in humans will be needed to confirm whether these mechanisms identified in animals translate effectively into therapeutic benefits for patients with depression.

In conclusion, this systematic review provides robust evidence that electroacupuncture exerts antidepressant effects through multiple complementary biological mechanisms, including hormonal regulation, improvement of neuroplasticity, modulation of neurotransmitters, and reduction of brain inflammation. These findings support the use of electroacupuncture as a promising therapeutic option for the treatment of depression, offering a potentially safer approach with fewer side effects than conventional pharmacologic treatments. However, more clinical research in humans is needed to fully validate these benefits and establish optimized treatment protocols for different types of depressed patients.