Efficacy and underlying mechanisms of acupuncture therapy for PTSD: evidence from animal and clinical studies

This comprehensive review investigated the efficacy and underlying mechanisms of acupuncture in the treatment of Post-Traumatic Stress Disorder (PTSD), a debilitating mental condition that affects millions of people globally and generates economic costs exceeding $232.2 billion annually in the United States alone. The study was structured in three main sections: meta-analysis, acupoint analysis, and mechanistic research, offering a holistic view of the therapeutic potential of acupuncture.

The meta-analysis included eight randomized controlled trials with 656 PTSD patients, comparing acupuncture (including manual acupuncture, electroacupuncture, and transcutaneous electrical stimulation) with pharmacotherapy or psychotherapy. Results were consistently favorable to acupuncture across multiple assessment scales. On the CAPS scale (Clinician-Administered PTSD Scale), acupuncture showed significant superiority with a mean difference of -10.34 points compared to control. Similarly, on the PCL-C scale (PTSD Checklist-Civilian), the difference was -8.38 points in favor of acupuncture.

For symptoms of anxiety (HAM-A) and depression (HAM-D), improvements were -3.69 and -3.20 points respectively, demonstrating multidimensional benefits of the treatment.

The acupoint analysis revealed interesting patterns in clinical practice and research. Point GV-20 (Baihui) emerged as the most commonly used, present in 78.6% of studies, both in clinical research and in animal models. In clinical studies, the four most frequent points were GV-20, GV-24, GB-20, and EX-HN1, all located in the cranial region, reflecting the traditional Chinese medicine approach of treating mental disorders through points that directly influence the brain. In animal studies, in addition to GV-20 and GV-24, ST-36 and HT-7 were also frequently used, demonstrating a more simplified but effective selection.

Treatment parameters varied across studies, but a pattern emerged of 30 minutes per session for 7-21 days in animal studies, and 4-12 weeks in clinical studies. Low-frequency electroacupuncture (2 Hz) predominated in animal models, while high-frequency (100 Hz) was more common clinically, possibly reflecting physiologic differences between species and application conditions.

Mechanistic investigation revealed that acupuncture acts through multiple neurobiological pathways. At the brain structural level, acupuncture demonstrated significant neuroprotective effects in the hippocampus, reducing microglial activation and the expression of pro-inflammatory molecules such as lipocalin-2, while restoring abnormal neural electrical activity in the CA1 and CA3 regions. In the amygdala, it increased BDNF expression and modulated tyrosine hydroxylase expression, promoting neuroprotection and regulating fear responses. In the prefrontal cortex, acupuncture reduced IL-6 and increased BDNF, improving emotional regulation and executive function.

In the neuroendocrine system, acupuncture demonstrated the ability to regulate the hypothalamic-pituitary-adrenal (HPA) axis, frequently dysregulated in PTSD. It significantly reduced levels of corticotropin-releasing hormone (CRH) and corticosterone, while increasing mineralocorticoid receptor expression, restoring the negative feedback crucial for stress homeostasis. Additionally, it modulated the endocannabinoid system through increased DAGL-α and CB1R expression, contributing to anxiety reduction.

Cellular signaling pathways were also targets of acupuncture's action. The BDNF-TrkB pathway proved fundamental, with acupuncture increasing phosphorylation of key enzymes such as PI3K, Akt, MEK, and CREB, promoting neuronal survival and synaptic plasticity. The Keap1-Nrf2 pathway was activated, increasing expression of antioxidant factors such as HO-1, protecting against oxidative stress. The mTOR pathway was also modulated, with increases in p-mTOR and downstream proteins related to protein synthesis and neural plasticity.

In terms of safety, acupuncture demonstrated an excellent profile, with adverse effects limited to mild discomfort at the needle site, minimal superficial bleeding, and small hematomas. This contrasts favorably with the frequent side effects of conventional pharmacotherapy, including gastrointestinal symptoms, autonomic dysfunction, and psychiatric symptoms. The low dropout rate in acupuncture studies suggests greater tolerability and patient acceptance.