Abstract
Accumulating studies had been performed using magnetic resonance imaging (MRI) to understand the neural mechanism of acupuncture therapy for depression. However, inconsistencies remain due to differences in research designs and MRI analytical methods. Therefore, we aim to summarize the current MRI research and provide useful information for further research by identifying papers published in English and Chinese about MRI studies on acupuncture for depression up to November 2020. A total of 22 studies met the inclusion criteria, including 810 depression patients and 416 health controls (HCs). The applied designs of these studies are mainly random control trial and pre–post designs. The MRI analytical methods are mainly (fractional) amplitude of low-frequency fluctuation (fALFF/ALFF) and functional connectivity (FC), whereas a small subset of studies used voxel-based morphometry (VBM) and diffusion tensor imaging (DTI). The most consistent functional MRI (fMRI) results showed increased N-acetylaspartate/creatine (NAA/Cr) ratios, increased ALFF in the right precuneus, decreased ALFF in the inferior frontal gyrus (IFG), and increased FC of the anterior cingulate cortex (ACC). In contrast, no significant neurological changes were identified in any of the DTI or VBM studies. However, clear, reliable conclusions cannot be drawn due to the use of different designs, analytical methods, seed points selected, types of depression, acupuncture points, and so on. Improved report specifications, well-designed studies, consistent analytical methods, and larger sample sizes will enable the field to better elucidate the underlying mechanisms of acupuncture in depressed patients.
Highlights
Depression is a common mental illness, which has been recognized as a major public health problem that has a substantial impact on an individual’s ability to function within daily and societal environments (1)
With our review, we aim to provide a systematic overview of the existing evidence regarding changes in brain structure, function, and metabolism underlying the effects of acupuncture therapy on depression by summarizing the characteristics, methods, and conclusions of relevant magnetic resonance imaging (MRI) research
Regional homogeneity (ReHo), amplitude of lowfrequency fluctuation [(f)ALFF], and functional connectivity (FC) were applied in 22 studies; whereas magnetic resonance spectroscopy (MRS), structural MRI (sMRI), and diffusion tensor imaging (DTI) were only used in two studies (Tables 2–5)
Summary
Depression is a common mental illness, which has been recognized as a major public health problem that has a substantial impact on an individual’s ability to function within daily and societal environments (1). Major depressive disorder (MDD) is the most common and severe mental disorder with a lifetime prevalence of 6–15% (7, 8). Faced with limitations of conventional treatments, patients suffering from depression often seek alternative forms of treatment, such as acupuncture therapy (12), one of the world’s oldest recognized medical treatments, which has been used to relieve pain and treat mental illness (13, 14) for 1,000’s of years. Several systematic reviews (1, 15, 16) have shown that a single acupuncture therapy session or combination of acupuncture with a suitable adjunct was significantly effective in reducing the severity of depression. An increasing number of animal experiment researches identified that the effective mechanism of acupuncture for depression may be through regulation of the hypothalamic–pituitary–adrenal axis (18, 19), neurotransmitter (20–22), anti-inflammatory (23– 25), and signaling pathways (26–29)
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