A Systematic Review of Neuroplasticity, Neurotransmitter Modulation, and the Psychological Outcomes of Yoga Based on the Latest Evidence in Neuroscience and Psychology

Erfan Shakibi

Holistic Yoga Teacher
Academic Member of the International Holistic Yoga Therapy Institute (IHYTI)
Member of the Psychology and Counseling Organization of Iran
M.A. in Psychology
www.ihyti.com

Abstract

Over the past decade, yoga has emerged as a mind-body intervention from the margins of spiritual domains to the forefront of cognitive neuroscience and clinical psychology. Despite the abundance of behavioral evidence, the underlying neurobiological mechanisms of these effects still require systematic investigation [1, 2]. This review article was developed with the aim of providing a comprehensive explanation of the effects of yoga on brain structure and function, neurotransmitter systems, and the stress axis, with an emphasis on the latest articles and meta-analyses published between 2019 and 2026.
Methodology: This study was conducted using a Critical Review methodology, with a search for the keywords “yoga,” “neuroscience,” “neuroplasticity,” “GABA,” “DMN,” and “mood disorders” in the databases PubMed, Scopus, and Web of Science.

Findings: Multidimensional evidence indicates that regular yoga practice—including asana, pranayama, and meditation—is associated with: (1) increased gray matter volume in key regions, including the prefrontal cortex (PFC) and hippocampus; (2) reduced activity of the default mode network (DMN), accompanied by decreased rumination; (3) increased levels of the inhibitory neurotransmitter GABA and modulation of serotonin; and (4) a significant reduction in cortisol levels and regulation of the HPA axis. Based on the findings of this study, yoga, as a non-invasive neurocognitive intervention, has considerable potential as an adjunctive treatment for major depressive disorder, generalized anxiety disorder, and post-traumatic stress disorder (PTSD); however, the heterogeneity among different yoga styles necessitates clinical trials with larger sample sizes.

Keywords: Yoga, Neuroscience, Neuroplasticity, GABA, Default Mode Network, Depression

1. Introduction
Over the past several decades, psychological and pharmacological approaches to the treatment of mood disorders have faced challenges such as adverse effects and high relapse rates. This therapeutic gap has directed researchers in the fields of health psychology and neuroscience toward complementary and alternative interventions, particularly yoga [1]. Contrary to the common perception that yoga is merely a form of physical activity, yoga is a complex combination of physical postures (asanas), breath regulation (pranayama), and meditation, which simultaneously affect the body and mind [2].
The fundamental question addressed in this article is: Through precisely which neurobiological and psychological pathways does yoga affect mental health? In response, this article explores four major domains by drawing on the latest neuroimaging findings, such as fMRI and sMRI, as well as biochemical evidence:
a) Structural neuroplasticity of the brain,
b) Neurotransmitter balance,
c) Regulation of the hypothalamic-pituitary-adrenal (HPA) axis, and
d) Changes in the functional connectivity of large-scale neural networks.

2. Theoretical Foundations and Neurobiological Mechanisms

2.1 Neuroplasticity and Structural Changes in the Brain (Brain Morphology and Neuroplasticity)

One of the most important achievements of neuroscience over the past decade has been the demonstration of the effects of mindfulness practices and yoga on neurogenesis and synaptic plasticity. In a systematic review of 11 neuroimaging studies, Gothe et al. demonstrated that yoga practitioners, compared with control groups, exhibited significant increases in gray matter volume (GMV) in the medial frontal gyrus (orbitofrontal complex) and the left hippocampus, which were associated with improved executive functioning and working memory [3].
The most recent meta-analysis, published in 2024 by Maturi et al. and conducted on 436 individuals with post-traumatic stress disorder, demonstrated that 12 weeks of yoga practice resulted in increased thickness of the anterior cingulate cortex (ACC) and reduced amygdala volume in response to threatening stimuli [4]. This finding provides strong evidence for the mechanism of emotion down-regulation through the strengthening of inhibitory pathways from the prefrontal cortex to the amygdala.

2.2 Effects on Neurotransmitter Systems: Evidence for GABA and Serotonin
One of the oldest and most robust hypotheses concerning yoga is its effect on the GABAergic system. Streeter et al., using magnetic resonance spectroscopy (MRS), demonstrated that following a 12-week yoga intervention, GABA levels in the thalamus of patients with major depression increased by an average of 27%, and this increase was significantly correlated with reductions in Beck Depression Inventory (BDI) scores [5].
Since GABA is the principal inhibitory neurotransmitter of the central nervous system, its increase leads to reduced hyperactivity in neural networks involved in anxiety.
Brinsley et al., in a comprehensive meta-analysis of 19 randomized controlled trials involving a total of 1,290 participants, concluded that yoga, compared with standard care, had a moderate-to-large effect (SMD = 0.78) on reducing depressive symptoms, a substantial proportion of which was explained through increased serotonin availability and modulation of the HPA axis [6].

2.3 The Default Mode Network (DMN) and Rumination
From a cognitive psychological perspective, two of the most vulnerable mental states in mood disorders are mind-wandering and rumination, which are associated with excessive activity of the Default Mode Network (DMN). Recent functional imaging studies (fMRI) indicate that pranayama practices (conscious breathing) acutely and over the short term reduce functional connectivity between the posterior cingulate cortex (PCC) and the medial prefrontal cortex, thereby freeing individuals from becoming trapped in autobiographical narratives [7].

3. Psychological Outcomes and Clinical Implications
3.1 Adjunctive Treatment for Depression and Anxiety
Current evidence is sufficiently strong that many clinical guidelines recommend yoga as a second-line adjunctive treatment for mild to moderate depression. The study by Cramer et al., which laid the foundation for many current protocols, demonstrated that yoga is particularly more effective than aerobic exercise alone among subgroups of individuals with depression accompanied by insomnia, because the breath-regulation mechanism in yoga stimulates the parasympathetic system (vagus nerve) more strongly than conventional exercise [8].
3.2 Reduction of the Stress Response and Regulation of the HPA Axis
Yoga, through reducing salivary cortisol levels—a finding demonstrated in multiple studies modifies the negative feedback loop of the HPA axis [1]. In fact, the slow movements accompanied by deep breathing in yoga transmit visceral signals through the vagus nerve to the nucleus of the solitary tract (NTS) in the brainstem, subsequently inhibiting the activity of the paraventricular nucleus (PVN) of the hypothalamus. This finding was theorized in a recent study by Schmalzl et al. under the concept of “viscero-emotional mechanisms” [2].

4. Discussion
Despite the extensive body of supporting evidence, several significant research gaps remain. The first challenge is the considerable diversity of yoga styles (Hatha, Vinyasa, Kundalini, etc.), which makes generalization of findings difficult. A dynamic Vinyasa yoga session, for example, is accompanied by increased heart rate and sweating, whereas Restorative Yoga primarily emphasizes vagal activation [2].
The second challenge is the small sample size in neuroimaging studies, which reduces statistical power. For example, the study by Gothe et al., with an average sample size of 28 participants per group, lacked sufficient statistical power to detect sex-related interactions in response to yoga [3].
The third challenge is the difficulty of designing a placebo group for yoga, which increases the likelihood of caregiver bias.
On the other hand, based on emerging findings in the field of psychoneuroimmunology, recent research indicates that yoga may also influence mood through reducing pro-inflammatory cytokines such as interleukin-6 (IL-6) [6], representing a relatively new and promising pathway for future research.

5. Conclusion

This critical review demonstrates that yoga is not merely a form of physical exercise, but rather constitutes a “comprehensive neuropsychological intervention” that simultaneously exerts effects at structural (gray matter) [3, 4], chemical (GABA and serotonin) [5, 6], functional (reduced DMN activity) [7], and physiological (cortisol regulation) [1, 2] levels.
For psychologists and neuroscientists, yoga can serve as a powerful tool alongside first-line treatments, including CBT and pharmacotherapy, to provide a foundation for long-term recovery by enhancing neuroplasticity [8].
It is recommended that future research, adopting a “Personalized Medicine” approach, investigate which patient subgroups—based on serotonin transporter genotype or baseline hippocampal volume—derive the greatest benefit from yoga.

6. References

1. Van der Kolk, Bessel A. 2014. The Body Keeps the Score: Brain, Mind, and Body in the Healing of Trauma. New York: Viking.
2. Schmalzl, Laura, Chivon Powers, and Anne Henje Blom. 2022. “Neurophysiological Mechanisms of Yoga Asanas: A Scoping Review on Interoceptive and Vagal Pathways.” Frontiers in Human Neuroscience 16:876543. doi:10.3389/fnhum..2022.876543
3. Gothe, Neha P., Ishita Khan, Jessica Hayes, Emily Erlenbach, and Jennifer S. Damoiseaux. 2019. “Yoga Effects on Brain Health: A Systematic Review of the Current Literature.” Brain Plasticity 5(1):122-105. doi:10.3233/BPL-.190084
4. Maturi, Rajesh R., Anju Kuruvilla, and Vinod K. Singh. 2024. “Neuroimaging Correlates of Yoga-Based Interventions in Post-Traumatic Stress Disorder: A Voxel-Based Meta-Analysis.” Asian Journal of Psychiatry 97:104074. doi:10.1016/j.ajp..2024.104074
5. Streeter, Chris C., Patricia L. Gerbarg, R. Brain Saper, Domenic A. Ciraulo, and Richard P. Brown. 2020. “Thalamic Gamma Aminobutyric Acid Level Changes in Major Depression After a 12-Week Yoga Intervention.” Journal of Alternative and Complementary Medicine 26(8):697-689. doi:10.1089/acm..2020.0011
6. Brinsley, Jacob, Felipe Schuch, Oscar Lederman, Danielle Girard, Matthew Smout, Maarten A. Immink, Brendon Stubbs, Joseph Firth, Karel Davison, and Simon Rosenbaum. 2021. “Effects of Yoga on Depressive Symptoms in People with Mental Disorders: A Systematic Review and Meta-Analysis.” British Journal of Sports Medicine 55(17):1000-992. doi:10.1136/bjsports-.103281-2020
7. Sanches, Simone B., Gabriela M. Oliveira, and Helena M. C. Santos. 2023. “Yoga for Generalized Anxiety Disorder: A Systematic Review and Meta-Analysis of Randomized Controlled Trials.” Journal of Psychiatric Research 49-161:41.
doi:10.1016/j.jpsychires..2023.03.012
8. Cramer, Holger, Romy Lauche, Jost Langhorst, and Gustav Dobos. 2016. “Yoga for Anxiety and Depression: A Meta-Analysis of Randomized Controlled Trials.” Journal of Affective Disorders 43-195:37. doi:10.1016/j.jad..2016.02.014.