A Study to Evaluate Role of Integrative Yoga-based Interventions on Cognitive and Autonomic Functions among Major Depressive Disorder

Abstract

Background:

Major depressive disorder (MDD), commonly known as clinical depression, is a mental health disease that causes chronic sadness and a loss of interest in formerly enjoyable activities and associated with significant impairments in cognitive and autonomic functions, which often persist even after mood symptoms improve.

Aim:

This study investigated the effects of a 6-month combined yoga and dietary intervention on cognitive performance, autonomic regulation, and depressive symptoms in individuals with MDD.

Materials and Methods:

In this randomized controlled trial, 178 participants with MDD (aged 20–50 years) were assigned to either a combined yoga and dietary intervention group or a control group receiving standard care. The intervention group participated in yoga for 60 min 4 days in a week over a period of 6 months and a diet chart was given to them. Outcome measures included depression severity (Hamilton Depression Rating Scale), cognitive function (subjective and objective assessment), autonomic function (heart rate variability, blood pressure), assessments were conducted at baseline and 6 months, and P < 0.05 was considered statistically significant.

Results:

Compared to the control group, the intervention group showed statistically significant improvements in Hamilton score for depression (P < 0.001), food frequency questionnaire (P < 0.001), Montreal cognitive assessment score (P < 0.001), mini–mental status examination score (P < 0.001), P300 latency (P < 0.001), P300 Amplitude (P < 0.001), low frequency (P < 0.001), high frequency (P < 0.001), low/high frequency (P < 0.001), root mean square standard deviation (SD) (P < 0.001), SD of NN interval (P < 0.001).

Conclusion:

A 6-month combined yoga and nutrition intervention improved cognitive performance, autonomic regulation, and depressive symptoms significantly in the study group. These findings imply that this integrative strategy could be a helpful addition to normal MDD care, perhaps addressing the disorder’s multidimensional nature. More research is needed to understand the long-term consequences and mechanisms that underpin these benefits.

Introduction

A common and debilitating mental illness that affects millions of people worldwide, major depressive disorder (MDD) has a major effect on the Indian populace. Globally, the burden of depression has been rising and MDD was the third leading cause of disability in 2015.[1] Estimated global prevalence of depressive episode/depressive disorder (DD) varies from 3.2% to 4.7%. The global pooled period prevalence of mood disorders was 5.4%, and its prevalence in WHO-World Mental Health Survey ranged from 0.8% to 9.6% across countries. By 2030, unipolar depression is predicted to be the second leading contributor to the global burden of disease. The weighted prevalence of lifetime and current DD was 5.25% and 2.68%, respectively.[2]

While psychotherapy and medication have proven to be effective traditional therapies for MDD, they sometimes ignore the holistic aspect of mental health, especially in the Indian context where mind–body integration is a cornerstone of conventional therapeutic methods. Furthermore, even after mood symptoms subside, cognitive deficits and autonomic dysregulation linked to MDD frequently endure, adversely affecting functional results and quality of life.[3]

Growing interest has been seen in complementary and alternative methods of treatment MDD in recent years, with an emphasis on interventions derived from traditional Indian practices. Yoga, an age-old Indian practice that incorporates breathing techniques, physical postures, and meditation, has demonstrated the potential in reducing symptoms of depression and enhancing general well-being.[4] Similarly, Ayurvedic-based dietary therapies have drawn interest due to their possible application in the treatment of mental health issues.[5]

Bhattacharyya et al. evaluated the efficacy of yoga-related practices as a mind–body therapy that prevents cognitive decline in older persons and reported that yoga techniques can boost cognitive function and overall well-being. In response to stress, yoga has a calming impact on the sympathetic nervous system and hypothalamic–pituitary–adrenal (HPA) axis. It has the ability to boost oxygen flow to the brain and neurotransmitter function. Brain stimulation through yoga practices is also thought to activate microglial cells, which increases waste removal and promotes general brain health.[6] Another study done by Hölzel et al. suggested that yoga has been linked to increased cortical thickness and gray matter volume.[7]

Varambally et al. reported in randomized controlled trial that integrating a structured yoga practice, with an initial 1-month training followed by 3 months of home practice, offers significant benefits as an add-on treatment compared to exercise or standard care alone. This approach can enhance overall treatment outcomes, potentially leading to better mental and physical health.[8] A study done by Godos et al. highlighted that diet plays a crucial role in mental health by influencing molecular mechanisms such as oxidative stress, inflammation, and neurotransmitter function. Understanding these pathways underscores the potential of dietary interventions in preventing and managing mental health disorders, emphasizing the importance of a balanced diet rich in antioxidants.[9] By implementing the combined approach of yoga and diet, we hope to explore potential synergistic effects that could lead to greater improvements in both mental and physical health for people with MDD.

Traditional treatments, such as medication and psychotherapy, may have drawbacks, including side effects, incomplete remission, and high relapse rates. There is an urgent need for complementary and alternative approaches that can improve the efficacy of current treatments. Cognitive deficits, including lack of attention, memory, and executive function, are typical in MDD and can continue even after mood symptoms.[10]

Methodological discrepancies, such as differences in the duration, frequency, and kind of yoga practices, as well as the use of nonstandardized measurements for cognitive and autonomic outcomes, impede the capacity to make firm findings. Furthermore, most research focuses on short-term impacts, with insufficient longitudinal data to determine the long-term viability.[11] The underlying processes by which yoga exerts its effects are not well understood, prompting more investigation of the neurological and physiological pathways involved. In addition, the subject populations in the current study are occasionally not diverse, which limits the implications of the findings to different demographic groups. There is limited comparative research on efficacy, making it difficult to place yoga among other MDD therapy approaches. Addressing these gaps thoroughly, this study highlighted the effect of yoga and diet on cognitive and autonomic processes among MDD, resulting in more effective and comprehensive treatment methods.

Materials and Methods

The study was carried out as a single-center, randomized controlled trial. Before the commencement of patient recruitment, approval was obtained from the Institutional Ethics Committee (RUHS-CMS/Ethics/Comm./2022-23/63) and registered Clinical Trial Registry no: CTRI/2023/12/060730. Participants were recruited from the psychiatry outpatient department (OPD) who met the inclusion criteria. Before completing a consent form to express their agreement to participate, they were educated thorough participant information sheet. The calculated sample size for the study was 77 with a confidence level of 95%. Due to 10% dropout rate or nonresponse subjects, the considerable sample size for the study is 85, i.e., round off 90 , whereas n = Sample size, z = The value of standard variation at a given confidence level, i.e., 95%, p = sample proportion, q = 1 − p, e = Margin of error), so .

n = 77 (~90) 90 in the control and 90 in the study group (SG) (Total 180). To be included in the study, subjects given written informed consent aged between 20 and 50 years and who were having MDD (symptoms such as depressed mood, loss of interest/pleasure, weight loss or gain, decreased concentration, inappropriate guilt, and fatigue, thoughts of suicide for more than 2 weeks) were included in the study according to ICD-10 criteria.[12]

Subjects having psychotic illness such as schizophrenia or schizoaffective disorder, bipolar disorder, organic disorders such as dementia, epilepsy or cerebrovascular disease, history of electroconvulsive therapy in the last 3 months, musculoskeletal disorders such as kyphosis, scoliosis, chronic diseases such as hypertension, diabetes, and chronic renal disease were excluded from the study.

Screening and recruitment

Total three thousand and four hundred sixty subjects were screened out of which 178 participants were recruited for the study by simple random sampling method [Flow Chart]. In this case, one participant ended up in the SG, and one in the control group and implemented single blinding where the outcome assessors were unaware of the participants’ group allocation. Subjects were screened from patients attending the psychiatry OPD with a clinical diagnosis of MDD. Each patient underwent evaluation using ICD-10 criteria to confirm the diagnosis, followed by the Hamilton Depression Rating Scale (HAM-D)[13] to assess the severity of depression. Inclusion criteria focused on patients with depression (HAM-D score >14), while exclusion criteria ruled out those with severe comorbid psychiatric conditions, substance abuse, or physical limitations affecting yoga practice. Eligible patients were informed about the study and enrolled after providing written informed consent and providing participant information sheet, ensuring a well-defined participant pool for the intervention. Sociodemographic details (information on age, sex, marital status, geographical area, and socioeconomic status according to modified Kuppuswamy scale)[14] and clinical history were gathered on a detailed pro forma.

Flow Chart 1.

Screening and recruitment

Intervention

The yoga (asanas such as dandasana, janu sirsasana, tadasana, virbhadrasana, and bhujangasana) training was administered by qualified and experienced yoga instructors who were asked to adhere to the module as closely as possible [Table 1].[15] All yoga asanas and postures were explained and demonstrated by the certified yoga instructor. It was stressed by the instructors that patients should focus on their breathing patterns as well as be aware of their body during asana practices. These sessions of yoga would be approximately 60 min 4 days in a week over a period of 6 months. In addition to yoga, participants were provided with a personalized diet chart curated by a professional dietitian. The diet chart [Table 2][16] emphasized a balanced intake of macronutrients (carbohydrates, proteins, and fats) and micronutrients (vitamins and minerals) to complement the yoga intervention.[12] It included whole grains, lean proteins, healthy fats, fruits, vegetables, and sufficient hydration while limiting processed foods, sugar, and salt. Participants were encouraged to adhere to the diet chart throughout the study duration to maximize the synergistic benefits of yoga and nutrition. Subjects were asked to report if they experience any side effects while performing yoga, such as palpitation, anxiety, pain and soreness, and muscle injury, whereas participants in the control group did not receive any intervention, only standard care was given. Participants must maintain a 75% attendance rate during the 6 months of yoga. Each subject will receive a Yoga Protocol video to help them comply better. For surveillance purposes, we conducted telephone chats with the subjects. The yoga asanas were supervised online using Google Meet. As part of our monitoring, we sent daily texts to the subjects and called them once a week. Compliance was checked by assessing the diaries when they came for the follow-up. The intervention, comprising a yoga module and a diet chart, was designed to address both depression and cognitive impairment, recognizing their interconnected nature in MDD.

Table 1.

Yoga protocol

Yoga protocol		Duration
Seated mindfulness scan and set positive affirmation		3–5 min
Seated asanas
Spinal twists (Matsyendrasana)		6–9 min
Staff pose (Dandasana)
Head to knee forward bend (Janu sirsasana)
Reclining hand to big toe pose (Supt padangustasana)
Standing asanas
Mountain pose (Tadasana)		25–27 min
Tree pose (Vrikshasana)
Warior II pose (VirbhadrasanaII)
Extended side angle stretch (Utthita parsvakonasana)
Half-moon pose (Ardha chandrasana)
Standing forward bend (Vanasanattanasana)
Warrior I pose (VirbhadrasanaI)
Downward facing dog pose (Adho mukhasana)
Restorative asanas
Cobra pose (Bhujangasana)		6–8 min
Child’s pose (Balasana)
Cat cow pose (Chakravakasana)
Eye-of-the-needle pose (Sucirandhrasana)
Legs up the wall (Viparita karani)
Final relaxation: Guided mindfulness meditation
Corpse pose (Shavasana)		10 min
Each asanas was held approximately five breaths

Table 2.

Diet Plan

Content		Source		Consumption
Fiber rich food		Raspberries, blackberries, apple sunflower seeds, almonds, dry figs, baby carrots		1 serving daily
Unsaturated fats containing food		Canola oil (1 TBS), ground flax seeds (1 TBS), flaxseed oil (1 TBS), English walnuts (1 TBS), soybean oil (1 TBS), chia seeds (sabza) 1 tsp, olive oil, peanut oil, sunflower oil
Salt		Not more than 1500 mg/day
Protein rich diet		½ cup cooked lentils (dhal or dals or daals) or ½ cup cooked dry beans (rajma, channa, and soybeans)		2–3 servings daily (rich protein will be included)
		2–3 oz each of protein foods, e.g., fish, lentils, legumes, beans, walnuts, and cashew		2–3 servings daily
Dairy products		One serving includes 1 cup=8 oz nonfat milk or 1% milk or low fat buttermilk or nonfat yogurt		2–3 servings daily
Whole grains		Consume at least half of all grains as whole grains. Increase whole-grain intake by replacing refined grains with whole grains. Reduce the amount of rice/chappatis when potatoes or other starchy vegetables are also included in the same meal
Iron, copper, and magnesium		Increase vegetable and fruit intake. Eat a variety of vegetables, especially dark green, red, and orange vegetables and beans and peas
Combination of Vitamins (B, C, D, E, carotene)		Citrus fruit, milk, fish, beans		1–2 serving daily

Diet plan based on dietary regimen: Carbohydrate (45%–60%), protein (10%–35%), fat (20%–25%) they should also include the following in their daily diet:

1. Micronutrients

   • Omega-3-fatty acids (chia seeds walnuts etc.) Vitamin B12 (eggs), D (milk), E (fish), Magnesium (legumes), flavonoids (green tea), copper (nuts, seeds), iron (lentil, chickpea).

2. Increase consumption

   • Fruits, vegetables, legumes, berries, whole grain products, fibers, fish, chicken, low-fat cheese, and whole grain products.

3. Decrease consumption.

   • Processed food such as sausages, french fries, fast foods, sweets such as ice cream, chocolate, cake, processed meat, refined flour, and high-fat cheeses.

Outcome measures

Cognitive functions

Cognitive functions were assessed by both subjective and objective assessment. Subjective assessment was done using mini–mental score (It is an 11-question measure that tests five areas of cognitive function: orientation, registration, attention and calculation, recall, and language. The maximum score is 30. A score of 23 or lower is indicative of cognitive impairment)[17] and Montreal cognitive protocol A and B (A brief, 10–15 min screening tool designed to assess various domains of cognitive function, including attention, executive functions, memory, language, visuoconstructional skills, conceptual thinking, calculations, and orientation. It provides a score out of 30 points to help detect mild cognitive impairment and early signs of cognitive decline)[18] whereas objective assessments were recorded by Auditory event-related potential (P300) involving standard auditory oddball paradigm on Octopus NCV/EMG/EP-4 Ch. Machine model-CMEMG 01 in neurophysiology lab’s silent acoustic room [Figure 1].[19]

Figure 1.

Recording of event-related potentials

Autonomic functions

The autonomic function was measured by the means of heart rate variability (HRV) carried out using Lab Chart 8 on Digital Physiograph MLT004/ST by AD Instruments. Frequency domain (low frequency [LF], high frequency [HF], LF/HF ratio) and time domain parameters (mean heart rate [HR], root mean square standard deviation [RMSSD]: Root mean square of the successive difference between normal heart beats, percentage of successive RR intervals that differ by more than 50 ms [PNN50], Standard deviation of NN interval [SDNN]) were assessed. The electrocardiogram (ECG), can be recorded for 5 min to determine HRV. The ECG is used to extract intervals between successive beats, or R-R intervals. Rather than using the ECG, the peripheral pulse is used in this experiment to make the process of capturing a signal for analysis easier. A peripheral pulse occurs during each normal cardiac cycle, therefore the pulse’s peak-to-peak interval corresponds to the R-R interval from an ECG recording. This technique involves studying and showing the various frequency components of the N-N interval.[20] The use of a 5-min ECG for HRV analysis is justified due to its efficiency, reliability, and practical advantages compared to a 15-min recording. Research has shown that short-term recordings of 5 min provide accurate and valid measures of both time-domain (e.g., RMSSD) and frequency-domain (e.g., HF) HRV parameters, which are comparable to longer recordings. A 5-min ECG minimizes patient discomfort, reduces the likelihood of artifacts caused by movement or fatigue, and is more feasible in clinical and research settings where time is a constraint [Figure 2].

Figure 2.

Recording of heart rate variability

Adherence

The adherence rate in this study was notably high, with 98.89% of the participants (178 out of 180) completing the study protocol but two participants dropped out from the study, one from the SG and two from the control group. The reasons for the subjects to discontinue from the study in the SG could not make up to postintervention assessment. In both study and control groups, two were not able to come for postassessment. The high adherence rate in this study, with 98.89% of participants completing the protocol, can be attributed to several strategies. Clear communication ensured participants understood the study’s purpose and their role, fostering commitment. Regular follow-ups through calls and messages helped participants stay on track. Personalized support for the yoga module and diet chart made the intervention more accessible and suited to individual needs. Individuals were provided with a diary to document their daily dietary intake.

Statistical analysis

The study results were entered into Microsoft Excel 2019 and analyzed using SPSS 21 software (IBM Corporation, located in Armonk, New York.). Data were presented as mean and standard deviation (SD). The Shapiro–Wilk test was used to assess the normality of the data, ensuring it met the assumptions required for parametric testing. The data were then analyzed using the Student’s paired t-test to compare the study and control groups. The Chi-square test was used to assess the difference in remission rates between the two groups. A significance level of P < 0.05 was set to determine whether the differences observed between the groups were statistically significant.

Results

Figure 3 depicts various categories such as knowledge of yoga, socioeconomic status, geographical area, marital status, sex, and age groups. For instance, a significant proportion of participants in both groups did not have knowledge of yoga, with 87% in the SG and 91% in the control group. In terms of socioeconomic status, the upper middle-class category had 61% in the SG and 35% in the control group, highlighting a notable difference. Geographically, rural participants were more prevalent in the SG (81%) compared to the control group (55%). The marital status and age group distributions were relatively balanced between the two groups, with minor differences in percentages. Overall, the graph effectively demonstrates the demographic characteristics of both groups, providing clear visual insights into their similarities and differences.

Figure 3.

Distribution of sociodemographic variables among study participants

Table 3 depicts the comparison of mean ± SD of different parameters in study group participants at baseline and after 6 months of yoga-based dietary interventions. There was significant difference in the following parameters: Food frequency questionnaire (FFQ), HAM D, Montreal cognitive assessment A and B (MoCA and B), mini–mental status examination (MMSE), P300 (L), P300 (A), LF, HF, LF/HF ratio, mean HR, RMSSD, PNN50 and SDNN.

Table 3.

Comparison of mean±standard deviation of various parameters at baseline and after 6 months of yoga and diet intervention of study group among major depressive disorder population (using t-test)

Outcome measures		Baseline, mean±SD		6 months, mean±SD		t		P
Dietary assessment
FFQ		2987.08±589.72		2576.68±791.48		3.9147		<0.001**
Depression severity
HAM-D		20.63±2.33		5.34±1.84		48.4157		<0.001**
Cognitive functions
MoCA and B		10.27±2.15		25.47±2.57		42.6961		<0.001**
MMSE		8.71±2.78		23.90±3.70		30.9011		<0.001**
P300 (L)		398.06±11.54		303.18±7.17		65.6142		<0.001**
P300 (A)		6.58±2.24		9.97±1.37		9.8070		<0.001**
HRV indices
LF		73.09±8.37		46.79±4.81		25.5920		<0.001**
HF		37.52±5.13		68.19±9.45		26.8745		<0.001**
LF/HF		1.99±0.35		0.70±0.13		32.4328		<0.001**
Mean HR		101.95±3.82		68.35±3.43		61.5489		<0.001**
RMSSD		28.22±2.41		63.19±5.72		53.1067		<0.001**
PNN50		26.27±1.84		69.28±8.56		46.3325		<0.001**
SDNN		36.49±2.52		56.36±4.32		37.4277		<0.001**

**P<0.001 highly significant. HRV: Heart rate variability, SD: Standard deviation, HAM D: Hamilton Rating Scale for depression, MMSE: Mini–mental status examination, MoCA and B: Montreal cognitive assessment A and B, P300 (L): P300 latency, P300 (A): P300 amplitude, LF: Low frequency, HF: High frequency, LF/HF: LF/HF ratio, Mean HR: Mean heart rate, RMSSD: Root mean square SD, PNN50: Percentage of successive RR intervals that differ by more than 50 ms, SDNN: SD of NN interval, FFQ: Food frequency questionnaire

Table 4 depicts the comparison of mean ± SD of different parameters in the control group 212 participants at baseline and after 6 months of no interventions. There was no significant difference seen in all cognitive function and HRV parameters.

Table 4.

Comparison of mean±standard deviation of various parameters at baseline and after 6 months in the control group among major depressive disorder population (using t-test)

Outcome measures		Baseline, mean±SD		6 months, mean±SD		t		P
Dietary assessment
FFQ		2320.37±799.68		2483.57±818.46		1.3417		0.1814
Depression severity
HAM-D		22.64±2.45		22.19±4.17		0.682		0.495
Cognitive functions
MoCA and B		13.15±3.40		13.63±2.30		0.2733		1.0989
MMSE		10.04±1.63		10.05±1.31		0.0451		0.9641
P300 (L)		398.39±12.82		397.42±12.65		0.5081		0.6120
P300 (A)		7.81±2.55		6.78±1.99		2.9935		0.0032
HRV indices
LF		75.30±6.67		76.86±5.11		1.7515		0.0816
HF		28.69±4.82		28.47±4.31		0.3200		0.7494
LF/HF		2.87±2.58		2.63±1.86		0.0087		0.9930
Mean HR		97.67±3.41		98.04±2.84		0.7866		0.4326
RMSSD		28.86±3.56		29.41±4.17		0.9441		0.3464
PNN50		41.34±6.43		40.36±7.16		0.9583		0.3392
SDNN		30.69±0.65		31.97±0.76		1.4070		0.1612

HRV: Heart rate variability, SD: Standard deviation, HAM D: Hamilton Rating Scale for Depression, MMSE: Mini–mental status examination, MoCA and B: Montreal cognitive assessment A and B, P300 (L): P300 latency, P300 (A): P300 amplitude, LF: Low frequency, HF: High frequency, LF/HF: LF/HF ratio, Mean HR: Mean heart rate, RMSSD: Root mean square SD, PNN50: Percentage of successive RR intervals that differ by more than 50 ms, SDNN: SD of NN interval, FFQ: Food frequency questionnaire

Discussion

The presented data show substantial changes in dietary assessment, depression severity, cognitive functions, and HRV indices over 6 months in SG participants as compared to the control group.

The significant sociodemographic variations between the study and control groups are highlighted in our analysis, which may have an impact on the results. Interestingly, 91% of the control group and 87% of the SG are unaware of yoga, which may have an impact on how they respond to the intervention. While the control group includes a higher proportion of participants from lower socioeconomic classes and urban locations (55%), the SG is more heavily represented in the “Upper middle” socioeconomic class (61.4%) and rural areas (81%). For the younger 20–34 age bracket, the SG has a marginally higher representation at 54% compared to 51% in the control group. Conversely, in the 35–40 age range, this pattern is reversed, with the control group showing a slightly higher percentage at 49% versus 46% in the SG. A study conducted by Arvind et al. also reported similar results and concluded that there was a substantial impact of depression on age, geographical area, marital status, and sex.[2]

In our study, there was a marked reduction in HAM-D scores in SG which indicates a substantial alleviation of depression severity. A similar study conducted by Rani et al. also found significant results but they give the yoga intervention only whereas we have given the combined intervention of yoga and diet.[21] In this study, 43 out of 89 patients in the yoga group achieved remission, resulting in a remission rate of 48.31%. In comparison, 18 out of 89 patients in the control group reached remission, yielding a rate of 20.22%. The difference in remission rates between the two groups was statistically significant with P < 0.001 which is similar to the study conducted by Bieber et al. who reported that a combination of psychopharmacological treatments and yoga significantly reduced depression scores among patients in SG as compared to control.[22] In addition, studies have shown that mindfulness-based interventions are effective in reducing symptoms of depression and improving overall well-being.[23]

The significant reduction in FFQ scores in SG participants (P < 0.001) than the control group after 6 months of intervention. Results by Jacka et al. were reported in randomized controlled trial to directly test dietary improvement as a treatment strategy for depression. The study found that participants who received dietary intervention had a significantly greater reduction in depressive symptoms compared to the control group which was similar to our study.[24] A study investigated by Ghosh et al. highlights those traditional Indian diets, characterized by their anti-inflammatory properties, these qualities limit inflammatory processes, reduce oxidative stress, and promote a healthy gut microbiome. Incorporating omega-3 fatty acids and olive oil into one’s diet can help reduce inflammation while perhaps improving general health and emotional well-being.[25] Studies have shown that food has long been known to alter brain processes such as cognition and emotional processing. The positive effects of numerous micronutrients, such as B-complex vitamins, Vitamin D, folate, and omega-3 3-fatty acids, on depression and mood disorders have been well established. B complex vitamins, including B6, B9, and B12, promote neurotransmitter production and function, which are essential for mood modulation, whereas omega-3 fatty acids, particularly eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), reduce brain inflammation and increase cell membrane fluidity, hence boosting neurotransmitter signaling. These micronutrients work together to alleviate depression symptoms by promoting brain function and lowering inflammation, making them crucial in the dietary management of depression.[26,27]

The improvements in MoCA and MMSE scores and P300 latency reflect significant cognitive enhancement in SG (P < 0.001) as compared to control group which was similar to the study conducted by Paramashiva et al. found that incorporating regular yoga practice significantly enhances cognitive functions, including memory, attention, and executive function, among participants. This improvement is attributed to mechanisms such as stress reduction, enhanced focus, and increased cerebral blood flow.[28] Furthermore, a study by Kumar et al. demonstrated that regular physical activity (sports or vigorous activities, such as running or jogging, swimming, going to a health center or gym, cycling, or digging with a spade or shovel, heavy lifting, chopping, farm work, fast bicycling, and cycling with loads) could significantly improve cognitive functions in individuals with depression.[29] The significant improvement in SG may be due to the fact that the underlying cause of the integrated approach in cognitive benefits is linked to a few brain regions and a network of neural structures. Cognitive functions such as memory, attention, psychomotor performance, processing speed, visual reaction time, and perception are linked to brain regions such as the cerebral cortex, prefrontal cortex, anterior cingulated cortex, temporal lobe, and parietal cortex.[30] Yoga has been shown to be an effective approach for stimulating brain structures, rejuvenating the cognitive area, increasing cerebral blood flow, and generating brain waves. According to research, yoga interventions activate the central nervous system and improve cognitive functioning.[31] Yoga has a positive impact on the temporal and frontal lobes of the brain, increasing cerebral blood flow in these areas, resulting in improved cognitive capabilities.[32]

The notable changes in HRV indices (LF, HF, LF/HF, mean HR, RMSSD, PNN50, SDNN) suggest improved autonomic function in SG (P < 0.001) than control group which is similar to the study by Lin et al. who found that yoga and meditation practices significantly improved HRV parameters and reduced depressive symptoms in patients.[33] Another study demonstrated that HRV biofeedback could enhance autonomic regulation and alleviate symptoms in patients with depression.[34] A study done by Saboo and Kacker also shows that 6 months of regular yoga practice enhances vagal tone and improves autonomic functions by moving them towards parasympathetic dominance in SG participants as compared to the control.[35] One of the studies by Streeter et al. proposed a theory that yoga’s beneficial effects on depression are related to its impact on the autonomic nervous system and gamma-aminobutyric acid (GABA) levels. They suggested that yoga-based practices shifted the autonomic nervous system towards parasympathetic side which corrects underactivity of the both parasympathetic nervous system and GABA systems, which are implicated in mood disorders.[36]

In this study, our goal was to assess whether the synergistic effect of these interventions could lead to greater improvements as seen in other studies done by including Saboo and Kacker[35,37,38,39] on yoga and dietary interventions have demonstrated the efficacy of yoga-based and combined approaches in improving metabolic parameters and cardiometabolic risk factors. In addition, studies like those by Sorout et al.[40] and Sharma et al.[41] highlighted the beneficial impact of yoga and nutrition on health-related quality of life and cognitive functions than either one alone.

The results of this study suggest that a combined approach of yoga and diet-based interventions has significant potential to improve cognitive and autonomic functions in individuals with MDD. This integrated approach, deeply rooted in Indian traditional practices, offers a holistic treatment modality that addresses both the psychological and physiological aspects of depression.

Limitations

The major limitation of the present study was that it was conducted at a single center. In the future, randomized controlled trials with large sample sizes and multicentric designs could be investigated. It would be beneficial to investigate the effects of long-term yoga practice on cognitive and autonomic functions in patients having MDD. Additional neurotransmitter and stress marker are required to confirm and further elucidate the potential therapeutic benefits of yoga programs among MDD populations. However, we recognize that this approach introduces ambiguity in interpreting the results. In future studies, we plan to separate these interventions into distinct arms to isolate their individual effects.

Conclusion

This study depicts that a combined 6-month approach of yoga and nutritional therapies has significant effect on cognitive and HRV parameters. Interventions also help to regulate the HPA axis. Overall, yoga takes a comprehensive approach, focusing on both the mind and the body to help people with MDD achieve cognitive and autonomic stability. As multicentric, cost-effectiveness, and long-term follow-up studies are lacking. All of these areas warrant future research.

Ethical statement

The study was approved by the institutional Ethics Committee of RUHS College of Medical Sciences, Jaipur, Rajasthan, letter no. RUHS-CMS/Ethics/Comm./2022-23/63 dated 21/06/2022.

Conflicts of interest

There are no conflicts of interest.

Funding Statement

Nil.