Green tea and its polyphenolic compounds have been shown to exert positive effects in individuals with psychological disorders. The protective role of green tea against stuttering or its related consequences, depression, anxiety and stress, were evaluated in adolescents with moderate stuttering (MS). A total of 60 adolescents aged (
Stuttering is a serious communication disorder, characterized by involuntary disruptions in speech, and it significantly affects or impedes the capacity of individuals to communicate efficiently (
The occurrence of stuttering may be related to cellular physiological, genetic, neurological and psychological disorders, and this is significantly affected by environmental factors (
Previous studies proposed that the neuropathophysiology of stuttering may involve deficiencies in connectivity amongst the cortical networks of regions that normally allows left-sided engagement of the inferior frontal and premotor cortices for efficient planning and execution of sound production, and have also suggested that this deficiency in connectivity of the left premotor/motor areas may be related to differences in the right hemisphere and subcortical activity in individuals who stutter (
Previous studies have shown that the core symptoms of stuttering required abnormal function of the neural circuits, whereas the individual manifestations of stuttering behavior can vary (
Spontaneous normal recovery from stuttering ranges from 40-80% in children <10 years old (
Adolescents and older adults who stutter exhibit more severe negative psychological states, particularly depression and anxiety, and score lower on mental health assessments (
Different treatment approaches for stuttering have shown to be most amenable for younger aged individuals compared with individuals in adulthood who stutter. This may be related to the greater degree of neuronal plasticity in individuals of a younger age compared with the less tractable and far less responsive to treatment neurons of adults, for whom it has often been a long-term problem (
Although positive clinical results with traditional drugs, such as biperiden, clomipramine and haloperidol have been reported (
Alternative medicine strategies based on the use of herbal medicines to treat stuttering or related consequences such as depression, anxiety and other mental health problems are poorly represented in the field of stuttering therapeutics.
Green tea (
Recently, the safety, tolerability and pharmacokinetic properties of the administration of EGCG as a single dose (ranging from 50-1,600 mg) were assessed. The results showed that administration of >1 g of purified EGCG or in green tea has a mean terminal elimination half-life (t1/2z) of 1.9-4.6 h. The data showed that doses of purified EGCG ≤1,600 mg were generally well tolerated (
Epidemiological studies have identified an association between caffeine intake and mental health stress and lifestyle (
A total of 60 school students (median age, 12.1; age range, 12-18 years old; female/male, 9/51) who following the same academic curricula were selected from different public schools and randomly invited to participate in this study. A sample size of 60 was selected from the public schools to give an estimated power of 96% and a significance level of 0.05, with an expected frequency of 8.3%. For all participants, to estimate the severity of the stuttering, one standardized questionnaire (depression anxiety stress scale-42; DASS-42) and one standardized test material (Stuttering Severity Instrument, 4th Edition; SSI-4) were used as previously reported (
The SSI-4 quantifies disfluency duration, frequency and physical features in preschool children through to adulthood (
Commercial decaffeinated green tea bags produced by Kao Ltd., were purchased from a convenience store. Green tea leaves (tea bags) were analyzed for the presence of catechins and caffeine constituents in green tea (100 mg) according to previously reported preparation techniques (
A HP1050 Knauer liquid chromatograph equipped with a 200x4.6 mm, dp 5 µm, Hypersil ODS column, a UV-visible detector (230 nm), and a Rheodyne injector with a 20-µl loop was used to estimate the contents of catechins and caffeine constituents in the leaves of decaffeinated green tea bags. A total of 5 µl aqueous extract was injected. Total run time for the separation was 15 min at a flow rate of 0.60 ml/min and the mobile phase yielded results of 40% methanol: 60% distilled water. The phenolic contents of the extracts were determined by use of calibration plots constructed for every standard. Finally, the peaks of each phenolic content was identified and measured at 520 nm. For all the phenolic acids, calibration plots were linear in a range of 0.0625-1 mg ml-1 (R2>0.9980) (
Previous research studies have showed that individuals who drank 2-3 cups of green tea a day benefitted the most from the full antioxidant benefits of the polyphenols in green tea (
All participants were subjected to the estimation of negative emotional states pre- and post-green tea administration (six cups/day for 6 weeks). Before and after green tea administration, all participants were under careful follow up by an Expert Speech Language Pathologist with >15 years of experience in their respective field. The initial changes in the scores of depression, anxiety, stress and mental health, as measures of the individuals psychological state, were evaluated before and after green tea supplementation as follows.
All participants underwent estimation of negative emotional states of depression, anxiety and stress using DASS, as previously reported (
Mental health status was evaluated in all participants using the 12-item General Health Questionnaire (GHQ 12) as previously reported (
Blood samples were taken once from for all participants at 8.30 AM pre and post green tea consumption (all 6 cups). After centrifugation, serum samples of all tests were stored at -80˚C until required. Several adrenal hormones were measured in order to detect several major adrenal pathways. Both cortisol and acetylcholine (ACTH) were measured in serum samples using RIA-ELISA (cat. no. KIPI28000; DPC Inc.) and SIA-ELISA kits (cat. no. M046006; MD Biosciences Inc.), respectively according to the manufacturer's protocol. Serum levels of DHEA were measured using an immunoassay according to the manufacturer's protocol (cat. no. DHA31-K01; IMMULITE 1000, Diagnostic Products Corporation), with an intra-assay coefficient of variation of <5.2%. Serum levels of corticosterone were measured using a quantitative competitive enzyme immunoassay technique that measures corticosterone levels according to the manufacturer's protocol (cat. no. EC3001-1; Assay pro LLC.).
Statistical analysis was performed using SPSS version 17 (SPSS Inc.). Data are presented as the mean ± SD. For all continuous variables, such as the levels of stress hormones, and the renal and hepatotoxicity parameters, a paired t-test was used. A Wilcoxon signed rank sum test was performed for non-parametric data (depression, anxiety, stress and mental health scores). Pearson's correlation analysis was performed to calculate the correlations between the levels of adrenal hormones and the scores of stuttering, stress, anxiety and depression in adolescents with moderate stuttering. P<0.05 was considered to indicate a statistically significant difference.
In this study, the beneficial effects of green tea supplementation on stuttering and its associated negative psychological states were evaluated in adolescents. A total of 60 adolescents aged 12-18 years old of both sexes were enrolled in the present study, and classified using SSI-4 for estimation of the severity of the stuttering. The participants were classified into two groups; normal healthy group (n=30) and the MS group (n=30), as shown in
Green tea polyphenolic compounds were evaluated using liquid chromatography analysis as shown in
The cumulative side effects of administration of six cups of decaffeinated green tea containing EGCG and other catechins for 6 weeks on both the liver and kidneys were estimated (
The correlation between negative psychological states and the incidence of stuttering amongst adolescents was evaluated using DASS and GHQ 12 tests (
The effect of green tea supplement on the severity of stuttering among adolescents was evaluated using the SSI-4 test (
To study the relationship between the physiological response of adrenal stress hormones with both stuttering and a negative psychological status, the expression levels of cortisol, DHEA, ACTH, corticosterone and the cortisol:DHEA ratio were assayed in all participants (
Together, the results highlight the beneficial effects of decaffeinated green tea on stuttering and mental health. In addition, the changes in expression of adrenal stress hormones were significantly associated with the improvements in depression, anxiety, stress and mental health status amongst adolescents who stuttered (
In this study the administration of six cups/day of green tea for 6 weeks significantly reduced depression, anxiety, stress and the mental health consequences associated with stuttering in adolescents. The severity of stuttering was significantly reduced to a mild status amongst adolescents who suffered from MS.
Approximately 4-5% preadolescents suffer from some degree of stuttering compared with ≤1% in adults (
In this study, depression, anxiety, stress and mental health status were significantly reduced in both the control group and adolescents who stuttered following green tea supplementation. The data significantly correlated with the reduction in the severity of stuttering from moderate to mild, highlighting the significant improvement in clinical response to green tea. This indicates an interesting association between green tea consumption in everyday life and mental health problems associated with stuttering. It has been widely reported that mental stress, anxiety and depression have a significant influence on the psychological status of people who stutter (
Several studies have reported on the association between changes associated with cellular physiological changes and the levels of stress hormones, particularly in individuals with psychological disorders (
The levels of stress hormones were significantly improved and this was positively correlated with the reduction in the scores of stuttering and the related depression, anxiety, stress and mental health consequences. The data confirmed the potential protective role of green tea against the severity of stuttering, particularly among younger individuals. This may be due to the relaxing effect as well as other biological activities of the polyphenolic compounds present in green tea (
Recent clinical trials have shown that higher consumption of green tea significantly lowers the prevalence depression-like symptoms in elderly Japanese individuals (
In conclusion, the present study showed that green tea as a source of natural polyphenols improved psychological disorders associated with stuttering in adolescents. Higher consumption of green tea (six cups/day) significantly improved the severity of stuttering and the related negative psychological states; depression, anxiety, stress and general mental health status in adolescents with MS. In addition, the improvement in stuttering and other consequences correlated positively with the reduction in the expression levels of adrenal stress hormones. However, additional studies with larger cohorts are required for a more thorough evaluation of the biological effects of green tea on stuttering.
The authors are grateful to the Deanship of Scientific Research at King Khalid University, Abha, Saudi Arabia for funding this work through a Research Group Project under grant number (RGP2/205/43).
The datasets used and/or analyzed during the present study are available from the corresponding author on reasonable request.
AA and SAG conceived and designed the study, performed the practical work, analyzed the data, and wrote and edited the manuscript. AA and SAG have read and approved the final manuscript. AA and SAG confirm the authenticity of all the raw data.
The aims and methodology of this study as well as a complete description of the potential effects of green tea were explained to all participants. Informed consent was obtained from the parents of all students recruited in the present study. Research involving human subjects complied with all relevant national regulations and institutional policies, and were approved by the Review Board (HAPO-06-B-001) of The Deanship of Scientific Research, King Khalid University (Abha, Saudi Arabia; approval no. ECM#2019-117). All studies complied with the guidelines described in the 1975 Declaration of Helsinki.
Not applicable.
The authors declare that they have no competing interests.
Graphical representation of the scores obtained for DASS and GHQ-12 scores for estimating the negative psychological states (A) depression, (B) anxiety, (C) stress and (D) and mental health in the control and MS patients pre- and post-green tea consumption (six cups/day for 6 weeks). The results showed a significant decrease in the negative psychological traits of depression, anxiety, stress and mental health status in the Control (P=0.01; pre vs. post) and adolescents with MS (P=0.001; pre vs. post). The results are presented as the mean ± SD. A Wilcoxon signed rank sum test was performed for analysis of non-parametric data, including depression, anxiety, stress and mental health scores. P<0.05 was considered to indicate a statistically significant difference. DASS, depression anxiety stress scale; GHQ, General Health Questionnaire; MS, moderate stuttering.
Graphical representation of the scores obtained for SSI-4 for estimating frequency, duration of speech behavior and physical concomitants as measures of stuttering in (A) the Control group and (B) adolescents with MS pre- and post-green tea supplement (six cups/day for 6 weeks). There was a significant decrease in stuttering scores amongst healthy Control subjects and adolescents with MS. The SSI-4 scores for estimating parameters of stuttering, such as DSP and PC were statistically analyzed using a Wilcoxon signed rank sum test. SSI-4, Stuttering Severity Instrument; MS, moderate stuttering; F, frequency; DSP, duration of speech behavior; PC, physical concomitants.
Levels of adrenal stress hormones in (A) the Control group and (B) adolescents with MS. The results showed a significant decrease in the expression of cortisol, DHEA, ACTH and corticosterone, and increase in the cortisol:DHEA ratio in the Control and MS groups following administration of green tea (six cups/day for 6 weeks). All continuous variables, including the parameters of adrenal stress hormones were analyzed using a paired t-test. MS, moderate stuttering; DHEA, dehydroepiandrosterone; ACTH, acetylcholine.
Demographics and baseline characteristics of the participants
Parameters | Control group | Moderate stuttering group | Degree of freedom | t (P-value) |
---|---|---|---|---|
N | 30 | 30 | - | - |
Male/female | 25/5 | 26/4 | - | - |
Age, years, | 12.3±4.1 | 11.9±5.8 | 198 | -0.231 (0.82) |
Body mass index, kg/m2 | 22.8±3.2 | 23.7±1.8 | 198 | -1.57 (0.01 |
Waist-hip ratio | 0.82±0.09 | 1.38±0.05 | 198 | -26.1 (0.001 |
aP≤0.01,
bP≤0.001.
cData are presented as the mean ± SD.
Daily dosage of catechins from green tea
Phenolic compound, mg | 1 cup | 4 cups | 5 cups | 6 cups |
---|---|---|---|---|
EGCG | 96 | 396 | 476 | 548 |
EGC | 54 | 218 | 287 | 332 |
ECG | 39 | 156 | 210 | 238 |
EC | 31 | 128 | 156 | 189 |
Total catechin |
256 | 986 | 1350 | 1536 |
Theanine | 0.03 | 0.13 | 0.16 | 0.18 |
a1 cup=300 ml.
bTotal catechin concentration was defined as the sum of EGCG, EGC, ECG, and EC values. EC, epicatechin; ECG, epicatechin gallate; EGC, epigallocatechin; EGCG, epigallocatechin gallate.
Hepatotoxic and renal effects of administration of drinking six cups of green tea/day for 6 weeks
Control group | Moderate stuttering group | |||||
---|---|---|---|---|---|---|
Parameters | Before | After | P-value | Before | After | P-value |
AST, U/l | 13.8±3.6 | 13.9±2.9 | 0.142 | 14.3±2.5 | 14.5±1.9 | 0.18 |
ALT, U/l | 11.5±5.7 | 12.6±5.2 | 0.381 | 13.3±2.5 | 13.7±2.8 | 0.36 |
Total-bilirubin | 0.45±0.12 | 0.50±0.34 | 0.145 | 0.52±0.15 | 0.58±0.18 | 0.16 |
Creatinine | 0.57±0.18 | 0.62±0.12 | 0.134 | 0.61±0.21 | 0.68±0.31 | 0.14 |
aData are presented as the mean ± SD. AST, aspartate transferase; ALT, alanine transferase. Normal values of AST are ≤40 U/l of ALT are ≤41 U/l, of total-bilirubin are ≤g.dl and of creatinine are ≤1.2 g/dl.
Improvement of stuttering and mental status in adolescents with moderate stuttering before and after the green tea regimen
Stuttering and psychological status | Clinical response | |||||
---|---|---|---|---|---|---|
Parameters | Before | After | P-value | Before | After | P-value |
Depression score | 22±3 | 11±2 |
<0.001 |
Moderate | Mild |
<0.001 |
Stress score | 24±5 | 10±2 |
<0.001 |
Moderate | Mild |
<0.001 |
Anxiety score | 15±3 | 8±2 |
<0.01 |
Moderate | Mild |
<0.01 |
Mental health scores | 6.8±3.5 | 4.3±2.8 |
<0.01 |
Moderate | Mild |
<0.01 |
Total stuttering score (F+DSP+PC) | 32±6 | 23±5 |
<0.001 |
Moderate | Mild |
<0.001 |
aP<0.01 (before vs. after) for stuttering and psychological status following treatment.
bP<0.001 (before vs. after) for clinical response of stuttering.
cData are presented as the mean ± SD. A Wilcoxon signed rank sum test was used for analysis of stuttering and psychological status. F, frequency; DSP, duration of speech behavior; PC, physical concomitants.
Correlation analysis of adrenal hormones with stuttering, stress, anxiety, and depression scores in adolescents with moderate stuttering following the green tea regimen
Cortisol | DHEA | Cortisol; DHEA ratio | Acetylcholine | Corticosterone | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Parameter | Before | After | P-value | Before | After | P-value | Before | After | P-value | Before | After | P-value | Before | After | P-value |
Depression score | 0.12 | 0.231 | <0.01 |
0.125 | 0.29 | <0.001 |
0.35 | 0.28 | <0.01 |
0.22 | 0.58 | <0.001 |
0.38 | 0.36 | <0.001 |
Stress score | 0.23 | 0.258 | <0.01 |
0.326 | 0.35 | <0.001 |
0.36 | 0.38 | <0.01 |
0.32 | 0.56 | <0.001 |
0.45 | 0.47 | <0.001 |
Anxiety score | 0.125 | 0.321 | <0.01 |
0.258 | 0.38 | <0.001 |
0.27 | 0.32 | <0.01 |
0.28 | 0.86 | <0.001 |
0.65 | 0.65 | <0.001 |
Mental health score | 0.231 | 0.145 | <0.01 |
0.231 | 0.26 | <0.001 |
0.82 | 0.78 | <0.01 |
0.31 | 0.27 | <0.001 |
0.54 | 0.47 | <0.001 |
Stuttering score | 0.114 | 0.256 | <0.01 |
0.321 | 0.37 | <0.001 |
0.89 | 0.34 | <0.01 |
0.28 | 0.31 | <0.001 |
0.47 | 0.61 | <0.001 |
aP<0.01,
bP<0.001 (Before vs. After).
cData are presented as Pearson's (R) coefficients adjusting for variables identified as cofounders for analyses. DHEA, dehydroepiandrosterone.