Association between Sedentary Behaviour and Depression, Stress and Anxiety among Medical School Students in Chennai, India
Vinoth Gnana Chellaiyan1, Fasna Liaquath Ali2, Jasmine Maruthappapandian3
1 Assistant Professor, Department of Community Medicine, Chettinad Hospital and Research Institute, Kancheepuram, Tamil Nadu, India.
2 Postgraduate, Department of Community Medicine, Chettinad Hospital and Research Institute, Kancheepuram, Tamil Nadu, India.
3 Postgraduate, Department of Community Medicine, Chettinad Hospital and Research Institute, Kancheepuram, Tamil Nadu, India.
NAME, ADDRESS, E-MAIL ID OF THE CORRESPONDING AUTHOR: Fasna Liaquath Ali, 13/168, Kasimvayal, Gudalur, The Nilgiris-456001, Tamil Nadu, India.
E-mail: fasnaliaqathali@gmail.com
Introduction
Physical inactivity has been found to be a major contributing factor for occurrence of non-communicable diseases like cardio vascular diseases, type 2 diabetes, dyslipidemia and also certain mental illnesses. With the higher prevalence of sedentary behaviour among medical students in India, the researches on sedentary behaviour related to mental illness (depression, anxiety, self-esteem, psychological stress, and quality of life) have become the focus considering the medical students role in future physicians and public health intervention programme. The prevalence and association of sedentary behaviour and certain mental illnesses has been explored in this study.
Aim
To find the prevalence of physical inactivity among medical school students and its association with anxiety, stress and depression.
Materials and Methods
A cross-divtional study was conducted among medical students of Tagore Medical College, Chennai, Tamilnadu. Total 507 medical school students who were >18 years of age from all academic years (First year MBBS to Fourth year MBBS) students were included. A pretested, structured study tool was used which comprised of five divtions-Socio-demographic profile, International physical activity questionnaire, Perceived Stress Scale, Generalised Anxiety Disorder–7 and Beck Depression Inventory. Data was analysed with SPSS-IBM software version 21. Prevalence of physical inactivity was measured in proportions. Chi-square test and Mann Whitney test was applied. A p-value of <0.05 was considered significant.
Results
Among the study participants, 73% and 53.5% had moderate and severe intense activity, respectively. Out of 507 study participants, 21.5% were sedentary. Significant association was found between depression and sedentary behaviour. (p-value-0.049). There was a significant mean difference in depression scores among participants with sedentary and non-sedentary behaviour. (p-value-0.046).
Conclusion
The study was able to find significant association between sedentary behaviour and depression. Promotion of physical activity could help in improvement of negative emotional effects.
Introduction
Physical inactivity has been found to be a major contributing factor for occurrence of non-communicable diseases [1]. It has been found that younger age group have sedentary behaviour due to technological advances and there has been reduction in the participation in active pursuits [2,3]. Sedentary behaviour has been defined as activities which utilises energy expenditure of ≤1.5 Metabolic Equivalent (MET) [4]. Scientific evidences show that sedentary behaviours are not only associated with increased risk of cardio-metabolic disease, but also attributes to all causes of mortality and various physiological and psychological problems [5-7]. Studies have found an association between sedentary behaviour and negative emotions including depression [8,9]. Review articles suggest major evidences on anxiety associated with sedentary behaviour [10]. Sedentary behaviour like screen based entertainment lead to anxiety through biological pathway, increase in the arousal of central nervous system, disrupted sleeping behaviours, poor metabolic health [11]. Animal studies proved that exercise has positive impact on pathophysiology pathways of anxiety [12]. Interventions targeted supervised physical activity has better anxiety outcomes [13]. It overcomes anxiety by lipolysis during moderate to intense physical activity which alters the tryptophan mechanism which is a neurotransmitter associated with mood [14]. Physical activity also offers benefits comparable to established treatment in anxiety order [15]. Moderate to intense physical activity is a valuable mental health promotion in reducing the risk of anxiety and depression [16,17]. A review conducted among South Asian studies reported that leisure related inactivity was >75% in South Asia. Higher prevalence of sedentary behaviour among medical students has been reported in India [18]. The prevalence of sedentary behaviour among medical school students and its association with anxiety, depression and stress remains little explored and the present study was an attempt to explore the physical activity pattern among medical school students. The aim of the study was to find the prevalence of physical inactivity among medical school students and its association with anxiety, stress and depression.
Materials and Methods
The study was a cross-sectional study conducted in a tertiary care teaching hospital, located in Southern Chennai Tamil Nadu, India. The study population comprised of medical students of Tagore Medical College in Chennai, Tamil Nadu. Medical school students who were >18 years of age from all academic years (first year MBBS to fourth year MBBS) who gave consent to participate were included in the study. The students who could not be contacted even after three visits were excluded. The total number of students in medical school at the time of study was 547. Complete enumeration of all the students was done. Total 507 students were included in the present study. The study period is from April 2016 to March 2017. After obtaining written informed consent, the content of the questionnaire was explained to the study participants and self administered for data collection. Institutional Ethical Committee approval was obtained before starting of the study (IEC NO: 40/March 2016). Confidentiality of study participants was maintained in all the phases of the study.
The study tool was pretested, validated and structured questionnaire. Few modifications had been done to adapt the questionnaire to local condition. The scales used for assessing negative emotions are used for screening purpose. The study tool comprised of five sections: 1) Socio-demographic profile and anthropometry of the study participants; 2) The International Physical Activity Questionnaire (IPAQ) [19], self-administered short version was designed for use among young and middle aged adults for assessing physical activity. The questionnaire inquires four activity types during the last week: “vigorous activity” periods for atleast 10 minutes; “moderate activity” periods for at least 10 minutes, “walking” periods for atleast 10 minutes and times spent “sitting” on weekdays. Those who do not undertake any of the above activities were considered to be sedentary. Frequency of activity is measured in days and duration in hours and minutes. 3) The Perceived Stress Scale (PSS) [20] consists of items designed to tap how unpredictable, uncontrollable, and overloaded respondents find their lives. The PSS was designed for use in community samples with at least a junior high school education. Score more than seven was considered as cut-off point; 4) Generalised Anxiety Disorder 7 (GAD-7) [21] is a sensitive self-administrated test to assess generalised anxiety disorder, normally used in outpatient and primary care settings that has seven items, that measure severity of various signs of GAD. Those with a score of more than 10 were considered to be anxious; 5) The Beck Depression Inventory (BDI) [22] self-administered instrument used to screen the presence and degree of depression. It evaluates 21 symptoms of depression which covers emotions, behavioural changes, and somatic symptoms. Each answer on a scale given a value of 0-3. Those with score of above 10 were considered to be depressed [23].
Study participants were referred to Department of psychiatry for further evaluation of those who had positive scores of any of the negative emotional effects (anxiety, stress and depression).
Statistical Analysis
Data was analysed with Statistical Package for Social Sciences (SPSS-IBM) software version 21. For qualitative variables proportions, for quantitative variables mean, median, range and standard deviation were calculated. Prevalence of physical inactivity was measured in proportions. Mean and Standard deviation of the scores were calculated. Chi-square test was applied to find the association between physical activity and anxiety, stress and depression scale scores were done. Mann-Whitney test was applied to find out differences in mean. A p-value of <0.05 was considered significant.
Results
The study was conducted among 507 medical school students. A 71.6% of the medical students stay in hostels within the medical school campus. A 67.3% had their permanent residence in urban area. An 81% belong to upper socio-economic class according to modified BG Prasad scale-2016 updated [Table/Fig-1] [24].
Socio demographic profile (n=507).
| S. No. | Profile | n (%) |
|---|
| 1. | Gender |
| Male | 217 (42.8) |
| Female | 290 (57.2) |
| 2. | Academic year |
| I MBBS | 111 (21.9) |
| II MBBS | 143 (28.2) |
| III MBBS | 139 (27.4) |
| IV MBBS | 114 (22.5) |
| 3. | Current residence |
| Hosteller | 363 (71.6) |
| Day Scholar | 144 (28.4) |
| 4. | Permanent residence |
| Rural | 166 (32.7) |
| Urban | 341 (67.3) |
| 5. | Occupation of Father |
| Professional | 86 (17.0) |
| Semiprofessional | 246 (48.5) |
| Clerk/Shop owner | 10 (2.0) |
| Skilled worker | 76 (15.0) |
| Semiskilled worker | 67 (13.2) |
| Unskilled worker | 4 (0.8) |
| Unemployed | 18 (3.6) |
| 6. | Occupation of Mother |
| Professional | 33 (6.5) |
| Semiprofessional | 127 (25.0) |
| Clerk/Shop owner | 4 (0.8) |
| Skilled worker | 9 (1.8) |
| Semiskilled worker | 16 (3.2) |
| Unskilled worker | 2 (0.4) |
| Home maker | 316 (62.3) |
| 7. | Education of Father |
| Primary | 22 (4.3) |
| Middle | 47 (9.3) |
| Higher secondary | 61 (12.0) |
| Graduate | 200 (39.4) |
| Postgraduate | 160 (31.6) |
| Illiterate | 17 (3.4) |
| 8. | Education of Mother |
| Primary | 42 (8.3) |
| Middle | 63 (12.4) |
| Higher secondary | 71 (14.0) |
| Graduate | 151 (29.8) |
| Postgraduate | 137 (27.0) |
| Illiterate | 43 (8.5) |
| 9. | Socioeconomic Class |
| Upper | 411 (81.0) |
| Upper Middle | 70 (13.8) |
| Middle | 12 (2.4) |
| Lower Middle | 13 (2.6) |
| Lower | 1 (0.2) |
The mean (SD) body weight (in kg) among males and females were 66 (±10.7) and 55 (±9.6) respectively. The mean (SD) height (in cm) among males and females were 171 (±7.4) and 158 (±6.8) respectively. BMI among males and females were 22 (±3.5) and 21 (±3.6) respectively.
Physical Activity
Among the study participants, 73% and 53.5% undertook moderate and severe intense activity respectively. Out of 507 study participants, 21.5% were sedentary [Table/Fig-2].
Distribution of study participants according to their physical activity using International physical activity questionnaire (IPAQ) (n=507) [21].
| S. No. | Physical activity | n (%) |
|---|
| 1. | Moderate intense activity |
| Yes | 370 (73.0) |
| No | 137 (27.0) |
| Frequency of such activity |
| Daily | 155 (30.5) |
| 4-6 days per week | 40 (7.9) |
| 2-3 days per week | 108 (21.3) |
| One day per week | 67 (13.2) |
| None of the above | 137 (27.0) |
| Time duration of activity per day |
| One hour per day | 95 (18.7) |
| 30 minutes per day | 96 (18.9) |
| 20 minutes per day | 86 (17.0) |
| <20 minutes per day | 93 (18.3) |
| Not applicable | 137 (27.0) |
| 2. | Severe intense activity |
| Yes | 271 (53.5) |
| No | 236 (46.5) |
| Frequency of such activity |
| Daily | 94 (18.5) |
| 4-6 days per week | 55 (10.8) |
| 2-3 days per week | 62 (12.2) |
| One day per week | 60 (11.8) |
| None of the above | 236 (46.5) |
| Time duration of activity per day |
| One hour per day | 124 (24.5) |
| 30 minutes per day | 59 (11.6) |
| 20 minutes per day | 44 (8.7) |
| <20 minutes per day | 44 (8.7) |
| None of the above | 236 (46.5) |
| 3. | Sedentary activity |
| Yes | 109 (21.5) |
| No | 398 (78.5) |
The physical activity was assessed using International physical activity questionnaire (IPAQ) [21].
Negative Emotional Effects
Around 15% of study participants were normal with respect to anxiety scale. A total of 83 (16.4%) were anxious taking a cut-off of 10 score in the scale. Only 15.2% of study participants were not stressed. 49.5% were not depressed and 11.4% had severe depression as per the depression scale [Table/Fig-3].
Distribution of study participants according to self-reported anxiety, stress and depression scores. (n=507)
| S. No. | Scores | n (%) |
|---|
| 1. | Anxiety scale |
| Normal (0-5) | 258 (50.9) |
| Mild (6-10) | 166 (32.7) |
| Moderate (11-15) | 58 (11.4) |
| Severe (15-21) | 25 (4.9) |
| 2. | Stress scale |
| Normal (0-6) | 15 (3) |
| Low (7-13) | 62 (12.2) |
| Moderate (14-26) | 383 (75.5) |
| Severe (27-40) | 47 (9.3) |
| 3. | Depression scale |
| Normal (0-13) | 251 (49.5) |
| Mild (13-19) | 107 (21.1) |
| Moderate (20-28) | 91 (17.9) |
| Severe (29-63) | 58 (11.4) |
The self-reported anxiety, stress, depression is assessed using-The Perceived Stress Scale (PSS), Generalized Anxiety Disorder 7 scale (GAD-7), The Beck Depression Inventory (BDI) [21-23].
Sedentary Behaviour and Negative Emotional Effects
The proportion of depression was higher among those who were sedentary. This was found to be statistically significant (p-value-0.049). However, no significant differences were obtained with anxiety and perceived stress emotions [Table/Fig-4]. There was a significant mean difference in depression scores (p-value -0.046) [Table/Fig-5].
Association between sedentary behaviour and negative emotional effects.
| S. No. | Emotion | Sedentary behaviour | p-value |
|---|
| Yes n (%) | No n (%) |
|---|
| 1. | Anxiety scale | 0.623 |
| Normal (0-5) | 55 (21.3) | 203 (78.7) |
| Mild (6-10) | 34 (20.5) | 132 (79.5) |
| Moderate (11-15) | 12 (20.7) | 46 (79.3) |
| Severe (15-21) | 8 (32) | 17 (68) |
| 2. | Stress scale | 0.181 |
| Normal (0-6) | 6 (40) | 9 (60) |
| Low (7-13) | 9 (14.5) | 53 (85.5) |
| Moderate (14-26) | 84 (21.9) | 299 (78.1) |
| Severe (27-40) | 10 (21.3) | 37 (78.7) |
| 3. | Depression scale | 0.049 |
| Normal (0-13) | 12 (4.7) | 239 (95.3) |
| Mild (13-19) | 8 (7.5) | 99 (92.5) |
| Moderate (20-28) | 57 (62.6) | 34 (37.4) |
| Severe (29-63) | 32 (55.1) | 26 (44.9) |
Chi-square test applied, p-value ≤0.05 is significant
Sedentary behaviour and mean negative emotional effects score.
| No. | Negative emotions | Sedentary behaviour | Mean rank | Sum of ranks | Mann-Whitney U | Z-value | p-value |
|---|
| 1. | Anxiety | Yes | 246.31 | 26847 | | | |
| No | 256.11 | 101930 | 20852.5 | -0.621 | 0.535 |
| 2. | Stress | Yes | 251.87 | 27453 | | | |
| No | 254.58 | 101324 | 21458.5 | -0.172 | 0.863 |
| 3. | Depression | Yes | 257.93 | 100167 | | | |
| No | 251.68 | 27598 | 57766.0 | -23.94 | *0.046 |
*Mann-Whitney test, p-value ≤0.05 is significant
Discussion
The present study explored the relationship between sedentary behaviour and negative emotional effects (stress, anxiety and depression) and tries to find out whether physical activity could serve as the non-pharmacological remedy for reducing the symptoms of stress, anxiety, and depression. Approximately, one-fifth of the students had sedentary behaviour. Higher prevalence of negative emotions in our study could be justified as these scales are screening scales and inclusion of those who had mild symptoms to diseased category.
In the present study, it was found that around 20% were sedentary and sedentary behaviour was higher among females (58.7%) when compared to males (41.3%). Also, it was found that only half of the participants undertook vigorous activity. In a previous study done by Banerjee A et al., reported that only around 40% underwent vigorous activity [18]. Similar results with higher physical activity among males have been reported in a study done by Rajappan R et al., [25]. It is assumed that knowledge about healthy lifestyle and dietary food habits must be more in medical school students than other college or university students. However, one fifth of students were sedentary and more than 15% of sedentary students were females. This could be attributed to the attitude towards health promotion and physical activity and its relation with disease prevention.
The study found a modest association between sedentary behaviour and depression. This finding was similar to a study done by Asare M et al., which found a significant negative correlation between physical activity and depression (r=-0.78, p<0.001) [26]. However, a study done by Hume C et al., found no association between different types of physical activity and depression [27]. One of the important hypothesis is ‘endorphin hypothesis in which beta-endorphin is an opioid secreted by pituitary gland during activity which produces feeling of sense of well-being and euphoria by reducing cortisol level in the body [28]. Serotonin hypothesis suggest that serotonin secretion and function is modulated by moderate exercise in brain areas like midbrain, striatum, hypothalamus and hippocampus. This modulation in serotonin system during acute physical exercise is considered as keystone in decreasing psycho-emotional system like depression and anxiety [29-31].
In the present study, there was no significant association between sedentary behaviour and stress levels. However, in previous studies, association was found between sedentary behaviour and stress levels [32,33]. Nguyen-Michel ST et al., reported no association between stress levels and physical activity [34]. As stress is a multi-faceted construct and is influenced by many factors, physical activity could be one of the factors which influences stress levels.
The study was one among few of its kind to evaluate physical activity with all mental health conditions such as depression, anxiety and stress. In previous studies, a negative relationship has been found between anxiety and exercise [35]. The relation between anxiety and physical activity is explained by endorphin hypothesis.
Limitation
One of the limitations of the study is that the study assessed physical activity in previous one week period, which could not be representative of overall physical activity of rest of the days of the year.
Conclusion
The study was able to find an association between sedentary behaviour and depression. However, significant association between sedentary behaviour and anxiety and stress levels could not be ascertained with the present study. Though aetiology of anxiety and stress are multi-factorial, physical inactivity could be one among the factors attributing to these negative emotional effects. Promotion of physical activity could help in reducing the negative emotional effects among medical students.
Funding: Indian Council of Medical Research
This study has been a part of short term studentship program by ICMR (Ref No. 2016-02065)
[1]. Lee IM, Shiroma EJ, Lobelo F, Puska P, Blair SN, Katzmarzyk PT, Effect of physical inactivity on major non-communicable diseases worldwide: an analysis of burden of disease and life expectancy Lancet 2012 380:219-29.10.1016/S0140-6736(12)61031-9 [Google Scholar] [CrossRef]
[2]. Valkenburg PM, Peter J, Online communication among adolescents: an integrated model of its attraction, opportunities, and risks J Adolesc Health 2011 48:121-27.10.1016/j.jadohealth.2010.08.02021257109 [Google Scholar] [CrossRef] [PubMed]
[3]. Witt EA, Massman AJ, Jackson LA, Trends in youth’s videogame playing, overall computer use, and communication technology use: The impact of self-esteem and the Big Five personality factors Comput Hum Behav 2011 27:763-69.10.1016/j.chb.2010.10.025 [Google Scholar] [CrossRef]
[4]. Stephenson A, McDonough S, Murphy M, Nugent C, Mair J, Using computer, mobile and wearable technology enhanced interventions to reduce sedentary behaviour: a systematic review and meta-analysis International Journal of Behavioural Nutrition and Physical Activity 2017 14(1):10510.1186/s12966-017-0561-428800736 [Google Scholar] [CrossRef] [PubMed]
[5]. Treuth MS, Catellier DJ, Schmitz KH, Pate RR, Elder JP, McMurray RG, Weekend and weekday patterns of physical activity in overweight and normal-weight adolescent girls Obesity (Silver Spring) 2007 15(7):1782-88.10.1038/oby.2007.21217636097 [Google Scholar] [CrossRef] [PubMed]
[6]. Katzmarzyk PT, Church TS, Craig CL, Bouchard C, Sitting time and mortality from all causes, cardiovascular disease, and cancer Med Sci Sports Exerc 2009 41:998-1005.10.1249/MSS.0b013e318193035519346988 [Google Scholar] [CrossRef] [PubMed]
[7]. Owen N, Bauman A, Brown W, Too much sitting: a novel and important predictor of chronic disease risk? Br J Sports Med 2009 43(2):81-83.10.1136/bjsm.2008.05526919050003 [Google Scholar] [CrossRef] [PubMed]
[8]. Teychenne M, Ball K, Salmon J, Sedentary behaviour and depression among adults: a review Int J Behav Med 2010 17(4):246-54.10.1007/s12529-010-9075-z20174982 [Google Scholar] [CrossRef] [PubMed]
[9]. Teychenne M, Ball K, Salmon J, Physical activity, sedentary behaviour and depression among disadvantaged women Health Educ Res 2010 25(4):632-44.10.1093/her/cyq00820145009 [Google Scholar] [CrossRef] [PubMed]
[10]. Biddle SJH, Asare M, Physical activity and mental health in children and adolescents: a review of reviews Br J Sports Med 2011 45(11):886-95.10.1136/bjsports-2011-09018521807669 [Google Scholar] [CrossRef] [PubMed]
[11]. Teychenne M, Costigan SA, Parker K, The association between sedentary and risk of anxiety: a systematic review BMC Public Health 2015 15:51310.1186/s12889-015-1843-x26088005 [Google Scholar] [CrossRef] [PubMed]
[12]. Anderson E, Shivakumar G, Effects of exercise and physical activity on anxiety Front Psychiatry 2013 4:2710.3389/fpsyt.2013.0002723630504 [Google Scholar] [CrossRef] [PubMed]
[13]. Conn VS, Anxiety outcomes after physical activity interventions: meta-analysis findings Nurs Res 2010 59(3):224-31.10.1097/NNR.0b013e3181dbb2f820410849 [Google Scholar] [CrossRef] [PubMed]
[14]. De Mello MT, Lemos V, Antunes HKM, Bittencourt L, Santos-Silva R, Tufik S, Relationship between physical activity and depression and anxiety symptoms: a population study J Affect Disord 2013 149(1-3):241-46.10.1016/j.jad.2013.01.03523489405 [Google Scholar] [CrossRef] [PubMed]
[15]. Jayakody K, Gunadasa S, Hosker C, Exercise for anxiety disorders: systematic review Br J Sports Med 2014 48(3):187-96.10.1136/bjsports-2012-09128723299048 [Google Scholar] [CrossRef] [PubMed]
[16]. Mammen G, Faulkner G, Physical activity and the prevention of depression: a systematic review of prospective studies Am J Prev Med 2013 45(5):649-57.10.1016/j.amepre.2013.08.00124139780 [Google Scholar] [CrossRef] [PubMed]
[17]. Cooney GM, Dwan K, Greig CA, Lawlor DA, Rimer J, Waugh FR, Exercise for depression Cochrane Database Syst Rev 2013 9:CD00436610.1002/14651858.CD004366.pub624026850 [Google Scholar] [CrossRef] [PubMed]
[18]. Banerjee A, Khatri S, A study of physical activity habits of young adults Indian J Community Med 2010 35(3):450-51.10.4103/0970-0218.6929221031126 [Google Scholar] [CrossRef] [PubMed]
[19]. Guidelines for the data processing and analysis of the International Physical Activity Questionnaire 2005. accessed from: [http://www.ipaq.ki.se/ipaq.htm] [Google Scholar]
[20]. Cohen S, Kamarck T, Mermelstein R, A Global Measure of Perceived Stress Journal of Health and Social Behaviour 1983 24(4):38510.2307/2136404 [Google Scholar] [CrossRef]
[21]. Spitzer RL, Kroenke K, Williams JBW, Lowe B, A brief measure for assessing generalized anxiety disorder Arch Inern Med 2006 166:1092-97.10.1001/archinte.166.10.109216717171 [Google Scholar] [CrossRef] [PubMed]
[22]. Beck A, An inventory for measuring depression Archives of General Psychiatry 1961 4(6):56110.1001/archpsyc.1961.0171012003100413688369 [Google Scholar] [CrossRef] [PubMed]
[23]. Home [Internet]. Pearsonclinical.com. 2018 [cited 4 August 2018]. Available from: https://www.pearsonclinical.com/ [Google Scholar]
[24]. Sharma R, Revision of Prasad’s social classification and provision of an online tool for real-time updating South Asian J Cancer 2013 2(3):15710.4103/2278-330X.11414224455606 [Google Scholar] [CrossRef] [PubMed]
[25]. Rajappan R, Selvaganapathy K, liew L, Physical activity level among university students: a cross sectional survey Int J Physiother Res 2015 3(6):1336-43.10.16965/ijpr.2015.202 [Google Scholar] [CrossRef]
[26]. Asare M, Danquah SA, The relationship between physical activity, sedentary behaviour and mental health in Ghanaian adolescents Child and Adolescent Psychiatry and Mental Health 2015 9:1110.1186/s13034-015-0043-x25945123 [Google Scholar] [CrossRef] [PubMed]
[27]. Hume C, Timperio A, Veitch J, Salmon J, Crawford D, Ball K, Physical activity, sedentary behaviour, and depressive symptoms among adolescents J Phys Act Health 2011 8(2):152-56.10.1123/jpah.8.2.15221415441 [Google Scholar] [CrossRef] [PubMed]
[28]. Paluska SA, Schwenk TL, Physical activity and mental health Sports Med 2000 29:167-80.10.2165/00007256-200029030-0000310739267 [Google Scholar] [CrossRef] [PubMed]
[29]. Soares J, Naffah-Mazzacoratti MG, Cavalheiro EA, Increased serotonin levels in physically trained men Braz J Med Biol Res 1994 27:1635-38. [Google Scholar]
[30]. Chaouloff F, Effects of acute physical exercise on central serotonergic systems Med Sci Sports Exerc 1997 29:58-62.10.1097/00005768-199701000-000099000156 [Google Scholar] [CrossRef] [PubMed]
[31]. McAllister-Williams RH, Ferrier IN, Young AH, Mood and neuropsychological function in depression: the role of corticosteroids and serotonin Psychol Med 1998 28:573-84.10.1017/S00332917980066809626714 [Google Scholar] [CrossRef] [PubMed]
[32]. Brown J, Staying fit and staying well: Physical fitness as a moderator of life stress Journal of Personality and Social Psychology 1991 60(4):555-61.10.1037/0022-3514.60.4.5552037967 [Google Scholar] [CrossRef] [PubMed]
[33]. Carmack C, de Moor C, Boudreaux E, Amaral-Melendez M, Brantley P, Aerobic fitness and leisure physical activity as moderators of the stress-illness relation Annals of Behavioural Medicine 1999 21(3):251-57.10.1007/BF0288484210626033 [Google Scholar] [CrossRef] [PubMed]
[34]. Nguyen-Michel ST, Unger J B, Hamilton J, Spruijt-Metz D, Associations between physical activity and perceived stress/hassles in college students Stress and Health 2006 22:179-88.10.1002/smi.1094 [Google Scholar] [CrossRef]
[35]. Koçyiğit F, Torun ED, Aslan UB, Anxiety, depression, physical activity and quality of life in student physical therapists: a cross-sectional study American J of Edu Res 2015 3(10):26-29.10.12691/education-3-10A-4 [Google Scholar] [CrossRef]