Appetite 58 (2012) 1037–1040
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Effects of chewing gum on the stress and work of university students Andrew P. Smith ⇑, Martin Woods School of Psychology, Cardiff University, 63 Park Place, Cardiff CF10 3AS, UK
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Article history: Received 19 August 2011 Received in revised form 29 December 2011 Accepted 28 February 2012 Available online 5 March 2012 Keywords: Chewing gum Stress Academic work
a b s t r a c t Recent research has indicated that chewing gum can relieve perceptions of stress in an occupational sample (Smith, 2009). In the present study, 72 students completed 2 weeks of either chewing gum or refraining from chewing gum. They completed scales measuring perceived stress, anxiety, depression, and single item measures of work levels and tiredness. These were completed both pre- and post-treatment. Perceived stress decreased as a function of the amount of gum chewed. The chewing gum condition was also associated with a decrease in not getting enough academic work done. There were no signiﬁcant effects of chewing gum on mental health outcomes. These results conﬁrm some of ﬁndings from previous studies of chewing gum and stress in other samples. Ó 2012 Elsevier Ltd. All rights reserved.
Introduction There has been a considerable amount of research investigating the scale and nature of student stress (Rawson, Bloomer, & Kendall, 1994). Tanaka, Fukuda, Mizuno, Kurasune, and Watanabe (2009) report that severe fatigue impairs academic performance in medical students and stress can trigger the development of illness. Rawson et al. (1994) reported signiﬁcant, positive relationships between anxiety, depression and stress with illnesses in students. A way to reduce student stress could be beneﬁcial for their psychological well-being, energy levels, academic performance and health (Cohen, 2003). Chewing gum is often chewed to reduce stress. In a survey of 8930 university students, 41% reported that they chewed gum while revising to reduce stress (Princeton Review & Wrigley, 2005). If chewing gum’s beneﬁcial psychological effects are conﬁrmed, then it could provide an inexpensive and effective treatment of low to mild stress. Furthermore, it would be better for the individual’s overall health compared to other activities, especially negative health behaviours, which they may engage in when they become stressed, anxious and/or depressed, such as smoking, drugs, excessive drinking and eating (Cohen, Tyrell, & Smith, 1991). This experiment assessed the effect of chewing gum on student’s feelings of perceived stress, fatigue and amount of academic work done. The beneﬁcial effect of chewing gum on stress has been suggested since the late 1930s when the relaxing effects of chewing sweetened and ﬂavoured confectionary chicle (sap from the sapodilla tree) were ﬁrst claimed by Hollingworth (1939). He reported ⇑ Corresponding author. E-mail address: [email protected]
(A.P. Smith). 0195-6663/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.appet.2012.02.054
that chewing produced a 10% decrease in muscular tension observed as ‘restlessness’ and ‘feelings of strain’, perhaps better thought of nowadays as psychological stress. Hollingworth stated that chewing relieves stress through reducing excessive muscular tension and energy via masticatory movements. However, soon afterwards, Freeman (1940) disputed the effects of chewing gum on ‘relaxation’ as he found that foot tapping produced the same relaxing effect, concluding both chewing and foot tapping release excess energy and claimed there was nothing special to chewing. More contemporary research has added to the inconsistent ﬁndings of chewing gum’s effects on reducing stress (Smith, 2010; Torney, Johnson, & Miles, 2009; Zibell & Madansky, 2009). Studies can be grouped into two categories; those which manipulate stress experimentally, and those which measure the effects on stress caused by naturally occurring stressors. Studies of natural stressors appear to ﬁnd more consistent results of chewing gum’s stress alleviating properties than do experimentally induced stress studies. Experimentally induced stress Scholey et al. (2009) experimentally induced stress in 40 participants as they performed on a multi-platform task which increases feelings of stress by applying rising cognitive workload through a variety of tasks. The study employed a cross-over design where participants completed the tasks once while chewing, and again without chewing. It was found that scores on the state-trait anxiety inventory (STAI) were lower in the chewing group than control group, along with subjective stress ratings. Salivary levels of the stress hormone cortisol were also lower in gum chewers than non-gum chewers, which provided objective and physiological evidence of chewing gum’s stress reducing effect. Concurrently, they
A.P. Smith, M. Woods / Appetite 58 (2012) 1037–1040
also found that gum chewing was associated with greater alertness which was represented by better overall performance on cognitive tasks. Furthermore, the effects were found for a variety of gum ﬂavours. However, Johnson, Jenks, Miles, Albert, and Cox (2011) were unable to replicate the ﬁndings of Scholey et al. (2009). Similarly, Torney et al. (2009) also induced stress experimentally as participants tried to complete insolvable anagram puzzles, but found no effect of chewing gum on reducing stress. This might be due to the reduction in stress being a subsequent change due to improved task performance (which was impossible in the impossible task condition). Compared to Scholey et al. (2009) study where the task took around 20 min to complete, the anagram task used in this experiment was only 5 min long. Perhaps a greater period of chewing is needed to observe stress reduction. Therefore, participants in this study were asked to chew each stick for a minimum of 20 min to increase the probability that an effect would be observed. Scholey et al. conversely used a within subjects design due to the crossover employed, which may have given them increased power. In the present study a cross-sectional design was used but with a larger sample size than Torney et al. Smith (2010) examined the effects of chewing gum in stressful and non-stressful conditions. Hundred and thirty three participants completed a number of cognitive tasks and rated their mood in a cross-over design experiment. Half of the participants were exposed to noise of 75 dB to induce stress. The results showed that the effects of chewing gum were identical in noise and quiet conditions. Chewing gum was associated with greater alertness and a more positive mood. Reaction times were quicker in the gum condition, and this effect became bigger as the task became more difﬁcult. Chewing gum also improved selective and sustained attention. Heart rate and cortisol levels were higher when chewing which conﬁrms an alerting effect of chewing gum rather than a stress reducing effect. The participant’s personality, being of a low or high anxious disposition, made no difference to chewing gum’s stress alleviating effects. Beneﬁts of mint and fruit gum were found to almost be identical on task performance, and there were no differences between the ﬂavours for effects on mood. Naturally occurring stress Studies looking at naturally occurring stress have consistently found beneﬁcial effects of chewing gum on reducing stress. Zibell and Madansky (2009) carried out two online survey studies which assessed the effect of chewing in frequent chewers and non-frequent chewers. Two hundred and eighty participants completed the ﬁrst survey which required frequent chewers to refrain from chewing for 3 days, and then were allowed to chew for 3 days. The second study was performed by 212 participants who never chewed gum, or if so, very infrequently. All participants were required to refrain from chewing for 7 days prior to the experiment beginning. In contrast to the ﬁrst study, participants were not allowed to chew for 7 days in the ﬁrst stage, and were then allowed to chew for 7 days. Participants completed the self-report STAI before the study and after each stage of the experiment, providing three measures of anxiety and stress levels. The results showed that both groups reported increased stress levels while abstaining before chewing and decreased stress levels after chewing. The effect of chewing gum for non-chewers clearly suggests that there are physiological mechanisms associated with chewing gum which reduce levels of anxiety and stress. The results do not support a view that chewing gum’s effect on chewers’ stress levels is due solely to an association between chewing gum and feelings of calm and relaxedness, otherwise a reduction in stress levels for non-frequent chewers would not have been found. Unsurprisingly, the effects of chewing gum had no effect on reducing
stress to more severe natural stressors or tragedies. This suggests that chewing gum produces more subtle effects which are not easily observed or measured under conditions of intense stress. Smith (2009) reported that chewing gum reduced stress in a cross-sectional study of an occupational sample of 2248 full time workers. Participants reported their levels of perceived stress and their exposure to stressful events. The Hospital Anxiety and Depression Scale (HADS) was administered and the frequency of chewing gum was recorded. It was found that non-chewers were around twice as stressed at work, and nearly one and a half times more stressed at home than those participants who chewed. Chewers reported visiting their doctor less frequently and to suffer less from high blood pressure than non-chewers, and increased diagnoses of depression were more common in non-chewers than chewers. The effects of chewing gum remained signiﬁcant after logistic regression controlled for demographics, personality and negative work characteristics. However, we cannot readily draw cause and effect from cross-sectional data, as the association between stress and chewing gum may be bidirectional. Nevertheless, this study, along with many others assessing naturally caused stress, suggest a strong and consistent link between chewing gum and reductions in self-reported stress. This ﬁnding has been conﬁrmed by Smith (in press) and in this last study there was a clear dose response between amount of gum chewed and the reduction in stress. The problem with cross-sectional surveys is that they provide little evidence of causality. To address this, two intervention studies have been carried out with University staff. In the ﬁrst (Smith, Chaplin, & Wadsworth, 2012), volunteers chewed gum for 2 weeks and also had a 2 week ‘‘no gum’’ condition. Volunteers rated their mood, mental health and performance at work at the start of the study, after the gum condition and after the no gum condition. Hundred and one volunteers from Cardiff University completed the study. The results showed that chewing gum reduced stress (both at work and outside work), reduced fatigue, reduced anxiety and depression and led to a more positive mood. Chewing gum was also associated with perceptions of better performance (both at work and outside). The second study (Allen & Smith, in preparation, submitted) was very similar except the interventions only lasted for a single day. Chewing gum was associated with fewer reported cognitive problems and lower stress and fatigue. However, there was no evidence of chewing gum reducing anxiety or depression. Chewing gum and performance Laboratory studies provide some evidence for the view that chewing gum may improve cognitive function, although there are studies which have failed to demonstrate a beneﬁt (see Allen & Smith, 2011 for a review). Subjective reports of the effects of chewing gum suggest that it improves work performance (Allen & Smith, in preparation, submitted; Smith et al., 2012). Academic performance of adolescents has also been shown to be improved by chewing gum (Johnson, Tyler, Stansberry, Moreno, & Foreyt, 2011). This issue was also examined here. Possible underlying mechanisms Electroencephalography (EEG) studies have provided evidence that chewing gum produces brain wave patterns that are very similar to the brain state of people who are relaxed (Morinushi, Masumoto, Kawasaki, & Takigawa, 2000). Morinushi et al. (2000) also found that chewing gum increased brain waves associated with increased arousal (alpha waves). They called this ‘relaxed concentration’. This pattern of activity accounts for both the effects of relaxation and the increased alertness observed after chewing ﬂavoured gum.
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Koga and Takeuchi (1989) reported in an EEG study that the extent to which alpha waves are increased by chewing gum is related to the participant’s taste preference. Therefore, in this study, participants were given free choice of gum ﬂavours and were allowed to mix-and-match so that theoretically they chose their favourite ﬂavours and also to reduce boredom of chewing the same ﬂavour, as we wanted to encourage chewing as much as possible. The present study In this study students were randomly allocated to either a chewing group or a non-chewing group for 2 weeks. Participants completed a baseline questionnaire about their past 2 weeks which included measures of perceived stress, anxiety and depression, fatigue and amount of academic work done. Two weeks later they completed the same questionnaire again. We hypothesised, in accordance with previous results, that the chewing gum group would show signiﬁcantly lower perceived feelings of stress, lower anxiety and depression, less fatigue and more work done than the non-chewing group.
different severities/frequencies of their feelings of anxiety or depression over the past 2 weeks. Chewing gum Participants were allowed free choice from a variety of ﬂavours from the Wrigley’s sugar-free range to encourage and maintain chewing (Airwaves menthol and eucalyptus, Airwaves black mint, Airwaves cherry menthol, Extra cool breeze, Extra spearmint, Extra peppermint, Extra Ice, Orbit complete peppermint, Orbit complete spearmint). Participants in the chewing gum group recorded how many sticks of chewing gum they consumed each day, which was later analysed for a dose response. Design
The study was carried out with the approval of the ethics committee, School of Psychology, Cardiff University, and with the informed consent of the volunteers.
Chewing condition was a between subject variable. In order to examine both the difference between chewing gum and no chewing, and dose response, the chewing group were sub-divided into those who chewed a small amount and those who chewed more (based on a median split: 40 pieces of gum in the 14 day period). Covariates were the pre-intervention measures of stress, anxiety and depression, fatigue, amount of academic work done and amount of gum regularly chewed. The dependent variables were the post-intervention measures of stress, anxiety and depression, fatigue and amount of academic work done.
Seventy-eight ﬁrst and second year psychology students studying at Cardiff University signed up to the study through an electronic experiment participation system in exchange for study credits. The ages spanned from 18 to 24 (Mean = 19.5 years old, 91.67% = female). Participants were informed that the study was investigating the effects of chewing on perceived stress and were randomly allocated into two groups of non-chewers (N = 38) and chewers (N = 40).
As participants were recruited they were randomly assigned to the gum or no gum conditions. Participants were e-mailed, instructing them to visit the laboratory where they read the information sheet and signed the informed consent form. They also discovered which experimental group they had been allocated to. Those in the chewing gum group were told to chew a minimum of two sticks daily for 20 mins. ‘Chewers’ were also handed their chewing gum diary at this time. Those in the no-chewing gum condition were told that they would receive chewing gum at the end of the experiment. Participants were told that they would be emailed a link to the baseline questionnaire later the same day, and were instructed to complete the questionnaire as soon as possible. Participants were reminded that chewing gum or not chewing gum for 2 weeks would begin the following day. Two weeks later, participants were e-mailed a link to the posttreatment questionnaire. The following day, all participants came to the laboratory to be debriefed and either to collect chewing gum or hand in their chewing gum diaries depending on their experimental condition.
Materials The scales were combined into one questionnaire and were presented by SurveyTracker, an online, survey software. Participants were asked to indicate ‘how many packs of chewing gum they normally consume a week’ (0, 1, 2, 3, 4+). Demographics (date of birth, gender) were also recorded. Baseline and post treatment questionnaires were alike, except questions about gender and normal chewing gum consumption were omitted on the post-treatment questionnaire. Using a 7 point Likert scale, participants were asked to indicate how tired they felt in the past 2 weeks ranging from ‘not at all’ to ‘very tired’ (Smith et al., 2012). Participants completed a question relating to their ability over the last 2 weeks to complete as much academic work as they would have liked. This was measured on a 5 point Likert scale from ‘not at all’ to ‘very frequently’ (Smith et al., 2012). The Perceived Stress Scale-10 (PSS-10 – Cohen, Kamark, & Mermelstein, 1983) was used. It consists of 10 questions on the frequency of the participant’s perceptions of stressful situations and feelings over the last 2 weeks, all scored on a 5 point Likert scale ranging from ‘never’ to ‘very frequently’. Anxiety and depression were measured using the Hospital Anxiety and Depression Scale (HADS – Zigmond & Snaith, 1983). The HADS consists of 14 questions (7 anxiety, 7 depression) which participants answered by selecting one of four boxes, each representing
Results Six participants did not complete the study and the analyses were conducted on the data from the remaining 72 participants. Table 1 shows the adjusted post-intervention scores (pre-intervention scores as covariates) for the high/low chewing and non-chewing groups. Analyses of co-variance, with the pre-intervention score as the covariate were carried out for each outcome. Stress decreased in a dose related fashion, with those chewing more gum reporting lower stress levels. This conﬁrms previous ﬁndings and was signiﬁcant at the one-tail level (F2, 68 = 2.44 p < 0.05, 1-tail). The comparison between the no gum and >40 pieces of gum was signiﬁcant (t = 1.90, p < 0.05). Ratings for ‘‘not getting enough work done’’ decreased for both gum groups (F2,
A.P. Smith, M. Woods / Appetite 58 (2012) 1037–1040
Table 1 Effects of chewing gum on stress, work done and mental health (high scores = greater stress, not getting enough work done, and more mental health problems. Scores are the adjusted means, s.e.s in parentheses).
Stress Not getting enough work done Anxiety Depression Tiredness
No gum (N = 35)
<40 pieces of gum (N = 20)
>40 pieces of gum (N = 17)
15.87 (0.38) 3.76 (0.15) 6.84 (0.16) 8.64 (0.17) 3.67 (0.23)
15.66 (0.50) 3.11 (0.20) 6.88 (0.22) 8.03 (0.22) 3.53 (0.31)
14.42 (0.55) 3.19 (0.22) 6.55 (0.24) 8.79 (0.24) 3.47 (0.33)
68 = 4.05 p < 0.05) and both of the gum groups were signiﬁcantly different from the no gum condition (no gum v < 40 pieces t = 2.43, p < 0.05; no gum v > 40 pieces, t = 2.51, p < 0.05). There was no signiﬁcant effect of chewing gum on tiredness (F < 1) nor anxiety (F < 1). Chewing gum was associated with reduced depression, although it was the group that chewed less gum that reported the lowest depression score (F2, 68 = 3.19 p < 0.05) and it was only this group that was signiﬁcantly different from the no gum group (t = 2.05, p < 0.05). Discussion The results from the present study conﬁrm some of the ﬁndings from previous studies of stress and chewing gum. Those who chewed more than 40 pieces of gum over the 14 day period reported lower levels of stress than either the no gum chewers or those who chewed less gum. This dose response conﬁrms results from a recent cross-sectional survey of public sector workers (Smith, in press) and the ﬁndings from another 14 day intervention study using university staff as participants (Smith et al., 2012). Those who chewed gum also reported that they got more work done than the no gum group. This again conﬁrms results from other intervention studies (Smith et al., 2012). The mental health measures showed less evidence of effects of gum. Anxiety and fatigue showed no signiﬁcant effects of chewing gum. Depression was reduced by gum chewing but only in those who chewed a smaller amount of gum. The lack of effects of gum on mental health conﬁrms results from studies of the acute effects of chewing and from a one day intervention (Allen & Smith, in preparation). This suggests that either effects of chewing gum on mental health outcomes either require more frequent chewing or chewing over a longer time period. Anxiety and depression may also inﬂuence the amount of gum chewed which could plausibly explain why those who chewed more gum did not report reduced mental health problems. In addition, the sample in the present study was largely female and gender often inﬂuences the reporting of mental health problems which may mask any subtle effects of chewing gum. Research on the behavioural effects of chewing gum is now widespread and students are often aware of some of the past results. This may lead to demand characteristics associated with studies such as the present one. Recent research (Allen & Smith, submitted) has examined this issue and the results failed to show interactions between expectancies and gum conditions. The present results suggest that gum chewing may be a costeffective and easily implemented method of reducing stress and getting more work done. One must now consider whether there are underlying mechanisms that make this suggestion plausible. The literature reviewed in the introduction showed that there are
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