The aim of this study was to examine the effects of gum chewing for 14 days on mental health parameters. State-anxiety, mood, and fatigue were found to be improved after gum chewing in the intervention group as compared with the control group. At the follow-up assessment, the scores for the intervention and control groups were similar. These results suggest that the improvement by the intervention may not be maintained afterwards.
Our results support the hypothesis that regular gum chewing has an effect on psychological status. This trial examined the effect of gum chewing on both experimental stress and also social-related stress. The results of the previous studies that examined the effects of gum chewing on psychological stress test were controversial. Scholey et al.
] investigated the effects of gum chewing on task-induced stress. In this study, gum chewing was found to be associated with decreased levels of self-rated anxiety and stress and a reduction in salivary cortisol concentrations. Based on the Scholey study, the Toney’s participants performed an insoluble anagram task followed by a soluble anagram task [29
]. The performance of these tasks and the levels of stress were found to be similar with or without gum chewing.
In the present study, the scores for state -anxiety in the intervention group were better than those in the control group after gum chewing for 14 days. The scores for depression-dejection, fatigue, confusion in POMS and fatigue on VAS were also significantly different in both groups. On the other hand, the scores of vigor in POMS and the QOL scores except physical domain were similar between the two groups. These results suggest that regular gum chewing improves negative feelings rather than promotes positive feelings. The WHOQOL26 instrument evaluates not only physical and mental satisfactions but also the social and environmental aspects. The WHO states that this instrument assesses the individual’s perceptions in the context of their culture and value systems, as well as their personal goals, standards, and concerns [26
]. A longitudinal intervention is needed to confirm the influence on QOL.
The participants in the present study were nursing students. Generally, nursing students have high levels of stress and anxiety in the clinical learning environment [30
]. The present study was carried out while the students were not involved in clinical training. Their levels of anxiety and mood were similar to those of the previous Japanese studies [25
]. Even though many research articles have been published on a variety of strategies to help decrease students’ high levels of anxiety in the clinical learning environment [33
], few researchers have been successful in finding ways of decreasing student anxiety. Therefore, our results indicating that daily gum chewing influenced the anxiety levels and mood of nursing students seem to be important.
Gum chewing also was shown to relieve mental fatigue in the present study. Fatigue is related to stress [34
], and chronic fatigue has been found to induce serious conditions [35
]. Lasting fatigue is difficult to recover from by simple rest or task moderation. Our previous study showed that gum chewing during the time of a psychological stress test improved physical and mental fatigue after the test [36
]. According to the Japanese National Survey of Health in 2004 [37
], 49% of individuals aged 12 years or older reported experiencing stress in their daily lives. Finding ways to recover from fatigue after a stressful event may be helpful in stress management.
In Zibell’s study[17
], different intervention periods were applied for regular chewer and seldom chewer. The constant gum chewing was conducted in our study regardless of chewing habit, and then this gum chewing may affect the participant’s mental health. In this study, the quantitative frequency of gum chewing before the study were not clarify because the 4-points Likert scale to examine how the participants were familiar with gum chewing. Further investigation is necessary to better understand how cessation of chewing affects mental health of regular chewers and whether the improvement of mental state was larger in seldom chewers than regular chewers.
Various mental health programs have been developed to try to improve psychological status. Hollingworth (1939) described chewing as a technique of relaxation [38
]. Yoga also has been reported to improve levels of anxiety [39
]. Aroma has been shown to influence mood [21
], and meditation has been shown to reduce stress and improve mood [41
]. To get the beneficial effects of these techniques, participants must adhere to the technique and motivated. As gum chewing does not require any special preparation, skills, or equipments, it may be widely accepted.
The present study has some limitations. The sample size was small, and there was a selection bias in participants being recruited from only two colleges. We did not power analysis because there were no available preliminary studies that were referred to sample size, we recruited volunteers as much as possible. Also, the participants had motivation and interest in the study and gum chewing. Therefore, the results may not be applicable to general population who has no incentive.
To prevent dropout of the subjects, the intervention term was designed to use the minimum number of days that would allow us to estimate an effect. We did not instruct the control participants not to bite a mint product. Even if they bite mint product, however, this mint would dissolve in their mouth after a few bite. Therefore, chewing effect in this group seemed to be minimal. Also, we did not ask them to refrain gum chewing during the intervention period. Although two control participants chewed a gum more than once a day, we were not able to analyze because of small sample size.
Since there were no available data how the duration affects mental status, we adopted “5 minute” chewing. Consequently, the total duration of chewing may variety. In addition, the scores of subjective dietary chewing were different significantly between the intervention and control groups at 2 weeks and 4 weeks assessment. The intervention participants would come to chew in daily life by allocating the intervention group. Further studies needed to clarify not only the effects of duration and intervention period of gum chewing, but also dietary habit.
The subjects in this study were healthy condition in some psychological outcomes. To apply mental health care or stress-management, the effect of gum chewing will be examined in people under stressful environment. Another limitation of this study was that a double-blind design could not be applied because of the nature of this kind of interventions.
In conclusion, the results of the present study show that 14 days gum chewing improves the levels of anxiety, mood, and fatigue in healthy young adults.