Nurses function in a high-stress environment characterized by substantial physical, mental, and emotional demands, resulting in perceived fatigue levels significantly higher than those of workers in other professions [1]. Given that stress and fatigue contribute to various health issues among nurses and recognizing the correlation between nurses' health and patient outcomes, identifying effective methods for alleviating stress and fatigue is imperative [2].

Nurses working in hospitals care for patients with serious illnesses every day and interact directly with the families of patients at the end of life, which exposes them to various stressors [3]. Additionally, advances in medical technology have increased the number of tools that nurses must manage, and difficulties in communicating with healthcare professionals in different departments add to the everyday stress they experience [3]. Long-term exposure to these stressors can lead to physical health problems, such as stomach ulcers, heart disease, and high blood pressure, as well as mental health issues like depression, insomnia, and anxiety. This highlights the need for effective strategies to manage stress and promote overall well-being [4]. Shift nurses, in particular, experience irregular sleep patterns and sleep loss due to the nature of their work, which can result in sleep deprivation [5]. Additionally, high-intensity and continuous stress can activate the sympathetic nervous system, leading to poor sleep quality [5]. In response to sustained stress, the body manifests various physical symptoms such as headaches, insomnia, fatigue, gastrointestinal discomfort, and musculoskeletal pain as well as physiological responses such as increased heart rate, elevated blood pressure, and muscle tension through the autonomic nervous system and the hypothalamic-pituitary-adrenal axis [6]. When the homeostatic balance of the body is disrupted by heightened stress, reduced sleep quality, and fatigue, the overall quality of life (QoL) diminishes [5].

The QoL of the nurses in their job as healthcare providers is highly related to both nurses’ own comfort as well as patient comfort [7]. Shift work leads to irregular life patterns that can negatively affect nurses’ satisfaction with life and lower their QoL, which can also decrease their interest in patients and have negative effects on overall patient care [7,8]. Nurses with a high QoL are better capable of providing high-quality nursing services in response to patients’ requirements, which in turn enhances their satisfaction and further increases the productivity and efficiency of nursing care [8,9]. Accordingly, when nurses’ QoL is high, their happiness and satisfaction with life increase, leading to positive outcomes, such as job satisfaction, high-quality nursing care, and reduced turnover intentions; as such, QoL management is important [8,10].

Apart from having lower QoL, nurses also score lower on the happiness index than members of the general public, and nurses with low happiness scores present low job satisfaction and high turnover intentions [10]. Decreased happiness can lead to sleep disorders, anxiety, and depression; moreover, it can cause burnout at work, which has a detrimental effect on work performance [11]. Low happiness has also been reported to cause a decrease in nurses’ QoL, which adversely affects their productivity, patients, and organizations [12]. Happiness reduces stress, improves mental and physical health, and has positive impacts on life and job satisfaction for most people, including nurses [12]. Thus, interventions are needed that boost nurses’ happiness, reduce stress, improve their QoL, and encourage their efficiency during work [7,12].

Historically, psychiatric drug therapy has been the primary method for treating stress-related conditions and promoting mental health; however, its high costs and potential adverse effects have led to growing interest in complementary and alternative therapies [13].Thus, there is interest in integrative interventions that apply complementary and alternative therapies in the medical community and among the general public [13]. Complementary and alternative therapies include energy therapies, such as magnetic field therapy, acupuncture and meridian therapies; manual therapies, such as scent therapy and massage therapy; biological therapies that involve herbs and vitamins; and mind-body therapies, such as relaxation and meditation therapies [14,15].

Among such alternative therapies, music therapy, effective in reducing blood pressure and alleviating symptoms of depression, and aromatherapy, beneficial for stress and immunity management, are receiving increasing research attention [16-18]. Music therapy positively influences the brain and autonomic nervous system, effectively reducing anxiety, relieving stress, and improving symptoms of depression [19-21]. One advantage of music therapy is that participants can select and listen to music according to their mood or emotional state without limitations of time and place [22,23]. In aromatherapy, essential oils extracted from plants are utilized to promote mental and physical well-being [24]. Aromatherapy has been shown to relieve stress and negative emotions, improve sleep quality, and enhance immunity; through the commonly used inhalation method, individuals can easily apply therapeutic essential oils without any formal training [17,25].

While numerous prior studies have established the effectiveness of aromatherapy and music therapy as means of stress reduction [26,27], investigations into their impacts on happiness are relatively scarce. One notable study has compared the effectiveness of these two complementary and alternative therapies but only assessed the effectiveness of a one-time intervention [17]. Based on prior research suggesting that a week of music therapy or aromatherapy can enhance stress levels [28,29], this study applied both therapies over a one-week duration. To address these gaps in the literature, this study aims to provide foundational data on intervention methods that can effectively reduce stress and enhance happiness among shift nurses by examining the effects of music therapy and aromatherapy on the stress levels, QoL, and happiness of participating shift nurses.

After seven days of experimental treatment, perceived stress scores decreased by 11.08 for the music therapy group, 10.77 for the aromatherapy group, and 3.15 for the control group, compared with that before the experimental treatment. This is consistent with a previous study that reported decreases in perceived stress when intensive care unit nurses listened to their preferred music [22] and another study reporting decreased stress when nursing students inhaled lavender oil [29]. The music used in the present study has been found to promote the generation of alpha-waves, enhancing inner tranquility and peace through meditation, and can effectively contribute to mental and physical stability by applying various effective scientific principles, such as stereophonic sound [36]. Such results imply that music can stabilize the mind and body while positively reducing perceived stress, and that inhaling aroma oils enhances emotional relaxation and calm [37,38], making it effective in reducing perceived stress.

No significant differences were observed in stress Index among the three groups after seven days of experimental treatment. The results of this study are consistent with those of a previous study that reported no changes in the sympathetic and parasympathetic nervous systems after applying music therapy [39]; however, the current results differ from those of studies that reported a decrease in sympathetic nervous system activity and an increase in parasympathetic nerve system activity in the experimental group of healthy adults after music therapy [40]. The results of this study are consistent with studies showing that adults’ stress index decreased after aromatherapy treatment [22,29]. However, music therapy does seem to have various effects on the autonomic nervous system, with variables such as work intensity, personal environmental situation, and music preference affecting the autonomic nervous system. In addition, as the experimental environment in the current study differs from that in previous stress index studies, and none of them compared the stress of the participants who received music therapy and aromatherapy in the same environment, there is a limitation in interpreting these study results. Compared to previous studies using the same tool with nurses [5,41], the stress index was found to be low, while perceived stress levels were similar. The participants in this study are believed to be particularly sensitive to stress, as their perceived stress is high despite the low physiological stress index. In addition, in the stress index, there was no difference in the T0 of the pre-test and the T0 of the post-test in each group, so it can be interpreted that music therapy was only performed regularly and did not have a long-term effect. Future research should consider measuring baseline stress levels and conducting experiments with high-stress groups to assess the effectiveness of interventions. The lavender oil used in aromatherapy in this study is known to stimulate the parasympathetic nervous system [42] and have calming and relaxing effects on the central nervous system, as well as anti-depression and anti-anxiety effects [37]. The effects of ylang-ylang include emotional relaxation and the relief of nervous system tension [38], which seem to effectively reduce stress index.

These results indicate that music therapy is helpful in reducing perceived stress and that aromatherapy can be used as an effective intervention for relieving perceived stress as well as stress index. In particular, the results of this RCT indicated that stress was significantly reduced among the experimental groups compared with the control group. Thus, considering the intervention’s effects were verified to be long-lasting based on the present one-week study, long-term intervention strategies to lower subjective and objective stress are feasible.

According to the examination of the effects of music therapy and aromatherapy on the QoL of shift nurses, the QoL of the music therapy and aromatherapy groups improved after the experimental treatment, but there were no changes in the control group’s QoL. These results are similar to those of a study on music therapy for elderly people living alone [43] and an aromatherapy for pediatric with migraines [44].

QoL is a person’s perception of their overall condition [45]. The music used in this study was intended to generate A-waves [36] that improved nurses’ QoL by enhancing mental and physical stability and comfort. Based on evidence from previous studies related to individuals’ overall condition and QoL that various music-based therapies, such as singing and dancing therapies, are effective in improving QoL [43,46], it is expected that music programs that include singing, performance, and dancing are effective in improving QoL. Furthermore, among the essential oils used in the blend in this study, lavender and ylang ylang relieve stress, tension, headaches, and insomnia; affect the nervous system to alleviate emotions, such as depression, anxiety, and anger; and effectively evoke feelings of comfort [47,48], thereby improving sleep quality, and may effectively improve QoL by arousing happy emotions and moods. Thus, music therapy and aromatherapy are considered effective at increasing QoL. In this study, music appeared to provide emotional comfort and aromatherapy to provide relief from negative emotions.

As a result of the happiness scores, no significant differences were observed in the post hoc analysis; however, There was a significant difference between the three groups. The happiness scores of both the music therapy group and the aromatherapy group increased following the experimental treatment, while the happiness scores of the control group decreased. The results of this study are consistent with those of a study reporting that a song-centered music therapy program increased happiness and QoL among older adults [49]. The present findings are consistent with a previous study that found nurses’ happiness increased after inhaling aromatic oils [7]. Since there are few studies on the effects of music therapy on happiness, and most of those were conducted with infants or the older adults, the usefulness of comparing them with this study is limited. However, it has been reported that music-based activities induce positive emotions such as happiness and joy, and that happiness and satisfaction caused by these positive emotions have a substantial positive impact on QoL [49]. Thus, it is necessary to conduct research on the relationship between music therapy and happiness among young and middle-aged people in the future.

The music used in this study during the music therapy intervention has been reported to support mental and physical stability, reduce anxiety, and relieves tension and stress [36]. The essential oil blend used in the aromatherapy interventions has known positive effects as follows. Lavender relieves mental fatigue, anxiety and depression, and induces comfortable sleep, whereas ylang ylang relieves tension, provides a sense of comfort and happiness, and is effective for nervousness and insomnia [47,50], and lemon (used in smaller doses) can relieve the pain of migraines and headaches [48]. Thus, the nurses who used the music in this study may have experienced increased emotional stability and restoration, and relief from mental fatigue, and those who used the aromatherapy oils may have also experienced increased QoL and improved happiness through relief of physical and mental fatigue, thereby reducing insomnia and evoking a sense of happiness.

In conclusion, based on the present findings of increased QoL and happiness among nurses who received music therapy and those who received aromatherapy for one week, music therapy and aromatherapy seem to be effective in improving QoL and happiness for shift nurses. In addition, considering the scarcity of studies that used QoL and happiness as variables when examining the effects of music therapy and aromatherapy on population other than infants and older adults, the results of this study can serve as framework for the effects of music therapy and aromatherapy on QoL and happiness of younger adults.

This study is notable for comparing the effects of interventions using experimental music therapy and aromatherapy treatments on the interaction between time and group, and the findings verified the positive effects of prolonged (one-week) music therapy and aromatherapy. The study is also valuable because it incorporated both perceived stress and stress index as dependent variables.

The music used in the intervention is one of the study’s limitations. According to the experimental design, the researcher-therapist chose 15 songs initially, and then the research participants chose additional music; thus, their music preferences may have been overlooked. Future studies should consider including music preferences and varieties as study variables. Furthermore, the participants were recruited through convenience sampling and were limited to shift-nurses aged 23~32, restricting the generalizability of the findings. Another limitation of this study is that complete blinding was not achievable due to the nature of the experimental treatments.

This study was an RCT that aimed to investigate the effects of music therapy and aromatherapy on stress, happiness, and QoL among shift nurses. When applied to shift nurses, music therapy and aromatherapy helped reduce perceived stress over time and improve QoL and happiness. As such, music therapy and aromatherapy are recommended for shift nurses to reduce their stress and improve their QoL and happiness.