Our study was conducted using a three-year periodic survey with consistent measurements to identify KM trends in the general public in South Korea. In this study, we explored the perceptions and use of KM and examined chronological differences. The reasons why the general public chooses KM therapies have been previously discussed but are not fully understood [10, 14]. Previous studies indicated that KM users were more likely to be female, to trust KM, or to have more education [11, 12]. There might be additional complex psycho-social factors associated with the use of KM. It has been reported that patients frequently use KM because they are not satisfied with conventional treatments.

Trust is an essential prerequisite for the effectiveness of healthcare and leads to the specific expectation that human actions will be beneficial rather than detrimental. However, the association between trust in KM and its general use has seldom been reported. Trust in a healthcare system is not a simple concept; it consists of multi-dimensional features based on values, beliefs, experiences, personality, health status, individual needs, the presence of an illnesses or symptom, and KM practitioners’ demeanor [15,16,17,18,19]. Nevertheless, it is worth noting that trust is a very important factor in the decision to visit a KM clinic or to use KM. We found that the rate of trust was positively linked to the usage of KM modalities. Compared to participants who distrusted KM, those who trusted KM were more likely to receive KM therapies. Interestingly, the respondents who distrusted KM therapies were more likely to use Chuna (15%) and other therapies (5%) than those who trusted KM. It is likely that the people who distrusted KM therapies preferred externally applied KM therapies such as moxibustion, cupping and Chuna to internally applied KM therapies such as acupuncture and herbal medicine.

The most commonly used KM therapies were acupuncture (91.2%), herbal medicine therapy (38.2%), cupping (30.8%), and moxibustion (27.6%). It has been reported that satisfaction and attitudes toward acupuncture among Western-trained medical doctors and patients were favorable [14]. The use of acupuncture has spread to more than 140 countries and regions. More than 800 diseases are treated with acupuncture in clinics around the world [20]. Acupuncture is practiced for the relief or prevention of pain and for various other health conditions [21]. Unexpectedly, our study found a sudden decrease in the use of moxibustion between 2011 and 2014, which might be correlated with low trust in moxibustion. The mechanisms of moxibustion mainly relate to the thermal effects, radiation effects, and pharmacological actions of moxa and its combustion products [22]. Moxa smoke can be used in air disinfection and as an antiviral and antifungal agent [22]. However, there are concerns regarding the safety of moxa smoke. Some reports have shown that moxa smoke may be harmful to the human body, such as causing allergic reactions [22,23,24]. Moreover, moxibustion requires extreme care due to the risk of burns. Although the decline in the use of moxibustion is difficult to explain, and it is unclear whether this trend is a transient phenomenon, the reason appears multifactorial, including factors such as growing concern about safety and discomfort in usage.

Women have generally shown more favorable attitudes toward alternative medicine than men in most countries [25]. Similarly, women (61.8%) showed more trust than men (57.0%) in our study. However, the overall reasons for trust did not differ substantially by gender (Table 3). It is interesting that the reasons for KM distrust apparently differed by gender. The main reason for distrust of KM among females was “suspicion of KM safety”, which was cited at a rate nearly twice that of men (47.4% in women versus 25.2% in men) (Table 4). This finding is notable because women were more commonly consumers of herbal medicine than men (41.4% of women versus 34.7% of men) (Table 6). This distrust might be attributed to concerns regarding the safety of herbal medicines. KM herbs are prescribed according to formulas from ancestors found in classic literature. Herbal medicines are used to treat disease, enhance general health and restore health. The use of herbal medicines by the general population or patients has increased. However, there is great concern regarding the risk that these herbal medicines are potentially harmful in unknown ways because there remains an incomplete understanding of how herbal substances react in the body. Unfortunately, some KM doctors have insisted on using secret recipes when prescribing herbal medicine formulas for treating specific illnesses. Based on KM doctors’ private clinical experiences, they can omit any part of the treatment described in classic references or add hidden materials to form their own “secret formula” without rigorous safety testing. This is one of the key reasons for KM distrust because women are more sensitive to negative emotions, meaning that women may react differently than men [26]. To shore up public trust, the safety of herbal medicines for various illnesses must be ensured by applying scientific research approaches (scientification). As a good example of how to increase trust, evidence-based medicine (EBM) has been applied to KM, particularly to explore potential benefits and safety. EBM makes the explicit, judicious, and conscientious use of the best evidence to make decisions regarding preventing diseases, promoting recovery, and improving quality of life [27, 28].

We found that the use of KM therapies, which was previously on the rise, has decreased slightly. Overall, the 1-year prevalence of KM use was 66.6% in 2011 and 59.4% in 2014. Significant declines were found in men and younger participants in their 20s and 30s. There was a remarkable decrease in the trust of KM among men (66.5% in the 2011 survey and 57.0% in the 2014 survey). Comparing our results with those of previous KM surveys, we found a much higher prevalence of use by participants in their 20s and 30s than that reported by Shin et al. [12]. However, we also observed a dramatic reduction in KM trust and usage in those generations compared to our previous survey in 2011 [11]. Although the definitive reason is unclear, several unique demographic features and socio-environmental conditions are suggested. First, younger generations are more likely to believe in the importance of scientification or standardization of medicines compared to their parents’ generation. Younger participants who were born between 1977 and 1994 and were 22–39 years of age as of 2016 are called “generation Y” (Gen Y), and potential reasons for their divergence from older generations are the immense technological development and high educational standards of this period. Members of Gen Y react strongly to real-life examples, and they favor the truth and what is real [29, 30]. In contrast, despite enormous scientific efforts, KM is currently not fully understood in terms of its efficacy and adverse effects. The demanding minds of Gen Y may seek medicines that have been more scientifically proven under rigorous healthcare standards. Second, individuals belonging to Gen Y are less economically advantaged than those of other generations because the majority are financially vulnerable in their careers. Currently, a monthly dose of herbal medicine typically costs approximately 400,000 won (US $352). Since late 2011, crude herb prices have increased sharply, up to three-fold, because of decreases in imports from China. Furthermore, KM therapies are not fully covered under national health insurance. High prices may result in an out-of-pocket economic burden, particularly for those who are most vulnerable to financial strains, although other patients are less price sensitive if they believe they are receiving superior medical services and good products. Third, Gen Y individuals have different motivations for medical consumption and purchase engagement. They are reported to be loyal online customers and to show greater confidence and trust in the brand names of their choice compared to all other generations [31, 32]. These younger consumers may be attracted to easier and more convenient purchase options. In fact, they are well accustomed to internet shopping, even for healthcare products. The online/wireless markets related to health foods grew steadily between 2011 and 2014. During this time, Gen Y was the main force behind online shopping [33, 34]. However, the expansion of internet health food markets is one of the greatest challenges facing KM because these markets are becoming alternatives to KM modalities [35].

There were several limitations to our survey. First, we included only six major KM modalities in this survey to follow the same measurements used in the 2011 survey. Because the main focus of our study was the comparison between the two surveys, as previously stated, we did not provide many options for respondents to mention other KM modalities. Second, the data were based entirely on laypeople’s self-reporting within a specified period. Therefore, there is potential recall bias. Furthermore, our approach was cross-sectional, indicating that the sample used different panels from the 2011 survey. Because our survey instruments were mostly determined by the 2011 survey, we did not evaluate validity or reliability. However, we consulted with several experts to determine whether the questions were clear, understandable, and presented in a logical order prior to conducting the survey.