The study was conducted in mainland China from 10 July 2021 to 15 September 2021, using a multi-stage sampling method. The specific research design is described in our group’s previously published paper (Zhang Z et al., 2022).

The questionnaire consists of three parts focusing on the current status of residents’ self-medication behaviors and related influencing factors. The first part investigated the social-demographic characteristics of the residents, such as gender, age, province, place of permanent residence (urban, rural), education level, per capita monthly income of the family, marital status, the current main way of bearing medical expenses, current occupational status (student, on-the-job, no fixed occupation or retired), currently diagnosed chronic diseases, etc. The second part investigates the current status of residents’ self-medication behaviors and important considerations, including 3 questions (1 single-choice question, and 2 multiple-choice questions). The third part is a series of standard scales, including the 10-item short version of the Big Five Inventory (BFI-10), the Short-Form Health Literacy Instrument (HLS-SF12), and the EQ-5D visual analogue scale (EQ-VAS). Permission was obtained from the developers of HLS-SF12, while the other two scales are available for free for non-commercial use (Duong, T. V et al., 2019; EQ-5D-5L Scale, 2021; Rammstedt and John, 2007; Carciofo et al., 2016).

Data entry and analysis were performed using SPSS™ for Windows (version 27.0) (SPSS Inc, Chicago, IL, United States of America). First, the common method bias was tested. Then the quantity and percentage of categorical variables were calculated using descriptive statistics. Scale scores were tested for normality. For normally distributed data, the mean and standard deviation were used for statistical description, and non-normally distributed data, the median and interquartile range were used for statistical description. Regarding the relevant literature, all scale scores were converted into dichotomous variables (high grouping and low grouping). The independent variables in the study include the demographic and sociological characteristics, health literacy, personality, and self-assessed health status of the respondents. There are two dependent variables, which are whether the respondents consider drug efficacy or safety as an important factor when purchasing OTC drugs. The Chi-square test was used for univariate analysis. In the study, the percentage of respondents who cited drug efficacy or safety as an important consideration in purchasing OTC drugs both exceeded fifty percent. In this case, using traditional logistic regression for multifactor analysis may overestimate the association between the independent and dependent variables; therefore, multilevel log-bionmial regression was used for multifactor analysis to overcome the level effects (Barros and Hirakata, 2003; Deddens and Petersen, 2008; Knol et al., 2012; Marschner and Gillett, 2012), and conduct stratified analysis according to different locations (Eastern part of China, Central part of China and Western part of China). Unless otherwise stated, the test level of statistical tests was α = 0.05. A supplementary subgroup analysis of demographic characteristics was performed, and subgroups were divided according to gender (male, female), age (35 years old and below, above 35 years old), permanent residence (urban, rural) in the proportion of residents considering efficacy or safety in different regions of China are highlighted in the paper.

The study conducted two rounds of pre-investigation and two rounds of expert consultation before the formal survey. Trained investigators distributed questionnaires to respondents and registered their codes one-on-one and face-to-face. Every Sunday evening during the investigation process, members of the research group communicated with the investigators to summarize, evaluate, and give feedback on the questionnaires they collected. After the questionnaires were collected, two people conducted back-to-back logic checks and data screening. If singular values are found during data analysis, the original questionnaire must be found and checked with the investigator before proceeding to the next step of the analysis.

Harman’s single-factor method showed five factors with eigenvalues greater than 1, and the variance contribution rate of the first main factor was 34.98%, which did not exceed 40%, indicating that there was no common method bias (Podsakoff et al., 2003).

The investigation showed that 99.06% (9256 of 9344) of Chinese people aged 18 years or older had self-medication behaviors.

Among respondents 9256 who had self-medication behaviors, there were 4289 males (46.3%) and 4967 females (53.7%) among the respondents; 4722 (51.0%) were located in eastern China, 2391 (25.8%) were located in central China, and 2143 (23.2%) were located in western China; 6674 (72.1%) were urban residents, 2582 (27.9%) were rural; 4246 (45.9%) were 19–35 years old, and 3935 (42.5%) were 36–59 years old, 1075 (11.6%) were aged 60 and above. The demographic and sociological characteristics of the survey respondents are shown in Table 1.

Among respondents 9256 who had self-medication behaviors, the investigation showed that 99.1% (9256 of 9344) of Chinese people aged 18 years or older had self-medication behaviors. The types of drugs used by the respondents during self-medication are shown in Figure 2. Antipyretic analgesics (5421, 58.6%) and vitamins/minerals (4851, 52.4%) ranked the top two among all types of drugs. In addition to the “other” option, the number of users of gynecological drugs (1057, 11.4%) and anti-allergy drugs (1322, 14.3%) ranked the bottom two.

Among the 16 factors to be considered, the top three selected are medical staff advice (7979, 86.2%), drug safety (5901, 63.7%) and drug efficacy (5492, 59.3%), the last three choices were exquisiteness of medicine packaging (445 people, 4.8%), the taste of medicines (871 people, 9.4%) and advertising (878 people, 9.5%) (Figure 3).

The scores of the respondents on each scale are shown in Table 2. Since the scores on each scale do not satisfy the normal distribution, the median and upper and lower quartiles were used to describe the central tendency and dispersion of the scores of each scale. 5942 respondents (64.2%) had high health literacy; There are 3349 people (36.2%) with high extroversion, 5182 people (56.0%) with high agreeableness, 4757 people (51.4%) with high conscientiousness, 2257 people (24.4%)with high neuroticism, 3565 people (38.5%)with high openness; and 5460 people (59.0%) with high self-rated health status.

Univariate analysis was performed using the chi-square test for the likelihood that respondents considered drug efficacy or safety as an important consideration. The possibility of respondents taking drug safety as an important consideration varies in gender, age, region, mode of paying medical expenses, chronic disease, extraversion, agreeableness, conscientiousness, neuroticism, openness, health literacy and self-assessed health status (p < 0.05). The possibility of respondents taking drug efficacy as an important consideration varies in gender, age, region, marital status, occupational status, chronic disease, extraversion, agreeableness, conscientiousness, openness, health literacy, and self-assessed health status (p < 0.05). The results of the chi-square test are shown in Supplementary Tables S1, S2.

A chi-square test was used to conduct a single factor analysis of differences in the percentage of residents who focused on safety or efficacy when self-medicating. The results of the chi-square test are shown in Supplementary Tables S1, S2. The results showed that the distribution of residents who focused on safety o refficacy differed across different regions of China (east, central, and west) (Safety:p = 0.001; Efficacy: p < 0.001). Multiple comparisons were further performed by the Bonferroni method, and it is shown that a significantly higher percentage of residents in the west (66.8%) focus on safety than those in the east (63.5%) and central (61.5%) regions. As for efficacy, the proportion of residents in the central region (55.7%) who focused on efficacy was significantly lower than those in the eastern (60.2%) and western regions (61.4%) (See Figure 4 for details).

Self-medication is becoming an increasingly common behavior, and people are becoming more independent in making decisions about their health management. Self-medication can help reduce the cost of producing, selling, and administering prescription drugs. However, people may suffer from misdiagnosis, prolonged or insufficient medication, neglect of drug interactions, and overdose due to their improper self-medication behaviors, which can delay their recovery process and even have serious, life-threatening consequences (Hughes et al., 2001).

Self-medication is a common practice around the world. The prevalence of self medication in Thailand reached 88.2% (Chautrakarn et al., 2021). The prevalence of self medication in the Indian population ranges from 8.3% to 93% (Rashid et al., 2020). 67.3% of people in Syria take drugs by themselves (Abdelwahed et al., 2022). In a study involving several European countries, self-medication rates among residents ranged from 33% in Turkey to 92% in the Czech Republic and 97% in Cyprus (Kamekis et al., 2018). This indicates that in many countries and regions, a large number of residents purchase and use OTC medicines by themselves as an important means of treating their diseases. Self-medication is also prevalent in China. The self-medication rate among the respondents in this study was 99.1%. The two most common types of OTC drugs purchased and used by the respondents were antipyretic and analgesics (5421 people, 58.6%) and vitamins/minerals (4851 people, 52.4%). Long et al. found that the self-medication rate of urban residents in China was 73.5%. A 2017 study by Chang J et al. showed that in China, 32.7% of people aged 45 and older used OTC for self-treatment within 4 weeks before the survey (Chang et al., 2017). Many studies have shown that self medication is related to sociodemographic characteristics and economic conditions (Subashini and Udayanga, 2020; Zeid et al., 2020).

The safety and efficacy of drugs are important considerations for most residents purchasing OTC drugs (Hanna and Hughes, 2011). A global study covering 51 countries reported similar findings that consumers value safety (“I know it is safe”) and effectiveness (“I know it works”) as the most important considerations while buying OTC drugs ⁴². This study showed that the number of respondents who purchased OTC medicines mainly considered drug safety as an important factor reached 5901, accounting for 63.7%, and the number of people who took drug efficacy as an important consideration reached 5492, accounting for 59.3%. An investigation of Australian consumers’ considerations for purchasing OTC drugs also showed that most consumers cite efficacy (1420/1627, 87%) and safety (1348/1625, 83%) as important considerations for purchasing OTC drugs (Bevan et al., 2019). In Japan, a developed region in Asia, information about self medication can be obtained from the Internet and government publicity. People with high quality of life can manage their symptoms according to their knowledge (Ohta et al., 2022). German research also shows that providing more OTC information for patients may improve patient safety (Eickhoff C,. et al., 2012). Self medication is associated with more severe disease grade and lower economic level of quality of life (Parvinroo et al., 2022).

We used log-binomial regression to analyze the associated factors of the dependent variables. In the log-binomial regression analysis of safety, gender, location, employment status, the main way of medical expenses borne, agreeableness, conscientiousness, neuroticism, openness, health literacy, and self-rated health status were significantly associated with the likelihood of drug safety being a consideration when purchasing OTC drugs.

Self-medication behaviors carry potential risks, so safety should be an important consideration when engaging in self-medication, and safety awareness should be an important part of how patients can manage their health. In this study, females were more likely to consider drug safety as an important consideration. This finding is in line with a previous study on drug safety awareness, in which males were more willing to accept risks, while females were more likely to seek information about drugs and place greater importance on safety (See et al., 2020).

Respondents who were retired were more likely to pay great attention to drug safety. Because retired people were elder and pays attention to safety, and has a certain level of knowledge and social experience, so that can make decisions on drug safety. Respondents those who mainly used ways including basic medical insurance for employees, commercial medical insurance, free medical treatment to cover their medical cost were more likely to consider drug safety as an important factor. People who participate in these types of insurance have a stronger risk awareness, and will pay more attention to safety when reimbursement funds are available.

Personality largely determines patients’ health behaviors, and when purchasing OTC drugs, personality may influence how much importance patients place on them. In this study, we found that people with high agreeableness, high conscientiousness, high neuroticism, and high openness were more likely to regard drug safety as an important consideration. High conscientiousness is a state of caution or vigilance that shows a desire to do something well (Vlieland et al., 2019). Therefore, people with high conscientiousness will pay more attention to the potential risks of OTC drugs to their health and are sensitive to safety. A higher level of neuroticism predicts anxiety due to worry-related problems (Beyer et al., 2015). This group is more worried about the adverse consequences when buying OTC drugs and thinks that drug safety is extremely important. People with high agreeableness and high openness will consider the advice of professionals more and make choices about their safety. Health beliefs are closely related to self-medication (Ting et al., 2018). People with high health literacy and self-assessed health levels have stronger health beliefs and safety awareness and are more likely to pay attention to drug safety when purchasing OTC drugs.

Another important factor in purchasing OTC drugs is the efficacy of the drug. In the log-binomial regression analysis of efficacy, we found that gender, location, employment status, the main way of medical expenses borne, chronic disease, agreeableness, conscientiousness, openness, and self-rated health status were all related to drug efficacy when respondents purchased OTC drugs. Many studies have shown that efficacy (usually determined by personal experience or advice from health professionals) is one of the factors most valued by consumers when considering safety (Hanna and Hughes, 2011). Compared with males, females cited drug efficacy as an important consideration when purchasing OTC medications (p < 0.05). Females visit pharmacies more frequently and may receive more information about drugs. A previous study in Sweden showed that females paid more attention to drug efficacy (Håkonsen et al., 2020). Compared to people without chronic diseases, people with chronic diseases pay more attention to drug efficacy due to the need for frequent medication, and they need cost-effective and effective medicines to treat diseases and relieve symptoms. Respondents who were unemployed were less likely to consider drug efficacy as an important factor. The knowledge level and social experience of unemployed are low, and their understanding of the practicality of drugs is insufficient (Chiappini et al., 2022). Respondents whose main way of medical expenses borne was Out-of-pocket Payment, were more likely to consider drug efficacy as an important factor, and this was because this group pays more attention to the cost-effectiveness (Lai et al., 2021).

When residents self-medicate, the proportion of residents in the east, central and western regions who consider safety is 63.5%, 61.5%, and 66.8% respectively. The proportion of curative effect was 60.2%, 55.7%, and 61.4% respectively. The results of multifactor analysis showed that the residents in the west considered the safety of medication more than those in the east, while the residents in the middle considered the efficacy less than those in the east.

Stratified analysis of individual personality, health literacy, and the impact of self-assessment of health status on safety effectiveness in the eastern, central and western regions shows that in the eastern region, residents who are more agreeableness, more conscientiousness, and have higher health literacy, and who have higher self-rated quality of life pay more attention to safety. In the central region, residents with agreeableness, more conscientiousness, more neurotic and higher self-rated quality of life pay more attention to safety. In the western region, more agreeableness, and openness residents pay more attention to safety. In terms of curative effect, in the east, residents with more agreeableness, conscientious and self-rated quality of life pay more attention to drug effect. In the central region, residents with more agreeableness, conscientious and higher self-rated quality pay more attention to drug effect. For the western region, residents with more agreeableness and conscientious pay more attention to effect.

With the expansion of China’s regional economic development gap, the supply of medical and health services is unbalanced in the east, central and western regions, and the supply level of medical and health services in the eastern region is the highest (Cavaco et al., 2018). There is inequality in the distribution of economic and medical resources among different regions in China, and there are significant differences in the practice and guarantee of drug safety among regions. The study found that the drug safety practice of pharmacists in regions with high per capita GDP and rich medical resources is better than that in regions with low per capita GDP and relatively scarce medical resources (Tang L, 2012). Because the safety practice of drug use in the western region is lower than that in the central region, they are more likely to be unable to receive timely treatment due to the fear of adverse drug use events and when they experience adverse drug events such as anaphylactic shock. This is why western respondents tend to take drug safety as an important consideration compared with eastern respondents.

The research shows that in China, the score of openness in the western region is higher than that in other regions and provinces, and the openness of the central and western residents of the Big Five personality is more obvious (Xu L et al., 2022). The results of this study show that when self-medication, the openness characteristics of the Big Five personality of Chinese residents also appear in the western region, and the western residents with high openness are more concerned about the safety of self-medication. The agreeableness and conscientious personality traits significantly predict drug compliance (Abu EK L et al., 2022), suggesting that agreeableness and conscientious traits can significantly affect residents’ ability to make healthy choices. A sense of responsibility can enhance healthy behaviors, and a high sense of responsibility is related to beneficial self-care behaviors (Skinner et al., 2014). Therefore, both eastern and western regions show that the more pleasant and responsible they are, the more attention they pay to safety and effectiveness in self-medication.

People in the eastern region are changing their living habits and improving their health management ability. The overall health literacy in the central and western regions is not high. We should pay attention to strengthening health education and popularizing health knowledge. Therefore, residents with different levels of health literacy only show differences in the eastern region when considering the safety of self-medication behavior (Wang F et al., 2022). Both the multifactor analysis of safety and effectiveness and the subgroup analysis of the region showed that the patient compliance EQ-VAS was positively correlated with the health compliance medication behavior. Social determinants are closely related to health and play an important role in health-related quality of life. The eastern provinces of China are better than the central and western provinces in terms of population density, culture, economic status, and social infrastructure, affecting the significant differences in health-related quality of life between the eastern provinces and the central and western provinces. The EQ-VAS of residents in the east is higher, which significantly affects the consideration of the safety and effectiveness of self-medication.

High agreeableness, high conscientiousness, high openness, and high self-rated health status group were more likely to consider drug efficacy as an important factor. People with high conscientiousness pay more attention to whether OTC drugs would achieve a beneficial effect on the body. When purchasing OTC medicines, people with high agreeableness and high openness will listen more to the explanations of professionals and pay more attention to drugs when communicating with medical staff. People with high-level of self-assessed health status are in better health and therefore will pay more attention to their health and consider whether the drug can restore and maintain their health quickly and effectively when taking medication.

This study has several advantages. First, we obtained extensive and representative data using cross-sectional survey data across mainland China in 2021. In addition, this study combined the Big Five personality, health literacy, and health-related quality of life theories to analyze residents’ purchase behavior of OTC drugs. Theories such as the Big Five have made empirical contributions and expanded the value of new theoretical applications of self-medication health behaviors. At the same time, it makes targeted suggestions for the future practice of self-medication supervision and health education. It makes further practical contributions.

The study also has several limitations. First, the data were based exclusively on self-report questionnaires, which may be influenced by social expectations, self-report errors, and poor memory. Second, this study used a cross-sectional design, and the results were only used to explore the correlates of the dependent variables. Third, the participants in this study were all located in China, and the sample was homogeneous and cannot be generalized to other countries. We used the most recent data available to us (2021), however, the behavioral characteristics of residents and the important factors considered in OTC drug purchases are likely to change further in the ensuing years. Also, Due to the limited length of the paper, only two important properties of the drugs themself, namely, drug efficacy and safety, are discussed in this paper. Other considerations for purchasing OTC drugs will be further investigated in follow-up studies.