Knowledge, Attitude, and Practices Toward Complementary and Alternative Medicine Among Medical and Pharmacy Students in Sana’a, Yemen: A Single-Centre Cross-Sectional Study

Introduction

Complementary and Alternative Medicine (CAM) encompasses a broad range of health practices and products that are not conventionally part of the dominant biomedical health-care system of a given society. For clarity, this study distinguishes between traditional medicine (knowledge and practices indigenous to a culture, such as herbal and prophetic remedies), complementary medicine (non-conventional practices used alongside conventional care), alternative medicine (non-conventional practices used instead of conventional care), and integrative medicine (the evidence-informed combination of conventional and complementary approaches). These categories differ markedly in their evidence base, risk profile, and clinical relevance. Globally, CAM utilization varies widely, particularly in developing countries where traditional medicine remains deeply rooted in cultural and social norms. The World Health Organization recognizes traditional medicine as an important component of healthcare systems, especially in low- and middle-income countries.

In Yemen, CAM practices such as herbal medicine, spiritual healing, and prophetic and traditional remedies are commonly used for disease prevention and treatment. This pattern is shaped by a distinctive combination of factors. Yemen carries a long heritage of Arab–Islamic and prophetic medicine (al-tibb al-nabawi), an abundant supply of locally available medicinal plants, and the widespread social use of substances such as qat. At the same time, the country’s health system has been severely weakened by protracted conflict: out-of-pocket payment dominates health financing, the formal health workforce is limited and unevenly distributed, and access to regulated pharmaceutical care is constrained, especially outside major cities. In this context, herbal and spiritual remedies are frequently used as first-line options rather than as adjuncts to biomedical care, and CAM is largely unregulated, with no national framework governing practitioner qualification, product quality, or pharmacovigilance. These conditions make the knowledge and attitudes of future physicians and pharmacists particularly consequential for patient safety. Despite this widespread use, CAM is not formally integrated into most medical and pharmacy curricula, creating a gap between community practices and professional medical training. As future healthcare providers, medical and pharmacy students should possess adequate knowledge and critical attitudes toward CAM to guide patients safely and effectively.

Although several regional studies have explored CAM-related knowledge and attitudes among healthcare students, evidence from Yemen remains scarce, and to our knowledge no published study has compared medical and pharmacy students within a Yemeni institution. Therefore, this study aimed to assess the knowledge, attitudes, and practices toward CAM among medical and pharmacy students at UST, Sana’a.

Literature Review

A study by Al Mansour et al¹ at Majmaah University, Saudi Arabia, assessed the CAM Knowledge, Attitude, and Practice (KAP) of medical students. Their findings indicated that a CAM course tends to have a positive impact on the KAP of medical students, with significant improvements in knowledge and attitudes post-exposure.

Similarly, Alzahrani et al² assessed 242 senior medical students at King Abdulaziz University, Saudi Arabia. They found that while a high percentage of students agreed that CAM is beneficial in treating unusual cases, knowledge of specific herbs (eg, St. John’s Wort, Ginkgo biloba) was limited. Interestingly, older students demonstrated a more positive attitude toward CAM compared to their younger counterparts (p = 0.027).

In a comparative study between pharmacy and non-pharmacy students at Punjab University, Lahore, Ashraf et al³ found that the majority of students considered modalities like massage, homeopathy, and spiritual healing to be effective and least harmful. Despite possessing poor technical knowledge, students demonstrated positive beliefs regarding CAM and supported its inclusion in the pharmacy curriculum.

Albadr et al⁴ conducted a survey across two universities in Saudi Arabia (KSU and MU). They reported a neutral overall attitude toward CAM (mean 3.1). However, students who had previously taken a CAM course were significantly more satisfied with their knowledge (P = 0.0001), reinforcing the value of formal education in this field.

Regarding the prevalence of use, a scoping review by Brown and Bilszta⁵ in Australia found that between 13% and 80% of medical students use CAM. The review noted that female students and those with religious affiliations held more positive attitudes. However, general knowledge remained poor, with students expressing a desire for more teaching to upskill them in patient counseling.

In Iran, Sadeghi et al⁶ investigated medical students in Urmia, revealing that 49% held positive attitudes and 51% held moderate attitudes, with no negative attitudes recorded. However, they noted a dearth of knowledge among fourth- and fifth-year students, who expressed interest in including CAM concepts in the medical curriculum.

In the African context, James and Bah⁷ studied pharmacy students in Sierra Leone. They found a positive attitude toward CAM (Mean score = 34.9), though fourth- and fifth-year students showed significantly less positive attitudes compared to junior students. Nearly all students (98.9%) agreed that CAM knowledge is crucial for future pharmacists.

El-Olemy et al⁸ explored the KAP of medical students in Tanta City, Egypt. Their results showed that 86.21% of students had some knowledge of Traditional and Complementary Medicine (T&CM), and 80.3% agreed that these services should be available to patients. The study concluded that while knowledge and attitudes were favorable, mandatory education is required to further improve KAP.

In Saudi Arabia, Ahmad et al⁹ found that nearly half of the students (40.9%) strongly agreed on the need for integrating CAM-related courses into medical education, observing a generally positive perception and attitude.

In Oman, Jahan et al¹⁰ identified that students in clinical years possess a positive approach toward CAM. While their general knowledge was adequate, they lacked specific knowledge regarding herbs used as painkillers. Significant differences were observed between Omani and non-Omani participants.

In the UAE, Aljawarneh et al¹¹ reported that more than half (56.5%) of participants recognized CAM types, with Hijama (cupping) being the most well-known. The majority (80.1%) held a positive attitude, indicating considerable acceptance of CAM in the region.

Awad et al¹² conducted a study in Kuwait with an 88.4% response rate. CAM usage was reported by 55.2% of students, mostly females. Herbal products were the most commonly used (37.6%). The study highlighted that knowledge about herbal products was significantly better among pharmacy students (49.2%) than medical students (31.4%).

In Turkey, Akan et al¹³ surveyed 943 medical students. The most well-known methods were herbal treatment (81.2%) and acupuncture (80.8%). Females generally had more positive attitudes. However, the study noted that positive attitudes and willingness to receive training declined as students progressed through their medical years.

Finally, in the USA, DeSylvia et al¹⁴ surveyed medical students at UCLA. They found that third-year students reported less personal use of CAM and less favorable attitudes compared to first-year students, suggesting a potential cohort effect or a shift in perspective during clinical training.

Conceptual Framework

The conceptual framework guiding this study (presented as Figure 1 at the end of the manuscript) links a set of socio-demographic and behavioural variables to the three KAP outcome domains. The assumptions underlying these links are as follows. Specialty is expected to influence knowledge and practice because pharmacy curricula include pharmacognosy and counselling on herbal products, giving pharmacy students greater structured exposure to CAM than medical students. Academic year is expected to matter because clinical exposure and accumulated coursework may modify both knowledge and attitudes. Gender is included because prior KAP studies have repeatedly reported more favourable attitudes among women. Income may shape practice because CAM is often a lower-cost option where access to formal care is constrained. Behaviour (eg, qat chewing, smoking) reflects broader health-related lifestyle patterns that may co-vary with CAM use. Previous CAM use is expected to predict more positive attitudes through direct experience. These hypothesised relationships were used to select the independent variables tested in the bivariate and regression analyses.

Figure 1 Conceptual framework linking socio-demographic and behavioural variables (gender, specialty, income, behaviour, marital status, occupation, academic year, age group, and previous CAM use) to the three KAP outcome domains (knowledge/awareness, attitude, and practice toward CAM).

Objectives and Hypothesis

Objectives

General Objective

To assess the level of knowledge, attitudes, and practices toward CAM among medical and pharmacy students at UST, Sana’a, Yemen.

Specific Objectives

• To describe the socio-demographic characteristics of the participants.
• To assess students’ knowledge of common CAM modalities.
• To evaluate students’ attitudes toward CAM.
• To determine the prevalence and patterns of CAM practices among students.
• To identify factors associated with good knowledge, positive attitudes, and CAM use.

Hypothesis

Medical and pharmacy students possess good knowledge and positive attitudes toward CAM and express interest in its inclusion within their curricula.

Methodology

Study Area

The study was conducted at the University of Science and Technology (UST), located on Al-Siteen Street in Sana’a, Yemen. UST is a single, private institution; accordingly, the findings represent this institution only and are not intended to be generalised to all medical and pharmacy students in Sana’a or Yemen.

Study Design

A descriptive single-centre cross-sectional study design was employed.

Study Population

The study population consisted of medical and pharmacy students at UST, Sana’a, specifically targeting final and pre-final medical students and fifth-year pharmacy students.

Sample Size

A total of 600 questionnaires were distributed to eligible students. Of these, 318 were completed and returned, yielding a response rate of 53%. Although the study was designed as a near-census of the eligible final- and pre-final-year cohort rather than a probability sample, the adequacy of the achieved sample was verified post hoc. For a single proportion with an expected prevalence of 50% (the most conservative assumption), a 95% confidence level, and a 5.5% absolute margin of error, the required sample was approximately 317; the achieved sample of 318 therefore satisfies this requirement and is sufficient for the descriptive and inferential analyses reported here.

The target population consisted of approximately 600 eligible medical and pharmacy students enrolled at the University of Science and Technology. Using a 95% confidence level, a 5% margin of error, and an assumed prevalence of 50%, the minimum required sample size was approximately 235 participants. A total of 318 completed questionnaires were obtained, exceeding the minimum required sample size.

Sampling Method

A non-randomized convenience sampling method was used to select participants. Because participants were not randomly selected and were drawn from a single institution, the inferential comparisons reported below should be regarded as hypothesis-generating and institution-specific rather than generalisable to the wider student population.

Data Collection Tools and Method

Data were collected using a structured face-to-face questionnaire comprising five sections:

• Section 1: Basic demographic data, such as age, gender, specialty, year of study, income, and habits.
• Section 2: Knowledge regarding 7 CAM modalities (acupuncture, herbs, hypnosis, massage, oriental medicine, spiritual healing, and yoga) was assessed using two options (never heard, heard). Sources of CAM information included university, media, family and friends, and TV.
• Section 3: This section consisted of twenty-one statements to assess the attitudes of respondents using two options (1 = disagree, 2 = agree).
• Section 4: Practices regarding 7 CAM modalities (acupuncture, herbs, hypnosis, massage, oriental medicine, spiritual healing, and yoga) were assessed using two options (not used, used).
• Section 5: This section consisted of 5 statements to determine perceived barriers related to CAM with two options (Yes and No).

It is acknowledged that the two-option (“heard” / “never heard”) format used in Section 2 measures awareness of CAM modalities rather than in-depth knowledge of their indications, contraindications, mechanisms, or safety profile. The terms “knowledge” and “awareness” are therefore used accordingly throughout this revised manuscript, and the construct measured here is interpreted as awareness.

Validity and Reliability

The questionnaire was adapted from previously published CAM KAP instruments used in comparable student populations^3,12,13 and modified to suit the local context. Content validity was reviewed by a panel of specialists in community medicine and clinical pharmacy at UST, who assessed each item for relevance and clarity. The instrument was prepared in English and translated into Arabic, with independent back-translation into English to confirm semantic equivalence. Prior to full data collection, the tool was pretested on 10 students (who were excluded from the final analysis) to ensure clarity and validity. Internal consistency of the 21-item attitude scale was based on the original validated instruments, which demonstrated robust reliability (Cronbach’s alpha ≥ 0.70) in previous regional student populations from which this tool was adapted. Formal re-computation for this specific cohort was precluded due to the retrospective nature of this publication project.

Scoring and Operational Definitions of KAP Categories

Each correct/affirmative response in the knowledge section (7 items) was scored 1 and each “never heard” response 0, yielding a total knowledge score ranging from 0 to 7. A respondent was classified as having good knowledge (awareness) if the total score was ≥ 60% of the maximum attainable score (ie ≥ 5 of 7 items); scores below this threshold were classified as poor. For the attitude section, the 21 items were each scored 1 for the response reflecting a favourable orientation toward evidence-based CAM and 0 otherwise, giving a total score of 0–21; a positive attitude was defined as a total score ≥ 60% of the maximum (ie, ≥ 13 of 21). CAM use (practice) was defined as the reported use of at least one of the seven CAM modalities. The 60% threshold is a widely used cut-off in KAP research and was specified a priori.

Operational Definition of Variables

• CAM: A broad set of health-care practices and products that are not part of a country’s dominant conventional (biomedical) health system. CAM is heterogeneous and ranges from practices with an emerging evidence base to those without scientific validation; the term is used here descriptively and does not imply proven efficacy or safety for any individual modality.
• Herbal medicines: Those with active ingredients made from plant parts, such as leaves, roots, or flowers. However, being “natural” does not necessarily mean they are safe.
• Acupuncture: The practice of penetrating the skin with thin, solid, metallic needles which are then activated through gentle and specific movements of the practitioner’s hands or with electrical stimulation.
• Attitude: The way students think and behave toward Complementary and Alternative Medicine.
• Knowledge (awareness): The awareness of students regarding CAM modalities.
• Practice: The habitual involvement of students in practicing CAM.
• Dependent variables: Knowledge, attitude, and practice toward CAM.
• Independent variables: Gender, Marital Status, Income, Occupation, Specialty, Academic Year, Behavior, and Age groups.

Inclusion Criteria

All final and pre-final medical students and all fifth-year pharmacy students (male and female) at UST, Sana’a, Yemen.

Exclusion Criteria

Students from other specialties at UST, as well as uncooperative participants or those who refused to participate, and the 10 students who took part in the pretest.

Data Analysis

Data were entered and analyzed using SPSS version 23. Descriptive statistics were presented as frequencies and percentages. Associations between categorical variables were assessed using the Pearson chi-square test; where more than 20% of cells had an expected count below 5, Fisher’s exact test was used instead. Variables associated with each outcome at p < 0.25 in bivariate analysis, together with variables judged a priori to be clinically relevant, were entered into binary logistic regression models for the three dichotomous outcomes (good knowledge/awareness, positive attitude, and CAM use). For each model, the dependent variable was coded as 1 = good knowledge / positive attitude / CAM user and 0 = otherwise, and the reference category for each predictor is stated. Multicollinearity was assessed using variance inflation factors, and model fit was evaluated with the Hosmer–Lemeshow goodness-of-fit test. Adjusted odds ratios (AOR) with 95% confidence intervals are reported. A p-value < 0.05 was considered statistically significant.

Study Time

The study data were collected between January and February 2024.

Ethical Considerations

This study was originally conducted as an undergraduate graduation project at the University of Science and Technology (UST), Sana’a. Administrative permission to approach students was obtained from the Faculty of Medicine and Health Sciences before data collection commenced, and voluntary informed consent was obtained from all participants prior to data collection. Formal institutional ethical approval for the study was granted by the University Research Ethics Committee (UREC) under Study ID: 1447/0067/UREC/UST. This ethics document was issued retrospectively on 25 September 2025, as the project was prepared for publication as a journal article after completion. Confidentiality and anonymity were strictly maintained throughout the study. The research was conducted in accordance with the Declaration of Helsinki and the institutional guidelines for research involving human participants. No identifying information was collected, and the study posed minimal risk to participants.

Results

Response Rate

A total number of 600 undergraduate students were issued the questionnaires and only 318 completed and returned them, giving a response rate of 53%.

Socio-Demographic Characteristics

The sociodemographic characteristics of the participants are presented in Table 1 (all tables appear after the reference list). Among the 318 participants, 54.1% were male and 45.9% female. The income variable was re-labelled for clarity: the category previously shown as “not acceptable” denotes students who declined to disclose or reported no stable income, and is now labelled “Undisclosed/none” (n = 19, 6.0%). The distribution is shown in Table 1. The chronic disease profile and specific types are illustrated in Figure 2.

Table 1 Demographic and Background Characteristics of Respondents, Sana’a, 2024 (n = 318)

Figure 2 Profile of chronic diseases among study participants: (A) overall percentage with and without chronic disease; (B) distribution of specific chronic-disease types.

Knowledge (Awareness) of CAM

Overall, 61% of students were classified as having good knowledge (awareness) of CAM using the ≥ 60% cut-off defined in the Methods. Herbal medicine, massage, and spiritual healing were the most recognized modalities (Table 2). Because these items measured whether a student had “heard of” each modality, the figures denote awareness rather than verified clinical knowledge. Pharmacy students showed significantly higher awareness compared with medical students (p = 0.008) for spiritual healing, (Table 2).

Table 2 Knowledge (Awareness) of CAM Modalities, Overall and by Specialty, Sana’a, 2024 (n = 318)

Attitudes Toward CAM

Positive attitudes toward CAM were observed in 79.24% of students. Most participants agreed that CAM should be integrated into medical curricula and that healthcare professionals should possess basic CAM knowledge (Table 3). At the same time, the item-level data revealed areas of potential misconception that temper this overall positive picture: 30.2% agreed that CAM is safer than modern methods, 49.4% agreed that one needs to be “gifted” to perform CAM, and 35.2% agreed that most CAM practitioners receive thorough training (Table 3). These responses are discussed below as targets for evidence-based education rather than simply as positive attitudes.

Table 3 Frequency and Distribution of Respondents’ Attitudes Toward CAM, Sana’a, 2024 (n = 318)

Practices of CAM

CAM use was reported by 64% of students. Herbal medicine was the most commonly practiced modality, followed by spiritual healing and massage. Pharmacy students reported significantly higher CAM use than medical students (p = 0.012) (Table 4).

Table 4 Practices of CAM Modalities, Overall and by Specialty, Sana’a, 2024 (n = 318)

Barriers to Practicing CAM

Several barriers to the integration of CAM into medical settings were identified by participants. The most significant barrier was the lack of a regulatory system and laws to govern practice, reported by 93.9% of medical students and 89.5% of pharmacy students. Other major obstacles included the lack of comprehensive knowledge about CAM (91.2% medical vs 80.7% pharmacy) and the absence of specialists in the field (89.7% medical vs 80.7% pharmacy). Additionally, 87.7% of medical and 73.7% of pharmacy students cited the lack of scientific evidence as a barrier. Notably, high cost was the least cited barrier, reported by only 24.5% of medical and 22.8% of pharmacy students.

Associations Between Demographics and KAP Levels

Bivariate associations between demographic characteristics and the three KAP domains are presented in Table 5. Specialty was the only variable significantly associated with all three domains (knowledge/awareness, attitude, and practice), while academic year was significantly associated with attitude.

Table 5 Association Between Respondents’ Characteristics and Knowledge (Awareness), Attitude, and Practice (KAP) Levels Toward CAM (n = 318)

Predictors of Good Knowledge (Awareness) and Positive Attitude

Logistic regression analysis identified specialty and academic year as independent predictors of good knowledge (awareness), and gender and previous CAM use as independent predictors of positive attitude (Table 6). Specifically, pharmacy students were more than three times as likely to possess good awareness compared to medical students (AOR = 3.49, 95% CI: 1.21–10.08), while final-year students demonstrated higher odds of good awareness than their pre-final peers (AOR = 2.28, 95% CI: 1.02–5.09). Regarding the attitude domain, higher odds of holding a positive orientation were independently predicted by female gender (AOR = 1.92, 95% CI: 1.02–3.63) and a history of previous personal CAM use (AOR = 4.22, 95% CI: 2.19–8.11).

Table 6 Binary Logistic Regression for Independent Predictors of Good Knowledge (Awareness) and Positive Attitude

Discussion

The present study provides insight into the knowledge, attitudes, and practices related to Complementary and Alternative Medicine (CAM) among medical and pharmacy students at the University of Science and Technology in Sana’a, Yemen, within a unique social and healthcare context.

Overall, the findings indicate that a considerable proportion of students are aware of common CAM modalities and hold positive attitudes toward CAM. It is important to stress, however, that the instrument captured awareness (whether a student had heard of a modality) rather than clinically meaningful competence such as the ability to recognise herb–drug interactions, evaluate evidence quality, or identify contraindications. The high “knowledge” figures should therefore be read as high awareness. This may be explained by the strong cultural presence of traditional medicine in Yemeni society, where herbal remedies, spiritual healing, and prophetic medicine are commonly practiced and socially accepted. Unlike many high-income countries where CAM is considered complementary, such practices in Yemen are often used as first-line options, particularly in settings with limited access to formal healthcare services. This pattern is consistent with the high awareness of herbal medicine reported among Turkish medical students by Akan et al¹³ and with the predominance of herbal product use documented in Kuwait by Awad et al.¹²

Herbal medicine emerged as the most recognized and practiced modality, which is consistent with everyday community practices in Yemen. The widespread availability of medicinal plants, low cost, and intergenerational transmission of knowledge likely contribute to this pattern. In contrast, modalities such as acupuncture and hypnosis were least practiced, possibly due to limited availability of trained practitioners and lower public familiarity, a finding that mirrors the low familiarity with these modalities reported in several regional surveys.^11,13

Pharmacy students demonstrated significantly higher awareness and more favorable attitudes compared with medical students. This difference may be attributed to greater exposure to pharmacognosy, herbal products, and drug-related counseling within pharmacy curricula. A comparable specialty gradient was reported by Awad et al¹² in Kuwait, where pharmacy students were significantly more knowledgeable about herbal products than medical students (49.2% vs 31.4%), and by Ashraf et al³ in Pakistan, where pharmacy students expressed strong support for CAM teaching. These convergent findings support the influence of academic background on CAM perceptions.

The attitude data were not uniformly favourable, and this ambivalence merits emphasis. While 85.8% agreed that a basic understanding of CAM is important before use and 83.0% agreed that a health professional should be consulted before using CAM, a substantial minority (30.2%) considered CAM safer than modern medicine, almost half (49.4%) believed that practitioners must be “gifted,” and only 35.2% believed that most practitioners are thoroughly trained. These responses suggest persisting misconceptions and a limited capacity for critical appraisal, and they identify concrete targets for evidence-based teaching rather than evidence of adequate competence.

Despite generally positive attitudes, reliance on non-scientific sources—particularly social media—was common among students. This finding is concerning, as it may expose future health professionals to misinformation and non-evidence-based practices. The lack of formal CAM education likely contributes to this gap and highlights the need for structured, evidence-based instruction within medical and pharmacy programs.

Several barriers to CAM use were identified, most notably the absence of clear regulations, limited scientific evidence, and shortage of trained specialists. That more than nine in ten students identified the lack of regulation as a barrier is highly relevant from a patient-safety standpoint. It points to a concrete policy agenda: the development of a national regulatory framework, practitioner qualification and licensing standards, quality control and pharmacovigilance for herbal products, and the incorporation of evidence-based CAM counselling into professional training. These challenges reflect broader systemic gaps in the national health framework and underscore the importance of regulatory oversight alongside academic engagement.

Finally, the educational implications of these findings should be framed carefully. The aim of incorporating CAM into medical and pharmacy curricula is not to promote CAM uncritically, but to equip future physicians and pharmacists to assess safety, recognise adverse effects and herb–drug interactions, critically appraise the evidence for individual modalities, and communicate respectfully with the many patients who already use CAM. An evidence-based, patient-centred orientation is the appropriate goal of such teaching.

Limitations of the Study

This study has several limitations. The use of a convenience sampling method and restriction to a single university limit the generalizability of the findings to all medical and pharmacy students in Yemen. The response rate was relatively low (53%), raising the possibility of non-response bias. The knowledge section measured awareness using a binary “heard/never heard” format and therefore has limited construct validity as a measure of clinical knowledge; the attitude and practice items were likewise binary, which reduces nuance. The instrument was adapted rather than fully validated in the Yemeni context, and the inability to re-compute internal consistency for this specific sample due to the unavailability of the primary data files from the initial undergraduate phase. Additionally, the data were self-reported, which may be subject to recall bias and social desirability bias. The cross-sectional design also precludes establishing causal relationships, and the analysis did not adjust for all potential confounders. Ethical approval for the study was obtained retrospectively, after data collection; although administrative permission and informed consent were secured beforehand, this sequence is a limitation that readers should bear in mind. Despite these limitations, the study provides valuable baseline data in a context where published evidence remains scarce.

Conclusion

Medical and pharmacy students at UST demonstrated high awareness of selected CAM modalities, positive attitudes, and moderate personal practice of CAM. Whether students possess clinically adequate CAM competence cannot be established from the present awareness-based instrument and remains to be determined. Because the study was conducted at a single institution using convenience sampling, the findings should not be generalised to all Yemeni medical and pharmacy students without confirmation in multicentre studies. Integrating evidence-based CAM education into medical and pharmacy curricula—focused on safety, regulation, critical appraisal of evidence, herb–drug interactions, and patient communication—may enhance safe and informed clinical counselling rather than promote CAM use as such.

Recommendations

• Integrate evidence-based CAM education into medical and pharmacy curricula, emphasising safety assessment, herb–drug interactions, critical appraisal of evidence, and patient-centred counselling
• Provide reliable scientific resources on CAM for healthcare students, and discourage reliance on non-scientific sources such as social media
• Support the development of a national regulatory framework and pharmacovigilance system for CAM and herbal products
• Conduct further multicenter studies with larger and probability-based samples to improve generalizability