The present systematic review and meta-analysis found that overall substance use prevalence among medical students in India is about 40%. Alcohol use seemed to be the most common substance use, followed by tobacco, primarily in smoked form. Cannabis use was present in about 8% of the sample, and sedative-hypnotics were used by about 4% of the sample of medical students. Substance use was generally more common in male students than females.

Alcohol and tobacco being the common substances of abuse among medical students were in line with the findings from other parts of the world. The prevalence rates of alcohol and tobacco use reported in the present meta-analysis were higher than a previous one which covered 106 studies from various parts of the world.[1] On the other hand, the rates of alcohol use among Indian medical students were much lower than reported in a review of substances among medical students in Brazil.[2]

The use of cannabis was reported in about 8% of the medical students. The rates of use were lower than the worldwide average, where lifetime use was reported in about a third of the medical students.[76] However, the same systematic review reported that the rates of cannabis use among medical students in the Asian countries were around 6%, much closer to the rates reported in the present study. While cannabis is the most common illicit substance of use in India and the world, most users do not become dependent users. Nonetheless, it may become a gateway drug for the use of other substances. The use of sedatives was also reported by some of the participants, probably reflecting easy availability to the medical students, and possible use to improve sleep before the examinations. However, it must be noted that the use of sedatives and tranquilizers may affect cognitive abilities if taken in the longer run. Fortunately, the use of stimulants and hallucinogens was rare, probably reflecting the low overall use of these substances in India.

The use of substances, as mentioned above, has multiple consequences for medical students and the medical fraternity. For medical students, the use of these substances may lead to regular and subsequently problematic use. One should be cautious in interpretation as not every substance user would develop a substance use disorder, or suffer from harmful consequences. However, the use of substances raises the chances of developing a substance use disorder subsequently. Also, the use of substances recreationally may divert away attention from coursework and lead to deficient or falling academic performance. Moreover, substance use by the medical students may lead to an image of the profession being blemished, though it could be argued that the medical students are also humans who are equally vulnerable to human iniquities. The impact of substance use among medical students can impact patient care adversely in some circumstances, especially when students are given tasks and responsibilities in patient care.

The literature over the last about 20 years of substance use among medical students has expanded considerably. Studies have emerged from different regions of the country, including north, south, east, west, and central India. The studies have been generally conducted in single institutions, though some of the studies have enrolled students from many places. Studies by Goel et al.[23] and Philip et al.[24] could be considered truly pan-national recruiting students from all parts of the country. Most commonly, the assessment was done using a self-developed questionnaires to assess the use of substances. While this has the advantage of the simplicity of assessment, it makes comparisons difficult, especially when the questions are worded substantially differently.

The available literature points toward the need to address substance use among medical students. There are several things that can be done for the prevention of substance use/substance use disorder on individual and systemic levels. From a general population level, outlet density control for alcohol and tobacco sales, increasing the legal age of buying, increased taxation, awareness campaigns, and enforcement of drunk driving policies are likely to be effective in reducing the prevalence of substance use. From a systemic level, curricular emphasis on substance use and consequent harms might be useful. The literature is most prominent on tobacco and alcohol use among students. Medical students are likely to be cognitively aware of the adverse consequences of tobacco or alcohol use on the body and the role of the use of tobacco or alcohol in the genesis of a host of medical illnesses. Information may be given early about the course of the evolution of tobacco and alcohol use disorder, and the treatment approaches can be emphasized. Clinical exposure to diseases where tobacco or alcohol has played a major role and where tobacco and/or alcohol use is addressed in the management plan can help medical students to internalize that these issues can be handled professionally. At the same time, campus proctors, in-charges, or wardens need to enforce institute/university regulations to deter substance use. Rules like the establishment of shops selling alcohol or tobacco away from educational institutions can be enforced more strictly. Tobacco and alcohol-free campus campaigns can be beneficial, along with encouraging students to make Information Education and Communication material for patients pertaining to the harms of tobacco and alcohol. Peer-led interventions can also be considered.

From an individual student perspective, who have been using substances, student wellness services may help to address these when they become problematic. Addressing the physical and mental health issues of students in a confidential and responsive manner would probably address their concerns and prevent the self-prescription/unregulated use of medications. In case the students are not willing to seek care in their own medical setting (attributable to logistic and confidentiality-related issues), telepsychiatry can be used as a modality for providing help for cessation of use of substances. In addition, seeking help for substance use should be de-linked from academic or hostel allocation strictures, which may enable students to seek services more freely when they need them. Focusing on students showing recent academic deterioration or absenteeism from clinical rotations may be another approach to help the students in need. Involving families with due consent and linking up with consultants in the psychiatry department may help to liaison for better care for such students.

There was a high degree of heterogeneity across the studies in the present review (as reflected by the I² tests in the pooled prevalence). Several issues may be contributory to this high heterogeneity. The major reason of statistical heterogeneity is the differences in prevalence rates across the studies. The prevalence rates have been measured using different methodologies and may also reflect the actual differences in the prevalence of substance use across different regions or differences in samples and settings. The implication of interpretation of heterogeneity lies in the fact that while pooled prevalence provides an idea of overall substance use, each individual study also needs to be paid attention to while drawing inferences. The locally available prevalence (if available) needs to be used in conjunction with the pooled prevalence while planning intervention for a set of students.

Some of the limitations of this study merit attention. There was considerable heterogeneity in the manner in which the substance use was ascertained and evaluated in the different studies. We took a broad outlook of the definition and took “ever use” as definition wherever possible to capture lifetime use. This was done as substance dependence is uncommon in the adolescent age groups and has been seldom reported by studies among medical students. We looked at two important databases, that is, PubMed and Google Scholar. These databases do cover most of the published literature, though the Google Scholar database provides results using a different algorithm than PubMed. Also, smoked and smokeless tobacco users could not be grouped in some of the studies, as there was likely to be an unknown overlap between the two groups. Hence, smoked tobacco was used as the reference category for estimating the prevalence of tobacco use, leading to the underestimation of tobacco users. Also, the maximum prevalence from the reported figures of substance use was taken, though there was heterogeneity in reporting of the outcome measures. Furthermore, the systematic review does not report on the etiological or risk factors for substance use in this population. Such a question would be best addressed by a systematic review with a different approach and encompassing studies that do not necessarily report prevalence figures. And finally, the search strategy might have omitted some studies focused on cannabis or other illicit substance use. Despite the limitations, the study provides insights into the extent of substance use among medical students and provides reasonably reliable quantitative estimates. Since the locally relevant literature is often under-referenced,[77] the meta-analysis included those studies which are published in non-indexed journals to bring the pertinent evidence into consideration, suitably citing the relevant literature, which might be otherwise skipped.

To conclude, this study suggests that alcohol and tobacco use was present among a substantial proportion of medical students and that illicit substance use may occur in some students. Addressing substance use in these students may prevent substance use disorder from occurring. Future studies can look at the longitudinal trajectories of substance use among medical students as they move into residency or practice. Endeavors may also look into the circumstances and opinions about cannabis intake and when the use of cannabis is considered problematic. Also, the acceptance and efficacy of peer-led or student welfare activities in reducing the use of substances among medical students can be considered.