ReviewKratom use and mental health: A systematic review
Introduction
Kratom (Mitragyna speciosa; also known as krathom or ketum) is a psychoactive plant in the Rubiaceae, or coffee, family that has been used medicinally for centuries in Southeastern Asia (Cinosi et al., 2015, Pendell, 2010). In Thailand and Malaysia, individuals use kratom across diverse contexts; as an opium substitute and to relieve symptoms of opioid withdrawal, medicinally to relieve pain, diarrhea, and cough, and by manual laborers to enhance stamina and energy (Tanguay, 2011, Prozialeck et al., 2012). People chew raw leaves of the kratom plant, boil them and serve as a tea, or smoke or vaporize them. Recent years have witnessed the expansion of kratom use beyond Asia; kratom leaves, powders, gums, capsules, and extracts are widely accessed via the internet and retail outlets across North America and Europe (Prozialeck et al., 2012, Singh et al., 2016), leading to novel concerns regarding the potential for adverse consequences of use (Boyer et al., 2008, Ward et al., 2011). In the absence of robust scientific data, some warnings about kratom from government and press sources exhibit features of drug hysteria (Hart, 2013), threatening researchers’ ability to study the plant and the public’s ability to evaluate pros and cons of kratom use, making this a critical time for collecting and evaluating evidence for the risks and benefits of this substance. Some of the most important potential risks and benefits of kratom are in the mental health realm. For this reason, we conducted a systematic review of all identified studies on kratom use and mental health.
As with many psychoactive substances before it, several factors have led to baseless and potentially unwarranted fears about kratom in North America; these include the marketing of kratom as a “legal high” (Cinosi et al., 2015), the confusion between kratom and other novel psychoactive substances (e.g., synthetic cannabis, bath salts), and sensationalized media coverage of putative harms (e.g., “Kratom: The supplement that will kill Godzilla”; Bloom, 2016). In the medical literature, the number of published case studies that have highlighted adverse events coincident with kratom use including liver toxicity and death (Kapp et al., 2011, McIntyre et al., 2015, Neerman et al., 2012, Nelsen et al., 2010, Sheleg and Collins, 2011) is disproportionately high relative to the number of rigorous investigations. Case studies present a relatively low level of evidence due to overrepresentation of extreme events, unknown validity and generalizability, and other potential biases (Merriam, 2009). These limitations render a causal linkage between kratom and serious adverse events impossible. Nonetheless, results of these studies have contributed to the issuance of dire public warnings. For example, the U.S. Centers for Disease Control and Prevention (CDC) and Drug Enforcement Administration (DEA) have explicitly warned that kratom may cause psychosis or death (Anwar et al., 2016, DEA, 2016) and the DEA has recommended criminalizing kratom possession and distribution despite robust public opposition to “cruel and irresponsible” governmental policy (Swogger, 2016) and the clear failure of such measures to do public good (Mallea, 2014).1
Kratom is understudied and, as such, the risks and benefits of kratom use have not been characterized in detail. Whereas caution in light of this lack of research is warranted, recent public discourse and policy approaches related to kratom exhibit characteristics associated with a drug hysteria (see Hart, 2013), including the promulgation of sensationalistic and biased information and the pursuit of regulatory approaches that appear overmatched to apparent risks. Indeed, dangers of drug hysterias include the tendency toward the adoption of blunt and reactive strategies that risk inhibiting scientific study and thus deprive the public of useful medicine. Drug hysteria also creates harmful stigma around users and increases the risk of ineffective and harsh policies that lead to unnecessary incarceration. The need for evidence-based policy to manage the growing adoption of kratom in North America and Europe makes this a critical time for evaluating risks and benefits. Moreover, the potential salutary role of kratom use in the context of opioid use, coupled with increasing demand for effective options for reducing harms associated with problematic opioid use, make the investigation of kratom a critical research priority. Understanding the influence of kratom use on mental health and well-being is important for evaluating the therapeutic potential of kratom in the context of harmful opioid use and other psychopathology, as psychological factors are key determinants of the acceptability kratom-based medicines.
Increased scientific attention is beginning to organize and clarify the state of knowledge about kratom. Thorough reviews describe the longstanding uses of kratom in Southeastern Asia and detail modes of consumption, side effects (including withdrawal), and kratom’s legal and social status in different parts of the world (Aziz, 2014, Hassan et al., 2013, Singh et al., 2016). They indicate kratom’s potential to help with a variety of problems, perhaps most notably pain (Ahmad and Aziz, 2012, Grundman, 2017). Importantly, kratom use also impacts several domains of mental health. The nascent scientific literature on kratom’s beneficial impact on mood and as a substitute for opioids deserves careful attention, as do the potential mental health risks of kratom use. To this end, the present work is the first to systematically review the literature on kratom and mental health. In this review, we aim to inform clinicians practicing in mental health or substance use treatment settings who may encounter kratom use in the course of their clinical work, policy-makers interested in understanding the potential public health impact of kratom use, and researchers who will base their scientific investigations on this preliminary knowledge.
Section snippets
Search strategy
We conducted a search for literature that addresses kratom use and mental health. In order to ensure coverage of all relevant studies and guided by recent, high-quality mental health review papers (e.g., Walker et al., 2015, Walsh et al., 2017), we chose search terms that comprise the broad emotional, psychological, and social domains of mental health (Ryff and Keyes, 1995). Electronic databases (Psycinfo, Medline) were used to identify all published studies using human samples between January
Results
Our search yielded 49 results. After eliminating redundant results, theoretical and review papers without novel empirical data (n = 19), case studies (n = 9), and papers determined to contain no data relevant to mental health (n = 6), we examined 15 studies. We then eliminated studies (n = 2) whose methods were inadequately reported for us to evaluate their limitations. Thirteen studies were retained for full review. The combined sample for these studies is 28,745, of which 25,189 were drawn
Discussion
We conducted a comprehensive systematic review of the scientific literature on kratom use and mental health. Perhaps our most robust finding is that the study of kratom’s effects on humans, and mental health in particular, is in its infancy. This was revealed by a lack of rigorous, well-controlled, prospective studies; the kind that will eventually lead to a sophisticated and nuanced clinical understanding of the benefits and harms of kratom use. Females were excluded or underrepresented in
Conflict of interest
No conflicts declared
Contributors
Dr. Swogger conducted the research for and wrote initial drafts. Dr. Walsh provided additional text and substantive input that contextualized findings within the broader literature. All authors approved of the submission.
Role of funding source
Nothing declared
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