Past-Year Kratom Use in the U.S.: Estimates From a Nationally Representative Sample

Past-Year Kratom Use in the U.S.: Estimates From a Nationally Representative Sample

Published:April 29, 2021DOI:https://doi.org/10.1016/j.amepre.2021.02.004

Introduction

Kratom is a plant with partial opioid agonist effects, and its use has become popular to ameliorate symptoms of opioid withdrawal. However, use has been linked to thousands of poisonings, although most have involved use of other drugs. Little is known regarding prevalence and correlates of use in the general U.S. population.

Methods

Data were examined from the 2019 National Survey on Drug Use and Health, a nationally representative probability sample of non-institutionalized individuals aged ≥12 years in the U.S. (N=56,136). Prevalence and correlates of past-year kratom use were estimated. Data were analyzed in 2020.

Results

An estimated 0.7% (95% CI=0.6, 0.8) of individuals in the U.S. have used kratom in the past year. Past-year proxy diagnosis of prescription opioid use disorder was associated with increased odds for kratom use (AOR=3.20, 95% CI=1.38, 7.41), with 10.4% (95% CI=6.7, 15.9) of those with use disorder reporting use. Opioid misuse not accompanied with use disorder was not associated with kratom use. Those reporting past-year cannabis use both with (AOR=4.33, 95% CI=2.61, 7.19) and without (AOR=4.57, 95% CI=3.29, 6.35) use disorder and those reporting past-year cocaine use (AOR=1.69, 95% CI=1.06, 2.69) and prescription stimulant misuse (AOR=2.10, 95% CI=1.44, 3.05) not accompanied with use disorder were at higher odds for kratom use.

Conclusions

Kratom use is particularly prevalent among those with prescription opioid use disorder, but it is also prevalent among people who use other drugs. Research is needed to determine reasons for use and potential dangers associated with adding kratom to drug repertoires.

INTRODUCTION

Kratom (Mitragyna speciosa) is a plant with psychoactive effects that has recently acquired popularity in the U.S.1 The substance is most commonly ingested,2 and it typically provides stimulant effects at low doses and analgesic effects at higher doses.3 These analgesic effects occur because kratom acts as a partial opioid agonist.4 Because of these effects, in recent years, some people have begun to use kratom as a substitute for classical opioids in an effort to ameliorate withdrawal or to self-treat opioid use disorder.5,  6,  7,  8 Others use kratom to self-treat depression and anxiety or to reduce pain or symptoms related to chronic conditions.6,9
The U.S. Drug Enforcement Administration has identified kratom as a drug of concern, and the U.S. Food and Drug Administration has issued multiple warnings about kratom, recommending individuals not to use the substance because its safety is still being evaluated.10,11 However, kratom remains unscheduled at the federal level, and it is legal in most U.S. states, despite increasing state-level regulation. Long-term or high-frequency use can lead to dependence, tolerance, and withdrawal,12 and major adverse effects have been reported, including agitation, seizures, central nervous system depression, and neonatal abstinence syndrome.2,13 Adverse effects associated with use have typically been mild,3 but between 2011 and 2018, a total of 2,312 kratom exposures were reported to the National Poison Data System, with a large increase after 2015.2 Of these exposures, 60% involved other drugs. Hundreds of deaths related to use have also occurred, with most cases involving use of other drugs. An analysis of 156 deaths involving kratom determined that 87% involved use of other drugs,14 and another study examined 152 related deaths, of which 65% involved fentanyl use and 33% involved heroin use.11 Although most poisonings and deaths have involved use of opioids, deaths have also involved benzodiazepines, cocaine, and psychiatric medications.11,14 More nuanced investigation is needed to investigate kratom use in relation to use of other drugs.
Most epidemiologic research on kratom use has focused on online samples of individuals who use. Two national studies were utilized recently to estimate use,15,16 but neither utilized probability samples, and both were conducted online and were limited to adults. This study, conducted throughout 2019, focuses on a probability sample of non-institutionalized individuals aged ≥12 years in the U.S. to estimate past-year use and correlates of use of this substance.

METHODS

 Study Population

Data were examined from the National Survey on Drug Use and Health, a nationally representative cross-sectional survey of non-institutionalized individuals aged ≥12 years in the U.S. The sample was obtained through a multistage design, and surveys were administered via computer-assisted interviewing conducted by an interviewer using audio computer-assisted interviewing.17 Analysis focused on the 2019 sample only, because this was the first year kratom use was queried. The sample size was 56,136, and the weighted interview response rate was 64.9%. This secondary analysis was exempt from review by the New York University Langone Medical Center IRB.

 Measures

Participants were asked their age, sex, race/ethnicity, educational attainment, and annual family income, and experience of a major depressive episode or serious mental illness in the past year was determined through psychiatric modules.17,18 With respect to past-year substance use, participants were asked Whether they had used kratom, which can come in forms such as powder, pills, or leaf, and they were also asked about use of alcohol, cannabis, cocaine, heroin, and methamphetamine and about misuse of prescription opioids, sedatives/tranquilizers, and stimulants. Misuse was defined as using without one's own prescription; using in larger amounts, more often, or for longer than directed; or use in any way not directed by a doctor. Those reporting past-year (mis)use of a drug were asked questions to indicate whether they met criteria for proxy diagnosis of abuse or dependence using DSM-IV19 criteria. Those meeting criteria for either were coded as having use disorder.20,21 Drug use variables were coded to indicate: (1) no past-year use, (2) past-year (mis)use but not with use disorder, and (3) use disorder. Participants were also asked if they injected any drugs in the past year.

 Statistical Analysis

First, prevalence of kratom use was estimated; then, demographic and drug use correlates of use were examined in a bivariable manner using Rao–Scott chi-square tests.22 All covariates were then fit into a multivariable logistic regression model. Sample weights (provided by the National Survey on Drug Use and Health) were used to account for the complex survey design, nonresponse, selection probability, and population distribution. Data were analyzed in 2020 using Stata, version 13 SE.



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RESULTS

An estimated 0.7% (95% CI=0.6, 0.8) of individuals in the U.S. have used kratom in the past year. Sample characteristics and bivariable and multivariable correlates of past-year kratom use are presented in Table 1. Compared with adolescents, individuals in adult age groups aged <50 years were at about 2–3 times the odds for use, and compared with male participants, female participants were at decreased odds for use (AOR=0.70, 95% CI=0.51, 0.97). Compared with White individuals, Black (AOR=0.27, 95% CI=0.15, 0.47) and Hispanic (AOR=0.39, 95% CI=0.26, 0.59) individuals were at lower odds for use.
Table 1Correlates of Past-Year Kratom Use Among Individuals Aged ≥12 Years in the U.S., 2019
CharacteristicsFull sample,% (95% CI)No kratom use,% (95% CI)Kratom use,% (95% CI)AOR (95% CI)Age, years 12‒179.1 (8.8, 9.3)99.7 (99.6, 99.8)0.3 (0.2, 0.4)⁎⁎⁎1.00 18‒2512.3 (12.0, 12.6)98.7 (98.4, 98.9)1.4 (1.1, 1.6)2.40 (1.41, 4.08)⁎⁎ 26‒3414.7 (14.2, 15.1)98.6 (98.4, 98.9)1.4 (1.1, 1.7)3.00 (1.86, 4.84)⁎⁎⁎ 35‒4922.1 (21.7, 22.6)99.2 (99.0, 99.3)0.8 (0.7, 1.0)2.55 (1.56, 4.18)⁎⁎⁎ ≥5041.9 (41.0, 42.8)99.7 (99.5, 99.8)0.3 (0.2, 0.5)1.39 (0.77, 2.52)Sex Male48.5 (47.9, 49.2)99.1 (98.9, 99.2)0.9 (0.8, 1.1)⁎⁎1.00 Female51.5 (50.8, 52.1)99.4 (99.3, 99.5)0.6 (0.5, 0.7)0.70 (0.51, 0.97)*Race/ethnicity Non-Hispanic White62.0 (61.0, 63.0)99.1 (98.9, 99.2)0.9 (0.8, 1.1)⁎⁎⁎1.00 Non-Hispanic Black12.1 (11.3, 12.9)99.8 (99.6, 99.9)0.2 (0.1, 0.4)0.27 (0.15, 0.47)⁎⁎⁎ Hispanic17.2 (16.5, 18.0)99.6 (99.5, 99.8)0.4 (0.2, 0.5)0.39 (0.26, 0.59)⁎⁎⁎ Other/mixed8.7 (8.2, 9.2)99.5 (99.1, 99.7)0.5 (0.3, 0.9)0.67 (0.40, 1.10)Education High school or less36.3 (35.5, 37.1)99.3 (99.1, 99.4)0.7 (0.6, 0.9)*1.00 Some college30.7 (30.0, 31.4)99.0 (98.8, 99.2)1.0 (0.8, 1.2)1.05 (0.81, 1.36) College degree33.0 (32.2, 33.8)99.4 (99.2, 99.5)0.6 (0.5, 0.8)0.83 (0.54, 1.26)Annual family income, $ <20,00014.7 (14.2, 15.2)99.1 (98.8, 99.3)0.9 (0.7, 1.2)1.00 20,000–49,99928.3 (27.4, 29.1)99.3 (99.1, 99.4)0.7 (0.6, 0.9)0.95 (0.64, 1.41) 50,000–74,99915.8 (15.3, 16.3)99.4 (99.2, 99.6)0.6 (0.4, 0.8)0.73 (0.42, 1.24) ≥75,00041.2 (40.3, 42.2)99.3 (99.2, 99.5)0.7 (0.6, 0.8)0.89 (0.62, 1.28)Major depressive episode No91.4 (91.0, 91.8)99.4 (99.3, 99.5)0.6 (0.5, 0.7)⁎⁎⁎1.00 Yes8.6 (8.3, 9.0)98.0 (97.5, 98.4)2.0 (1.6, 2.6)1.28 (0.76, 2.14)Serious mental illness No94.7 (94.4, 95.0)99.4 (99.3, 99.4)0.6 (0.6, 0.7)⁎⁎⁎1.00 Yes5.3 (5.0, 5.6)97.1 (96.2, 97.8)2.9 (2.2, 3.8)1.55 (0.87, 2.74)Past-year other drug use Alcohol No use35.0 (34.4, 35.6)99.7 (99.5, 99.8)0.4 (0.2, 0.5)⁎⁎⁎1.00 Use without disorder59.7 (59.1, 60.3)99.2 (99.0, 99.3)0.8 (0.7, 1.0)1.12 (0.70, 1.80) Use disorder5.3 (5.0, 5.6)97.9 (97.3, 98.3)2.1 (1.7, 2.7)1.07 (0.58, 1.97) Cannabis No use82.4 (81.9, 82.9)99.7 (99.6, 99.7)0.3 (0.3, 0.4)⁎⁎⁎1.00 Use without disorder15.8 (15.4, 16.3)97.5 (97.0, 97.9)2.5 (2.2, 3.0)4.57 (3.29, 6.35)⁎⁎⁎ Use disorder1.8 (1.6, 1.9)96.5 (95.1, 97.5)3.5 (2.5, 4.9)4.33 (2.61, 7.19)⁎⁎⁎ Cocaine No use98.0 (97.9, 98.2)99.4 (99.3, 99.5)0.6 (0.5, 0.7)⁎⁎⁎1.00 Use without disorder1.6 (1.5, 1.8)94.4 (92.3, 95.9)5.6 (4.1, 7.7)1.69 (1.06, 2.69)* Use disorder0.3 (0.3, 0.4)91.4 (84.4, 95.5)8.6 (4.5, 15.6)1.99 (0.71, 5.56) Methamphetamine No use99.3 (99.1, 99.4)99.3 (99.2, 99.4)0.7 (0.6, 0.8)⁎⁎⁎1.00 Use without disorder0.3 (0.3, 0.4)95.4 (89.4, 98.1)4.6 (2.0, 10.6)1.35 (0.43, 4.26) Use disorder0.4 (0.3, 0.5)92.8 (88.2, 95.7)7.2 (4.3, 11.8)0.94 (0.44, 2.01) Tranquilizers/sedatives No misuse97.8 (97.6, 98.0)99.4 (99.3, 99.5)0.6 (0.5, 0.7)⁎⁎⁎1.00 Misuse without disorder2.0 (1.8, 2.2)95.6 (93.9, 96.8)4.5 (3.2, 6.1)1.46 (0.92, 2.32) Use disorder0.3 (0.2, 0.3)91.8 (86.3, 95.2)8.2 (4.8, 13.7)1.14 (0.45, 2.88) Prescription stimulants No misuse98.2 (98.0, 98.3)99.4 (99.3, 99.5)0.6 (0.5, 0.7)⁎⁎⁎1.00 Misuse without disorder1.6 (1.5, 1.7)93.8 (91.4, 95.5)6.2 (4.5, 8.7)2.10 (1.44, 3.05)⁎⁎⁎ Use disorder0.2 (0.2, 0.3)90.6 (81.7, 95.4)9.4 (4.6, 18.3)2.55 (0.97, 6.72) Prescription opioids No misuse96.5 (96.2, 96.7)99.4 (99.3, 99.5)0.6 (0.5, 0.7)⁎⁎⁎1.00 Misuse without disorder3.0 (2.8, 3.3)97.4 (96.3, 98.2)2.6 (1.8, 3.7)1.27 (0.83, 1.94) Use disorder0.5 (0.4, 0.6)89.6 (84.1, 93.3)10.4 (6.7, 15.9)3.20 (1.38, 7.41)⁎⁎ Heroin No use99.7 (99.6, 99.8)99.3 (99.2, 99.4)0.7 (0.6, 0.8)⁎⁎⁎1.00 Use without disorder0.1 (0.1, 0.2)94.8 (84.1, 98.4)5.2 (1.6, 15.9)0.67 (0.11, 4.16) Use disorder0.2 (0.1, 0.2)84.0 (73.6, 90.7)16.0 (9.3, 26.4)1.48 (0.43, 5.07) Past-year injection drug use No99.7 (99.7, 99.8)99.3 (99.2, 99.4)0.7 (0.6, 0.8)⁎⁎⁎1.00 Yes0.3 (0.2, 0.3)89.0 (81.8, 93.6)11.0 (6.4, 18.2)1.48 (0.49, 4.49)
Note: Boldface indicates statistical significance.

With respect to drug use, past-year proxy diagnosis of prescription opioid use disorder was associated with higher odds for kratom use (AOR=3.20, 95% CI=1.38, 7.41), with 10.4% (95% CI=6.7, 15.9) of those with use disorder reporting use. Those reporting past-year cannabis use both with (AOR=4.33, 95% CI=2.61, 7.19) and without (AOR=4.57, 95% CI=3.29, 6.35) use disorder and past-year cocaine use (AOR=1.69, 95% CI=1.06, 2.69) and prescription stimulant misuse (AOR=2.10, 95% CI=1.44, 3.05) not accompanied by use disorder were at higher odds for kratom use.

DISCUSSION

This was the first study to estimate past-year kratom use from a national probability sample including adolescents. This study's estimate of past-year use of 0.7% is nearly identical to the estimate of 0.8% by another national study that did not utilize a probability sample.15 This study adds to previous literature linking kratom use with opioid misuse,15,16 because results suggest that, whereas those proxy diagnosed with opioid use disorder are at high odds for use, those who misuse prescription opioids but do not have use disorder are not at increased odds for use. Cannabis use and use disorder, however, were independently associated with increased odds for use, as were cocaine use and prescription stimulant misuse without use disorder. Although previous research suggests that most people who use kratom also use cannabis,15,16 more research is needed to determine whether kratom is also used to alleviate symptoms associated with cannabis use disorder or disorders treated with cannabis. Research is also needed to determine whether kratom is merely another substance added to drug use repertoires.

 Limitations

Some populations, such as the homeless who do not use shelters, were under-represented in this study. Therefore, prevalence of heroin use may be underestimated. The National Survey on Drug Use and Health did not ask about all forms of kratom (e.g., liquid), so use might have been under-reported. Over-reporting also could have occurred because of individuals using products mislabeled as kratom.

CONCLUSIONS

Kratom use is particularly prevalent among those with opioid use disorder, but it is also prevalent among people who use other drugs. Use has been associated with numerous adverse events, although most have involved use of other drugs. Research is needed to determine reasons for use and dangers associated with adding kratom to drug repertoires.

ACKNOWLEDGMENTS

Research reported in this publication was supported by the National Institute on Drug Abuse of the NIH under Award Number R01DA044207 .
The content is solely the responsibility of the author and does not necessarily represent the official views of NIH .
No financial disclosures were reported by the author of this paper.

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