BACKGROUND

Methamphetamine use is increasing1 along with a five-fold increase in methamphetamine overdose deaths from 2012 to 2018.2 While methamphetamine use can complicate the management of existing chronic diseases, little is understood of the chronic disease profile of people who use this illegal stimulant.

OBJECTIVE

To inform healthcare delivery efforts, we estimated prevalence of various chronic conditions, medical multimorbidity, mental illness, and substance use disorders (SUDs) among adults who report past-year methamphetamine use.

METHODS AND FINDINGS

We analyzed data from the 2015 to 2019 National Survey on Drug Use and Health (NSDUH),3 a nationally representative annual cross-sectional survey of non-institutionalized individuals in the USA. The survey asks about past-year use of methamphetamine, alcohol, cannabis, cocaine, heroin, and prescription opioids, stimulants, and tranquilizers/sedatives. Participants were assessed for DSM-IV criteria of substance “abuse” and “dependence,” and while not a diagnostic interview, we considered the proxy diagnoses of either as SUD.3 Regarding past-year mental illness, NDSUH developed an indicator based on level of depression, emotional distress, functional impairment, and suicidal thoughts. Our variable used criteria for moderate or severe mental illness, equivalent to a Global Assessment of Functioning score of < 60.4 Participants were also asked if they have been told by a doctor that they had chronic diseases. We considered all 10 chronic diseases queried and we also coded a variable indicating whether participants reported being diagnosed with ≥ 2 conditions to indicate medical multimorbidity.

Bivariable comparisons were conducted using chi-square to determine differences in prevalence regarding mental illness, chronic conditions, and SUD according to whether methamphetamine use was reported. We then utilized separate generalized linear models using Poisson and log link to determine whether methamphetamine use is associated with increased likelihood of each outcome, adjusting for year and demographic characteristics. To account for potential family-wise error, we used a Bonferroni correction (α = 0.05/24 outcomes = 0.002) to determine significance. Survey weights were used for all analyses3 and this secondary analysis was exempt from review at the New York University’s institutional review board.

Results suggest that, compared to those not reporting methamphetamine use, those reporting use were more likely to have mental illness (adjusted prevalence ratio [aPR = 3.15], 95% confidence interval [CI]: 2.91–3.41), medical multimorbidity (aPR = 1.86, 95% CI: 1.64–2.10), and any substance use disorder (aPR = 4.17, 95% CI: 3.80–4.57) (Table 1). They were also more likely to have each combination of outcomes examined, including SUD and mental illness (aPR = 7.30, 95% CI: 6.23–8.55), medical multimorbidity and mental illness (aPR = 4.83, 95% CI: 4.00–5.85), SUD and medical multimorbidity (aPR = 9.07, 95% CI: 7.16–11.49), and all three simultaneously (aPR = 13.52, 95% CI: 10.14–18.01).

Table 1 Chronic Disease, Mental Illness, and Substance Use Disorder Among US Adults who Have Used Methamphetamine in the Past Year, 2015–2019
Full size table

DISCUSSION

Compared to adults who have not used methamphetamine in the past year, adults who use methamphetamine have a higher prevalence of co-occurring mental illness, SUDs, and medical multimorbidity. Mental illness and SUDs are themselves chronic diseases and coupled with medical conditions result in a high level of multimorbidity. Methamphetamine itself can be toxic for multiple organs including the cardiovascular, pulmonary, neurological, and hepatic systems,5 and injection use can increase risk for infectious disease. In addition to higher prevalence of medical multimorbidity, we detected high prevalence of lung disease, liver disease, and HIV among people who use methamphetamine. Reducing methamphetamine use is challenging as the evidence base for its treatment is still developing. Further complicating is the interaction of methamphetamine with other SUDs, such as opioid use disorder (OUD). Consistent with national trends of sharp increases in methamphetamine use among people reporting prescription opioid misuse and heroin use,1 we found considerably higher likelihood of heroin and prescription opioid use disorders among adults who use methamphetamine. This places users at elevated risk for overdose and may complicate the treatment of OUD.6 Consequently, methamphetamine use adds complexity to the already-challenging care of adults who have multiple chronic conditions.

This study has limitations including self-report, individuals experiencing homelessness may be underrepresented, and temporal associations could not be deduced.

Methamphetamine use, SUDs, mental illness, and chronic medical disease are interrelated and place people at high risk for poor outcomes and death. The complexity of caring for individuals who use methamphetamine along with compound multimorbidity mandates a harm reduction and patient-centered approach to care that can coordinate management of mental illness, medical disease, and SUDs. Integrated interventions that can address all conditions along with associated social risks are needed for this population.