‘Resurgent’, ‘twin’ or ‘silent’ epidemic? A select data overview and observations on increasing psycho-stimulant use and harms in North America

In the initial decade of the 2000s, a growing body of evidence documented increasing use of psycho-stimulants (e.g., crack-cocaine, methamphetamine) especially among street-involved persons with drug use in North America (i.e., the United States and Canada) in the [1‐3]. Moreover, data consistently showed that exposure to psycho-stimulants predicted higher risk for adverse (acute and chronic) health outcomes in the context of drug use. Select studies of marginalized populations with drug use found crack-cocaine use to be increasingly prevalent, if not predominant across Canada. For example, among persons using injection drug in Vancouver, the prevalence of crack-cocaine use had multifold increased to > 40% by 2005 from previous years [4, 5]. Cocaine (injection or inhalation) use – whether by itself or in combination use with other drugs – was found associated with generally worse physical and mental health status compared to non-users, more socio-economic marginalization, and distinctly elevated risk for human immunodeficiency virus/hepatitis C virus (HIV/HCV) infection as well as (fatal and non-fatal) overdose [6‐10]. Methamphetamine was identified as a main risk factor for severe mental health problems (including suicide), drug use risk behaviors (e.g., bingeing or equipment sharing), infectious disease (HIV and HCV) transmission, and overdose among young and other high-risk populations with drug use [11‐14]. Psycho-stimulant use and its related harms presented itself as an acute, yet widely neglected epidemic of drug use and adverse public health impacts [5, 15]. Given the mounting evidence, yet faced with rather limited intervention options and resources (especially when compared to other drugs, e.g., opioids), intensifying consideration and discussions occurred by around 2010 as to what appropriate treatment and public health measures were for psycho-stimulant use, and how to more effectively design and deliver interventions to at-risk individuals involved with drug use [16‐20].

Yet then, a distinct and extreme phenomenon of substance use and health that came to be dubbed the ‘opioid epidemic’ started to gradually unfold in the first decade of the 2000s. Initially facilitated by unprecedented high and rapidly rising levels of prescription opioid dispensing in North America beginning in that decade, potent opioid drugs (initially: morphine, oxycodone, hydromorphone formulations) were amply diverted and available from medical sources for non-medical use, and became the drug of choice, not only for marginalized individuals with drug use but for large general population segments in North America [21‐24]. In the US, the opioid epidemic has been characterized by ‘three waves’, although these are not categorically separate but overlapping phenomena; the first of which involved prescription opioids (− 2010), followed by heroin (2010–2012) and illicit/synthetic opioids (2012 onward) [25, 26]. Among street-involved individuals with drug use, the use of heroin – and possibly that of psycho-stimulants - became substantially reduced and widely replaced by use of prescription opioids as the primary substance during the initial phase of the opioid epidemic [27, 28].

The rapidly expanding use of prescription opioids in both street-involved and general populations went hand-in-hand with corresponding, multifold increases in opioid-related morbidity (e.g., hospitalizations, treatment admissions) as well as mortality (e.g., accidental poisoning deaths) in both the United States (US) and Canada [29‐33]. By about 2015, amidst select intervention and policy measures implemented to reduce rampant prescription opioid dispensing and harms in North America, a range of highly potent and toxic, illicit/synthetic opioids (e.g., fentanyl) quickly proliferated on the drug markets and became widely consumed, further accelerating opioid-related morbidity and mortality tolls. By 2018, there were an annual 46,802 opioid-related fatalities (combined from both prescription and illicit opioid products) in the United States, an approximately five-fold increase from 2001 [32, 34]; in Canada, similarly, the opioid-related mortality toll had increased to a count of 4372 and a comparable population rate of deaths, in 2018 [35, 36]. In both countries, the persistently high rates of opioid-related mortality, a disproportionate number  of which occurring among young adults, were adversely affecting life expectancy in the general population [37, 38].

The excessive and persistent burden of opioid-related morbidity and mortality led to the implementation and/or expansion of a series of prevention and treatment measures targeting individuals with at-risk opioid use in Canada, including: widespread naloxone availability and distribution (for opioid overdose reversal); officially sanctioned, and informal ‘supervised consumption sites/facilities; ‘drug-checking’ services, an increasingly diverse range of opioid pharmacotherapy options for the treatment of opioid use disorder, and initial efforts of ‘safer opioid supply’ programming that were offered to an increasingly large proportion of the ‘at-risk’ populations involved in opioid use [39‐45]. The twenty-first century’s second decade (2010–2019) became the decade of the ‘opioid crisis’. It is not an unreasonable assessment to suggest that attention, focus and efforts by scientists, program/service and policy officials in related fields in Canada was almost exclusively focused on and devoted to the unprecedented problem of opioid use, harms, and finding possible solutions – even though this only occurred with limited success, as key opioid-related use and harm (e.g., mortality) indicators remained high [35, 43, 46].

Increasing evidence solidly documents an emerging extent and burden of psycho-stimulant use and related harms in North America, including Canada, in recent years. This phenomenon represents both an extension or ‘resurgence’ of a psycho-stimulant crisis initially observed in the early years of the twenty-first century, as well as a ‘twin epidemic’ co-occurring – and likely related causally at least to some degree - with the longstanding and persistent ‘opioid crisis’ that has imposed extensive health and social harm burden across North America. On the individual use-level, a large extent of the ‘twin epidemic’ is unfolding in form of actual ‘co-use’ of psycho-stimulants and opioids, and a likely further elevated risk for adverse health (e.g., overdose/mortality) harm by use of either substance category alone (which is already extensive). A first important implication of this epidemiological situation is that both popular and scientific/specialist perspectives in North America urgently need to be updated and corrected towards acknowledging and focusing on this ‘twin epidemic’, rather than the outdated framing of a singular ‘opioid crisis’. A second crucial implication is  the need for efforts towards the broad-based development and implementation of efforts across the full range (e.g., prevention to treatment) of interventions that effectively aiming and addressing the epidemiological realities of the present co-use/‘twin-epidemic’ scenario. This is much easier advised, or said, than done. As shown, the current toolbox of therapeutic interventions, or even pragmatic public health-oriented measures options for psycho-stimulants is highly limited in availability and efficacy. Even available interventions for psycho-stimulants (e.g., supervised inhalation/consumption as an illustrative example) are commonly considered or applied as secondary or disadvantaged ‘add-on’ type of measure. Beyond, the epidemiological realities of the ‘twin epidemic’ requires intervention efforts that are both feasible and effective for persons with co-use of both substance types, which inevitably renders an even more formidable challenge. Whether ‘resurging’ or ‘twin’ epidemic (or realistically both) – the present scenario of the crisis psycho-stimulant use and harms is equally real and  active in Canada as it is in the US. It requires to be pulled from the silencing shadows of the ‘opioid crisis’, and  addressed with urgent action and progress for interventions. Otherwise, it is possible that the unprecedented health and social harm burdens experienced from and attributed to opioids in North America since the early 2000s will not only persist, but may overall continue to rise due to the increasing hazards and harms added by psycho-stimulants.