24th November 2021
Currently, addiction theories pivot on a shared substrate of dopaminergic transmission; in other words, the wanting/liking systems of the brain. Substances which ‘hijack’ dopamine systems are addictive, due to their effects of heightened pleasure. A common narrative around the persistent use of such substances is centred upon the attempt to reach the same intensity as that first experienced. Clinically, this is termed tolerance, a concept well explained by the altered sensitivity of dopaminergic pathways. However, further nuances of addiction are left unexplained by our dopamine-based theories.
Pathology and environment are well connected in other areas of disease, but not addiction. We have embedded the role of the environment in depression (where natural light is implicated), Alzheimer’s (where personal relationships are protective), and heart disease, in which stress is a risk factor. Similar considerations are yet to make their way to form clinical understandings of addiction. This is despite growing evidence for an ‘environmentally cued double dissociation’ between stimulant and sedative drug use; sedative drugs appear to be preferred in home environments, whilst stimulant drugs are favoured outside. These trends have been demonstrated by placing drug users in fMRIs, through patient reporting, and rodent studies. However, COVID-19 offered a unique opportunity to bridge the moral ground between lab-based experiments with rats and drug-free brain scanning; with the imposing of restrictions, changes to drug use could be used to corroborate highly controlled animal studies.
Over the summer, streams of drug-use data concerning wastewater metabolites, overdoses (OD) related hospital admissions, alcohol consumption, drug demand, and clinical reports were analysed, confirming the messy picture of drug use both during and after lockdown. Headlines around the intensifying opioid crisis peppered newspapers between coronavirus updates and coincided with CDC reports of accelerated OD related deaths in the US. This was mirrored in Canada too, with a 60% increase in overdoses following lockdown implementation. Within clinical spaces, reports from medics in addiction-related services emphasised increased alcohol and pharmaceutical opioid consumption during restrictions. User surveys reiterated this picture of increasing sedative use.
If we look at acquisition, alcohol sales increased internationally following announcements of lockdowns. Monitoring illicit drug sales was less easy, yet not impossible; the dark markets ‘Hydra’ and ‘Cannazon’ saw increased traffic. Whilst prices remained stable for sedative drugs, bulk-buy offers for stimulant drugs indicated a drop in demand.
Regular testing for drug metabolites in wastewater across EU cities has taken place for years. During COVID-19, a drastic reduction was observed for cocaine and MDMA use, despite year-on-year upward trends. Drug and service users bolstered this reduction in stimulant use through self-reporting and hair analysis. Furthermore, clinician reports found that the most drastic reductions were in cocaine and amphetamine use, confirming the ‘home’ side of the environmentally cued double dissociation.
The results of drug trends under this new norm have been mirrored by ‘outside of the home’ experimentation in labs. Stimulant use has returned to, and in some cases exceeded, pre-lockdown levels. Sedative use has remained elevated – most notably with the onset of polydrug use involving benzodiazepines. Although these results do not tidily fit into the double-dissociation expected by animal models, they still raise questions concerning the simplicity of our dopaminergic theories.
A wealth of experimental data from global surveys has shown that both cognitive narratives and emotional valence shape drug related behaviours. By missing these elements from our explanations of addiction, we are potentially excluding a fundamental aspect of substance misuse disorders. Indeed, if we are to develop effective support for individuals, we must integrate such aspects into a more holistic, theoretical, and practical view of addiction which more accurately reflects the complexity of their illness.
Before embarking on the MSc Translational Neuroscience course here at Imperial College London, Sarah studied at the University of Sussex, earning a degree in Neuroscience and Cognitive Science. She is interested in pursuing a PhD in her field and graduate medical school.