A Review on Fentanyl and The Neuroscientific Roots of Criminal Behaviour: Forensic and Legal Reflections

Abstract

Background: The global diffusion of illicitly manufactured fentanyl represents a critical intersection between neuroscience, law, and public health. Originally developed as a potent analgesic in the XX century, fentanyl’s low production cost, chemical adaptability, and high lethality have enabled its rapid proliferation through transnational criminal networks. While North America remains the epicenter of the crisis, with synthetic opioids accounting for the majority of overdose deaths, recent evidence indicates the gradual expansion of fentanyl and its analogues into Europe, where emerging threats include nitazenes and xylazine-adulterated compounds. Methods: This study adopts a multidisciplinary approach combining neuroscientific, criminological, and legal perspectives to analyze the roots and repercussions of fentanyl use and distribution. Through a systematic review of biomedical and legal literature, the research outlines the neurobiological mechanisms underlying opioid dependence, particularly the role of craving and impaired reward circuitry involving the mesolimbic dopaminergic system. Results: These findings reveal structural and functional brain alterations that significantly affect volitional control, thereby challenging the traditional legal assumption of free will as a prerequisite for culpability. Epidemiological data from 2019–2025 demonstrate a continuous rise in fentanyl-related mortality, particularly among adolescents and first-time users exposed to adulterated substances. Conclusions: Although harm-reduction strategies, such as naloxone distribution, fentanyl test strips, and medication-assisted treatment, have yielded measurable benefits, they remain insufficient to counter the evolving complexity of synthetic opioid markets. Overall, the findings underscore the urgent need to align legal and criminal policy frameworks with neuroscientific evidence, promoting a balanced paradigm that integrates public health, justice, and human rights in addressing the global fentanyl crisis.