Association between problematic internet use and depressive symptoms among individuals at high-risk of cannabis use disorder: a cross-sectional study in Quebec (Canada).

In our ever-changing world, pandemics will continue to pose a substantial risk to the well-being of our societies. While we cannot predict when or how the next crisis will emerge, its arrival appears inevitable because pathogens and societies coevolve: emerging infectious diseases drive societies to adapt through new technology, medicine, and preventive measures, thereby applying developmental pressure and prompting pathogen selection and ongoing evolution., , , , As a result, no two pandemics are identical. Each pandemic possesses unique characteristics defined by, e.g., its transmission routes, clinical manifestations, and societal impacts. Yet, whether hidden deep down or visible in plain sight, fundamental similarities exist in how outbreaks unfold and can be controlled. These similarities arise from recurring epidemiological, behavioral, and societal dynamics that shape the spread of infectious diseases across contexts. Because these “mechanisms” are grounded in natural laws and the structure of our biology and society, they are likely to remain relevant in future pandemics even when the pathogen itself is novel. Importantly, these mechanisms reflect fundamental principles that can inform public health decision-making even before detailed quantitative evidence becomes available. Because they capture fundamental properties of disease spread and societal response, they remain valuable under substantial uncertainty, including when the characteristics of a novel pathogen are still only partially understood. In this paper, we therefore compile and synthesize core mechanisms of pandemics across disciplines, many of which are familiar to specialists but less accessible to decision-makers outside those fields, and present them in a form accessible to readers involved in pandemic preparedness and decision-making, including policymakers, public health practitioners, and interdisciplinary researchers. We refer to them as the mechanics of pandemics. Whether an outbreak escalates into a pandemic depends on the characteristics of the pathogen and the society in which it spreads, encompassing behavior, governance, and technological capabilities., , Although definitions vary across the literature, here we define a pandemic as an epidemic that has spread across multiple countries or continents, typically affecting a large proportion of the population. Based on lessons from recent pandemics, some fundamental epidemiological and transmission principles have become widely recognized, such as the initial exponential growth of cases. At the same time, outbreaks are shaped by dynamic social and behavioral responses, such as changing risk perception and solidarity circles. These mechanisms and others will be discussed in this paper. While they can be considered individually, pandemics emerge from their interaction, and we therefore also discuss how these mechanisms reinforce or counteract one another in practice. To obtain a broader perspective on the mechanisms that will shape our understanding of the next pandemic, we invited experts who work at the interface of epidemiology, sociology, physics, and public health to each distill a specific mechanism underlying disease transmission, control, or prevention. The contributions were iteratively reviewed, edited, and discussed. Rather than advancing a single disciplinary perspective, this paper aims to integrate complementary insights from multiple fields into a coherent conceptual synthesis. Importantly, the work is not intended as a unified predictive model; instead, the mechanisms are presented as conceptual principles rather than empirically calibrated predictions. Our examples are not intended to be exhaustive; rather, they synthesize expert perspectives and lessons learned from recent pandemics, focusing on the fundamental aspects that can guide our understanding and mitigation of future pandemics.