Causes & Mechanisms
To analyze overdose deaths from a public health perspective, it is essential to understand the underlying causes and mechanisms, much like epidemiologists study the transmission of a disease. An overdose is not merely an event but the culmination of a hazardous process. The “hazard” is the substance or combination of substances; the “vulnerability” includes individual factors like addiction, co-occurring mental health disorders, and lack of social support; and “exposure” relates to the availability and accessibility of these substances, whether through prescription or illicit markets.
The primary mechanism in many overdose deaths is central nervous system (CNS) depression. The central nervous system, comprising the brain and spinal cord, controls essential life functions, including breathing and heart rate. Many drugs, including opioids (like oxycodone, heroin, and fentanyl), benzodiazepines (like Xanax and Valium), and alcohol, are CNS depressants. When taken in high doses or in combination, their effects multiply, slowing down bodily functions to a critical, and often fatal, level. The respiratory drive is suppressed, leading to oxygen deprivation, brain damage, and death.
A recurring theme in many of these tragic stories is polypharmacy, which is the simultaneous use of multiple drugs to treat a single ailment or condition. In the context of overdose, it often refers to the mixing of different classes of drugs, which can have a synergistic and deadly effect. For example, combining an opioid with a benzodiazepine exponentially increases the risk of respiratory depression compared to taking either drug alone. These combinations are sometimes prescribed by unknowing physicians, procured from multiple doctors, or mixed without knowledge of their interactive dangers.
The overdose crisis can be viewed as a “slow-moving disaster,” an ongoing event with a cumulative toll far exceeding many natural disasters. It is an epidemic characterized by waves, from the over-prescription of opioid painkillers in the 1990s and 2000s, to the subsequent rise in heroin use, and most recently, the catastrophic impact of illicitly manufactured synthetic opioids like fentanyl. This public health emergency requires a coordinated response, much like any other mass casualty event. Public health information is available from agencies like the CDC and the WHO.
