What are some common explanations for heroin overdoses? 

Heroin overdose is a pressing issue, with about 1 to 3% of heroin users dying from an overdose every year. In the United States in 2011, almost 11,000 people died from a heroin overdose. Accurate explanations are needed for why some addicts overdose so work can be done to reduce heroin-related deaths. One reason often given for these deaths is that the addict had taken other drugs in coordination with heroin. Heroin is a central nervous system depressant drug, so its combination with other depressants (like alcohol) can sometimes be fatal. However, most cases of heroin overdose are not due to drug mixing. 

A second reason cited frequently as a cause for a heroin overdose is that addicts lose tolerance after abstaining from using the drug for a long period. According to this theory, when the addicts eventually use heroin again the drug will have a much stronger effect on their body, potentially resulting in overdose. Yet, there is evidence to suggest that drug tolerance in humans does not deteriorate after months or even years of abstaining from use. This can be shown using segmental hair analysis because temporal patterns of drug use can be seen by examining an individual’s hair. Based on the hair strands of recently deceased overdose victims, researchers have found that there is no link between recent abstinence and overdose. 

What is the heroin overdose mystery? 

The heroin overdose mystery refers to the fact that there is often no obvious reason for why an addict overdoses on a specific day. Post-mortem procedures for overdose victims include measuring the amount of morphine in the blood (because morphine is the metabolized version of heroin). It has been found that morphine levels in the blood of overdose victims are often — about 75% of the time — no higher than other heroin users who have not overdosed. Considering this, it is concluded that the causal factor of death by heroin overdose is not typically the actual amount of the drug in the body. In fact, in many cases, it has been noted that the overdose victim used the same amount of heroin the day before, and it was non-fatal. Simply put, many (if not the majority) of heroin “overdoses” are not true pharmacological overdoses. There is clearly another factor at play, and many theories have been suggested for what exactly that factor is; this article argues that it is due to the Pavlovian conditioning of drug users. 

What is the Pavlovian conditioning explanation for heroin overdoses? 

The theory of Pavlovian conditioning in the context of heroin overdoses is based on the finding that most overdoses occur in drug-administration environments that are new to the addict. In Pavlovian conditioning, there is a conditional stimulus, a conditional response, an unconditional stimulus, and an unconditional response. Concerning drug use, the unconditional stimulus is the drug itself, while the unconditional response is the homeostatic counter-response to the pharmacological effect of the drug on one’s body (for example, if the drug decreases heart rate, the homeostatic response would increase heart rate to counter the effect of the drug). The conditional stimulus, on the other hand, is the setting in which the drug is administered, and the conditional response is again the homeostatic counter-response, which this time occurs in anticipation of the drug’s effect. These homeostatic counter-responses to the drug lower its effects and lead to acute tolerance (a decrease of the drug’s effect during the span of one drug administration). 

Chronic tolerance is obtained after repeated use of a drug and is mediated by the conditional, drug-effect-decreasing response. This conditional-response can be life-saving. When in novel drug-administration settings, chronic tolerance will not be displayed due to an absence of the conditional response. The body will not produce the conditional (drug-counteracting) response because it is not paired with the conditional stimulus (the typical drug-administration setting). Therefore, whether or not a heroin user suffers an overdose is highly contingent on whether the drug is being administered in a familiar or novel environment. This effect has been replicated several times in experiments with both animals and humans. 

The rate of death from drug overdoses in the United States is about one and a half times as high as is the rate of death from automobile accidents. Heroin is the drug most commonly to blame for these overdoses. Most heroin users are unaware that ingesting the drug in an unfamiliar environment is very dangerous. Certainly, mere knowledge of this fact could save many lives.