US Overdose Mortality Saw First Drop Below the Jalal-Burke Exponential Growth Curve in 2024

US overdose mortality rates dropped below the historically established Jalal-Burke exponential growth curve for the first time in 2024, driven by a sharp decline in fentanyl-related deaths despite a rising share of stimulant and xylazine-involved fatalities.

The Gist

The Big Picture: The "Runaway Train" Finally Stopped

Imagine the United States' drug overdose crisis as a runaway train speeding down a track. For decades (from 1979 to 2016), this train didn't just speed up; it accelerated exponentially. Scientists named this pattern the "Jalal-Burke Curve." It was so predictable that if you drew a line on a graph, the train stuck to it perfectly, like a train on a magnetic track.

Usually, when things get worse (like during the pandemic), the train would jump above the track, going even faster. But it had never gone below the track.

The News: In 2024, for the first time in history, the train didn't just slow down; it actually dropped off the track entirely. The number of overdose deaths fell so sharply that it went below the predicted "exponential growth" line for the first time since 2001.

The Four "Waves" of the Crisis

To understand why this happened, the authors look at the crisis in four distinct "waves," like a surfer riding different sets of waves:

1. Wave 1 (Prescription Pills): The first big wave was caused by legal painkillers. This wave has already crashed and is receding.
2. Wave 2 (Heroin): The second wave was heroin. This one also peaked and is going down.
3. Wave 3 (Fentanyl alone): The third wave was pure, super-potent fentanyl. This peaked recently and is starting to drop.
4. Wave 4 (Fentanyl + Stimulants): The current wave is a dangerous mix of fentanyl and drugs like meth or cocaine. This is the big news: This wave finally peaked in 2024 and started to turn downward.

The "New Villains" in the Story

While the main "villains" (fentanyl and opioids) are finally losing their grip, the story isn't over yet. The paper warns that while the main monster is shrinking, some new, smaller monsters are growing.

• The "Stimulant" Problem: Deaths involving methamphetamine and cocaine (without fentanyl) are actually rising. It's like the main fire is being put out, but the embers are spreading to a new part of the house.
• The "Xylazine" Problem: A new drug called Xylazine (often mixed with fentanyl) is becoming more common. It's a "zombie drug" that causes severe skin wounds. While the total number of deaths is dropping, the share of deaths involving this nasty drug is going up.

Why Did the Train Slow Down?

The authors don't know exactly why the train stopped, but they have a few theories:

• The "Susceptible" Pool: Maybe the people most likely to die from these drugs have already passed away, leaving a population that is slightly more resilient (a sad but real statistical concept).
• Better Tools: We have more "fire extinguishers" now. More people have access to Naloxone (Narcan), which reverses overdoses, and more people are getting treatment for addiction.
• Changing Habits: People might be smoking drugs instead of injecting them, which can sometimes be safer.
• Supply Shifts: The "potency" of the drugs might be fluctuating, or the supply chain is getting disrupted.

The Bottom Line

This is great news, but we shouldn't pop the champagne just yet.

Think of it like a pandemic. We finally saw the first day where new cases dropped below the predicted curve. It's a massive victory. However, the virus hasn't disappeared; it just mutated. The US drug crisis is shifting. The "easy" exponential growth has stopped, but we are now facing a more complex mix of drugs.

The Takeaway: The worst part of the "runaway train" era might be over, but the track is still dangerous. We need to keep our eyes on the new threats (meth, cocaine, and Xylazine) and keep our safety gear (Narcan and treatment) ready, because if we aren't careful, the train could start speeding up again.

Technical Summary

1. Problem Statement

For nearly four decades (1979–2016), US drug overdose mortality rates followed a remarkably consistent exponential growth curve, as described by Jalal and Burke (2018). This model demonstrated an $R^2$ of 0.99, suggesting a mathematically predictable trajectory of increasing deaths. While subsequent analyses noted that the curve experienced temporary spikes above the predicted trend due to supply shocks and the COVID-19 pandemic, no study had previously demonstrated a large-magnitude, sustained deviation below this exponential growth projection.

With preliminary data indicating a sharp decline in overdose deaths during 2023–2024, the authors sought to determine if this represented a return to the historical baseline or a fundamental structural break in the trajectory of the US drug crisis.

2. Methodology

The study utilized a retrospective, ecological analysis of national mortality data to recreate and test the Jalal-Burke model against updated data.

• Data Sources:
  • Timeframe: January 1979 to December 2024.
  • Primary Source: National Vital Statistics System (NVSS) via CDC WONDER.
  • Pre-1999 Data: Sourced from a secondary publication (Compton et al., 2022) as CDC WONDER does not host pre-1999 records.
  • Definition of Overdose: Broadly defined using ICD-10 codes for unintentional (X40–X44), suicide (X60–X64), homicide (X85), and undetermined intent (Y10–Y14). This broader definition aligns with recent federal literature, though accidental overdoses still constitute ~92% of total deaths.
• Statistical Modeling:
  • Curve Fitting: A bivariate linear regression model was fitted to the natural log of overdose death rates per 100,000 population against the year of occurrence, using data from 1979 to 2016.
  • Projection: The resulting model was linearly extrapolated to predict rates for 2017–2024.
  • Confidence Intervals: 95% confidence intervals (CIs) were calculated assuming a normal distribution to establish the bounds of the "expected" exponential growth.
• Substance Stratification:
  • Deaths were analyzed by specific substance involvement: Prescription opioids, Heroin, Synthetic opioids (Fentanyl), Cocaine, Psychostimulants (Methamphetamine), and Xylazine.
  • Wave Analysis: The authors applied the "four-wave" paradigm (Ciccarone, 2021) to track the rise and fall of specific drug classes:
    1. Prescription opioids
    2. Heroin
    3. Fentanyl (without stimulants)
    4. Fentanyl (with stimulants)

3. Key Contributions

• First Empirical Evidence of a "Below-Curve" Deviation: The study provides the first quantitative evidence that US overdose mortality has dropped significantly below the long-standing Jalal-Burke exponential growth projection.
• Substance-Specific Decomposition: The paper dissects the aggregate decline, identifying that the drop is driven primarily by the reversal of the "fourth wave" (fentanyl + stimulants), while other segments (stimulants without fentanyl, xylazine) continue to rise.
• Re-evaluation of Crisis Trajectory: It challenges the assumption that the crisis is merely a temporary fluctuation, suggesting a potential structural shift toward a logistic (S-shaped) curve or a bell-shaped decline, though the permanence of this trend remains to be confirmed.

4. Key Results

• Overall Mortality Trend:
  • 2020–2023: Overdose rates remained elevated above the exponential curve, peaking at approximately 32 deaths per 100,000.
  • 2024: Rates fell precipitously to 23.7 deaths per 100,000.
  • Significance: This 2024 rate fell below the lower bound of the 95% CI of the Jalal-Burke projection (24.98 per 100,000) for the first time since 2001, and represents the first large-magnitude dip below the curve in the dataset's history.
• Substance-Specific Trends (2024):
  • Declining Waves: All four waves of the crisis have reached inflection points and are declining. Specifically, deaths involving fentanyl with stimulants (Wave 4) began to reverse in 2024.
  • Rising/Static Threats:
    • Stimulants without Fentanyl: Deaths involving methamphetamine and cocaine (without fentanyl) increased. In 2024, the rate of stimulant-only deaths (5.64/100k) nearly equaled fentanyl-only deaths (5.87/100k).
    • Xylazine: Deaths involving xylazine held steady (~1.89/100k) but represent an increasing proportion of fentanyl-involved deaths.
• Magnitude of Decline: The drop from ~32/100k (2021–2023) to 23.7/100k (2024) is a substantial reduction, though the absolute rate remains ~400% higher than the year 2000.

5. Significance and Implications

• Public Health Milestone: The deviation below the exponential curve suggests that the mechanisms driving the crisis (e.g., susceptible populations, drug potency, use practices) may be shifting. Potential drivers include increased access to naloxone/Medication for Opioid Use Disorder (MOUD), shifts in drug use practices (e.g., smoking vs. injecting), and changes in fentanyl potency.
• Shifting Landscape: While the overall trend is positive, the crisis is evolving. The rising share of deaths involving stimulants and xylazine indicates that the nature of the threat is changing. These substances are associated with different non-fatal health harms (e.g., severe skin lesions from xylazine, cardiovascular issues from stimulants), necessitating tailored interventions beyond traditional opioid-focused strategies.
• Future Outlook: The authors caution that this trend could be temporary. The underlying structural conditions (social, economic, political) that fueled the exponential growth remain. If novel synthetic drugs (e.g., nitazenes) proliferate, the curve could revert to exponential growth.
• Global Relevance: The US experience with the rapid transition from agricultural to synthetic drugs serves as a critical case study for other nations currently experiencing initial increases in overdose deaths due to synthetic opioids.

Conclusion: The paper concludes that while the 2024 data represents a historic and positive deviation from decades of exponential growth, the US drug crisis is not "solved." The focus must shift to addressing the rising mortality from stimulants and xylazine while monitoring for potential future surges driven by new synthetic threats.