The Vowles Study[1] — Cited Widely[2] as Supposed Proof of Opioid Addiction Rates — Is Misleading & Unreliable

Following criticism of the Vowles study soon after its publication in 2015,[3] Vowles himself acknowledged:

“… we agree that opioid use is not inherently risky, most patients seem to use opioids without misuse or addiction, and access to effective interventions (including pain-relieving medications, but also including rehabilitative interventions aiming to restore effective functioning) is paramount.”

On the importance of clear comparisons and a methodologically rigorous empirical literature in evaluating opioid use in chronic pain: a response to Scholten and Henningfield, August 2015[4]

Inaccurate Premise:
Addiction rate among chronic opioid patients is 8-12%


Only 5 of the 38 studies Vowles reviewed were designed to evaluate addiction.


The study samples Vowles reviewed are biased because they are drawn from high-risk populations, such as patients already suspected of misuse or patients from VA medical centers, and thus are not representative samples of the overall population.


The underlying studies employed inconsistent definitions of “addiction” and “misuse,” and included criteria such as opioid tolerance, which is not a valid measure of addiction.


The studies used by Vowles had varying follow-up windows, and no study truly evaluates lifetime odds of addiction.

Vowles admits the weaknesses of the study, but ignores the elephant in the room:

An addiction rate of 8-12% would mean that up to 16 million Americans are clinically addicted, which is nearly 6-9x the estimated 2 million Americans with opioid use disorder.

Addiction Specialist Testifies to Inaccuracy of Vowles Study: “It’s of zero assistance.”[5]

“But there was a big hole in the study, Tucker testified: It was a survey of 38 studies on opioid use disorder prevalence, not incidence. Prevalence is how many people in the population have a condition at a given time, whereas incidence is how many new people get the condition. The takeaway for Tucker was that Vowles far overstated the tendency of opioid prescriptions to cause opioid use disorder.

Dr. Douglas Tucker, June 30, 2021[5]