About 18% of adults experiencing homelessness have a chronic substance use disorder, according to federal point-in-time counts. That’s roughly six times the rate of severe substance use disorder in the general population (about 3%), but it also means the large majority of people without housing do not have a diagnosed addiction. The real picture is more nuanced than either extreme of the debate suggests.
What the Numbers Actually Show
The 18% figure comes from HUD’s annual point-in-time count, which surveys people in shelters and on the streets on a single night. It captures those with a chronic, identified substance use disorder, not casual or occasional use. A broader look at drug use patterns tells a different story than addiction rates alone.
A large UCSF study found that about 37% of people experiencing homelessness reported regular drug use in the prior six months. Around 65% said they had used illicit drugs regularly (at least three times a week) at some point in their lives. And 25% had never used drugs at all. So depending on whether you’re asking about current use, lifetime use, or clinical addiction, the number shifts dramatically, anywhere from one in four having zero drug history to roughly two in three having used regularly at some point.
Which Came First: Drugs or Homelessness?
One of the most common assumptions is that drug use causes homelessness. For some people, that’s true. About 42% of those surveyed in the UCSF study said they began using drugs regularly before they lost housing for the first time. But 23% said their regular drug use started after they became homeless. That’s a meaningful split. For nearly a quarter of people who use drugs while homeless, the addiction developed in the context of life on the streets, not before it.
This distinction matters because it shapes what kinds of interventions actually work. Treating addiction alone won’t solve homelessness for people whose drug use began as a coping mechanism after they lost stable housing. For that group, housing itself is part of the treatment.
Mental Health and Substance Use Together
Between 10% and 20% of people experiencing homelessness have what clinicians call a dual diagnosis: a serious mental illness combined with a substance use disorder. This group faces some of the steepest barriers to recovery because each condition makes the other harder to treat. Someone dealing with untreated psychosis or severe depression is more likely to self-medicate with drugs or alcohol, and ongoing substance use makes mental health symptoms worse.
This overlap also helps explain why this population is disproportionately visible. People with co-occurring mental illness and addiction are more likely to be unsheltered, meaning they’re the individuals the public most commonly encounters on sidewalks and in encampments. That visibility can skew the perception of how common addiction is across the entire homeless population.
Overdose Is the Leading Cause of Death
Even though most people experiencing homelessness don’t have a substance use disorder, drug overdose is still the single deadliest risk for those who do use. In Los Angeles County, drug and alcohol overdose accounted for 45% of all deaths among unhoused individuals in 2023. Of those overdose deaths, more than 70% involved fentanyl.
The concentration of fentanyl in the illicit drug supply has made any drug use far more dangerous than it was even five years ago. Someone using drugs occasionally or recreationally faces a much higher risk of fatal overdose than they would have a decade ago, which is one reason overdose deaths among homeless populations surged before beginning to plateau in 2022 and 2023.
Young People Face Different Patterns
Among homeless youth specifically, the numbers look somewhat different. Nearly 60% of young people experiencing homelessness reported drug use in one national study, but only about 20% described themselves as having a drug addiction, and 13% reported an alcohol addiction. The gap between use and addiction is important. Many young people on the streets use substances without developing a clinical dependency, though the risks of escalation are high given the instability of their living situations.
Why Estimates Vary So Widely
If you search this topic, you’ll find numbers ranging from 18% to over 60%, and none of them are necessarily wrong. They’re measuring different things. The 18% figure counts people with a diagnosed, chronic substance use disorder. The 37% figure captures anyone using drugs regularly in the past six months. The 65% figure includes anyone who ever used drugs regularly at any point in their life, including years or decades ago.
Survey methods matter too. Point-in-time counts rely on outreach workers identifying substance use disorders during brief encounters, which likely undercounts. Self-reported surveys can overcounted or undercount depending on how questions are framed and how comfortable respondents feel disclosing. The homeless population itself is also not static. On any given night, the mix of people in shelters and on the streets includes individuals in short-term crises (job loss, eviction, domestic violence) alongside people who have been unhoused for years. These groups have very different relationships with substance use.
The most accurate way to think about it: roughly one in five people experiencing homelessness has a serious, ongoing substance use disorder. A larger share has used drugs at some point. And about one in four has never used drugs at all.