One of the most common misconceptions about the unhoused population as a whole is that most of the unhoused population is experiencing a substance use disorder. This is a toxic misconception and simply untrue of the entire population. The biggest reason people lose their housing isn’t addiction; it’s the price of housing.
The research tells the true story of why people are unhoused. In the largest study of its kind in decades, the UCSF California Statewide Study of People Experiencing Homelessness found that less than half of those unhoused regularly used illicit drugs. As the study’s lead researcher put it, “most people who are homeless aren’t using drugs regularly,” according to UCSF.
We want to pause for a second here because we don’t want to give the impression that substance use disorder is not active in this population; it is like many other populations. However, the important distinction is that not everyone who is unhoused found themselves in this situation due to addiction. And by far, not everyone who has a substance use disorder becomes unhoused.
The Leading Factor
The U.S. Government Accountability Office, a federal watchdog, found that every $100 increase in a community’s median rent is tied to a roughly 9% jump in homelessness. The pattern repeats: when rent climbs, more people end up without a home because they’ve been priced out.
When we combine rising housing costs with the fact that there simply aren’t enough affordable places to live, the country is short 7.1 million rental homes that the lowest-income renters can actually afford, according to the National Alliance to End Homelessness. When there aren’t enough affordable homes, people get left out of housing, a basic human right.
The Map Tells the Story
When researchers Gregg Colburn and Clayton Aldren compared cities across the country, they found that the places with the worst homelessness weren’t the ones with the most drug use or mental illness. They were the ones with the highest rents and the tightest housing markets. Their book says it right in the title: homelessness is a housing problem.
This data breaks the common misconception that substance use disorder is the leading cause of homelessness. Homelessness actually tends to be lower where poverty is higher, according to Colburn and Aldern. Those personal struggles didn’t explain why a city like Seattle has so much more homelessness than a city like Chicago. Their research points to two simple housing numbers: how high the rent is and how few apartments sit empty and available. When rent is steep, and there’s nowhere open to move, people fall through the cracks, no matter how hard they’re working to hold on.
There’s even a number for the moment things start to break. Researchers at Zillow pinpointed a tipping point: once households in a community spend more than 32% of their income on rent, homelessness starts to climb faster. It’s a simple line in the sand; cross it, and more people can’t keep up. Plenty of American cities are already well past that 32% mark, which is exactly why rent, not addiction, is the number to watch.
Furthermore, and closer to home, it is important to remember the ALICE (asset-limited, income-constrained, working) rate here in La Porte County. Of the county’s 43,030 households, 43% fall below the ALICE threshold, meaning they face significant financial hardship and struggle to afford basic necessities like rent. These are individuals who work yet do not qualify for assistance. These individuals are most at risk of becoming unhoused and of paying above that 32% mark.
Why It Matters
Addiction and mental illness are real, and some people do face these issues while unhoused. However, they’re threads in the story, not the cause of it. The true cause of homelessness is the lack of affordable housing.
Most of our unhoused neighbors don’t have a drug problem; they have a rent problem. This rent problem has a solution: a home. Housing is the answer.
Other Blog Posts in the Housing First Series:
What The Research Actually Shows About Housing First
Housing First, Explained: The Simple Idea That Stability Starts With a Home
Sources
1. University of California, San Francisco, “How Common Is Illegal Drug Use Among People Who Are Homeless?” (California Statewide Study of People Experiencing Homelessness; published in JAMA, Feb. 19, 2025). ucsf.edu
2. U.S. Government Accountability Office, “Homelessness: Better HUD Oversight of Data Collection Could Improve Estimates of Homeless Population,” GAO-20-433 (2020). gao.gov
3. National Alliance to End Homelessness, “What Causes Homelessness: A Shortage of Affordable Housing.” endhomelessness.org
4. Gregg Colburn and Clayton Page Aldern, Homelessness Is a Housing Problem: How Structural Factors Explain U.S. Patterns (University of California Press, 2022). ucpress.edu
5. Zillow Economic Research (Chris Glynn et al.), as summarized by the World Economic Forum, “Here’s a way of predicting when homelessness is likely to rise” — https://www.weforum.org/stories/2019/01/here-s-a-way-of-predicting-when-homelessness-is-likely-to-rise/
