For every three months during the study, participants drank an average of 8 percent fewer drinks on their heaviest drinking days.
They also had fewer instances of delirium tremens, a life-threatening form of alcohol withdrawal.
The findings were published in the American Journal of Public Health.
Housing for chronically homeless people usually comes with many conditions, including abstinence from drugs and alcohol and compliance with psychiatric and substance abuse treatment. But such requirements can become barriers to staying in housing.
"These individuals have multiple medical, psychiatric and substance abuse problems, and housing that requires them to give up their belongings, adhere to curfews, stop drinking and commit to treatment all at once is setting them up to fail. The result is that we are relegating some of the most vulnerable people in our community to a life on the streets," said Susan Collins, lead author and University of Washington research assistant professor of psychiatry and behavioral sciences.
Because they are unable to cope with the rules, they often do not qualify for housing or are asked to leave. Once back on the street, they cost taxpayers' money through use of emergency room visits, shelter and sobering center stays, arrests and jail bookings.
In response, an approach called project-based Housing First has been developed by the Downtown Emergency Service Center, a Seattle-based housing agency. Project-based Housing First provides immediate, permanent and supportive housing to chronically homeless people within a single housing project. It is considered "low-barrier" because it removes some of the traditional barriers to housing, such as abstinence from alcohol.
The idea behind it is that if chronically homeless people are provided with stable, permanent housing, then their medical, psychiatric and substance abuse problems will become more manageable.
Downtown Emergency Service Center's 1811 Eastlake housing project is the first project-based Housing First model in the United States to be scientifically studied. Residents agree to spend 30 percent of their income - if they have any - on rent, and in return they are provided with permanent housing and social services.
An earlier study published in the Journal of the American Medical Association found that, in its first year of operation, this housing project saved Seattle taxpayers more than $4 million in costs from publicly funded services. The new study shows that drinking also decreases.
"A lot of people believe in the 'enabling hypothesis' - that allowing homeless, alcohol-dependent individuals to drink in their homes will enable them to drink more, and their drinking will spiral out of control," Collins said. "But instead what we found are across-the-board decreases in alcohol consumption and problems."
Health also improved. Residents reporting recent bouts of delirium tremens dropped by more than half over the two-year study, from 65 percent to 23 percent.
In the study:
- 94 percent of the 95 participants were men and most were white (40 percent) or American Indian/Alaska Native (27 percent).
- The average number of drinks consumed on the heaviest drinking day of the month decreased from 40 to 26 across two years, a decrease of 35 percent.
- The median number of drinks, a more accurate view of drinking patterns for this study's participants, showed a change from 20 to 12 drinks per typical drinking day - a 40 percent drop.
- By the end of one year, 80 percent of participants remained in the study. That was reduced to 79 percent after 18 months and 61 percent after two years. Severity of drinking and demographic variables were ruled out as reasons why participants left the study.
People tend to think that chronically homeless people with severe alcohol problems are unable to control themselves or monitor their drinking, Collins said, but instead this study shows that they are "human beings who are capable of change if they are given the same chance as the rest of us."