Researchers find 5 types of alcohol dependence

Alcohol dependence manifests itself in many ways, but patients with this problem have enough in common that they can be placed in five categories, according to a study published online June 26 by the journal, Drug and Alcohol Dependence. The authors hope that subtyping patients in this manner will lead to the discovery of genes that increase the risk for the disorder's specific variations and to treatments that may be more effective for particular individuals.

"Assuming that the subtyping holds up and meets the test of time, we hope to identify specific treatments for specific types of alcoholics," said Howard B. Moss, MD, lead author and associate director for clinical and translational research at the National Institute on Alcohol Abuse and Alcoholism. "Some may be more amenable to medications to treat alcohol dependence than others, and researchers might find this information useful as they're putting together trials for new agents to treat alcoholism."

Researchers analyzed the characteristics of 1,484 people participating in the National Epidemiologic Survey on Alcohol and Related Conditions who fit the criteria for alcohol dependence. This project, run by NIAAA, is a longitudinal survey of a representative sample of more than 43,000 people.

The analysis of those who fit the diagnosis for pathological drinking found that 31.5% could be considered "young adult" drinkers. People in this category imbibe less frequently than other alcoholics but, when they do, it is to excess. They are also more likely to be involved in dangerous drinking.

About 19.4% could be thought of as "functional" drinkers because they earn more than other types of alcoholics and are more likely to have college degrees. Another 18.8% were labeled as "intermediate familial" because they tend to have numerous relatives with this disorder as well as having other substance-use problems and mental health issues themselves.

Approximately 21.1% were considered "young antisocial" because they are most likely to start drinking young and have alcohol-related problems early. Lastly, 9.2% were called "chronic severe." They also are most likely to have other mental health issues, fit the Alcoholics Anonymous definition of alcoholism and have the lowest socioeconomic status.

Advancing the understanding

Experts praised this paper for demonstrating that those who fit the DSM-IV criteria for alcohol dependence do not fit any one stereotype.

"This study is significant as it may change the way that we understand alcohol-use disorders," said Michael Miller, MD, president of the American Society of Addiction Medicine. "It is dangerous and inappropriate to generalize one mental model of what 'an alcoholic' is and try to apply that to all people with alcoholism."

Also, these data drew kudos for being derived from a population-based sample. Previous studies have attempted to improve the classification of alcoholism by interviewing people from clinic settings, although numerous papers have found the majority who abuse alcohol never seek treatment or are unable to access medical care for this problem. For example, a study also using this survey's data published in the July Archives of General Psychiatry found that 12.5% of participants fit the definition for alcohol dependence at some point in their lives, but only 24.1% of that group had ever received treatment.

"Studying only clinical samples leaves out the majority of people who meet the criteria for alcohol dependence," said Dr. Miller.

The question researchers now face is how to use these classifications. Those behind this project hope they will lead to the discovery of the different treatment needs of each subtype along with the identification of genes associated with specific forms of alcohol abuse. This advance is particularly crucial since none of the gene candidates suspected of conferring additional risk for this disorder have proven to have much of an effect on the broad population of those with alcohol dependence. The hope is that these genes may turn out to exert more influence in the development of specific types of alcoholism, although experts cautioned that this classification system did need to be supported by other research.

"This is a very important first step to the development of genetic-based therapies. Ultimately, it could be very exciting if they can use this to come up with more targeted treatments," said Peter Friedmann, MD, MPH, a substance abuse health services researcher and associate professor of medicine and community health at Warren Alpert Medical School at Brown University in Providence, R.I. "But it needs to be replicated in another sample. There's still a lot we don't understand about the family of alcohol use disorders."

Other emerging questions surround the stability of these classifications and whether people switch from one to another. Do some young drinkers grow out of the behavior? Or do they move on to another class of alcoholism? Do those who are well-functioning shift to categories that involve more mental illness along with greater legal issues? And what about people who don't fit neatly into these subsets?

"We don't know for sure how people change or why they change. There may be markers, but we just don't know what they are yet," said Daniel Vinson, MD, MSPH, professor of family and community medicine at the University of Missouri-Columbia who has researched screening for alcohol problems in the primary care setting. "The five subtypes make sense to me, and this is another step forward in the understanding of this complex disorder. But I'm sure there are people who don't quite fit and fall between the cracks."

These issues are expected to be addressed by the project in the future.