HEALTH HORIZONS : PSYCHOLOGY : Hitting the Bottle : Recent studies indicate it cannot be taken for granted that the problem of alcohol abuse stems from genetic factors.
What does it mean when someone drinks too much? Is hitting the bottle every day best viewed as a private decision, a reflection of hard times, a response to peer pressure, a sin, or an inherited disease? Any of these accounts might help to make sense of alcohol abuse, but only one--the last--is currently fashionable. Echoing the position of much of the mental health establishment and Alcoholics Anonymous, nearly nine of every 10 Americans think alcoholism is a disease, according to a Gallup poll.
Steven Paul, who directs all in-house research for the National Institute of Mental Health, says: “There is very good evidence that genetic factors play an important role. Certain forms of alcoholism seem to be highly inherited.”
But a growing number of recent studies are challenging the assumption that excessive drinking can best be explained as an illness that simply happens to people. “AA wants it to be a genetic disease, and people seem overly willing to accept the hypothesis of genetic influence,” says Robert Plomin, one of the country’s leading behavioral geneticists. But “the evidence isn’t all that convincing.”
The traditional wisdom has been that the best way to predict who will abuse alcohol is to look for a family history of such abuse--are children of alcoholics especially likely to drink heavily themselves? But several new studies raise doubts. In 1989, for example, a group of researchers in Philadelphia surveyed 83 male college students and found no differences in the amount or frequency of drinking between the sons of alcoholics and the sons of non-alcoholics.
Even more remarkable were the results of a study at the University of Michigan published last year. An examination of hundreds of offspring of men with drinking problems found that nearly two-thirds drank very little or not at all. The implication is not only that many such sons and daughters had an aversion to their fathers’ destructive habit but that they were able to choose moderation. “There is a strong, predictable generational pattern among the adult offspring ‘of heavy drinkers’ of . . . drinking less than their parents,” Dr. Ernest Harburg and his colleagues wrote in the Journal of Studies on Alcohol.
But even in cases where parent and child do share a tendency to drink to excess, it cannot be taken for granted that the problem is inherited. Junior’s similarity to dad may be due to sharing his home rather than his genes. This is why some researchers have conducted twin studies: to try to tease apart nature and nurture. If identical (monozygotic or MZ) twins are more likely than fraternal (dizygotic or DZ) twins to share the tendency to abuse liquor--which some studies have found--this is taken to mean the problem has a genetic component. The reason: MZs are genetically the same while DZs (like other siblings) share only about half their genes.
But not all studies have discovered such a gap. In a new report, University of Minnesota research psychologist Matt McGue and his colleagues found little difference between the likelihood that two MZs, on the one hand, and two DZs, on the other, would share a diagnosis of alcohol abuse or dependence. There was no evidence at all, moreover, to support a genetic explanation for the drinking habits of women or older men.
Regardless of their findings, though, twin studies have a problem: MZ twins share more of their environment than DZs, not just more of their genes. They’re raised more similarly, they spend more time with each other, and, as a 1988 study confirmed, the frequency of their contact is directly related to the similarity of their personalities.
According to research conducted in London, the greater similarity in drinking patterns between two MZs is substantially reduced once the tendency for identical twins to live together is factored in. In fact, fraternal twins who lived together were more likely to share a drinking problem than identical twins who lived apart. Once again, this is unsettling news for those who think that genes explain who abuses alcohol.
Another recently published paper adds further doubt. Taking a careful second look at the Swedish study that is most often cited to support the idea that alcoholism is inherited, psychologist John Searles of the University of Pennsylvania found that a peculiar criterion had been used to decide who qualified as a heavy abuser. When he analyzed the data again, he found that “environmental pressures . . . are substantially more important in determining alcohol abuse than are genetic factors.”
More recently, Kenneth Blum at the University of Texas, Ernest Noble at UCLA, and their colleagues announced that they had demonstrated a genetic contribution to alcoholism without doing a twin study. Following a path taken by other researchers, they conducted a “linkage” study in the laboratory to try to locate a particular gene that corresponds to the appearance of the disorder.
In April, 1990, they announced they had found it. After looking at the brain tissue of 70 deceased subjects (half of whom had been alcoholics), Blum and Noble said a particular gene appeared in 24 of the alcoholics but in only seven of the non-alcoholics. Newspapers across the country trumpeted the news--even though previous claims to have found a gene linked to schizophrenia and manic-depressive illness, respectively, had to be retracted over the last few years.
Sure enough, a team of researchers at the National Institute on Alcohol Abuse and Alcoholism (NIAAA) reported later that year that they were unable to replicate those results. Pointing out that Blum and Noble’s alcoholic brains had suspiciously low rates of the gene in question, they went on to show no difference in their own study. Last July, Blum and Noble struck back, claiming to have replicated their original findings and faulting the NIAAA group for excluding subjects with severe alcoholism. That controversy will likely continue for some time.
But despite their disagreement with Blum and Noble, the NIAAA researchers share the commonly accepted view and have written that “studies of twins, families and adopted children have indicated that genetic predisposition is significant in determining the risk for alcoholism.”
On the other hand, even researchers who insist that genes do play a role generally add that drinking is profoundly affected by one’s social and family environment, and the choices one makes--which means that the popular belief that some individuals are powerless over alcohol finds very little scientific support. Even Robert Cloninger of Washington University in St. Louis, a leading champion of the genetic position, has written that “major changes in social attitudes about drinking styles can change dramatically the prevalence of alcohol abuse regardless of genetic predisposition.”
The nature of that genetic predisposition--if it does exist--is also widely misunderstood. Students of the subject, including UCLA’s Noble, point out that there is almost certainly no gene just for alcohol abuse. “No geneticist claims that you inherit an inability to control your drinking--that doesn’t make sense genetically,” says Stanton Peele, a psychologist whose books on the subject include “Diseasing of America.” If genetics plays any role, it probably has to do with a person’s general inclination to act impulsively in seeking pleasure.
Nor have scientists found any proof that some people inherit an inability to metabolize alcohol efficiently and therefore become alcoholics. Two University of Colorado researchers reported in 1987 that people with a close relative who was an alcoholic were no different from other people “on alcohol metabolism, on sensitivity and acute tolerance to alcohol across several behavioral measures, or on perceived intoxication.”
Peele cites evidence to debunk still other myths on the subject. Most problem drinkers outgrow their tendency to abuse alcohol, or stop drinking on their own--meaning that alcoholism isn’t always a progressive disorder or one that requires a particular kind of treatment. And some former abusers manage to cut down their intake to an occasional drink--suggesting that quitting cold turkey isn’t necessary for everyone.
The current climate in our culture is ‘dominated by the view that alcoholism is a biologically determined medical disease,’ McGue and his colleagues have written. That may be part of the reason that NIAAA will be spending about $25 million during the first half of the 1990s to look specifically for a genetic basis rather than to investigate the social and economic forces that might lead to excessive drinking.
But the fact is, McGue and his colleagues continued, that “serious questions remain concerning the consistency of the empirical support for the existence of a genetic influence on alcoholism.” While McGue thinks genes will turn out to be related somehow to a risk for alcoholism, he adds that as far as the idea that alcohol abuse is simply a genetic disease is concerned, “The public has been sold a bill of goods.”
