Vol. 16, No. 6 November/December 1992
0145-6008/92/1606-1042$3.00/0 ALCOHOLISM: CLINICAL AND EXPERIMENTAL RESEARCH
Family History, Alcohol Use and Dependence Symptoms among Young Adults in the United States Thomas C. Harford, Douglas A. Parker, and Bridget F. Grant
Drawing upon data from the National Longitudinal Survey of young adults, this paper examines the effects of family history of alcoholism and current alcohol use by the young adults. A multivariate analysis of the data from the study indicates that there are both main and interaction effects of family history and current alcohol use on dependence symptoms among the young adults. Key Words: Alcoholism, Dependence, Family History.
HE IMPORTANCE OF genetic factors in alcoholism T has been suggested by family, twin, and adoption studies.'.' In a review of family studies, Cotton3 noted that the incidence of alcoholism was significantly higher among relatives of alcoholics than among relatives of nonalcoholics. With some exceptions, twin studies have found a greater risk for alcoholism in identical twins than in fraternal twin^.^,^ And adoption studies have found a risk of alcoholism among offspring of alcoholics that is several times greater than the risk among offspring of nonalcohohx6-* The effects of genetic and environmental factors can be disentangled by the design of adoption studies but such studies are expensive and time-consuming. The few adoption studies that have been completed provide the best evidence for a genetic factor in alcoholism, but the severity and extent of alcoholism among the biological parents in these studies may be different from that of the biological parents in the general population, which would limit the generalizability of the results.' As an alternative, family history studies have been conducted with samples from nonalcoholic populations even though the design of such studies does not allow investigators to disentangle genetic and environmental factors. Many of these studies have drawn upon convenience samples of volunteers or those in treatment that have yielded findings that cannot be generalized to the larger population, but recently investigators have begun to use random samples that produce findings that can be generalized. In the first examination of positive family history in the general population utilizing data from the 1979 From the Division of Biometry and Epidemiology, National Institute on Alcohol Abuse and Alcoholism, Rockville, Maryland (T.C.H., B.F.G.); and the Department of Sociology, California State University, Long Beach, California (D.A.P.). Received for publication March 10, 1992; accepted June 8, 1992 Reprint requests: Thomas C. Ha$ord, Division of Biometry and Epidemiology, Nationaf Institute on Alcohol Abuse and A fcoholism, Room 14C26, Parklawn Building, 5600 Fishers Lane, Rockville, MD 20857. Copyright 01992 by The Research Society on Alcoholism. 1042
National Drinking Practices Survey, Midanik reported the prevalence of alcoholism among first-degree relatives.lo In a subsequent analysis of the data from the 1979 national survey, Parker and Harford reported an increased risk of dependent problem drinking, marital disruption, and depressive symptoms among the adult children of alcoholics after adjustment for age, socioeconomic status, and race." The risk of -alcoholism appears to increase with the number of alcoholic relatives and their proximity to the subjects of the research.2 But investigators have argued that genetic influences account for only part of the risk, and that interactions between multiple genes and various environmental factors are necessary for the development of alcohol use disorder^.^,' One environmental factor, which has been hypothesized to increase that risk, is heavier consumption of a l c o h 0 1 . ' ~ ~ ~ ~ ' ~ Differential sensitivity to alcohol may increase the risk of developing alcoholism. SchuckitI4 reported that males with a positive family history of alcoholism may be less sensitive to the effect of ethanol (ie., exhibit less performance decrement), and thus may be less able to monitor and control their alcohol use. Other studies, however, have failed to find clear differences between the behavior of family history positive and negative drinkers. Vogel-Sprott and Chipperfield" found a greater sensitivity to alcohol among positive family history subjects. In examining the effects of parental alcoholism on marital disruption and depressive symptoms among the adult children in the national survey, Parker and Harford" controlled for the alcohol dependence of the adult children but not for their consumption of alcohol. Although an analysis of data from a later national survey found that alcohol intake and alcohol use disorders were strongly associated, particularly among younger men and women,I6 the question of whether there are effects of positive family history that are either separate from or interact with the current alcohol use of adult children is a question that remains to be addressed with general popu/ation data. Drawing upon data from the National Longitudinal Survey (NLS) of young adults, this paper examines the relationship between family history of alcoholism, current alcohol use, and alcohol dependence symptoms. In our analysis, we cannot disentangle genetic from environmental influences, but we can determine whether support can be found for the hypothesis that having both positive Alcohol Clrn Exp Res, Vol 16, No 6, 1992: pp 1042- 1046
1043
FAMllY HISTORY AND ALCOHOL DEPENDENCE
family history and greater alcohol use places adult men and women at elevated risk for symptoms of dependence. METHODS The NLS is a panel study that was initiated in 1979by the Department of Labor in order to study the transition of young persons into the labor force. The 1979 panel included 12,686 respondents between the ages of 14 and 21 as of January 1, 1979, and blacks, Hispanics, non-black and non-Hispanic economically disadvantaged youth, and youth in the military were ovenampled. The respondents have completed interviews each year since 1979 and approximately 82% of the original respondents remained in the study in 1988. In our examination of the relationship between family history, alcohol use, and dependence symptoms, we analyzed the dependence data from the sixth wave of the NLS in 1984 for the 10,123 respondents (aged 19-26) who described their family history of alcoholism in 1988. The data are weighted to adjust for different sampling and completion rates among the subgroups in the stratified probability sample.'' Dependence Symptoms
The alcohol dependence measure is based on the respondents' experiences of withdrawal (morning drinks, hand tremors), loss of control (inabilityto reduce drinking, fear ofbeing an alcoholic,difficulty stopping drinking before intoxication, breaking promises not to drink), and symptomatic behavior (gettingdrunk while drinking by oneself, having blackouts) during the year preceding their interviews. These self-reported experiences were summed to produce a score for dependence symptoms, which ranged from 0 to 8. In 1984, 32% of the men and 12% of the women in the study reported one or more dependence symptoms. Family History
Respondents were asked if any of their relatives had been alcoholics or problem drinkers at any time during their lives. Respondents were not provided with formal criteria of alcoholism or problem drinking and their reports were not validated by other sources. We do not know how the respondents decided that their relatives were alcoholics or problem drinkers. They may have based their judgments on difficulties experienced with parents rather than on the presence or absence of alcohol use disorders. Previous research has classified alcoholics on the basis of family history.'*-20Schuckit and Sweeney2O classified a sample of 864 young men, aged 21 to 25, into four mutually exclusive groups based on the distribution of alcoholism in their first- and second-degree relatives. Schuckit and Sweeney found that the highest number of alcoholic relatives was associated with the highest prevalence of alcohol-related problems among the men in the study, and the investigators suggested that alcoholism in multiple generations may express a relatively high genetic loading for the risk of developing alcoholism in the future. Whether such a family history reflects a genetic or an environmental influence (e.g., multiple generations of alcoholics might be found in a chronically disturbed extended family environment) cannot be determined here, but the classification can be used in order to examine the possibility of a genetic-environmental interaction involving family history and alcohol use. Following Schuckit and Sweeney,2"respondents were classified into four mutually exclusive groups; family history negative (FHN); famijy history positive involving alcoholism in only second-degree relatives (grandparents and other blood relatives) (FHPl); family history positive involving alcoholism in only first-degree relatives (parents and siblings) (FHP2); and family history positive involving alcoholism in both firstand second-degree relatives (FHP3). Three hundred twelve respondents who did not have alcoholic blood relatives but who were exposed to alcoholism through parental remarriage or adoption were excluded from the analysis.
Drinking Status
Respondents were asked whether they had ever consumed an alcoholic beverage and, if yes, whether they had consumed any alcoholic beverages during the past month. Abstainers were defined as never having used alcohol. Current drinkers were defined as consuming any amount of alcohol with any frequency during the past month. Noncurrent drinkers were defined as having consumed alcohol but not in the past month. Average Consuption
Our measure of the average number of drinks consumed during drinking days is based on self-reports concerning the number of days that the respondents consumed one, two, three, four, five, and six or more drinks during the month preceding their interviews in addition to reports concerning the total number of days that they had a drink during this period. Numbers of drinks were summed to yield the total number of drinks. Average consumption was obtained by dividing the total number of drinks by the total number of days alcohol was consumed in the past month. In order to assess the possibility of an interaction between alcohol use and family history, average consumption in drinks was recoded as follows: 0 = 0; 0.1-1.4 = I; 1.5-2.4 = 2; 2.5-3.4 = 3; 3.5-4.4 = 4; 4.5-5.4 = 5 ; and 5.5 or more = 6. Other Variables
Chronological age, education, marital status, and race were included in the analysis. Dummy variables were constructed for marital status: previously mamed (divorced, separated, or widowed), mamed and never mamed with the never married as the reference category. A dummy variable was also constructed for race where blacks are represented by 1s and the others are represented by 0s. The effects of these variables and the others were assessed in an analysis of variance. Approximately 20% of the cases in our multivariate analysis would be excluded because of missing data if family income were an additional covariate. We did, however, conduct an analysis with family income included as a covariate and the results from that multivariate analysis are essentially the same as those that are reported below.
RESULTS
In this national sample of young adults, 44% of the men and 52% of the women reported a positive family history of alcoholism. The distribution among the three groups is as follows: 2 1% of the men and 22% of the women had only second-degree relatives positive (FHPl), 14% of the men and 16% of the women had only first-degree.relatives positive (FHP2), and 9% of the men and 15% of the women had both first- and second-degree relatives positive (FHP3). Approximately 3% of the men and 4% of the women were abstainers, 17% of the men and 30% of the women were noncurrent drinkers, and 80% of the men and 66% of the women were current drinkers. Table 1 indicates that there are similar distributions of abstainers, noncurrent drinkers, and current drinkers across the family history groups. An analysis of variance was conducted in order to examine the impact of positive family history on average consumption of alcohol. Controlling for the effects of age, education, marital status, and race, the analysis indicates that family history is significantly associated with average consumption among both men and women as shown in Table 2. However, the unique variance in consumption
1044
HARFORD ET AL. Table I. Drinker Status by Family History of Alcoholism and Gender, in Percent' ~~
Men (N)
Abstainer Noncurrent drinker Current drinker
Women
FHN (2792)
FHPl (1045)
FHP2 (718)
FHP3 (481)
FHN (2472)
FHPl (1017)
FHP2 (857)
FHP3 (741)
4 16 80
1 20 79
2 15 82
3 14 82
6 30 64
4 29 67
3 30 67
30 69
1
* Percents are weighted figures and may not sum to 100 because of rounding errors; Ns are actual number of cases. The family history groups are as follows: FHN = Family history negative.
FHPl = Only second degree relatives positive. FHP2 = Only first degree relatives positive. FHP3 = First and second degree relatives positive. Table 2. Analysis of Variance of Average Alcohol Consumption by Family History and Demographic Factors Men df
Age Married Previously married Education Minority status Family history Error Total R Square
1 1 1
1 1 3 4898 4906 4.5
Women
Mean square 2.3 185.1 7.2 103.8 638.2 18.1 4.1
F-ratio
df
0.6 44.5' 1.7 24.V 153.6' 4.3'
1 1 1 1 1 3 4977 4985 9.9
Mean square 22.9 845.1 2.1 0.5 601.3 32.3 3.1
F-ratio 7.3' 268.4' 0.7 0.2 191.0' 10.3'
' p < 0 05.
accounted for by family history is less than 1% in both men and women. Average consumption in drinks is distributed in the following manner among the family history groups: 3.5 (FHN), 3.5 (FHPI), 3.6 (FHP2), and 3.7 (FHP3) among men; 2.6 (FHN), 2.6 (FHPI), 2.9 (FHP2), and 2.9 (FHP3) among women. In the Danish adoption study, Goodwin and his associates6 found that there was a possible genetic predisposition only for alcoholism and not also for heavier drinking6 Subsequent studies have also failed to find an association between positive family history and alcohol But all of these studies have had much smaller samples than the NLS sample used in the present analysis. These smaller samples might have made it more difficult to detect a genetic influence, which may be quite weak in terms of the variance accounted for. Another analysis of variance was conducted in order to assess the effects of family history and average consumption of alcohol on dependence symptoms. Since abstainers and noncurrent drinkers are not at risk for dependence symptoms, only the data for the current drinkers were included in the analysis. With the effects of age and the other covariates controlled, there are main effects of family history and average consumption among both men and women as Table 3 indicates. Although the variance accounted for by family history, alcohol consumption, and the covariates is 13%among the men and 12% among the women, the unique variance accounted for by average consumption is 7% for the men and 6% for the women, while that for family history is 2% for the men and I % for the women. There are also interaction effects of family history and average consumption on dependence symp-
toms among both men and women but the unique variance accounted for is approximately 1/2 of 1% for both men and women. Table 4 shows the effects of increasing consumption in each column of a family history group, and the effects of family history in each row of number of drinks consumed. In general, as alcohol consumption increases in each family history group, the means of dependence symptoms tend to increase; and, as the genetic loading increases (from family history negatives to family history positives with first- and second-degree relatives) at each level of alcohol consumption, the means for symptoms of dependence tend to increase. Interaction effects in the form of increased symptoms of dependence are displayed in the cells with both greater genetic loading and higher alcohol consumption. DISCUSSION
As others25have pointed out, the inheritance of susceptibility to alcohol use disorders implies only that there is a resemblance between parents and their offspring, not that the underlying mechanism involves genetic or environmental factors. Although we are unable to disentangle genetic from environmental influences in the data from the NLS, we do find support for the hypothesis that having positive family history and greater alcohol consumption places men and women at elevated risk for symptoms of dependence. Differences in sensitivity to alcohol may place offspring at risk for alcoholism. Newlin and Thomson26found that sons of alcoholic fathers had greater sensitization to alco-
FAMILY HISTORY AND ALCOHOL DEPENDENCE
1045
Table 3. Analysis of Variance of Alcohol Dependence Symptoms by Family History, Average Consumption and DemographicFactors
Men Mean square
df
Age Married Previously married Education Minority status Family history Average consumption FH x average consumption Error Total R Souare
8.1 28.5 12.6 69.3 33.4 51.9 78.9 5.6 1.7
1
1 1 1 1
3 5 15 3720 3748 12.8
Women
F-ratio
df
4.7 16.5' 7.3' 40.2* 19.3' 30.1' 45.8' 3.3'
1 1 1 1 1 3 5 15 2975 3003 11.9
Mean square
F-ratio
3.3 11.8 1.4 15.0 0.7 23.2 36.0 5.8 0.9
3.5 12.5' 1.5 15.8' 0.7 24.4' 37.9' 6.1'
Current drinkers only ' p < 0.05. Table 4. Adjusted Means for Dependence Symptoms by Gender, Average Consumption, and Family History'
Men Average consumption (in drinks) 0.1-1.4 1.5-2.4 2.5-3.4 3.5-4.4 4.5-5.4 5.5+
Women
FHN
FHPl
FHP2
FHP3
FHN
FHPl
FHPP
FHP3
0.24 0.47 0.71 0.73 1.14 0.86
0.43 0.60 0.59 1.11 1.47 1.05
0.41 0.61 1.04 1.29 1.26 1.60
0.53 0.85 0.76 1.54 2.03 1.85
0.09 0.23 0.38 0.37 0.68 0.54
0.18 0.33 0.48 0.96 0.51 0.84
0.09 0.45 0.36 0.80 0.94 0.56
0.19 0.27 0.80 0.90 0.99 1.90
' Current drinkers only. . AOe, - education, marital status and race are controlled. Each cell mean is based on more than 25 cases. The family history groups are as follows: FHN = Family history negative. FHPl = Only second degree relatives positive. FHP2 = Only first degree relatives positive. FHP3 = First and second degree relatives positive
hol while sons of nonalcoholic fathers exhibited greater tolerance. Newlin and Thomson acknowledged that further studies are needed in order to determine whether these findings are the result of greater sensitization among sons of alcoholics or greater tolerance among sons of nonalcoholics. The finding from our analysis that there is a significant interaction effect of family history and average consumption on dependence symptoms suggests that there is a greater sensitivity to alcohol among men and women with a positive rather than a negative family history of alcoholism. That our analysis disclosed a weak but significant relationship between positive family history and alcohol consumption may suggest that there is some continuity of a genetic influence along a continuum from abstainer to alcoholic. But the fact that other studies with smaller samples have not detected this continuity may also suggest that there is something not yet understood about the relationship between positive family history and the dependence symptoms (and impairments of social and occupational functioning due to alcohol) of the adult children in these other studies. Parker et al.,24in a reanalysis of the data from the 1979 National Drinking Practices Survey, found that almost all of the adult children who were classified as alcohol-dependent by a measure constructed to represent the alcohol dependence syndrome conceptualization27328 had experi-
enced both symptoms of dependence and impairments of social and occupational functioning such as losing a friend or a job because of drinking. Parker et al. also found that the group of adult sons that was influenced by positive family history was the group that had both dependence symptoms and impairments of social and occupational functioning related to alcohol. Parker et al. argue that adult children who have both dependence symptoms and social impairments related to alcohol should be given greater attention in further studies. Findings from previous analyses of general population survey data' 1,29,30 concerning the relationship of positive family history to dependence symptoms among offspring may have been distorted by the cross-sectional design of these surveys, which only affords an opportunity to obtain reports of family history and dependence symptoms at one point in time. Do respondents who report heavy drinking and alcohol dependence over-report the number of alcoholic relatives? Similarly, do respondents who deny alcohol problems also suppress reports of a positive family history of alcoholism? This design problem is not limited to self-reports in cross-sectional surveys, but extends to clinical studies of alcohol use as well. Many family studies of alcoholism draw upon biased and self-identifiedsamples of adult children of alcoholics. Reports from these samples may inflate the relationships between family history and dependence symptoms among adult children of alcoholics.
I046
HARFORD ET AL.
The design of a longitudinal survey such as the NLS of biological and cultural inheritance, in Gerson ES, Matthysse S, Breakeprovides the opportunity to obtain reports on family his- field XO, Ciaranello RD (eds): Genetic Research Strategies for Psychobiology and Psychiatry. Pacific Grove, CA, The Boxwood Press, 1981, tory at one point in time and to obtain reports on alcohol pp 319-330 consumption and dependence symptoms at another point 13. Kubicka L, Kozeny J, Roth Z Alcohol abuse and its psychosocial in time. The collection of these reports at different points correlates in sons of alcoholics as young men and in the general popuin time in the NLS may have minimized the potential for lation of young men in Prague. J Stud Alcohol 5 1:49-58, 1990 14. Schuckit MA: Ethanol-induced changes in body sway in men at response bias and for inflated estimates of the impact of a high alcoholism risk. Arch Gen Psychiatry 42:375-379, 1985 positive family history of alcoholism. 15. Vogel-Sprott M, Chipperfield B: Family history of problem drinkIt is more likely that the estimates of the impact of ing among young male social drinkers: Behavioral effects of alcohol. J family history are biased downward. Family history ac- Stud Alcohol 48:430-436, 1987 16. Grant BF, Harford T C The relationship between ethanol intake counted for only a small proportion of the variance (less than 3%) in alcohol dependence and there may have been and DSM-111 alcohol use disorders: A cross-perspectiveanalysis. J Subst Abust Treat 1:231-252, 1989 an attenuation of effects by unreliability in the reports of 17. McWilliams HA, Frankel M R The profile of American youth: family history. It is also possible that the effects of family Non-technical sampling report. National Opinion Research Center of history may be indirectly expressed through cognitive Chicago, unpublished paper 18. Alterman AI, Gerstley W, Goldstein G, Tarter RE: Comparisons functioning that is impaired and behavior that is impulsive or a n t i ~ o c i a l ~ or' ,may ~ ~ interact with such environmental of the cognitive functioning of familial and nonfamilial alcoholics. J Stud Alchol40:425-429, 1987 factors as low occupational or socioeconomic s t a t ~ s . ~ ~19. , ~Reed ~ R, Grant I, Adams KM: Family history of alcoholism does Future studies using general population surveys should not predict neuropsychological performance in alcoholics. Alcohol Clin explore the relationships between family history, alcohol Exp Res 11:340-344, 1987 20. Schuckit MA, Sweeney S: Substance use and mental health probconsumption, and dependence symptoms further by obtaining more detailed and elaborate data on family history lems among sons of alcoholics and controls. J Stud Alcohol 48528-534, 1987 of alcoholism and on the facets of psychological function2 I . Parker ES, Parker DA, Brody JA: The impact of fathers' drinking ing and socioeconomic status that may mediate the effects on cognitive functioning among social drinkers. in Galanter M (ed): of family history. Recent Developments in Alcoholism, vol 3. New York, Plenum Press, 1985, pp 227-240 REFERENCES 22. Alterman AI, Searles JS, Hall JG: Failure to find differences in I . Schuckit MA: Studies of populations at high risk for alcoholism. drinking behavior as a function of familial risk for alcoholism: a replication. J Abnorm Psychol 98:50-53, 1989 Psychiatr Dev 3:31-63, 1985 23. Engs RC: Family background of alcohol abuse and its relationship 2. Schuckit MA: A longitudinal study of children of alcoholics, in Galanter M (ed): Recent Developments in Alcoholism, vol9. New York, to alcohol consumption among college students: An unexpected finding. J Stud Alcohol 51:542-547, 1990 Plenum Press, 1991, pp 5-19 24. Parker DA, Harford TC, Levina M: Social constructionist and 3. Cotton NS: The familial incidence of alcoholism: A review. J epidemiological measures of alcohol dependence among adult children Stud Alcohol 4039-116, 1979 4. Schuckit MA: Twin studies on substance abuse: an overview, in of alcoholics in general population surveys. Unpublished manuscript, Gedda L, Paris P, Nance W (eds): Twin Research 3: Epidemiological 1990 25. Cloninger CR, Bohman M, Sigvardsson S, von Knomng A-L and Clinical Studies. New York, Alan R. Liss, 1981, pp 61-70 5. Murray RM, Gurling CC, Topham A, et al: Current genetic and Psychopathology in adopted-out children of alcoholics: The Stockholm adoption study. Pp. 37-5 I in Galanter M (ed): Recent Developments in biological approaches to alcoholism. Psychiatr Dev 2: 179-192, 1983 6. Goodwin DW, Schulsinger F, Hermansen L, et al: Alcohol prob- Alcoholism, vol 3. New York, Plenum Press, 1985, pp 37-5 1 26. Newlin DB, Thomson JB: Chronic tolerance and sensitization to lems in adoptees raised apart from alcoholic biological parents. Arch alcohol in sons of alcoholics. Alcohol Clin Exp Res 15:399-405, 199I Gen Psychiatry 28:238-243, 1973 27. Edwards G, Gross MM: Alcohol dependence: Provisional descrip7. Cadoret RJ, Cain CA, Grove WM: Development of alcoholism in adoptees raised apart from alcoholic biological relatives. Arch Gen tion of a clinical syndrome. Br Med J 1:1058-1061, 1976 28. Edwards G: The alcohol dependence syndrome: A concept as a Psychiatry 37;561-563, 1980 8. Cloninger C, Bohman M, Sigvardsson S: Inheritance of alcohol stimulus to enquiry. Br J Addict 81:171-183, 1986 29. Parker DA, Harford TC: Alcohol-related problems of children of abuse: Cross-fostering analysis of adopted men. Arch Gen Psychiatry heavy-drinking parents. J Stud Alcohol 48:265-268, 1987 38:861-868, 1981 30. Russell M, Cooper L, Frone MR: The influence of sociodemo9. Searles JS: The role of genetics in the pathogenesis of alcoholism. J Abnorm Psychol 97:153-167, 1988 graphic characteristics on familial alcohol problems: Data from a com10. Midanik L: Familial alcoholism and problem drinking in a na- munity sample. Alcohol Clin Exp Res 14:221-226, 1990 3 I . Knop J, Teasdale TW, Schulsinger F, Goodwin DW: A prospectional drinking practices survey. Addict Behav 8:133-141, 1983 1 1. Parker DA, Harford TC: Alcohol-related problems, marital dis- tive study of young men at high risk for alcoholism: Social behavior and ruption and depressive symptoms among adult children of alcohol abus achievement. J Stud Alcohol 46:273-278, 1985 sers in the United States. J Stud Alcohol 49:306-313, 1988 32. Harford TC: Antisocial behavior and alcohol abuse. Unpublished 12. Cloninger CR, Lewis C, Rice J, Reich T: Strategies for resolution manuscript, 1991
0145-6008/92/1606-1042$3.00/0 ALCOHOLISM: CLINICAL AND EXPERIMENTAL RESEARCH
Family History, Alcohol Use and Dependence Symptoms among Young Adults in the United States Thomas C. Harford, Douglas A. Parker, and Bridget F. Grant
Drawing upon data from the National Longitudinal Survey of young adults, this paper examines the effects of family history of alcoholism and current alcohol use by the young adults. A multivariate analysis of the data from the study indicates that there are both main and interaction effects of family history and current alcohol use on dependence symptoms among the young adults. Key Words: Alcoholism, Dependence, Family History.
HE IMPORTANCE OF genetic factors in alcoholism T has been suggested by family, twin, and adoption studies.'.' In a review of family studies, Cotton3 noted that the incidence of alcoholism was significantly higher among relatives of alcoholics than among relatives of nonalcoholics. With some exceptions, twin studies have found a greater risk for alcoholism in identical twins than in fraternal twin^.^,^ And adoption studies have found a risk of alcoholism among offspring of alcoholics that is several times greater than the risk among offspring of nonalcohohx6-* The effects of genetic and environmental factors can be disentangled by the design of adoption studies but such studies are expensive and time-consuming. The few adoption studies that have been completed provide the best evidence for a genetic factor in alcoholism, but the severity and extent of alcoholism among the biological parents in these studies may be different from that of the biological parents in the general population, which would limit the generalizability of the results.' As an alternative, family history studies have been conducted with samples from nonalcoholic populations even though the design of such studies does not allow investigators to disentangle genetic and environmental factors. Many of these studies have drawn upon convenience samples of volunteers or those in treatment that have yielded findings that cannot be generalized to the larger population, but recently investigators have begun to use random samples that produce findings that can be generalized. In the first examination of positive family history in the general population utilizing data from the 1979 From the Division of Biometry and Epidemiology, National Institute on Alcohol Abuse and Alcoholism, Rockville, Maryland (T.C.H., B.F.G.); and the Department of Sociology, California State University, Long Beach, California (D.A.P.). Received for publication March 10, 1992; accepted June 8, 1992 Reprint requests: Thomas C. Ha$ord, Division of Biometry and Epidemiology, Nationaf Institute on Alcohol Abuse and A fcoholism, Room 14C26, Parklawn Building, 5600 Fishers Lane, Rockville, MD 20857. Copyright 01992 by The Research Society on Alcoholism. 1042
National Drinking Practices Survey, Midanik reported the prevalence of alcoholism among first-degree relatives.lo In a subsequent analysis of the data from the 1979 national survey, Parker and Harford reported an increased risk of dependent problem drinking, marital disruption, and depressive symptoms among the adult children of alcoholics after adjustment for age, socioeconomic status, and race." The risk of -alcoholism appears to increase with the number of alcoholic relatives and their proximity to the subjects of the research.2 But investigators have argued that genetic influences account for only part of the risk, and that interactions between multiple genes and various environmental factors are necessary for the development of alcohol use disorder^.^,' One environmental factor, which has been hypothesized to increase that risk, is heavier consumption of a l c o h 0 1 . ' ~ ~ ~ ~ ' ~ Differential sensitivity to alcohol may increase the risk of developing alcoholism. SchuckitI4 reported that males with a positive family history of alcoholism may be less sensitive to the effect of ethanol (ie., exhibit less performance decrement), and thus may be less able to monitor and control their alcohol use. Other studies, however, have failed to find clear differences between the behavior of family history positive and negative drinkers. Vogel-Sprott and Chipperfield" found a greater sensitivity to alcohol among positive family history subjects. In examining the effects of parental alcoholism on marital disruption and depressive symptoms among the adult children in the national survey, Parker and Harford" controlled for the alcohol dependence of the adult children but not for their consumption of alcohol. Although an analysis of data from a later national survey found that alcohol intake and alcohol use disorders were strongly associated, particularly among younger men and women,I6 the question of whether there are effects of positive family history that are either separate from or interact with the current alcohol use of adult children is a question that remains to be addressed with general popu/ation data. Drawing upon data from the National Longitudinal Survey (NLS) of young adults, this paper examines the relationship between family history of alcoholism, current alcohol use, and alcohol dependence symptoms. In our analysis, we cannot disentangle genetic from environmental influences, but we can determine whether support can be found for the hypothesis that having both positive Alcohol Clrn Exp Res, Vol 16, No 6, 1992: pp 1042- 1046
1043
FAMllY HISTORY AND ALCOHOL DEPENDENCE
family history and greater alcohol use places adult men and women at elevated risk for symptoms of dependence. METHODS The NLS is a panel study that was initiated in 1979by the Department of Labor in order to study the transition of young persons into the labor force. The 1979 panel included 12,686 respondents between the ages of 14 and 21 as of January 1, 1979, and blacks, Hispanics, non-black and non-Hispanic economically disadvantaged youth, and youth in the military were ovenampled. The respondents have completed interviews each year since 1979 and approximately 82% of the original respondents remained in the study in 1988. In our examination of the relationship between family history, alcohol use, and dependence symptoms, we analyzed the dependence data from the sixth wave of the NLS in 1984 for the 10,123 respondents (aged 19-26) who described their family history of alcoholism in 1988. The data are weighted to adjust for different sampling and completion rates among the subgroups in the stratified probability sample.'' Dependence Symptoms
The alcohol dependence measure is based on the respondents' experiences of withdrawal (morning drinks, hand tremors), loss of control (inabilityto reduce drinking, fear ofbeing an alcoholic,difficulty stopping drinking before intoxication, breaking promises not to drink), and symptomatic behavior (gettingdrunk while drinking by oneself, having blackouts) during the year preceding their interviews. These self-reported experiences were summed to produce a score for dependence symptoms, which ranged from 0 to 8. In 1984, 32% of the men and 12% of the women in the study reported one or more dependence symptoms. Family History
Respondents were asked if any of their relatives had been alcoholics or problem drinkers at any time during their lives. Respondents were not provided with formal criteria of alcoholism or problem drinking and their reports were not validated by other sources. We do not know how the respondents decided that their relatives were alcoholics or problem drinkers. They may have based their judgments on difficulties experienced with parents rather than on the presence or absence of alcohol use disorders. Previous research has classified alcoholics on the basis of family history.'*-20Schuckit and Sweeney2O classified a sample of 864 young men, aged 21 to 25, into four mutually exclusive groups based on the distribution of alcoholism in their first- and second-degree relatives. Schuckit and Sweeney found that the highest number of alcoholic relatives was associated with the highest prevalence of alcohol-related problems among the men in the study, and the investigators suggested that alcoholism in multiple generations may express a relatively high genetic loading for the risk of developing alcoholism in the future. Whether such a family history reflects a genetic or an environmental influence (e.g., multiple generations of alcoholics might be found in a chronically disturbed extended family environment) cannot be determined here, but the classification can be used in order to examine the possibility of a genetic-environmental interaction involving family history and alcohol use. Following Schuckit and Sweeney,2"respondents were classified into four mutually exclusive groups; family history negative (FHN); famijy history positive involving alcoholism in only second-degree relatives (grandparents and other blood relatives) (FHPl); family history positive involving alcoholism in only first-degree relatives (parents and siblings) (FHP2); and family history positive involving alcoholism in both firstand second-degree relatives (FHP3). Three hundred twelve respondents who did not have alcoholic blood relatives but who were exposed to alcoholism through parental remarriage or adoption were excluded from the analysis.
Drinking Status
Respondents were asked whether they had ever consumed an alcoholic beverage and, if yes, whether they had consumed any alcoholic beverages during the past month. Abstainers were defined as never having used alcohol. Current drinkers were defined as consuming any amount of alcohol with any frequency during the past month. Noncurrent drinkers were defined as having consumed alcohol but not in the past month. Average Consuption
Our measure of the average number of drinks consumed during drinking days is based on self-reports concerning the number of days that the respondents consumed one, two, three, four, five, and six or more drinks during the month preceding their interviews in addition to reports concerning the total number of days that they had a drink during this period. Numbers of drinks were summed to yield the total number of drinks. Average consumption was obtained by dividing the total number of drinks by the total number of days alcohol was consumed in the past month. In order to assess the possibility of an interaction between alcohol use and family history, average consumption in drinks was recoded as follows: 0 = 0; 0.1-1.4 = I; 1.5-2.4 = 2; 2.5-3.4 = 3; 3.5-4.4 = 4; 4.5-5.4 = 5 ; and 5.5 or more = 6. Other Variables
Chronological age, education, marital status, and race were included in the analysis. Dummy variables were constructed for marital status: previously mamed (divorced, separated, or widowed), mamed and never mamed with the never married as the reference category. A dummy variable was also constructed for race where blacks are represented by 1s and the others are represented by 0s. The effects of these variables and the others were assessed in an analysis of variance. Approximately 20% of the cases in our multivariate analysis would be excluded because of missing data if family income were an additional covariate. We did, however, conduct an analysis with family income included as a covariate and the results from that multivariate analysis are essentially the same as those that are reported below.
RESULTS
In this national sample of young adults, 44% of the men and 52% of the women reported a positive family history of alcoholism. The distribution among the three groups is as follows: 2 1% of the men and 22% of the women had only second-degree relatives positive (FHPl), 14% of the men and 16% of the women had only first-degree.relatives positive (FHP2), and 9% of the men and 15% of the women had both first- and second-degree relatives positive (FHP3). Approximately 3% of the men and 4% of the women were abstainers, 17% of the men and 30% of the women were noncurrent drinkers, and 80% of the men and 66% of the women were current drinkers. Table 1 indicates that there are similar distributions of abstainers, noncurrent drinkers, and current drinkers across the family history groups. An analysis of variance was conducted in order to examine the impact of positive family history on average consumption of alcohol. Controlling for the effects of age, education, marital status, and race, the analysis indicates that family history is significantly associated with average consumption among both men and women as shown in Table 2. However, the unique variance in consumption
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HARFORD ET AL. Table I. Drinker Status by Family History of Alcoholism and Gender, in Percent' ~~
Men (N)
Abstainer Noncurrent drinker Current drinker
Women
FHN (2792)
FHPl (1045)
FHP2 (718)
FHP3 (481)
FHN (2472)
FHPl (1017)
FHP2 (857)
FHP3 (741)
4 16 80
1 20 79
2 15 82
3 14 82
6 30 64
4 29 67
3 30 67
30 69
1
* Percents are weighted figures and may not sum to 100 because of rounding errors; Ns are actual number of cases. The family history groups are as follows: FHN = Family history negative.
FHPl = Only second degree relatives positive. FHP2 = Only first degree relatives positive. FHP3 = First and second degree relatives positive. Table 2. Analysis of Variance of Average Alcohol Consumption by Family History and Demographic Factors Men df
Age Married Previously married Education Minority status Family history Error Total R Square
1 1 1
1 1 3 4898 4906 4.5
Women
Mean square 2.3 185.1 7.2 103.8 638.2 18.1 4.1
F-ratio
df
0.6 44.5' 1.7 24.V 153.6' 4.3'
1 1 1 1 1 3 4977 4985 9.9
Mean square 22.9 845.1 2.1 0.5 601.3 32.3 3.1
F-ratio 7.3' 268.4' 0.7 0.2 191.0' 10.3'
' p < 0 05.
accounted for by family history is less than 1% in both men and women. Average consumption in drinks is distributed in the following manner among the family history groups: 3.5 (FHN), 3.5 (FHPI), 3.6 (FHP2), and 3.7 (FHP3) among men; 2.6 (FHN), 2.6 (FHPI), 2.9 (FHP2), and 2.9 (FHP3) among women. In the Danish adoption study, Goodwin and his associates6 found that there was a possible genetic predisposition only for alcoholism and not also for heavier drinking6 Subsequent studies have also failed to find an association between positive family history and alcohol But all of these studies have had much smaller samples than the NLS sample used in the present analysis. These smaller samples might have made it more difficult to detect a genetic influence, which may be quite weak in terms of the variance accounted for. Another analysis of variance was conducted in order to assess the effects of family history and average consumption of alcohol on dependence symptoms. Since abstainers and noncurrent drinkers are not at risk for dependence symptoms, only the data for the current drinkers were included in the analysis. With the effects of age and the other covariates controlled, there are main effects of family history and average consumption among both men and women as Table 3 indicates. Although the variance accounted for by family history, alcohol consumption, and the covariates is 13%among the men and 12% among the women, the unique variance accounted for by average consumption is 7% for the men and 6% for the women, while that for family history is 2% for the men and I % for the women. There are also interaction effects of family history and average consumption on dependence symp-
toms among both men and women but the unique variance accounted for is approximately 1/2 of 1% for both men and women. Table 4 shows the effects of increasing consumption in each column of a family history group, and the effects of family history in each row of number of drinks consumed. In general, as alcohol consumption increases in each family history group, the means of dependence symptoms tend to increase; and, as the genetic loading increases (from family history negatives to family history positives with first- and second-degree relatives) at each level of alcohol consumption, the means for symptoms of dependence tend to increase. Interaction effects in the form of increased symptoms of dependence are displayed in the cells with both greater genetic loading and higher alcohol consumption. DISCUSSION
As others25have pointed out, the inheritance of susceptibility to alcohol use disorders implies only that there is a resemblance between parents and their offspring, not that the underlying mechanism involves genetic or environmental factors. Although we are unable to disentangle genetic from environmental influences in the data from the NLS, we do find support for the hypothesis that having positive family history and greater alcohol consumption places men and women at elevated risk for symptoms of dependence. Differences in sensitivity to alcohol may place offspring at risk for alcoholism. Newlin and Thomson26found that sons of alcoholic fathers had greater sensitization to alco-
FAMILY HISTORY AND ALCOHOL DEPENDENCE
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Table 3. Analysis of Variance of Alcohol Dependence Symptoms by Family History, Average Consumption and DemographicFactors
Men Mean square
df
Age Married Previously married Education Minority status Family history Average consumption FH x average consumption Error Total R Souare
8.1 28.5 12.6 69.3 33.4 51.9 78.9 5.6 1.7
1
1 1 1 1
3 5 15 3720 3748 12.8
Women
F-ratio
df
4.7 16.5' 7.3' 40.2* 19.3' 30.1' 45.8' 3.3'
1 1 1 1 1 3 5 15 2975 3003 11.9
Mean square
F-ratio
3.3 11.8 1.4 15.0 0.7 23.2 36.0 5.8 0.9
3.5 12.5' 1.5 15.8' 0.7 24.4' 37.9' 6.1'
Current drinkers only ' p < 0.05. Table 4. Adjusted Means for Dependence Symptoms by Gender, Average Consumption, and Family History'
Men Average consumption (in drinks) 0.1-1.4 1.5-2.4 2.5-3.4 3.5-4.4 4.5-5.4 5.5+
Women
FHN
FHPl
FHP2
FHP3
FHN
FHPl
FHPP
FHP3
0.24 0.47 0.71 0.73 1.14 0.86
0.43 0.60 0.59 1.11 1.47 1.05
0.41 0.61 1.04 1.29 1.26 1.60
0.53 0.85 0.76 1.54 2.03 1.85
0.09 0.23 0.38 0.37 0.68 0.54
0.18 0.33 0.48 0.96 0.51 0.84
0.09 0.45 0.36 0.80 0.94 0.56
0.19 0.27 0.80 0.90 0.99 1.90
' Current drinkers only. . AOe, - education, marital status and race are controlled. Each cell mean is based on more than 25 cases. The family history groups are as follows: FHN = Family history negative. FHPl = Only second degree relatives positive. FHP2 = Only first degree relatives positive. FHP3 = First and second degree relatives positive
hol while sons of nonalcoholic fathers exhibited greater tolerance. Newlin and Thomson acknowledged that further studies are needed in order to determine whether these findings are the result of greater sensitization among sons of alcoholics or greater tolerance among sons of nonalcoholics. The finding from our analysis that there is a significant interaction effect of family history and average consumption on dependence symptoms suggests that there is a greater sensitivity to alcohol among men and women with a positive rather than a negative family history of alcoholism. That our analysis disclosed a weak but significant relationship between positive family history and alcohol consumption may suggest that there is some continuity of a genetic influence along a continuum from abstainer to alcoholic. But the fact that other studies with smaller samples have not detected this continuity may also suggest that there is something not yet understood about the relationship between positive family history and the dependence symptoms (and impairments of social and occupational functioning due to alcohol) of the adult children in these other studies. Parker et al.,24in a reanalysis of the data from the 1979 National Drinking Practices Survey, found that almost all of the adult children who were classified as alcohol-dependent by a measure constructed to represent the alcohol dependence syndrome conceptualization27328 had experi-
enced both symptoms of dependence and impairments of social and occupational functioning such as losing a friend or a job because of drinking. Parker et al. also found that the group of adult sons that was influenced by positive family history was the group that had both dependence symptoms and impairments of social and occupational functioning related to alcohol. Parker et al. argue that adult children who have both dependence symptoms and social impairments related to alcohol should be given greater attention in further studies. Findings from previous analyses of general population survey data' 1,29,30 concerning the relationship of positive family history to dependence symptoms among offspring may have been distorted by the cross-sectional design of these surveys, which only affords an opportunity to obtain reports of family history and dependence symptoms at one point in time. Do respondents who report heavy drinking and alcohol dependence over-report the number of alcoholic relatives? Similarly, do respondents who deny alcohol problems also suppress reports of a positive family history of alcoholism? This design problem is not limited to self-reports in cross-sectional surveys, but extends to clinical studies of alcohol use as well. Many family studies of alcoholism draw upon biased and self-identifiedsamples of adult children of alcoholics. Reports from these samples may inflate the relationships between family history and dependence symptoms among adult children of alcoholics.
I046
HARFORD ET AL.
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