SIGNIFICANT SOURCES
OTHERS AS CORROBORATIVE FOR PROBLEM DRINKERS
WILLIAMR. MILLER*, V. LLOYD CRAWFORDand CHERYLA. TAYLOR University
of New Mexico
Ahstrati-Self-reported alcohol consumption data from clients in four treatment outcome studies other” collaterals. Overall were compared with corroborative data obtained from “significant product-moment correlations were strong and positive, supporting the validity of self-report. Approximately equal numbers of collaterals overestimated and underestimated clients’ own reports. Intercorrelation increased with repeated interviews.
The validity of self-reports of problem drinkers is a controversial issue directly affecting design and interpretation of treatment outcome research. In a frequently cited study Summers (1970) interviewed 15 male alcoholic inpatients at admission and again after two weeks of hospitalization. She found that on the average patients changed their answers to nearly half of 14 structured questions in her interview. She concluded that “drinking history cannot be assumed valid and therefore cannot be used in the evaluation of the effect of treatment (p. 974)” In response to this questioning of the validity of self-report of problem drinkers some studies have attempted to obtain corroborative data from various sources. Miller et al. (1974) used random in uiuo breath alcohol tests to confirm treatment outcome. Sobell et al. (1974) checked alcoholics’ self-reported arrest records against official records and found an overall product-moment correlation of 0.65. Still other investigators have interviewed “significant others” (e.g. friends, relatives, employers) to obtain corroborative data. Using a 20-item drinking history questionnaire Guze et al. (1963) found an overall agreement of 85% between alcoholics and their collaterals, although they omitted items regarding quantity and frequency of alcohol consumption because of the inability of significant others to provide these data. Although not reporting specific correlations, Sobell & Sobell (1972) found “excellent agreement” between self-report and collateral report of their clients’ daily drinking dispositions, a more specific measure of alcohol consumption. These latter studies generally support the validity of self-reported data from problem drinkers, at least when corroborative data are obtained. These studies have also indicated that when discrepancies exist between client and collateral reports, most often the client’s own data are less favorable (i.e. higher alcohol consumption, more severe drinking history). The first quantitative data relating problem drinkers’ estimates of their alcohol consumption to similar estimates obtained from significant others were reported by McCrady et al. (1977). Using consumption indices derived from Cahalan’s (1970) , Quantity-Frequency Index and from the Alcohol Use Questionnaire (Horn et al., 1973) they found product-moment correlations ranging from 0.34 to 0.65 between self- and spouse reports at various assessment points. Their data likewise indicated that a majority of spouses underestimated rather than overestimated clients’ self-reported alcohol consumption. The present report provides cumulative conspection data from four treatment outcome studies with problem drinkers. METHOD
Data presented in this report represent the combined findings from four comparative outcome studies of controlled drinking therapies (Miller, 1978; Miller et al., 1976, 1977; *Requests for reprints should be sent to William Mexico, Albuquerque, NM 87131, U.S.A.
R. Miller,
67
Department
of Psychology,
University
of New
68
WILLIAMR. MILLER,V. LLOYDCRAWFORDand CHERYLA. TAYLOR Table 1. Descriptive intake data regarding clients treated in studies 1-4
Total N Mean age Mean education Mean annual income (Total Family) Mean years of drinking Mean years of problem drinking % Male clients % Married clients Mean MAST Score?
Study lA*
Study lB*
Study 2
Study 3
Study 4
29 37.3 15.6 $14,703 23.9 10.7 62.8% 39.0% 18.4
17 35.9 11.9 $8226 19.6 7.7 82.4% 35.3”/ 9.1
31 39.0 15.0 $15,448 23.5 8.5 74.2% 64.7% 18.4
28 44.8 14.4 $14,000 28.5 8.6 64.3% 67.9% 15.5
40 45.4 15.8 $23,384 29.2 10.5 62.5% 70.0% 18.3
* Study I included clients from two sources: those self-referred (IA) and those referred by the courts following conviction for driving while intoxicated (1B). 3 Mean score on the Michigan Alcoholism Screening Test. All mean scores are well above the alcoholism cutoff score prescribed by Seizer (1971).
Miller & Taylor, 1978). (A brief summary of the first three studies has been provided by Miller, 1977). Descriptive intake data from the 145 clients treated in these studies are reported in Table 1, with data reported separately for each of the four studies. Clients’ self-reported drinking was assessed in each study by standardized interviewing’ procedures outlined by Marlatt (1976). Alcohol consumption data were converted into Standardized Ethanol Content (SEC) units, with 1 SEC = 0.5 oz (15 ml) of absolute ethanol (Miller, 1978). Each client was asked to provide the names of at least 2 and preferably 3 significant others who could provide corroborative observational reports of clients’ alcohol consumption. These collaterals were interviewed by telephone using parallel standardized procedures in each study, and every attempt was made to obtain quantitative data to compare with self-reports. We succeeded in interviewing an average of 1.72 collaterals per client and obtained 1.41 quantitative estimates of alcohol consumption per case. In each study client and collateral interviews were completed at intake, treatment termination, and 3 month follow-up. In cases where more than one collateral estimate was obtained, the higher (less favorable) report was always used. When avail-
Table 2. Self-report and highest collateral report of clients’ alcohol consumption at intake, treatment termination, and 3 month follow-up Intake Nt
Self-report Mean alcohol consumption (SEC Units) Standard deviation Collateral report Mean alcohol consumption (SEC Units) Standard deviation % Collaterals overestimating Mean overestimate “/, Collaterals underestimating Mean underestimate “i, Exact matches Correlationsj Study 1 Study 2 Study 3 Study 4 Overall
127
Termination 131
Follow-up 128
54.8
17.5
18.1
43.7
18.0
19.8
48.3
18.1
20.5
33.5 489, + 19.3 49% - 32.0 35; 0.06 0.64**
0.46* 0.41’ 0.48**
23.8 33% + 16.0 45% - 10.6 220; 0.47** 0.80** 0.42 0.59** 0.66**
27.2 36”; + 16.3 387; -8.8 26”,b 0.74** 0.92** 0.84** 0.68** 0.79**
t N = number of clients from all four studies for whom both self-report and collateral report were available. $ Correlation = Pearson product-moment correlation between self-report and highest collateral report for all available pairs. * P < 0.05. ** P < 0.01.
Significant
others
as corroborative
sources
69
able, data from clients who dropped out of treatment were also included in the analyses for the present report. RESULTS
The relationship between client and collateral reports can be seen in Table 2. All correlations between the two data sources were positive, ranging from 0.06 to 0.92. Approximately equal numbers of collaterals overestimated and underestimated client reports. DISCUSSION
Data from these four studies generally support the validity of clients’ self-report of drinking behavior. In all studies correlations were positive, and change score trends in self-report data were reflected in collateral data as well. Several factors may account for the wide range of correlation coefficients. The outlying lowest value (r = 0.06) was obtained from intake interviews of Study 1, where several unusual conditions prevailed. At this point only we relied upon the personnel of a court clinic to obtain collateral reports for court-referred clients. For all other studies and interview times, our research staff collected all data. The staff was also less accustomed to the interviewing procedures at the outset. Finally, Study 1 contained the lowest percentage of married clients, thus reducing the availability of one of the best collateral sources, the spouse. These conditions probably contributed to the outlying and nonsignificant value observed at intake in Study 1, where we also obtained the lowest percentage of collateral reports for clients. A general trend toward higher correlation coefficients with increased interviewer experience can be seen in spite of decreased variance among scores at later interviews. The same basic research staff conducted Study 1 and the subsequent Study 2. New interviewers collected data throughout Study 3, and yet another staff in Study 4. In addition to increased interviewer skill, increased honesty of reporting parties and/or increased awareness of clients’ drinking by collaterals may have contributed to rising correlation coefficients. The increase in exact matches between self- and collateral reports can be accounted for in part by the increasing number of clients who were totally abstaining at termination and at follow-up. The fact that our collateral reports almost as often overestimated as underestimated selfreports (in contrast to findings of previous research) may be attributed to our use of the highest collateral report when more than one was available. It is unclear whether accuracy of self-report data would be maintained if clients were unaware that collaterals would be contacted. Accuracy of report may also have been improved by the nature of this population, consisting (except in Study 1) primarily of self-referred individuals not publicly identified as alcoholics. The absolute accuracy of collaterals might be questioned as well, and could be checked against more objective data sources such as in vivo breath tests. Finally, these results, obtained from clinics where the goal of treatment was controlled drinking, may not be directly generalizable to treatment settings where total abstinence is emphasized, especially because evidence of physiological addiction served to exclude clients from participation in the controlled drinking programs evaluated in these studies (Miller & Caddy, 1977). Clarification of these issues remains for future research.
REFERENCES Cahalan, D. Problem Drinkers, a national survey. San Francisco: Jossey-Bass, 1970. Guze, S. B., Tuason, V. B., Stewart, M. A. & Picken, B. The drinking history: A by subjects and their relatives. Quarterly Journal of Studies on Alcohol, 1963. 24, Horn, J., Wanberg, K. W., Wright, J. & Foster, F. M. The Alcohol Use Questionnaire. Mental Health Center, 1973. Marlatt, G. A. The Drinking Profile: A questionnaire for the behavioral assessment Mash & L. G. Terdal (Eds). Behacior Therapy Assessment: Diagnosis, Design und Springer. 1976.
comparison
of reports
249-260.
Denver:
Fort
of alcoholism. Eculuation.
Logan In E. J. York:
New
70
WILLIAM R. MILLER, V. LLOYD CRAWFORD and CHERYL A. TAYLOR
McCrady. B. S.. Paolina. T. J., Jr, & Longabaugh. R. Correspondence between problem drinker and spouse report of drinking behavior and impairment. Paper presented at the NATO International Conference on Experimental and Behavioral Approaches to Alcoholism, OS. Norway, September, 1977. Miller. P. M., Hersen. M.. Eisler. R. M. & Watts. J. G. Contingent reinforcement of lowered blood/alcohol levels in an outpatient chronic alcoholic. Behuaiour Rcseurch and Thrrapy, 1974, 12, 261-263. Miller. W. R. Behavioral self-control training in the treatment of problem drinkers. In R. B. Stuart (Ed.). Bchuriorul Srlf-Munugtwwt: Strutqirs and Ourcor~s. New York: Brunner/Mazel. 1977. Miller. W. R. Behavioral treatment of problem drinkers: A comparative outcome study of three controlled drinking therapies. Journal of Consultiny and Clinicul Psycholoyy, 1978, 46, 74-86. Miller. W. R. & Caddy, G. R. Abstinence and controlled drinking in the treatment of problem drinkers. Journtrl of Studivson Akohol, 1977, 38, 9861003. Miller. W. R. & Taylor. C. A. Relative effectiveness of bibliotherapy. individual and group self-control training in the treatment of problem drinkers. Unpublished manuscript, University of New Mexico, 1978. Miller. W. R.. Gribskov. C. & Mortell. R. Etfectiveness of a self-control manual for problem drinkers with and without therapist contact. Unpublished manuscript. University of Oregon. 1976. Miller, W. R.. Pechacek. T. F. & Hamburg. S. Group behavior therapy for problem drinkers. Unpublished manuscript. Palo Alto Veterans Administration Hospital, 1977. Selzcr. M. L. The Michigan Alcoholism Screening Test: The quest for a new diagnostic instrument. American Journtrl of’ Psychiufry. 1971, 127, 1653-1658. Sobell. M. B. & Sobell. L. C. Individualized behavior therapy for alcoholics, Culijorniu Menful Health Research Monogrtrph. No. 13. 1972. Sobell. M. B.. Sobell. L. C. & Samuels. F. H. Validity of self-reports of alcohol-related arrests by alcoholics. Qutrrrrrly Journtrl qf’sttrdies on Alcohol. 1974. 35. 276280. Summers. T. Validity of alcoholics’ self-reported drinking history. Quurrerly Journal of Srudies on Alcokol, 1970. 31, 972-974.
OTHERS AS CORROBORATIVE FOR PROBLEM DRINKERS
WILLIAMR. MILLER*, V. LLOYD CRAWFORDand CHERYLA. TAYLOR University
of New Mexico
Ahstrati-Self-reported alcohol consumption data from clients in four treatment outcome studies other” collaterals. Overall were compared with corroborative data obtained from “significant product-moment correlations were strong and positive, supporting the validity of self-report. Approximately equal numbers of collaterals overestimated and underestimated clients’ own reports. Intercorrelation increased with repeated interviews.
The validity of self-reports of problem drinkers is a controversial issue directly affecting design and interpretation of treatment outcome research. In a frequently cited study Summers (1970) interviewed 15 male alcoholic inpatients at admission and again after two weeks of hospitalization. She found that on the average patients changed their answers to nearly half of 14 structured questions in her interview. She concluded that “drinking history cannot be assumed valid and therefore cannot be used in the evaluation of the effect of treatment (p. 974)” In response to this questioning of the validity of self-report of problem drinkers some studies have attempted to obtain corroborative data from various sources. Miller et al. (1974) used random in uiuo breath alcohol tests to confirm treatment outcome. Sobell et al. (1974) checked alcoholics’ self-reported arrest records against official records and found an overall product-moment correlation of 0.65. Still other investigators have interviewed “significant others” (e.g. friends, relatives, employers) to obtain corroborative data. Using a 20-item drinking history questionnaire Guze et al. (1963) found an overall agreement of 85% between alcoholics and their collaterals, although they omitted items regarding quantity and frequency of alcohol consumption because of the inability of significant others to provide these data. Although not reporting specific correlations, Sobell & Sobell (1972) found “excellent agreement” between self-report and collateral report of their clients’ daily drinking dispositions, a more specific measure of alcohol consumption. These latter studies generally support the validity of self-reported data from problem drinkers, at least when corroborative data are obtained. These studies have also indicated that when discrepancies exist between client and collateral reports, most often the client’s own data are less favorable (i.e. higher alcohol consumption, more severe drinking history). The first quantitative data relating problem drinkers’ estimates of their alcohol consumption to similar estimates obtained from significant others were reported by McCrady et al. (1977). Using consumption indices derived from Cahalan’s (1970) , Quantity-Frequency Index and from the Alcohol Use Questionnaire (Horn et al., 1973) they found product-moment correlations ranging from 0.34 to 0.65 between self- and spouse reports at various assessment points. Their data likewise indicated that a majority of spouses underestimated rather than overestimated clients’ self-reported alcohol consumption. The present report provides cumulative conspection data from four treatment outcome studies with problem drinkers. METHOD
Data presented in this report represent the combined findings from four comparative outcome studies of controlled drinking therapies (Miller, 1978; Miller et al., 1976, 1977; *Requests for reprints should be sent to William Mexico, Albuquerque, NM 87131, U.S.A.
R. Miller,
67
Department
of Psychology,
University
of New
68
WILLIAMR. MILLER,V. LLOYDCRAWFORDand CHERYLA. TAYLOR Table 1. Descriptive intake data regarding clients treated in studies 1-4
Total N Mean age Mean education Mean annual income (Total Family) Mean years of drinking Mean years of problem drinking % Male clients % Married clients Mean MAST Score?
Study lA*
Study lB*
Study 2
Study 3
Study 4
29 37.3 15.6 $14,703 23.9 10.7 62.8% 39.0% 18.4
17 35.9 11.9 $8226 19.6 7.7 82.4% 35.3”/ 9.1
31 39.0 15.0 $15,448 23.5 8.5 74.2% 64.7% 18.4
28 44.8 14.4 $14,000 28.5 8.6 64.3% 67.9% 15.5
40 45.4 15.8 $23,384 29.2 10.5 62.5% 70.0% 18.3
* Study I included clients from two sources: those self-referred (IA) and those referred by the courts following conviction for driving while intoxicated (1B). 3 Mean score on the Michigan Alcoholism Screening Test. All mean scores are well above the alcoholism cutoff score prescribed by Seizer (1971).
Miller & Taylor, 1978). (A brief summary of the first three studies has been provided by Miller, 1977). Descriptive intake data from the 145 clients treated in these studies are reported in Table 1, with data reported separately for each of the four studies. Clients’ self-reported drinking was assessed in each study by standardized interviewing’ procedures outlined by Marlatt (1976). Alcohol consumption data were converted into Standardized Ethanol Content (SEC) units, with 1 SEC = 0.5 oz (15 ml) of absolute ethanol (Miller, 1978). Each client was asked to provide the names of at least 2 and preferably 3 significant others who could provide corroborative observational reports of clients’ alcohol consumption. These collaterals were interviewed by telephone using parallel standardized procedures in each study, and every attempt was made to obtain quantitative data to compare with self-reports. We succeeded in interviewing an average of 1.72 collaterals per client and obtained 1.41 quantitative estimates of alcohol consumption per case. In each study client and collateral interviews were completed at intake, treatment termination, and 3 month follow-up. In cases where more than one collateral estimate was obtained, the higher (less favorable) report was always used. When avail-
Table 2. Self-report and highest collateral report of clients’ alcohol consumption at intake, treatment termination, and 3 month follow-up Intake Nt
Self-report Mean alcohol consumption (SEC Units) Standard deviation Collateral report Mean alcohol consumption (SEC Units) Standard deviation % Collaterals overestimating Mean overestimate “/, Collaterals underestimating Mean underestimate “i, Exact matches Correlationsj Study 1 Study 2 Study 3 Study 4 Overall
127
Termination 131
Follow-up 128
54.8
17.5
18.1
43.7
18.0
19.8
48.3
18.1
20.5
33.5 489, + 19.3 49% - 32.0 35; 0.06 0.64**
0.46* 0.41’ 0.48**
23.8 33% + 16.0 45% - 10.6 220; 0.47** 0.80** 0.42 0.59** 0.66**
27.2 36”; + 16.3 387; -8.8 26”,b 0.74** 0.92** 0.84** 0.68** 0.79**
t N = number of clients from all four studies for whom both self-report and collateral report were available. $ Correlation = Pearson product-moment correlation between self-report and highest collateral report for all available pairs. * P < 0.05. ** P < 0.01.
Significant
others
as corroborative
sources
69
able, data from clients who dropped out of treatment were also included in the analyses for the present report. RESULTS
The relationship between client and collateral reports can be seen in Table 2. All correlations between the two data sources were positive, ranging from 0.06 to 0.92. Approximately equal numbers of collaterals overestimated and underestimated client reports. DISCUSSION
Data from these four studies generally support the validity of clients’ self-report of drinking behavior. In all studies correlations were positive, and change score trends in self-report data were reflected in collateral data as well. Several factors may account for the wide range of correlation coefficients. The outlying lowest value (r = 0.06) was obtained from intake interviews of Study 1, where several unusual conditions prevailed. At this point only we relied upon the personnel of a court clinic to obtain collateral reports for court-referred clients. For all other studies and interview times, our research staff collected all data. The staff was also less accustomed to the interviewing procedures at the outset. Finally, Study 1 contained the lowest percentage of married clients, thus reducing the availability of one of the best collateral sources, the spouse. These conditions probably contributed to the outlying and nonsignificant value observed at intake in Study 1, where we also obtained the lowest percentage of collateral reports for clients. A general trend toward higher correlation coefficients with increased interviewer experience can be seen in spite of decreased variance among scores at later interviews. The same basic research staff conducted Study 1 and the subsequent Study 2. New interviewers collected data throughout Study 3, and yet another staff in Study 4. In addition to increased interviewer skill, increased honesty of reporting parties and/or increased awareness of clients’ drinking by collaterals may have contributed to rising correlation coefficients. The increase in exact matches between self- and collateral reports can be accounted for in part by the increasing number of clients who were totally abstaining at termination and at follow-up. The fact that our collateral reports almost as often overestimated as underestimated selfreports (in contrast to findings of previous research) may be attributed to our use of the highest collateral report when more than one was available. It is unclear whether accuracy of self-report data would be maintained if clients were unaware that collaterals would be contacted. Accuracy of report may also have been improved by the nature of this population, consisting (except in Study 1) primarily of self-referred individuals not publicly identified as alcoholics. The absolute accuracy of collaterals might be questioned as well, and could be checked against more objective data sources such as in vivo breath tests. Finally, these results, obtained from clinics where the goal of treatment was controlled drinking, may not be directly generalizable to treatment settings where total abstinence is emphasized, especially because evidence of physiological addiction served to exclude clients from participation in the controlled drinking programs evaluated in these studies (Miller & Caddy, 1977). Clarification of these issues remains for future research.
REFERENCES Cahalan, D. Problem Drinkers, a national survey. San Francisco: Jossey-Bass, 1970. Guze, S. B., Tuason, V. B., Stewart, M. A. & Picken, B. The drinking history: A by subjects and their relatives. Quarterly Journal of Studies on Alcohol, 1963. 24, Horn, J., Wanberg, K. W., Wright, J. & Foster, F. M. The Alcohol Use Questionnaire. Mental Health Center, 1973. Marlatt, G. A. The Drinking Profile: A questionnaire for the behavioral assessment Mash & L. G. Terdal (Eds). Behacior Therapy Assessment: Diagnosis, Design und Springer. 1976.
comparison
of reports
249-260.
Denver:
Fort
of alcoholism. Eculuation.
Logan In E. J. York:
New
70
WILLIAM R. MILLER, V. LLOYD CRAWFORD and CHERYL A. TAYLOR
McCrady. B. S.. Paolina. T. J., Jr, & Longabaugh. R. Correspondence between problem drinker and spouse report of drinking behavior and impairment. Paper presented at the NATO International Conference on Experimental and Behavioral Approaches to Alcoholism, OS. Norway, September, 1977. Miller. P. M., Hersen. M.. Eisler. R. M. & Watts. J. G. Contingent reinforcement of lowered blood/alcohol levels in an outpatient chronic alcoholic. Behuaiour Rcseurch and Thrrapy, 1974, 12, 261-263. Miller. W. R. Behavioral self-control training in the treatment of problem drinkers. In R. B. Stuart (Ed.). Bchuriorul Srlf-Munugtwwt: Strutqirs and Ourcor~s. New York: Brunner/Mazel. 1977. Miller. W. R. Behavioral treatment of problem drinkers: A comparative outcome study of three controlled drinking therapies. Journal of Consultiny and Clinicul Psycholoyy, 1978, 46, 74-86. Miller. W. R. & Caddy, G. R. Abstinence and controlled drinking in the treatment of problem drinkers. Journtrl of Studivson Akohol, 1977, 38, 9861003. Miller. W. R. & Taylor. C. A. Relative effectiveness of bibliotherapy. individual and group self-control training in the treatment of problem drinkers. Unpublished manuscript, University of New Mexico, 1978. Miller. W. R.. Gribskov. C. & Mortell. R. Etfectiveness of a self-control manual for problem drinkers with and without therapist contact. Unpublished manuscript. University of Oregon. 1976. Miller, W. R.. Pechacek. T. F. & Hamburg. S. Group behavior therapy for problem drinkers. Unpublished manuscript. Palo Alto Veterans Administration Hospital, 1977. Selzcr. M. L. The Michigan Alcoholism Screening Test: The quest for a new diagnostic instrument. American Journtrl of’ Psychiufry. 1971, 127, 1653-1658. Sobell. M. B. & Sobell. L. C. Individualized behavior therapy for alcoholics, Culijorniu Menful Health Research Monogrtrph. No. 13. 1972. Sobell. M. B.. Sobell. L. C. & Samuels. F. H. Validity of self-reports of alcohol-related arrests by alcoholics. Qutrrrrrly Journtrl qf’sttrdies on Alcohol. 1974. 35. 276280. Summers. T. Validity of alcoholics’ self-reported drinking history. Quurrerly Journal of Srudies on Alcokol, 1970. 31, 972-974.
