British Journal of Addiction (1992) 87, 1275-1280
RESEARCH REPORT
User reports of problems associated with alcohol and marijuana STEVE BLACK & SALLY CASSWELL Alcohol and Public Health Research Unit, University of Auckland, New Zealand
Abstract A general population sample of 5126 New Zealanders aged 15-45 in two regions was surveyed to determine their use of alcohol, tobacco, marijuana, and other illicit drugs. Self-reported problems were recorded on identical scales for alcohol and marijuana in order to make a direct comparison between alcohol and marijuana-related problems. The results suggest that alcohol-related problems were more common than marijuana-related ones in the general population, reflecting the fact that alcohol use was more widespread. Within the 17% of the sample who had used both alcohol and marijuana in the last 12 months more problems were reported from alcohol, once again reflecting differences in amounts consumed. Among heavier users of marijuana both alcohol and marijuana-related problems were more commonly reported than in the general sample. Problems were reported at similar levels for both drugs and the pattern ofproblems is somewhat similar.
Introduction Self-reported problems from alcohol have been widely studied within the general examination of alcohol-related problems in society.'•^•' Increasingly, surveys of alcohol consumption include the use of other drugs as part of the information collected. This broadening of context is a function of increasing sophistication in formulating research questions and in available methodology.'*'' In this paper the results of a baseline telephone survey on alcohol, tobacco, marijuana and other drugs are reported. This survey is intended to be the first in an ongoing series to monitor changes in patterns of drug use within New Zealand. Self-reported problems for both alcohol and marijuana were recorded on identical scales in the survey so that a direct comparison between alcohol and marijuana-related problems could be made. At the same time as the fieldwork was taking place in New Zealand a very similar study was running in Marin, California which included the same self-reported problem questions.* This offers an unusual opportunity to 1275
look at the relationship between alcohol and marijuana-related problems in two countries under very similar survey methods.
Methods Data for this analysis comes from a general population survey of drug use in New Zealand. Two samples of people aged 15-45 were interviewed by telephone between 1 September and 15 December 1990. The metropolitan sample included 4088 persons from Auckland, the largest city in New Zealand (28% of New Zealand's population). The provincial/rural sample included 1038 people drawn from the Bay of Plenty area, which contains 6% of New Zealand's population. The two regional samples were chosen to provide a cost-effective baseline sample for tracking future changes in drug use patterns. The two areas were not intended to provide a balanced fully national sample for New Zealand. The few regional differences found be-
1276
Steve Black & Sally Casswell
tween the samples are reported elsewhere.' In this report the two regional samples are combined. All interviews were conducted over the telephone by interviewers employed and trained by the Alcohol and Public Health Research Unit. Extensive training was given to all interviewers (about 30 hours) which included lectures, role playing and practice interviews within the training group. Early in the study design we consulted with Maori (the original inhabitants of New Zealand) and Polynesian immigrant groups to allow them to guide us in the best way to include these ethnic minorities in our research. As a result of this, all interviewers were exposed to sessions on cultural issues. In addition, Maori speaking interviewers were available and each respondent was given the opportunity to be interviewed in Maori. The CASES software system from the University of California at Berkeley was used for data collection. The software was run on a network of 10 interviewing PCs plus one supervisor station. All stations were equipped with headsets so that both hands were free to type responses into the computer. During the course of the study progress was monitored by supervisors who could monitor both the computer screens and the conversations as the interviews progressed. Discussion sessions and debriefings with the group of interviewers were also held so that they could share their experiences in handling difficult areas such as refusals and hostile respondents. Great care was taken during questionnaire development to keep the interview brief. The median length of calls was 22 minutes, including administration time spent on introducing the survey and choosing a respondent within the household. The interview itself was usually under 15 minutes. The survey was introduced as covering things people do in their spare time, and potential respondents were told that some of the questions were about alcohol, tobacco and drugs like marijuana. All potential respondents were informed that the survey was voluntary and completely confidential. The questionnaire and sample design were approved by the University of Auckland Human Subjects Ethics Committee. The questionnaire began with some questioning on frequency of exercise, concern over diet, and satisfaction with life and close friendships. Sections on alcohol, demographic information and tobacco followed, so that there was a good level of trust and rapport established between interviewer and respondent prior to the sections on illict drugs. Telephone numbers were selected at random
using the Waksberg method so that each household in the survey area had an equal chance of being selected.' Within each household one person aged 15-45 years was randomly selected for an interview. Weights were calculated in the analysis phase to adjust for different probabilities of selection in households of different size. All of the results presented here are based on these weighted results. The introduction of weights produced an average design effect of 1.23, and this reduced the effective sample size to 4167.' This has been taken into account in estimation of confidence intervals and tests of significance. The numbers of individuals reported are not adjusted to refiect effective sample size. Each telephone number was tried at least ten times in an effort to reach those people who were seldom at home. The response rate was 68% of all households with telephones. The denominator for this calculation included household and individual refusals, as well as all individuals who could not be contacted, or cases where an interview could not be carried out because of language or other problems. Businesses and group quarters (such as military barracks and university hostels) were excluded from the sampling frame. Telephone coverage of households in New Zealand is quite high, with 96% ± 1 % able to be reached by telephone (Department of Statistics).'" The use of random digit dialling also ensured that households with unlisted numbers were included. In order to assess the level of problems experienced with the use of alcohol and marijuana a set of questions was asked for each drug. The questions all began "In the last 12 months has your use o f . . . had any harmful effect on . . . " and were completed with eight different areas of life. These life area questions originated with the Berkeley Alcohol Research Group, and were subsequently extended for use in New Zealand surveys.""'^ Each question required a yes or no answer. As is clear from the form which this questioning took, it is the respondent's own attribution of problems which is under analysis. Thus an assumption underlying this analysis is that the respondents are correctly attributing problems which they experience to one drug or the other. The questions were asked separately for marijuana and alcohol in different sections of the questionnaire. The alcohol section was asked first, and this was separated from the marijuana section by sections about tobacco smoking and demographic information. There were no reports of respondent difficulties with these sections of the questionnaire.
User reported alcohol and marijuana problems
1277
Table 1. Reports of harmful effects in different areas of life in the past year attributed to alcohol and marijuana use. Percentages are based on the total sample Area of life
Alcohol (%)
Marijuana (%)
Any reported problem Your energy and vitality Your financial position Your health Your outlook on life Your friendships and social life Your home life Your work or work opportunities Your children's health or well-being
26 14 11(1) 7(6) 6(4) 4(3) 4(3) 2(1) 1
7 4 2(1) 2(1) 2(2) 1(1) 1(1) 1(1)
RESEARCH REPORT
User reports of problems associated with alcohol and marijuana STEVE BLACK & SALLY CASSWELL Alcohol and Public Health Research Unit, University of Auckland, New Zealand
Abstract A general population sample of 5126 New Zealanders aged 15-45 in two regions was surveyed to determine their use of alcohol, tobacco, marijuana, and other illicit drugs. Self-reported problems were recorded on identical scales for alcohol and marijuana in order to make a direct comparison between alcohol and marijuana-related problems. The results suggest that alcohol-related problems were more common than marijuana-related ones in the general population, reflecting the fact that alcohol use was more widespread. Within the 17% of the sample who had used both alcohol and marijuana in the last 12 months more problems were reported from alcohol, once again reflecting differences in amounts consumed. Among heavier users of marijuana both alcohol and marijuana-related problems were more commonly reported than in the general sample. Problems were reported at similar levels for both drugs and the pattern ofproblems is somewhat similar.
Introduction Self-reported problems from alcohol have been widely studied within the general examination of alcohol-related problems in society.'•^•' Increasingly, surveys of alcohol consumption include the use of other drugs as part of the information collected. This broadening of context is a function of increasing sophistication in formulating research questions and in available methodology.'*'' In this paper the results of a baseline telephone survey on alcohol, tobacco, marijuana and other drugs are reported. This survey is intended to be the first in an ongoing series to monitor changes in patterns of drug use within New Zealand. Self-reported problems for both alcohol and marijuana were recorded on identical scales in the survey so that a direct comparison between alcohol and marijuana-related problems could be made. At the same time as the fieldwork was taking place in New Zealand a very similar study was running in Marin, California which included the same self-reported problem questions.* This offers an unusual opportunity to 1275
look at the relationship between alcohol and marijuana-related problems in two countries under very similar survey methods.
Methods Data for this analysis comes from a general population survey of drug use in New Zealand. Two samples of people aged 15-45 were interviewed by telephone between 1 September and 15 December 1990. The metropolitan sample included 4088 persons from Auckland, the largest city in New Zealand (28% of New Zealand's population). The provincial/rural sample included 1038 people drawn from the Bay of Plenty area, which contains 6% of New Zealand's population. The two regional samples were chosen to provide a cost-effective baseline sample for tracking future changes in drug use patterns. The two areas were not intended to provide a balanced fully national sample for New Zealand. The few regional differences found be-
1276
Steve Black & Sally Casswell
tween the samples are reported elsewhere.' In this report the two regional samples are combined. All interviews were conducted over the telephone by interviewers employed and trained by the Alcohol and Public Health Research Unit. Extensive training was given to all interviewers (about 30 hours) which included lectures, role playing and practice interviews within the training group. Early in the study design we consulted with Maori (the original inhabitants of New Zealand) and Polynesian immigrant groups to allow them to guide us in the best way to include these ethnic minorities in our research. As a result of this, all interviewers were exposed to sessions on cultural issues. In addition, Maori speaking interviewers were available and each respondent was given the opportunity to be interviewed in Maori. The CASES software system from the University of California at Berkeley was used for data collection. The software was run on a network of 10 interviewing PCs plus one supervisor station. All stations were equipped with headsets so that both hands were free to type responses into the computer. During the course of the study progress was monitored by supervisors who could monitor both the computer screens and the conversations as the interviews progressed. Discussion sessions and debriefings with the group of interviewers were also held so that they could share their experiences in handling difficult areas such as refusals and hostile respondents. Great care was taken during questionnaire development to keep the interview brief. The median length of calls was 22 minutes, including administration time spent on introducing the survey and choosing a respondent within the household. The interview itself was usually under 15 minutes. The survey was introduced as covering things people do in their spare time, and potential respondents were told that some of the questions were about alcohol, tobacco and drugs like marijuana. All potential respondents were informed that the survey was voluntary and completely confidential. The questionnaire and sample design were approved by the University of Auckland Human Subjects Ethics Committee. The questionnaire began with some questioning on frequency of exercise, concern over diet, and satisfaction with life and close friendships. Sections on alcohol, demographic information and tobacco followed, so that there was a good level of trust and rapport established between interviewer and respondent prior to the sections on illict drugs. Telephone numbers were selected at random
using the Waksberg method so that each household in the survey area had an equal chance of being selected.' Within each household one person aged 15-45 years was randomly selected for an interview. Weights were calculated in the analysis phase to adjust for different probabilities of selection in households of different size. All of the results presented here are based on these weighted results. The introduction of weights produced an average design effect of 1.23, and this reduced the effective sample size to 4167.' This has been taken into account in estimation of confidence intervals and tests of significance. The numbers of individuals reported are not adjusted to refiect effective sample size. Each telephone number was tried at least ten times in an effort to reach those people who were seldom at home. The response rate was 68% of all households with telephones. The denominator for this calculation included household and individual refusals, as well as all individuals who could not be contacted, or cases where an interview could not be carried out because of language or other problems. Businesses and group quarters (such as military barracks and university hostels) were excluded from the sampling frame. Telephone coverage of households in New Zealand is quite high, with 96% ± 1 % able to be reached by telephone (Department of Statistics).'" The use of random digit dialling also ensured that households with unlisted numbers were included. In order to assess the level of problems experienced with the use of alcohol and marijuana a set of questions was asked for each drug. The questions all began "In the last 12 months has your use o f . . . had any harmful effect on . . . " and were completed with eight different areas of life. These life area questions originated with the Berkeley Alcohol Research Group, and were subsequently extended for use in New Zealand surveys.""'^ Each question required a yes or no answer. As is clear from the form which this questioning took, it is the respondent's own attribution of problems which is under analysis. Thus an assumption underlying this analysis is that the respondents are correctly attributing problems which they experience to one drug or the other. The questions were asked separately for marijuana and alcohol in different sections of the questionnaire. The alcohol section was asked first, and this was separated from the marijuana section by sections about tobacco smoking and demographic information. There were no reports of respondent difficulties with these sections of the questionnaire.
User reported alcohol and marijuana problems
1277
Table 1. Reports of harmful effects in different areas of life in the past year attributed to alcohol and marijuana use. Percentages are based on the total sample Area of life
Alcohol (%)
Marijuana (%)
Any reported problem Your energy and vitality Your financial position Your health Your outlook on life Your friendships and social life Your home life Your work or work opportunities Your children's health or well-being
26 14 11(1) 7(6) 6(4) 4(3) 4(3) 2(1) 1
7 4 2(1) 2(1) 2(2) 1(1) 1(1) 1(1)
