Marijuana Use and Prior Injury among Injured Problem Drinkers

Transcription

1 ACAD EMERG MED January 2003, Vol. 10, No CLINICAL PRACTICE Marijuana Use and Prior Injury among Injured Problem Drinkers Robert Woolard, MD, Ted D. Nirenberg, PhD, Bruce Becker, MD, Richard Longabaugh, EdD, P. Allison Minugh, PhD, Aruna Gogineni, PhD, Kathleen Carty, MSW, Patrick R. Clifford, PhD Abstract Objectives: The purpose of this paper is to better understand marijuana use among injured problem drinkers in the emergency department (ED). The specific objectives are: 1) to assess the prevalence of marijuana use; 2) to identify factors associated with marijuana use; 3) to determine whether prior injury is associated with marijuana use; and 4) to determine whether marijuana-using problem drinkers want to change behaviors. Methods: The authors conducted a post-hoc analysis on data obtained prospectively. Subjects had injury and problem drinking: either measurable alcohol level (blood alcohol concentration, BAC), report of drinking, or an Alcohol Use Disorders Identification Test (AUDIT) score of 8. The study was conducted on weekend nights; 3,776 injured ED patients were screened, 383 refused, 578 were enrolled, and 433 had complete data. Results: Of the 433 subjects, 48.3% reported using marijuana in the three months prior. Marijuana-using problem drinkers had more hazardous drinking, higher AUDIT scores (14.0 vs. 11.4, p < 0.001), and higher risk-taking scores (12.4 vs. 10.1, p < 0.001). More used other drugs (69.7% vs. 30.3%, p < 0.001). In regression analyses, marijuana use remained an independent predictor of prior injury (OR = 2.16, 95% CI = 1.25 to 3.75), particularly prior alcoholrelated (OR = 2.26, 95% CI = 1.45 to 3.53) and motorvehicle-related (OR = 1.69, 95% CI = 1.03 to 2.79) injury. Readiness-to-change scores were similar (4.14 vs. 4.22, p = 0.21) between users and nonusers. Conclusions: Marijuana use among injured problem drinkers is prevalent. Their risk of prior injury is increased. Counseling for alcohol and injury should address marijuana use. Key words: alcohol use; marijuana use; substance abuse; injury prevention; emergency medicine; brief intervention. ACADEMIC EMERGENCY MEDICINE 2003; 10: In the emergency department (ED), alcohol use is commonly encountered and often associated with injury. 1,2 Emergency physicians (EPs) are aware of the link between alcohol and injury. 3 7 Reckless driving and crash fatalities have been linked to alcohol and other drugs. 8,9 Routine screening of all trauma cases for drug use has been advocated by many EPs. 10 A few simple questions can be used to screen for alcohol problems. 11 However, once alcohol problems are identified, screening for other drugs is unusual. Few EDs routinely screen all injured patients for alcohol and other drugs. Marijuana use has not been as clearly linked to injury as has alcohol. However, there is a higher From the Brown University Medical School (RW, TDN, BB), Rhode Island Hospital (RW, BB), Injury Prevention Center (TDN), Center for Alcohol and Addiction Studies (RL, PAM, AG, PRC), and School of Social Studies (KC), Providence, RI; and the New York University Department of Health Studies (PRC), New York, NY. Received May 7, 2002; revisions received August 6, 2002, and August 14, 2002; accepted August 14, Address for correspondence and reprints: Robert Woolard, MD, Associate Professor, Brown University Medical School, Rhode Island Hospital, Department of Emergency Medicine, Providence, RI Fax: ; rwoolard@ lifespan.org. A related commentary appears on page 62. risk of injury when drinking is accompanied by marijuana or other drug use. Alcohol and marijuana, when used in combination, increase cognitive impairments additively on most cognitive tests Moderate use of marijuana and alcohol impairs driving performance. Most states have driving-under-the-influence statutes that recognize impairment at breath or blood alcohol concentration (BAC) 0.08 mg/dl. The combination of a moderate amount of alcohol (BAC = 0.04 mg/dl) and marijuana (tetrahydrocannabinol [THC] at 100 g/kg and 200 g/kg) causes effects equivalent to BACs 0.09 mg/dl. The higher marijuana dose taken with a moderate amount of alcohol causes drivers to spend 1.1% of their driving time out of their lane during driving tests. 16 Marijuana in combination with alcohol is present in 5 10% of injured drivers 17 and 37% of trauma admissions. 18 While alcohol remains the major risk factor for motor vehicle crashes and crash fatalities, marijuana use is the leading crash-related drug other than alcohol. When marijuana is detected in the blood of highway fatalities, 83% of the time it is found in combination with alcohol. 17,19 23 Behaviors such as alcohol and marijuana use may be important to change given the associated risk of

2 44 Woolard et al. MARIJUANA USE AMONG INJURED PROBLEM DRINKERS injury. Brief counseling interventions for alcohol are effective. 24,25 Marijuana users also respond to counseling However, alcohol and marijuana counseling are not a routine part of injury reduction interventions. The large number of injured patients presenting to EDs creates an opportunity for preventive counseling interventions. Emergency department screening, brief intervention, and referral for counseling can be inexpensive, placing minimal demands on providers. 29,30 When substance users come to the ED for treatment of an injury, they may acknowledge the harm of substance use and recognize its relationship to their injury. They may also expect further injury to result if they continue risk behaviors, thus motivating change. 31 The injury may provide an opportunity for intervention, a teachable moment. Advice during a teachable moment, such as after an injury event, may be more effective. 32,33 Emergency department counseling for injured problem drinkers reduces subsequent injury. The Rhode Island ETOH and Injury Study (REIS), a randomized, controlled trial of brief intervention for alcohol and injury, demonstrated that brief ED intervention reduces alcohol-related injuries. 34 While alcohol-related injuries were reduced, the overall number of injuries was not reduced by the alcoholfocused REIS intervention. To develop better interventions for injured patients, understanding not only the use of alcohol, but also marijuana and other drug use among injured ED patients, may be required. The purposes of this study were: 1) to assess the prevalence of marijuana and other drug use among injured problem drinkers; 2) to identify factors associated with use; 3) to determine whether prior injuries are associated with use; and 4) to measure readiness to change alcohol and risk behaviors. METHODS Study Design. We analyzed responses to questionnaires assessing factors associated with alcohol, marijuana use, and other drug use that were collected during REIS, a prospective, randomized controlled trial of brief counseling for alcohol and injury in the ED. 34 Patients completed questionnaires administered by research personnel. The research protocol was approved by a full review of the institutional review boards of the hospital and its affiliated university. Study Setting and Population. Patients presented for treatment at an adult (all patients aged 18 years or older), Level 1 trauma center with 69,000 patient visits per year. Patients were recruited from January 1996 through September 1998 on Thursday through Monday evenings from 8 PM to 6 AM. Approximately 70% of all injured patients are seen during this 40-hour segment of the week. Patients were eligible for enrollment if they had an injury that occurred within the previous seven days and did not require hospitalization. They had to be problem drinkers : either screen positive for hazardous drinking (Alcohol Use Disorders Identification Test [AUDIT] score 8), report drinking alcohol within six hours prior to the injury, or be breath-tested positive for alcohol. Participants had to live within one hour of the hospital and speak English or Spanish. They could not be under arrest. Study Protocol. Research assistants discussed the study with potential participants and administered a brief mental status examination. Interested patients who passed the mental status examination were quizzed to assure their comprehension of the study. The AUDIT, a breath alcohol test, and the patient s report concerning alcohol use prior to the time of the injury were obtained. Informed consent was obtained from patients with a BAC < 0.20 mg/dl. Patients could refuse to participate prior to determination of eligibility. Participants completed assessment questionnaires requiring minutes prior to leaving the ED. All measures used in this analysis are listed in Table 1. Outcome Variables. Injuries. The Injury Behaviors Checklist (IBC). The IBC was developed by Starfield as part of an Adolescent Health Status Instrument. 35 The patient records the number of times each of 18 different kinds of injuries occurred during the past year, whether the injury was treated by a doctor, and whether drinking occurred in the two hours prior to the injury. Based on IBC reports, we categorized injuries into motor vehicle injuries, assaults, sports injuries, and other injuries. The distribution of injuries is heavily skewed toward the low end of the curve, with the vast majority of patients experiencing one or no injury. For analysis injury variables are dichotomized: injury or no injury in the previous year. Readiness to Change. The patient s readiness to change his or her drinking behavior and risk behavior was measured using two Readiness to Change Contemplation Ladders. This measure is predictive of subsequent behaviors, such as attempts to quit smoking. 36 The patient is asked to mark his or her readiness to change on a rung of a contemplation ladder ranging from (0) no thought of changing to (10) taking action to change (e.g.,

3 ACAD EMERG MED January 2003, Vol. 10, No TABLE 1. Factors Entered into Analyses Variable Outcome variables All injuries Motor vehicle injuries Assault injuries Sports injuries Other injuries Alcohol-related injuries Doctor-treated injuries Readiness to change Alcohol Risk behaviors Description Any prior injury in the past year (0,1) Any prior alcohol-related injury in the past year (0,1) Any prior injury in the past year (0,1) treated by a doctor No (0) readiness or any (1 10) readiness (0,1) Independent variables Marijuana use No (0) or any marijuana use (1) over the past three months Marijuana frequency No marijuana use (0) monthly or less (1) weekly or more (2) Control variables Alcohol use, AUDIT* Other drug use Amphetamine Sedative Cocaine Opiate Hallucinogen Inhalant Steroid Risk-Taking/Impulsivity Scale Age Gender Socioeconomic status Educational level Marital status Race/ethnicity The total AUDIT score No (0) or any drug use (1) over the past three months Sum of risk scale (continuous) Age at time of selection (continuous) (0) Female or (1) male (0) Unemployed (1) Employed (0) Not currently a student (1) Currently a student Years (continuous) (1) Married (2) Divorced/separated (3) Widowed (4) Single (0) White (1) African American (2) Hispanic/Latino (3) Other *AUDIT = Alcohol Use Disorders Identification Test. cutting down). For analysis, the average scores on both readiness-to-change ladders and the scores dichotomized to some (1 10) or no (0) readiness to change are used. Independent Variables. Marijuana Use. A questionnaire with eight questions concerning marijuana and other drug use was developed for the REIS study to ascertain frequency of use in the last three months. The responses are 0 to 4, no use to daily use. For analysis, responses to the marijuana question are dichotomized into no use or any use and also trichotomized into no, monthly or less, and weekly or daily use. A marijuana user is defined by any use reported in the past three months from less than monthly to daily use. Control Variables. Alcohol Use Disorders Identification Test (AUDIT). The AUDIT is a ten-item questionnaire used to determine hazardous or harmful drinking. 37 The AUDIT has internal consistency (alpha = 0.80) and can reliably identify problem drinkers. 23,38 41 Cherpitel reported that in ED populations, an AUDIT cut-off score of 8 had an 85% sensitivity and an 88% specificity for harmful drinking and an 83% sensitivity and an 89% specificity for alcohol dependence. 42 The scores and the scores dicotomized to <8 or 8 are used in analysis. Other Drug Use. The questionnaire described above under marijuana use ascertains the frequency of other drug (cocaine, hallucinogens, inhalants, amphetamines, sedatives, opiates, and steroids) use. For analysis, use of each drug was dichotomized into no use or any use in the last three months. Risk-Taking/Impulsivity Scale. Patients completed a risk-taking/impulsivity scale with five items constructed by Cherpitel. 43 The items come from a larger survey conducted by the Alcohol Research Group. 3 The average of the five items is used in analysis. Demographic Measures. Socioeconomic Status. Socioeconomic status variables include educational level, student status, and employment status. Employment status and student status are measured as binary variables. Education is measured in years. Race/Ethnicity. Respondents were asked their race/ethnicity based on U.S. Census categories, which were then re-coded into four categories: white, African American, Hispanic/Latino, and other. Data Analysis. We examined the type and frequency of substance use among the sample using descriptive statistics and cross-tabulation. Variables were then analyzed individually using univariate methods in order to assess the overall differences between marijuana-using problem drinkers and non-users. Variables were examined using t-tests and chi-square analyses where appropriate, dependent upon their distribution. In addition, a Mantel-

4 46 Woolard et al. MARIJUANA USE AMONG INJURED PROBLEM DRINKERS Haenszel chi-square statistic was used to detect whether there was a significant increase in risk associated with increased frequency of marijuana use. Multivariate analyses were used to address the effects of several of these variables simultaneously, adjusting for each variable s individual effects. Forward stepwise logistic regression was used to assess the likelihood of each of the injury measures. Variables had to reach a p-level of =0.05 in order to enter into the model, and =0.10 to exit the model. A p-value of <0.05 is considered significant, so it is possible for a variable to remain in the model while not being significant. Odds ratios (ORs) and 95% confidence intervals (95% CIs) are displayed when appropriate. RESULTS Sample Characteristics. During the study, 3,775 patients presented to the ED with injuries and were not hospitalized; 383 refused to participate, 578 were studied, and 433 had complete answers to all questions. Of those with complete responses, 79% were male, and the mean age was years. The ethnic composition was 75% white, 11% Hispanic/Latino, 10% African American, and 4% other. Their mean educational level was years; 78% were single and 10% were married; 32% were students and 73% were employed. Prevalence of Marijuana and Other Drug Use. Figure 1 displays the prevalence of substance use in the study group. Out of the 433 injured problem drinkers, 58.51% reported drug use in the past three months. Marijuana was the drug used most often, with 48.27% reporting marijuana use in the last three months % reported using alcohol and marijuana, but no other drugs % used alcohol, marijuana, and other drugs, with most (16.40%) using marijuana more frequently than other drugs. 9.24% used alcohol and a drug other than marijuana. Univariate Analyses. Table 2 compares control variables between the marijuana-using problem drinkers and the non-users. Factors Associated with Marijuana Use. Demographics. There are significant differences between marijuana-using problem drinkers and non-users. As a group, marijuana-using problem drinkers are younger (24.1 vs years, p < 0.001), more likely to be male (85.2% vs. 72.8%, p = 0.002), less educated (12.0 vs years, p = 0.024), single (88.0% vs. 69.2%, p < 0.001), and white (81.3% vs. 69.6%, p = 0.005). Differences in employment status and student status are not statistically significant. Alcohol Use, Other Drug Use, and Risk Taking. There are differences between marijuana-using problem drinkers and non-users with regard to alcohol use, other drug use, and risk taking/impulsivity. Marijuana-using injured problem drinkers had higher AUDIT scores (14.0 vs. 11.4, p < 0.001). More marijuana-using problem drinkers used other drugs (44.0% vs 17.9%, p < 0.001). Marijuana-using problem drinkers score higher on the risk-taking/ impulsivity scale (12.3 vs. 10.1, p < 0.001). Univariate Analyses. Table 3 compares dependent variables among marijuana-using problem drinkers and non-users. Outcome Variables Associated with Marijuana Use. Injury. Among injured problem drinkers, the risk of any injury in the past year was higher when marijuana was used (OR = 2.89, 95% CI = 1.71 to 4.89). 89.0% of the marijuana users reported injuries Figure 1. Alcohol, marijuana, and other drug use.

5 ACAD EMERG MED January 2003, Vol. 10, No TABLE 2. Marijuana Use and Control Variables Results of Univariate Analyses Variable Marijuana Used Marijuana Not Used Total Sample Test Statistic Age mean ( SD) yr ( 6.34) yr ( 9.57) yr ( 8.56) t statistic*** 6.64 Education mean ( SD) yr ( 2.06) yr ( 2.46) yr ( 2.30) t statistic** 2.88 Gender male 85.2% (178) 72.8% (163) 78.8% (341) Chi-square** 9.94 Employment status employed 69.9% (146) 75.9% (170) 73.0% (359) Chi-square 2.00 Student status enrolled 35.9% (75) 28.6% (64) 32.1% (139) Chi-square 2.65 Marital status Married 3.2% (14) 8.5% (37) 11.8% (51) Chi-square*** Divorced 2.5% (11) 7.4% (32) 9.9% (43) Single 42.5% (184) 35.8% (155) 78.3% (339) Race White 39.3% (170) 36.0% (156) 75.3% (326) Chi-square* African American 3.9% (17) 6.0% (26) 9.9% (43) Hispanic/Latino 3.0% (13) 7.9% (34) 10.9% (47) Other 2.1% (9) 1.8% (8) 3.9% (17) Other drug use 44.1% (92) 17.9% (40) 57.5% (249) Chi-square*** AUDIT scale mean ( SD) ( 6.23) ( 7.13) ( 6.83) t statistic*** 4.05 Risk scale mean ( SD) ( 3.59) ( 3.74) ( 3.83) t statistic*** 6.33 *p < 0.05; **p < 0.01; ***p < AUDIT = Alcohol Use Disorders Identification Test. TABLE 3. Marijuana Use and Outcomes Results of Univariate Analyses Variable Marijuana Used Marijuana Not Used Total Statistic All prior injuries 89.0% (186) 73.7% (165) 81.1% (351) Chi-square*** Prior alcohol-related injuries 56.0% (117) 28.1% (63) 41.6% (180) Chi-square*** Prior doctor-treated injuries 57.9% (121) 46.9% (105) 52.2% (226) Chi-square* 5.26 Prior motor vehicle injuries 27.8% (58) 15.2% (34) 21.2% (92) Chi-square** Prior assault injuries 47.8% (100) 29.0% (65) 38.1% (165) Chi-square*** Prior sports Injuries 47.4% (99) 29.9% (67) 38.8% (166) Chi-square*** Other prior injuries 63.2% (132) 52.7% (118) 57.7% (250) Chi-square* 4.87 Readiness to change risk behaviors t statistic 0.14 Readiness to change alcohol consumption t statistic 0.21 *p < 0.05; **p < 0.01; ***p < occurring in the year prior to the ED visit versus 73.7% of non-users (p < 0.001). More marijuana-using problem drinkers have had alcohol-related (56.0% vs. 28.1%, p < 0.001), doctor-treated (57.9% vs. 46.9%, p < 0.022), motor-vehicle-related (27.8% vs. 15.2%, p = 0.001), assault-related (47.8% vs. 29.0%, p < 0.001), sports-related (47.4% vs. 29.9%, p < 0.001), and other (63.2% vs. 52.7%, p = 0.027) injuries. Figure 2 shows an injury dose response to frequency of marijuana use among injured problem drinkers. As marijuana use increases from none to infrequent to frequent use, more patients report prior injuries (73.7% vs. 83.5% vs. 93.2%, p < 0.001), as well as alcohol-related (28.1% vs. 49.5% vs. 61.0%, p < 0.001), doctor-treated (46.9% vs. 54.9% vs. 60.2%, p = 0.016), motor-vehicle-related (15.2% vs. 27.5% vs. 28.0%, p = 0.006), sports-related (29.9% vs. 38.5% vs. 54.2%, p < 0.001), assault-related (29.0% vs. 40.7% vs. 53.4%, p < 0.001), and other (52.7% vs. 54.9% vs. 69.5%, p = 0.004) injuries. Readiness to Change. There is no difference in readiness to change drinking (3.9 vs. 4.2, p = 0.579) or risk behavior (3.8 vs. 3.8, p = 0.887) between marijuana-using problem drinkers and non-users. The majority of both the marijuana-using and the nonusing problem drinkers expressed at least some readiness to change drinking (69.4% and 64.7%) and risk behaviors (72.2% and 61.6%). Multivariate Analyses. Table 4 lists the results of logistic regression for all prior injuries, alcohol-re-

6 48 Woolard et al. MARIJUANA USE AMONG INJURED PROBLEM DRINKERS Figure 2. Frequency of marijuana use and risk of injury. The odds of reporting injury are double-plotted, with frequency of marijuana use on the x-axis, overall injury odds plotted on the primary y-axis (left, for solid diamond), and odds for individual injuries on the secondary y-axis (right, for all other plots). TABLE 4. Risk Factors for Prior Injuries Significant Results of Multivariate Logistic Regression All Injuries Alcohol-related Injuries Doctor-treated Injuries 95% CI 95% CI 95% CI OR Lower Upper OR Lower Upper OR Lower Upper Risk scale 1.16*** *** *** Marijuana 2.16** *** AUDIT scale 1.08*** Education 0.88* Opiate 8.23* African American 2.32* *p < 0.05; **p < 0.01; ***p < AUDIT = Alcohol Use Disorders Identification Test. lated injuries, and doctor-treated injuries. Table 5 lists the results of logistic regression for mechanisms of injury. These tables display factors with significant effect on injury considering effects of marijuana use, demographics, alcohol use, other drug use, and risk taking/impulsivity. Independent Predictors of Prior Injury. Marijuana use is an independent predictor of injury and alcohol-related injury. Marijuana-using problem drinkers are 2.2 (95% CI = 1.24 to 3.75) times more likely to have a prior injury, 2.3 (95% CI = 1.45 to 3.53) times more likely to have had alcohol-related injury, and 1.7 (95% CI = 1.03 to 2.79) times more likely to have a motor-vehicle-related injury. Marijuana use is not an independent predictor of doctortreated injuries or any other mechanism of injury besides motor vehicle injury. Other factors are also independent predictors of injuries. Risk taking/impulsivity is an independent predictor of every category and mechanism of injury. Patients with higher AUDIT scores are more likely to report alcohol-related injuries. Within other drugs use, only opiate use is a significant predictor of doctortreated injury. Younger patients are more likely to report sports and assault injuries than older patients. African Americans are more likely to report alcohol-related and assault injuries. Males are more likely to report sports injuries. Less-educated patients are more likely to report motor vehicle, assault, and doctor-treated injuries. DISCUSSION In this ED, more than half of injured problem drinkers report using other drugs, mainly marijuana, in the three months prior to an ED visit. Injured problem drinkers who use marijuana are younger, less educated, white, and male. They have more problematic alcohol use, other drug use, and risk taking/impulsivity. After controlling for these factors, marijuana-using problem drinkers have more prior injuries, alcohol-related injuries, and motor vehicle injuries. Injured problem drinkers

7 ACAD EMERG MED January 2003, Vol. 10, No TABLE 5. Risk Factors for Mechanism of Prior Injury Significant Results of Multivariate Logistic Regression Motor Vehicle Sports Injuries Assaults Other Injuries OR 95% CI OR 95% CI OR 95% CI OR 95% CI Risk scale 1.09* * *** *** Age 0.92*** *** Education 0.86** * Male 3.91*** African American 3.01** Other race 4.45* Marijuana 1.69* *p < 0.05; **p < 0.01; ***p < who use marijuana are as ready to change their alcohol use and other risk behaviors as those who do not use marijuana. Emergency physicians need to be aware of this association and the need of many of their injured patients for both marijuana and alcohol counseling. Problematic Alcohol Use, Other Drug Use, and Risk Taking/Impulsivity. Marijuana users are more likely to have motor vehicle crashes the more often they use marijuana and drive. Marijuana users tend to binge drink, which contributes to their increased risk of injury. 44 Marijuana users often have experience with other drugs. This has led to a controversial theory of marijuana as a gateway drug. 45 Youth surveys have reported more risk behaviors in adolescent marijuana users. Marijuana users are not only more likely to drink and drive, but also to ride with a drunk driver. They are also less likely to wear a seat belt. 46 Our results are consistent with a theory of marijuana use among problem drinkers as a marker of a behavior pattern that includes even more problematic drinking, drug use, and risk taking. Injury Associated with Marijuana Use. Most investigations have examined the effects of marijuana alone, not combined effects of marijuana and alcohol. There are conflicting reports concerning marijuana use by itself and injury. Polen et al. reported that daily marijuana-using health maintenance organization (HMO) patients had more injuries during two years. 47 In two studies, marijuana users had twice the risk of being involved in crashes than non-users. 44,48 However, there are studies demonstrating no added injury risk with marijuana use. The three-year incidences of injury (56.5%) resulting in medical attention (36%), hospitalization (0.49%), and death (0.067%) were not different between marijuana users and non-users in a larger HMO study (N = 4,462). 49 Our results clearly demonstrate an association between prior injury and marijuana use in injured problem drinkers. Readiness to Change. Several studies report marijuana users responding to counseling. 26,27 Our study suggests that counselors will find marijuana-using problem drinkers ready to change and thus receptive to counseling. In the only published randomized, controlled trial of ED counseling for alcohol and injury, REIS, alcohol-related injuries were reduced. However, total injuries were not reduced. 34 Injured patients who use alcohol and marijuana may have more response to an intervention addressing both alcohol and marijuana. LIMITATIONS Several limitations of this study warrant discussion. 1. These are post-hoc analyses of data collected for other purposes. The hypotheses generated, tested, and reported here were derived after initial explorations of the data from a randomized trial revealing unexpected findings of high marijuana use. Hence, these findings of post-hoc analysis must be considered preliminary and should be subjected to explicit testing in future studies. 2. These data represent a sample of a unique population. The studied sample represents a group of injured problem drinkers who were willing to undergo counseling in a study. The high refusal rate limits the generalization of these results to all injured ED patients. Many may have refused because of the lengthy study protocol and the required follow-up session. All studies depend on willing volunteers. The patients who volunteered for this study may have wanted counseling. Most of the patients had an AUDIT score 8, indicating hazardous drinking. Refusers may have had relatively light consumption of alcohol. Light alcohol users might be expected to have less marijuana use and less severe injury. The high marijuana use rate, higher prior injury rate, and other associations

8 50 Woolard et al. MARIJUANA USE AMONG INJURED PROBLEM DRINKERS should be considered to apply only to the group of injured problem drinkers who volunteered. There may be considerable regional variation in the use of marijuana and other substances. Many patients were college students who may be novices experimenting with marijuana and other drugs. These findings may not generalize to other populations, cities, or more rural settings with different populations where marijuana use is not as prevalent. 3. Data were not collected concerning marijuana use in isolation. Isolated use of marijuana may or may not contribute to injury. This paper cannot add to that debate. 4. Data were not collected concerning the conjoint use of alcohol and marijuana and the proximity of substance use to the injury. No biochemical tests for marijuana use were administered. While our data demonstrate that being a marjiuana-using problem drinker is a risk factor for prior injury, we cannot determine whether conjoint use of alcohol and marijuana was a proximate, direct cause of injury. Emergency medicine practice includes injury prevention, since EDs serve as the primary source of care for injured persons. Currently, injured ED patients receive little preventive advice or counseling. Preventive counseling interventions for injured patients in the ED deserve additional research. Future studies should test brief interventions for alcohol, marijuana, and injury. The patterns of alcohol and marijuana use should be studied to identify possible causal links between injury and conjoint use of alcohol and marijuana. The most appropriate screening tools and criteria indicating an individual s need for an intervention should be identified. Studies of interventions need to examine which personnel physicians, nurses, or substance abuse specialists and what length, number, and type of counseling sessions are most efficient and effective. Studies should also compare intervention in the ED to referral for intervention provided outside the ED. CONCLUSIONS Marijuana use is prevalent among injured problem drinkers in the ED. Marijuana-using injured problem drinkers experience more injuries, including more alcohol-related and motor-vehicle-related injuries in the year prior to their ED visit. Marijuanausing injured problem drinkers are as ready to change their alcohol and risk behaviors as are nonusers. Given the prevalence of marijuana use, the effectiveness of brief intervention should be enhanced by broadening the focus to include marijuana. If using both alcohol and marijuana relates to injury, a timely dual-substance intervention should be more effective than counseling focused solely on alcohol. References 1. 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