Drug and Alcohol Review (1996) 15, 137-143

Correlates of the perceived health risks of marijuana use among Australian adults

W A Y N E H A L L 1 & J O A N N E L S O N 2

1National Drug and Alcohol Research Centre, University of New South Sydney; and 2RFJRK Research, Sydney, New South Wales, Australia

Abs~a~

Wales,

A quota sample of 3272 people from the Australian population was surveyed by telephone about the health risks of marijuana use. Three-fifths of the sample (62%) believed that there were health problems caused by marijuana use and one in four (27%) were uncertain. The most commonly cited health effects were: lung cancer, mental problems, memory loss and respiratory disease. The health risks of marijuana use were perceived to increase with increasing frequency of use, and to be greater when the user was a teenager rather than an adult. The perceived health risks of marijuana increased with age, were higher among women than men, decreased with increasing education and frequency and quantity of alcohol and were substantially lower among those who had used marijuana, and those who knew someone who had used marijuana. [Hall W, Nelson J. Correlates of the perceived health risks of marijuana use among Australian adults. Drug Alcohol Rev 1996;15:137-143]

Key words: health risks and marijuana; marijuana use.

Introduction

Marijuana is the most widely used illicit drug in Australia. In 1993 it was reported to have been used at some time by a third of all adult Australians and by 72% of young adults aged between 20 and 24 years [1]. The use of marijuana has increased dra- ma t i c@ over the past 20 years, with the proportion reporting ever having used increasing from 12% of adults in 1973 to 34% in 1993 [1,2].

Effective education about the health risks of mari- juana use presupposes an expert consensus upon what these health effects are. A continued contro- versy about the severity of the adverse health effects of marijuana has been a major obstacle to effective health education. In the absence of health education,

the Australian community has been exposed to po- larized views ranging from, on one hand, the view that marijuana is safer than aspirin [3] to, on the other hand, the view that marijuana is a deceptively dangerous drug [4]. Health educators have been understandably reluctant to provide health infor- mation on cannabis for want of knowing what sort of advice to give.

Uncertainty about the health effects of cannabis was reduced by the publication of a comprehensive review of the health and psychological effects of cannabis [5] commissioned by a National Task Force on Cannabis. It identified the clearest acute health risks as adverse psychological experiences, and

Wayne Hail, BA, PhD, Director, National Drug and Alcohol Research Centre, University of New South Wales, Sydney 2052, Australia; Joan Nelson, REARK Research, Sydney, Australia. Correspondence to Professor Hall

Received 4 July 1995; revised 13 January 1996; accepted for publication 25 January 1996.

0959-5236/96/020137-07 © Australian Professional Society on Alcohol and other Drugs

138 Wayne Hall ~ Joan Nelson

the possibility of an increased risk of motor vehicle accidents if people drive while intoxicated. The most probable chronic health risks of cannabis use when used daily over a period of years or decades were: an increased risk of developing chrohic bronchitis; the development of a dependence syndrome; and an exacerbation of the symptoms of schizophrenia. Other possible risks include: low birth weight babies for women who smoke cannabis during their preg- nancies, and respiratory cancers. High risk groups include: adolescents with poor school performance, women of child-bearing age; individuals with car- diovascular and respiratory diseases, and individuals with a personal or family history of psychotic illness [5].

Effective health education about cannabis also assumes some knowledge about what the community believes the health effects of marijuana to be. There have been no special purpose surveys of community knowledge of the effects of marijuana that have been conducted in Australia or in other countries to address this issue in detail. Johnston et al. [6] have reported data on young American adults' ratings of the risks of marijuana use at various frequencies of use, namely once or twice, "occasionally" and "regularly". Although the perceived risk has in- creased over time in tandem with declining mari- juana use, there has been no comparison of these risks with those of other drugs, and no exploration of what respondents believed the health risks of marijuana to be.

Limited information on the perceived health risks of marijuana use in Australia has been gathered en ])assant in population surveys of drug use [2], and in studies of the perceptions of the health risks of other illicit drugs among purposive samples of young adults [e.g. 7, 8].

General population surveys, such as the National Campaign Against Drug Abuse (NCADA) house- hold surveys [2] have consistently found that mari- juana is ranked second after heroin as the drug that people think of when asked without prompting what constitutes the "drug problem" [2]. Approximately a third of the population in each of the 1985, 1988 and 1991 surveys rated marijuana use as "a serious concern affecting the general community". Among the 5% of the sample who identified marijuana as the main drug of community concern the most common concerns were that it: "affects youth" (16%), is "available and cheap" (16%), "leads to hard drugs" (13%) and is "harmful to health" (8%).

A benign perception of the health risks of mari- juana use emerges from samples of young adults. In such samples marijuana use is typically perceived as not being very risky by comparison with the use of other illicit drugs. Homel et al. [7], for example, surveyed 500 young Sydney adults about their per- ceptions of the risks and attractions of various drugs in a study of the "drug market position" of cocaine. Respondents were asked to rate the risks of a "low level" of use of alcohol, tobacco, marijuana, cocaine, amphetamines and sedatives. Marijuana was grouped with alcohol and tobacco as drugs that posed a much lower risk to users than the other illicit drugs.

Similar findings emerged from Spooner et al.'s [8] street intercept survey of young illicit drug users. These investigators recruited a sample of 581 young adults aged 16-21 years who had used at least one illicit drug other than marijuana within the last 3 months. Almost all had used marijuana (98%) and 93% had used it within the past 3 months. They were asked about the health risks of marijuana, sedatives, amphetamine, cocaine, hallucinogens, in- halants, ecstasy and heroin. Marijuana was ranked on average sixth out of the eight illicit drugs on eight different health effects, and it received the lowest ranking for four of the eight. Only three health problems were identified with any frequency as consequences of marijuana use. These were: emotional problems (35%), lung problems (34%) and brain damage (32%).

The major aim of the current survey was to provide information on the perceived health effects of marijuana use in the general Australian popu- lation to inform health education programmes about marijuana use. It aimed to discover: what the public believes about the health risks of marijuana use to be, how they evaluated these risks in comparison with those of alcohol and tobacco, and how individ- ual characteristics were related to these beliefs.

Method

The survey of the public perception of the health risks of marijuana was preceded by 15 focus groups in a cross-section of Australian communities (Ade- laide, Ballarat, Brisbane, Melbourne, Mount Gam- bler, Sydney and Toowoomba). Efforts were made to recruit respondents who ranged in age from 12 to 45 years or more, with specific focus groups contain- ing individuals of similar age. The groups included

Perceived health risks of marijuana use 139

both men and women, and people who had and had not used marijuana. The comments and observations of the focus groups participants were used to gener- ate a draft interview schedule. Some questions were trialed in several of the focus groups that were conducted towards the end of the qualitative phase of the study in Sydney.

Samp~ng

The telephone survey was carried out using comput- erized assisted telephone interview technology. A national quota sample was drawn from CD-ROM disks containing up to date listings of the Tdecom White Pages. The sample was recruited from all states and territories, and from both capital cities and rural areas in each case. To select a respondent randomly from among the members of each house- hold the individual whose birthday was nearest to the date on interview was interviewed. The sample was allocated equally across states, with a minimum of 400 interviews per state. The lower age limit for inclusion in the sample was 14 years, in which case parental consent for the interview had to be ob- tained. Respondents from a non-English-speaking background were interviewed by bilingual interview- ers.

Interview schedule

The standardized interview schedule was arranged in several sections. First, a series of questions were asked about the benefits and risks of alcohol and tobacco, and the risks of amphetamine and heroin use. The second section contained the questions on the health risks of marijuana use. The third section included questions about the respondent's alcohol, tobacco and marijuana use. The final section asked questions about the respondent's social and demo- graphic characteristics.

Open-ended questions about the health effects of marijuana were supplemented by direct questions about specific adverse health effects of marijuana. Where appropriate existing questionnaire items were used to inquire about the health risks. For example, Johnston et al.'s [6] items on the perceived risks of marijuana with increasing frequency of use were used with minimal adaptation to specify frequency of use corresponding to such phrases as "occasionallf' and "regularly". Similarly, items were adapted from previous questionnaires in studies of the public per-

ceptions of the health effects of alcohol [9, 10]. When there were no existing survey items new questions were devised, reviewed by people who were knowledgeable in the drug and alcohol field and tested in the focus groups, and in 20 pilot interviews prior to the survey going into the field.

The term "marijuana" was used throughout the interview to describe any of the forms of cannabis (leaf, heads and resin). Although "cannabis" is the more correct term for all forms of drug derived from the plant cannabis sativa "marijuana" is the popular term used in ordinary language so it was used throughout the interview and in this report.

Results

Sample characteristics

The achieved sample consisted of 3273 people with an average age of 36 years, 52% of whom were women. Three-quarters of the sample (76%) were Australian-born from an English-speaking back- ground, 22% were born overseas, and 2% were Aboriginal or Tortes Strait Ishnders. More than half were married or in de facto relationships, 30% had not married and 14% were separated, divorced or widowed. Two out of five of the sample had some tertiary education, a third had a primary education, and one in five had a secondary education. More than half of the sample were in filll-time (40%) or part-time (12%) paid employment, while 18% were retired, 13% were students, 13% were employed in home duties and 4% were unemployed.

The sample only comprised 39% of eligible people who were contacted. This low response rate occurred because many people were not interviewed on first contact because it was inconvenient. The Common- wealth government which commissioned the survey wanted data collection completed within 2 weeks, so further numbers were called until a quota of inter- views from each state had been met. Despite the low response rate the sample characteristics were re- markably similar to those of the most recent Na- tlonal Drug Strategy Household Survey of Drug Use. The sample differed marginally in age, gender, marital and employment status, education, and al- cohol use from the 1993 NCADA household survey sample [11]. The current sample had a more equal representation of men and women, a slight over- representation in the 14-24-year and 40 + age group, more people with a tertiary education, and it

140 Wayne Hail ~ Joan Nelson

Table 1. Perceived health risks of marijuana use at varying frequencies of use (%)

Once or

Risk twice Occasionally Weekly Daily

No 74 45 19 5 Slight 14 27 19 6 Moderate 4 14 26 17 Great 2 6 27 65 Unknown 5 9 8 7

Mean rating 0.31 0.79 1.46 2.30

contained fewer regular weekly drinkers and more people who did not drink alcohol. The demographic characteristics of the sample were reasonably com- parable with those of the 1993 NCADA Household Drug Use Survey, with the exception that the pre- sent sample was marginally better-educated.

The great majority of the sample (93%) consumed alcohol. More than half (56%) drank at least weekly while 39% drank less often than weekly. The typical quantity consumed (in standard drinks) was one to two drinks for 55%, three to four for 26%, five to six for 10%, and seven or more drinks for 9%. The patterns of alcohol use in the current survey differed marginally from those reported in the 1993 NCADA Household Survey [11] in that the current sample contained fewer regular weekly drinkers than the N C A D A sample (54% versus 70%), and more people who did not drink alcohol. However, the distribution of the typical quantity of alcohol con- sumed per drinking occasion did not differ. There were no differences between the two samples in the patterns of tobacco use and a marginal difference in the proportion who had ever tried marijuana (38% versus 34%).

The perceived lsealtk risks of marijuana

Three-fifths of the sample (62%) believed that there were health problems caused by marijuana use and one in four (27%) were uncertain. The most com- monly cited health effects were: lung cancer (20%), mental problems (13%), memory loss (9%), respirat- ory disease (8%) and confusion (7%).

Respondents were asked to rate the degree of risk (no risk, slight, moderate and great risk) to health from using marijuana once or twice, occasionally, weekly and daily. The perceived risk increased stead- ily with increasing frequency of use. The proportion

who believed that there was a "great risk" increased from 2% for using marijuana once or twice to 65% using it daily. The relationship between perceived risk of marijuana use and frequency of use is most clearly shown when simple numerical scores are assigned to each level of risk (0 = no, 1 = slight, 2 = moderate and 3 = great risk). Table 1 shows a strong increase in the average perceived risk with increasing frequency of use.

There was no consensus as to what the specific health effects of marijuana were at each frequency of use. The risk most frequently mentioned at almost all frequencies of use was the risk of addiction or dependence which paradoxically decreased with in- creasing frequency of use (30%, 32%, 27% and 22%, respectively). The risks that were most dearly per- ceived to increase with increasing frequency of use were brain damage (8%, 15%, 23% and 29%) and lung damage (5%, 8%, 13% and 14%). Other risks that remained relatively constant across frequency of use were progressing to harder drugs (12%, 8%, 9%, 9%), behaviour change (6%, 5%, 5%, 6%) and im- paired driving (5%, 4%, 4%, 3%).

Respondents were also asked whether they be- lieved that regular and occasional marijuana use was "OK from a health angle" for an adult and a teenager. There was strong perception that both occasional and regular marijuana use were much more risky for a teenager than for an adult. The discrepancy in perceived risk was most marked with regular use: a third of the sample thought that regular use by an adult was "OK" but only 8% thought it was "OK" for an adolescent to do so.

There was also a lack of consensus about what the specific risks of adolescent marijuana use were. The most common responses were non-specific, such as that the respondent was generally opposed to any drug use by teenagers (17%) or that there were

Perceived health risks of marijuana use 141

unspecified "health reasons". More specific responses were that: teenagers were not old enough to decide (14%), they could become addicted (14%); marijuana use could adversely affect growing bodies (13%); and it impaired their ability to learn at school (10%).

Specific health effecls of marijuana

Addictive potential. Just under half of the sample (47%) believed that marijuana was "sometimes ad- dictive", one in four (29%) believed that it was "always addictive", 11% thought it was "never addic- tive", and the remainder (13%) were unsure. The responses of participants in the focus groups to a similar question suggests that the response "sometimes addictive" was taken to mean that mari- juana could be addictive for particular types of peo- ple who used the drug in particular ways (e.g. heavily).

el gateway drug. There was a similar qualified opinion about whether marijuana use could lead to the use of harder drugs such as heroin. Two-thirds of the sample (65%) believed that it sometimes did. Only 18% thought it always did, 11% thought it never did, and 6% were unsure.

Lung cancer. Just over half of the sample (56%) thought that marijuana smoking was likely or very likely to cause lung cancer. One in four (24%) were uncertain, and 19% thought it unlikely or very un- likely.

Driving accidents. The majority (88%) agreed that driving a car after using marijuana increased the risk of having an accident. The consensus was that the risk of drMng after using marijuana was no worse than the risks of drinking and driving: 39% believed that the chances of an accident after smoking mari- juana were less than those of drink driving, 33% believed that the risks were about the same, and only 12% that the risk was greater (with 17% unsure). The overwhelming majority (88%) also believed that the risks of an accident were greater when someone &ove a car after using both alcohol and marijuana than after using either drug alone.

Correlates of perceived health risks

A simple index of the perceived health risks of marijuana was constructed by combining answers on

a series of specific questions about the health risks of marijuana. These were: the four ratings of the health risks of increasing frequency of marijuana use; three items asking whether the drug was addictive, whether its use was likely to lead to the use of other drugs, and whether its use increased the risk of accidents; and four items inquiring whether it was "OK from a health angle" for an adult or a teenager to use marijuana "occasionally" or "regularly". These items were submitted to a principal components analysis (PCA) to discover if they comprised a simple scale of the perceived health risks of cannabis use, scores which could be obtained by adding the standardized scores on the items.

The PCA suggested that the items did comprise a scale of perceived risk. All 11 items had substantial positive correlations (all greater than 0.40) with scores on the first principal component which ac- counted for 42% of the variance in the items. The factor score coefficients for the items were approxi- mately equal, indicating that each item made an approximately equal contribution to the overall in- dex. Scores on the first principal component were accordingly used in analyses of correlates of per- ceived health risks of marijuana use. These scores were scaled to a distribution with a mean of 100 and a standard deviation of 15.

An analysis of univariate relationships between various respondent characteristics and scores on the index of perceived risk showed that women (M = 103.0) perceived marijuana use to be riskier to health than men ( M = 96.8, t = 9.34, p<0.001) , and the perceived health risks generally increased with age (r = 0.21, p < 0.01). Those who had known a marijuana user (M = 95.9), perceived a much lower risk than those who had not ( M = 107.5, t = 17.7, p < 0.001). Those who had used marijuana (214= 90.8) perceived a much lower health risk from marijuana use than those who had not (M = 106.9, t = 28.3, p < 0.001). Perceived risk also decreased with increasing frequency of alcohol consumption (r = - 0.17, p < 0.01), and increasing quantity con- sumed per drinking occasion (r = - 0.17, p < 0.01). Current cigarette smokers perceived a lower health risk of marijuana use ( M = 92.6) than ex-smokers 01//=100.0) and non-smokers (tV/=103.7, F[2, 1960] = 91.2, p < 0.001).

Since many of these correlates of perceived risk were correlated with each other multiple linear re- gression analyses were used to identify which vari- ables were most strongly related to perceived risk

142 Wayne Hall &Joan Nelson

115

110 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Q - - - - - ~ , ~ - - - |

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9 5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

9 14-19 20-24 25-29 30-34 35-39 40-54 55-69 70+

Age

Figure 1. Risk ratings by age and gender ([B males; @ females).

when account was taken of the relationships between them. The five variables that remained in the multi- variate regression model were: sex, knowing a mari- juana user, being a marijuana smoker, smoking status (non-smoker, ex-smoker and current cigarette smoker entered as two dummy variables) and having used marijuana (R2=0.33, F[5, 1941] =189.27). That is, being male (B = - 3.7, p < 0.001), being a marijuana user (B = - 12.5, p < 0.001), knowing a marijuana user (B = - 4.5, p < 0.001), and being a current cigarette smoker (B = - 3.5@ < 0.001) were all associated with a lower perceived health risk of marijuana use when account was taken of the rela- tionships between them. These results suggest that the gender difference in perceived risk (Fig. 1) was not explained by any of the other variables, while the large change in perceived risk with age was explained by the fact that younger adults were more likely" to have used cannabis and to know others who had used cannabis.

D i s c u s s i o n

Overall, two-thirds of the sample believed that mari- juana use could harm health. The most readily recognized health effects were the respiratory effects of smoking and "mental problems", including mem-

ory loss. The risks of drMng while intoxicated by marijuana were only recognized after prompting. The sample recognized that the health risks of marijuana use increased with increasing frequency of use, although there was little agreement on what specific health risks increased with increasing fre- quency of use. Many respondents, including a sub- stantial proportion of those who thought that marijuana use by adults was not very risky, believed that marijuana use had adverse effects on adolescent health. As in the 1993 NCADA survey [11], the reasons for this concern were not well formulated.

The perceived health risks of marijuana use were related to knowing someone who had used the drug, and to personal use of the drug. This probably explains the discrepancy between the perceived health risks of marijuana in general population sur- veys and surveys among young adults. Younger peo- ple were more likely to have either personal or vicarious knowledge of the acute health effects of marijuana. Since these acute effects are relatively innocuous by comparison with the acute and hang- over effects of alcohol, it is perhaps not surprising that marijuana is perceived as being safer than al- cohol and tobacco,

The current findings agree with the limited evi- dence available from previous studies. The health

Perceived health risks of mar~iuana use 143

risks of marijuana that were identified without prompting were also very similar to those reported by Bertram & Flaherty [10] in their survey of the Sydney Vietnamese-speaking community. The pro- portions recognizing adverse health effects were very similar as was the proportion that did not know if there were any health effects. The main health effects identified were also very similar, namely memory impairment (29%), mental health problems (18%), decreased concentration (18%) and lung can- cer (18%).

On the whole, the survey did not identify major discrepancies between what the research evidence indicates are the most probable adverse health effects of marijuana [5] (motor vehicle accidents, depen- dence and respiratory disease), and what the com- munity believes the health risks of marijuana use to be. The respiratory effects of marijuana smoking, for example, were well recognized, presumably by ex- trapolation from the respiratory risks of cigarette smoking. None the less, the community's awareness of the risk of being involved in an accident when driving while intoxicated with marijuana could be heightened since this was not volunteered without prompting.

There was also only a conditional recognition of the risks of marijuana dependence in that most respondents thought that users could "sometimes" become addicted to the drug. The discussion in the focus groups suggested that marijuana dependence was seen as a reflection of the user's personality rather than a specific drug effect, since dependence apparently only afflicts a minority of users. Perhaps the factors that increase the risk of marijuana depen- dence, especially daily marijuana use [5] could be better known.

Recognition of the major health risks of marijuana use could be reinforced by educational materials and programmes that stress the similarities between the health risks of alcohol, tobacco and marijuana. This could be done in the context of general educational programmes about the health risks of all forms of drug use, including alcohol and tobacco, rather than as part of a special purpose campaign that focused solely on the health risks of marijuana.

A caveat needs to be entered about the sample selected for the survey. Because it was a quota sample rather than a probability sample it may not be representative of the views of the Australian population. Its demographic characteristics and pat-

terns of drug use resembled those from recent na- tional household surveys but it would be desirable to include some of the questions from this survey in future household surveys. Repeated surveys would be useful in evaluating the impact of any educational campaigns about the health effects of cannabis that are implemented.

Acknowledgement

This study was funded by the Commonwealth De- partment of Health and Human Services, Australia.

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