Substance Use by Canadian Youth - A National Survey of Canadians' Use of Alcohol and Other Drugs - Canadian Addiction Survey (CAS)

Chapter 8: Changes Across Time

Highlights

• The rate of youth who were current drinkers, former drinkers and abstainers has remained relatively consistent across surveys conducted in 1989, 1994 and 2004.
• The lifetime and past-year reported use of marijuana among youth has increased steadily in the 15-year time span from the NADS (33.5% and 15.5%) to the CADS (39.2% and 22.2%) and the CAS (61.4% and 37.0%).
• There has been a consistent increase in the rate of use of cocaine, speed and LSD from the CADS to the CAS.

Introduction

This chapter compares results from the CAS with the NADS of 1989 and the CADS of 1994. The NADS and CADS are ancestors of the CAS. The CADS of 1994 was built and expanded on the NADS of 1989, and the CAS (2004) represents an expansion of both surveys.

Although comparable questions were asked across all three surveys, results were not subjected to a systematic trend analysis. Instead, following the method employed in the detailed report (Adlaf et al., 2005) confidence intervals were calculated for the NADS and CADS specifically for the purpose of making statements about the significance of results and differences between the three surveys. Confidence interval overlap was used to determine whether differences between the surveys were statistically significant. If there was no overlap between the confidence intervals for two estimates, these estimates were considered significantly different.

For more detailed information on the NADS (1989) and CADS (1994), please refer to Canadian Addiction Survey (CAS): A National Survey of Canadians' Use of Alcohol and Other Drugs: Prevalence of Use and Related Harms: Detailed Report (Adlaf et al., 2005).

Results

Alcohol

Prevalence of alcohol use by youth over time

Figure 8.1 examines the change in prevalence of alcohol use by youth between the three surveys: the 1989 NADS, the 1994 CADS and the 2004 CAS. The rate of current drinkers, former drinkers and abstainers among youth has remained relatively consistent across time; although a slightly higher proportion of youth today reported being current drinkers (83%) than in 1989 (81%) and 1994 (77%), this difference was not statistically significant.

Figure 8.1: Prevalence of alcohol use, Canada, aged 15-24, 1989, 1994 and 2004

Frequency of alcohol consumption by youth over time

Figure 8.2 examines the frequency of past 12-month alcohol consumption by youth across time. There has been a slight decrease from 1994 to 2004 in the proportion of youth current drinkers who reported drinking "less than once a month" and a slight increase in the proportion of those who indicate drinking "1 to 3 times a month." The proportion of youth reporting "once a week" or "more than twice a week" has fluctuated over the years, but overall there has been no significant change.

Figure 8.2: Frequency of alcohol consumption over the past 12 months, current drinkers, Canada, aged 15-24, 1989, 1994 and 2004

Heavy drinking by youth over time

Figure 8.3 demonstrates that the proportion of young current drinkers who reported consuming 5 or more drinks on at least one occasion over the past year was slightly higher in 2004 (75%) than in 1989 (67%); however, this increase was not statistically significant.

Figure 8.3: Proportion consuming 5 or more drinks on at least one occasion in past 12 months, Canada, current drinkers aged 15-24, 1989, 1994 and 2004

Changes in the rate of current drinkers aged 15 to 24 by region

Table 8.1 shows that the rate of current drinkers 15 to 24 years of age has remained fairly consistent across time. A comparison of the regional rates of past-year drinkers across the three surveys reveals only one case of a significant change; rates were significantly lower in 1994 in the Prairie region than in 1989.

Changes in the pattern of drinking among youth

Although the prevalence of past-year and lifetime alcohol consumption among youth has remained relatively stable over time, it is important to examine whether their drinking patterns have also remained stable, or if youth in 2004 tend to engage in more or less harmful patterns of drinking than they did 10 and 15 years ago. Table 8.2 reveals that the drinking patterns of youth over time have changed relatively little, with the exception of more youth drinking heavily infrequently in 2004 than in 1989 and 1994 (13.1% versus 8.5% and 9.0%).

Changes in reported harms from one's own alcohol use, lifetime and past year

Aside from patterns of drinking, it is important to examine whether youth today are reporting more harms from their own alcohol use than they did in the past. Table 8.3 reveals that with the exception of a slight increase from 1994 to 2004 in the proportion of youth who reported harms to friendships or social life (11.0% versus 15.9%), the lifetime reported harms by youth have remained fairly stable. Table 8.4 reveals that over time there has been no change in the past-year reported harms due to one's own alcohol use by youth. These findings are not surprising given the previous findings demonstrating that the prevalence of alcohol use, as little.

Changes in harms due to others' alcohol use

Table 8.5 examines harm and victimization experienced by youth as a result of the alcohol use of others. Youth in 2004 reported experiencing more family problems as a result of others' use of alcohol than did youth in 1994 (13.9% versus 7.8%). In addition, a higher proportion of youth in 2004 reported having been a passenger with a drunk driver than those in 1989 or 1994 (32.5% versus 23.1% and 19.7%, respectively). No other changes across time were evident for the other types of harm examined.

Cannabis

Differences over time in reported lifetime and current cannabis use by youth

Figures 8.4 to 8.7 examine changes in reported marijuana use among youth over time. The past-year reported use of marijuana among youth has increased steadily in the 15-year time span from the NADS (15.5%) to the CADS (22.2%) and the CAS (37.0%). The lifetime use of cannabis among youth, however, remained relatively stable from the NADS to the CADS (33.6% versus 39.2%) but increased significantly in the 10-year time span from the CADS to the CAS (39.2% versus 61.4%) (Figure 8.4).

Figure 8.4: Percentage of young Canadians who used cannabis in their lifetime and in past year, Canada, aged 15-24, 1989, 1994 and 2004

Changes in lifetime cannabis use broken down by sex and age

The lifetime use of cannabis was fairly stable for both males and females from the NADS to the CADS (36.8% versus 44.6% for males; 30.3% versus 33.6% for females), but rose significantly from the CADS to the CAS for both (44.6% versus 64.7% for males; 33.6% versus 58.0% for females) (Figure 8.5 and 8.6). This increase in the prevalence of lifetime use from the CADS to the CAS but not the NADS to the CADS was most pronounced for both males and females aged 17 to 19 and 20 to 24 but not for those aged 15 to 16. Instead, for both males and females aged 15 to 16, the lifetime cannabis use increased significantly from the NADS to the CADS, but the prevalence remained fairly steady in the 10-year period between the CADS and the CAS (Figures 8.5 and 8.6).

Figure 8.5: Percentage of young Canadians who used cannabis in lifetime, males, Canada, 1989, 1994 and 2004

Figure 8.6: Percentage of young Canadians who used cannabis in lifetime, females, Canada, 1989, 1994 and 2004

Changes in current cannabis use broken down by sex and age

Figures 8.7 and 8.8 reveal that unlike that demonstrated for lifetime cannabis use, among both males and females there has been a steady and consistent increase in cannabis use from 1989 to 1994 and 2004 (19.2%, 26.7% and 41.4%, respectively).

As with lifetime use, among males aged 15 to 16 the rate of current cannabis use increased significantly from 1989 to 1994 (10.4% versus 25.6%) but remained fairly consistent from 1994 to 2004 (25.6% versus 27.3%). Among 17- to 19-year-old males, the increase from 1989 to 1994 was not significant (16.6% versus 28.8%), but there was a significant increase between 1994 and 2004 (28.8% versus 47.0%). This pattern was also demonstrated for males aged 20 to 24 (23.7% versus 26.0% versus 42.0% (Figure 8.7).

Although the rate of current cannabis use was higher in 1994 than in 1989 and again higher in 2004, for females aged 15 to 16, these changes were not significant (11.2% versus 22.7% versus 23.5%). For females aged 17 to 19, there was a significant increase over the 15-year time span (9.8%, 21.4% and 39.6%). For females aged 20 to 24, the rate of use remained fairly consistent from 1989 to 1994 (13.0% versus 13.1%) and increased in 2004 (30.7%).

Figure 8.7: Percentage of young Canadians who used cannabis in past 12 months, males, Canada, 1989, 1994 and 2004

Figure 8.8: Percentage of young Canadians who used cannabis in past 12 months, females, Canada, 1989, 1994 and 2004

Changes in the frequency of cannabis use

Among youth overall there were no differences between the NADS and the CADS in frequency of cannabis consumption; however, in the 10-year time span between the CADS and the CAS there was a significant increase in the proportion of current users who used cannabis "at least once a week" over the past 3 months (43.7% versus 27.9%) (Table 8.6).

In terms of changes in the pattern of use among the different age groups of youth, some changes were apparent. For youth aged 15 to 19, there was a decrease from 1994 to 2004 in the proportion who stated that they used cannabis "1 to 3 times a month" (20.9% versus 9.5%). For youth aged 20 to 24, there was an increase from 1989 to 1994 in the proportion that used "less than monthly" (42.9% versus 67.3%), perhaps accounted for by a significant decrease in the proportion who used "1 to 3 times a month" (30.5% versus 12.7%). This increase in 1994 in the proportion of 20- to 24-year-olds used "less than monthly" decreased again from 1994 to 2004 (67.3% versus 42.1%). The decrease in 2004 can be accounted for by an increase in that used at least weekly (41.2% versus 20.0%).

Illicit Drugs

Differences over time in reported lifetime prevalence of illicit drugs among youth

Across surveys, there has been a consistent increase in the rate of use of cannabis, cocaine/crack, LSD, speed and heroin among youth. More specifically, the rate of use of cannabis increased from 33.6% in 1989 to 61.4% in 2004, cocaine increased from 4.9% to 12.5%, LSD increased from 3.5% to 16.4%, and speed increased from 1.8% to 9.8% (Figure 8.9).

Figure 8.9: Trends in the prevalence of lifetime cannabis, cocaine, LSD (acid) and speed (amphetamines) use, Canada, aged 15-24, 1989, 1994 and 2004

Overall, the proportion of youth who reported having used at least one of cannabis (including one time only), cocaine/crack, LSD in the CADS and hallucinogens in the CAS, speed and heroin in their lifetime has increased significantly from the CADS to the CAS (39.7% versus 62.0%), as has the proportion who reported past-year use (22.7% versus 37.9%). In addition, these rates of use have increased for both males and females over time (Table 8.7).

As is evident in Table 8.8, in 2004 the lifetime use of illicit drugs such as cannabis, cocaine/crack, LSD or hallucinogens, and the combination of LSD/speed/ heroin had increased significantly for youth overall and by sex.

Lifetime harm from one's own drug use

Table 8.9 presents the trend from 1994 to 2004 in the proportion of youth who reported experiencing harm in each of the areas examined as a result of their use of cannabis (excluding one time only), cocaine/crack, LSD/hallucinogens, speed, heroin, steroids or solvents. As evident from the table, the rate of lifetime harms experienced by youth as a result of their illicit drug use has remained relatively consistent across time for all areas examined: friendships and social life, physical health, home life or marriage, work/studies/ employment opportunities, and financial position.

Driving

Table 8.10 presents the changes over time in the proportion of youth who have driven after having two or more drinks in the previous hour or within 2 hours of using cannabis/hash. The rate of driving while impaired by alcohol has not changed significantly over time for youth (27.2% versus 25.4% versus 20.9%), nor has the rate of driving while impaired by cannabis/hash (25.8% versus 31.9% versus 39.8%).

Summary and Discussion

It is apparent from the data presented that over time the rate of use of some substances among youth, and the rate of experienced harms, have changed for some substances but not for others. More specifically, for alcohol, the picture is very clear: there has been relatively little change over the past 15 years in the prevalence of use, patterns of use and alcohol-related harms.

Contrary to this, there has been a significant increase in the lifetime and past 12-month use of cannabis over the past 15 years, with rates more than doubling among youth. When examining the trend broken down into the youth subgroups, however, it is apparent that this increase is fairly steady for 17- to 19- and 20- to 24-year-olds; however, for the 15- to 16-year-old age group there was an increase from 1989 to 1994 but the rate of use has remained fairly steady since that time. Reasons for the differential trend in cannabis use for 15- to 16-year-olds versus those 17 to 24 are beyond the scope of this study; nonetheless, this finding is interesting and in warrant of greater scrutiny.

Over the past 15 years, there has also been an increase in the rate of other illicit drugs such as cocaine, LSD and speed. However, it is important to note that while the rate of illicit drug use has increased for youth over the past 15 years, the increase in prevalence is not mirrored by an equal increase in drug-related harms. This does not mean that prevention and intervention efforts are not necessary; the rates of use are still quite high among the 15- to 24-year age group, and much higher than that demonstrated by adults.

While the CAS allowed comparison of estimates in 2004 with those of earlier years, it is important to point out that examining changes across the three separate surveys does have limitations. Nonetheless, with time and the development of a sustained monitoring and surveillance strategy, something that is currently in the process, a more comprehensive and sound examination of the changes in substance use and related behaviours over time will be made possible.