Research report no.12 2005

In the driver's seat:
Understanding young adults' driving behaviour

A report on the ATP Young Drivers Study from the collaborative partnership between the Australian Institute of Family Studies, the Royal Automobile Club of Victoria and the Transport Accident Commission of Victoria.

by Diana Smart and Suzanne Vassallo
with Ann Sanson, Samantha Cockfield, Anne Harris, Warren Harrison and Allison McIntyre

6. Relationship between unsafe driving and other problem behaviours

An important issue is taken up in this next section - namely, the degree to which unsafe driving is associated with other types of problem behaviours. As outlined earlier, it has been suggested that many problem behaviours (such as antisocial behaviour, substance use, other risk-taking behaviours) are related to each other, and may be caused by a common underlying trait or propensity for problem behaviour. According to this view, certain forms of unsafe driving (such as risky driving) should not be viewed as isolated problems, but rather as manifestations of a broader problem behaviour syndrome (Crettenden and Drummond 1994; Jessor 1987; Newcomb and McGee 1991; Swisher 1988; Williams 1998; Wilson and Jonah 1988).

If this theory is correct, then it would be expected that the pathways to these forms of unsafe driving would be similar to those found for other types of problems, such as antisocial behaviour and substance use. This would have important intervention and prevention implications, as it would mean that appropriately targeted efforts could have a broad impact, reducing a range of problematic behaviours. Nevertheless, without sound research evidence, a broad behaviour syndrome should not be assumed to account for unsafe driving behaviour.

In this section, the relationship between unsafe driving and other problem behaviours is explored by: investigating the similarity between the precursors of unsafe driving and those of other problem behaviours (that is, antisocial behaviour and substance use); examining rates of problem behaviours among unsafe drivers; exploring the connections between problem behaviours in adolescence and later unsafe driving behaviour in early adulthood; and determining whether there are specific risk factors for different combinations of problem behaviours in adulthood.

For the purposes of this examination, levels of risky driving (low, moderate or high) are used to indicate unsafe driving. This variable was selected as it encompasses a wide range of unsafe driving behaviours (speeding, failure to wear a seat-belt or helmet, driving when very tired or when under the influence of alcohol or illicit drugs) and is positively associated with negative driving outcomes (crash involvement and speeding violations).

Substance use (alcohol and marijuana use) and antisocial behaviour are the other problem behaviours examined here. These variables were selected due to their prevalence in this age group, the adverse effects they may have on an individual's life, and their close association with one another, which suggests they may reflect a broader underlying syndrome (Jessor 1987; Newcomb and McGee 1991).

Overlap between the precursors of risky driving and other problem behaviours

In order to examine the relationship between risky driving and other problem behaviours, the similarity between the longitudinal precursors of risky driving, antisocial behaviour and substance use was examined to see if similar personal and/or environmental characteristics predicted each type of outcome. For the purposes of this comparison the precursors of high risky driving identified earlier in this report were used, while precursors of antisocial behaviour and substance use were drawn from previous Australian Temperament Project (ATP) research. The precursors of adolescent antisocial behaviour were reported as part of the collaborative project between the Australian Institute of Family Studies and Crime Prevention Victoria (see Vassallo et al. 2002 for further details).

In the first of a series of reports from this collaborative project, 39 three distinct patterns of adolescent antisocial behaviour were identified using adolescents' reports of their own antisocial behaviour between the ages of 13 and 18 years. The most problematic of these was a 'Persistent' pattern of adolescent antisocial behaviour, which was characterised by high levels of antisocial behaviour 40 at multiple time points over adolescence. Individuals who engaged in Persistent adolescent antisocial behaviour could be distinguished from those who consistently engaged in little or no antisocial behaviour over adolescence (a Low/non antisocial pattern) from as early as five to six years of age. Group differences typically centred on individual characteristics (such as temperament style, externalising behaviour problems, social skills, coping styles and attraction to risk taking) as well as aspects of peer relationships and school adjustment. However, some family environment characteristics also differentiated the Persistent and Low/non antisocial groups. Group differences were generally to the disadvantage of the Persistent group.

The precursors of adolescent substance use are taken from a report commissioned by the Ross Trust (Williams et al. 2000). As part of a series of in-depth analyses, ATP participants who engaged in multiple licit and/or illicit substance use41 during mid-adolescence were compared to the remainder of the ATP sample on a wide range of characteristics, at each survey wave, to identify precursors for the adolescent multi-substance use. These analyses revealed that adolescents who became multisubstance users could be differentiated from the rest of the sample from as early as infancy. More specifically, multi-substance users generally had more problematic personal characteristics (such as a more 'difficult' temperament style, higher aggression and depression) and experienced poorer quality peer relationships than other young people. They also tended to be more sociable and less fearful. The risk factors identified for high risky driving, persistent adolescent antisocial behaviour and multi-substance use are summarised in Table 29. As a guide to interpreting this table, a 'tick' tick indicates that a particular characteristic (activity) was found to be a precursor of a specific outcome (persistent adolescent antisocial behaviour), while a 'cross' (X) indicates that this characteristic was not associated with the outcome in question. For example, the temperament characteristic of 'negative reactivity' was found to be a precursor of persistent adolescent antisocial behaviour but not high risky driving or multi-substance use.

As Table 29 shows, there was considerable overlap in the precursors of high risky driving, persistent adolescent antisocial behaviour and multi-substance use. For example, approximately one-fifth of the precursors listed in Table 29 predicted all three outcomes. Common predictors were found in the domains of temperament style (task persistence), behaviour problems (aggression, hyperactivity), school adjustment (school adjustment difficulties), peer relationships (friendships with antisocial peers) and parent-child relationships (attachment to parents).

Overlap between the precursors of high risky driving behaviour, persistent adolescent antisocial behaviour and adolescent multi-substance use

The highest degree of overlap was evident between the precursors of persistent adolescent antisocial behaviour and multi-substance use, which may in part be due to the time period at which these variables were measured. Antisocial behaviour and substance use were both measured during adolescence (13-18 years and 15-16 years, respectively), whereas risky driving was measured later, when participants were aged 19-20 years. More than half (55 per cent) of the predictors listed were common to both of the outcomes. However, there was also substantial overlap between the precursors of high risky driving and persistent adolescent antisocial behaviour (38 per cent of precursors in common), and to a lesser extent, high risky driving and multi-substance use (24 per cent in common). Interestingly, school readiness in early childhood (how well a child adapts to the transition to primary school) was the only characteristic that uniquely predicted high risky driving behaviour.

Fewer risk factors were identified for high risky driving than for persistent adolescent antisocial behaviour or multi-substance use. For example, whereas several temperament factors were identified as predictors of persistent adolescent antisocial behaviour and/or multi-substance use, only one temperament factor (persistence) was identified as a precursor of high risky driving. Similarly, more characteristics associated with interpersonal relationships (peer and parent-child) predicted persistent adolescent antisocial behaviour and/or multi-substance use, than high risky driving. However, as noted above, risky driving was measured at a later age than these other problem outcomes (early adulthood compared with adolescence), and the longer time span between risks and outcome for risky driving, may have contributed to the fewer number of precursors identified.

Taken together, these findings offer partial support for Problem Behaviour Theory (Jessor and Jessor 1977; Jessor 1987), as they suggest that high risky driving, persistent adolescent antisocial behaviour and multi-substance use are somewhat interrelated in terms of their precursors. However, it should be noted that high risky driving did not share as many precursors with multi-substance use or persistent adolescent antisocial behaviour as these problem behaviours did with each other; and the degree of overlap between the outcomes was not absolute.

Thus, these findings suggest that while some common factors may contribute to the development of these three problem behaviours (particularly persistent antisocial behaviour and multi-substance use), it is likely that some unique attributes or factors also play a role in their etiology. Consequently, the precursors and correlates of high risky driving, persistent adolescent antisocial behaviour and multi-substance use should not be assumed to be the same, and hence, need to be examined separately from each other.

Summary

In summary, there was some overlap in the precursors of high risky driving, persistent adolescent antisocial behaviour and multi-substance use, with aspects of temperament style, behaviour problems, school adjustment, peer relationships and the parent-child relationship, predicting all three outcomes. The highest degree of overlap was between the precursors of persistent adolescent antisocial behaviour and multi-substance use, although there was considerable overlap between the precursors of high risky driving and persistent adolescent antisocial behaviour, and to a lesser extent, high risky driving and multi-substance use. Only one risk factor uniquely predicted high risky driving (school readiness in mid childhood).

There were fewer risk factors for high risky driving than the other problem outcomes. This was particularly evident in the domains of temperament style and interpersonal relationships. However, as risky driving was measured later than antisocial behaviour and substance use, it is possible that the longer time span between risks and outcomes may have partly accounted for these findings.

While the findings were seen to partially support Problem Behaviour Theory (Jessor and Jessor 1977; Jessor 1987), given the differences between the precursors of these outcomes, the need to also examine separately the etiology of high risky driving, persistent adolescent antisocial behaviour and multi-substance use was highlighted.

The co-occurrence of problem behaviours at 19-20 years

Connections between risky driving and other problem behaviours were next investigated to determine whether individuals who engaged in high levels of risky driving were also more often involved in substance use and antisocial behaviour. 42

Substance use

Formation of groups
Problematic substance use was defined in terms of alcohol and marijuana use at 19-20 years of age, as there were insufficient numbers to investigate the use of other illicit substances such as ecstasy, amphetamines or heroin 43. Participants completed questions about the number of days during the past month in which they had used alcohol or marijuana, as well as questions about harms associated with such use (for example, trouble at work, injury, violence, dependence). Further details of the measures used may be found in Appendix 2. Both types of information (pattern of daily use and harms associated with use) were used to form low, moderate and high 'Alcohol Use' and 'Marijuana Use' groups.

The criteria used to select the groups, and the characteristics of the groups, are summarised in Table 30. To investigate whether use of both types of substances conveyed a heightened risk for risky driving, four groups with differing patterns of substance use were formed, using the criteria described in Table 30. These were: no substance use, marijuana use only, alcohol use only, and use of both substances. The criteria used, and the characteristics of the groups, are summarized in Table 31.

Definition and composition of alcohol and marijuana use groups at 19-20 years Definition and composition of combined substance use groups at 19-20 years

Findings
Individuals who engaged in high risky driving behaviour had significantly higher rates of alcohol44 and marijuana45 use than individuals whose driving pattern was less risky. Approximately 60 per cent of individuals in the moderate and high risky driving groups were moderate or high alcohol users, compared with 44 per cent of those in the low risky driving group (see Figure 28). In addition, while the great majority of individuals in all three risky driving groups were no / low marijuana users (ranging from 77 to 94 per cent), there were higher rates of moderate and high marijuana use among individuals in the moderate and high risky driving groups (Figure 29).

Odds ratios can be used to assess the likelihood of a particular outcome (for example, high levels of substance use) occurring if a certain factor (in this case, high risky driving) is present. The odds ratio is thus an estimate of the degree to which an individual who displays the risk factor under study is likely to display the other outcome, as compared to someone who does not display the risk factor 46. With regards to high alcohol use, the odds ratios indicated that high risky drivers were twice as likely as low risky drivers to be high alcohol users, while moderate risky drivers were 1.8 times more likely to be high alcohol users than low risky drivers 47. With regard to marijuana use, high risky drivers were four times more likely than low risky drivers to engage in high levels of marijuana use, while moderate risky drivers were 2.6 times more likely to be high marijuana users than low risky drivers 48.

Turning now to young adults' use of both alcohol and marijuana 49 (shown in Figure 30), more than half of the low risky driving group (56 per cent) were no/low users of both substances, while in contrast around two-thirds of moderate (62 per cent) and high (69 per cent) risky drivers reported moderate or high use of alcohol, marijuana, or both substances. For example, approximately half the moderate and high risky drivers were alcohol users only, while almost 20 per cent of high risky drivers used both alcohol and marijuana, double the rate among moderate risky drivers (10 per cent) and four times the rate of low risky drivers (5 per cent).

The odds ratios revealed that high and moderate risky drivers were almost twice as likely as low risky drivers to be moderate/high alcohol users only 50 (that is, not moderate/high marijuana users as well). With regard to moderate/high use of both alcohol and marijuana, high risky drivers were more than six times more likely than low risky drivers to have engaged in both types of substance use, while moderate risky drivers were 2.8 times more likely to have engaged in moderate/ high use of both substances51. This finding suggests that use of both types of substances was indeed more characteristic of the high risky driving group than the moderate and low risky driving groups. Due to the low numbers of individuals who were high marijuana users only (N = 19 across all three driving groups), adds ratios for this type of substance use could not be reliably completed.

Relationship between risky driving and alcohol use at 19-20 years Relationship between risky driving and marijuana use at 19-20 years Relationship between risky driving and combined alcohol and marijuana use at 19-20 years

Antisocial behaviour

Formation of groups
Questions concerning involvement in violence (for example, fighting, assault), property offences (for example, vandalism, stealing), and authority transgressions (for example, obtaining benefits to which one was not entitled, passing fake cheques) were used to measure antisocial behaviour at 19-20 years 52. The items used were drawn from the Self Report of Delinquency Scale (Moffitt and Silva 1988), with additional items added to assess newly emerging types of antisocial acts (for example, illegally accessing a computer system or network). Details of the questions used can be found in Appendix 3. Individuals were classified as showing high levels of antisocial behaviour if they reported engaging in three or more different types of antisocial acts during the previous 12 months, 53 while those who reported fewer than three different antisocial acts within this time span were classified as showing low levels of antisocial behaviour. Using this criterion, two groups were formed, as described in Table 32.

Definition and composition of antisocial behaviour groups at 19-20 years

Findings
Antisocial behaviour was clearly associated with risky driving, as shown in Figure 31. Considerably more high risky drivers (36 per cent) had engaged in high levels of antisocial behaviour, than moderate (14 per cent) and low (6 per cent) risky drivers. The association between high risky driving and high levels of antisocial behaviour appeared to be very powerful, with high risky drivers being found to be approximately nine times more likely than low risky drivers to engage in high levels of antisocial behaviour, according to the odds ratio analyses, and moderate risky drivers also at heightened likelihood of antisocial behaviour (odds ratio of 2.7) 54.

Relationship between risky driving and antisocial behaviour at 19-20 years

Summary

In summary, these findings suggest that individuals who engage in high levels of risky driving behaviour also tend to exhibit higher levels of other problem behaviours during early adulthood than young people who engage in little or no risky driving behaviour. For example, about 70 per cent of high risky drivers reported moderate or high use of alcohol, marijuana, or both substances (compared with 44 per cent of low risky drivers). More than one-third engaged in high levels of antisocial behaviour (compared with 14 per cent of moderate risky drivers only 6 per cent of low risky drivers).

While the majority of high risky drivers did not engage in marijuana use or antisocial behaviour (although many engaged in moderate or high alcohol use) rates of substance use and particularly antisocial behaviour were generally substantially higher among the high risky driving group, as indicated by odds ratios.

Connections between problem behaviours in adolescence and driving behaviour at 19-20 years

Connections between problem behaviours in adolescence and risky driving patterns in early adulthood were next investigated, to determine whether adolescent problem behaviours were predictive of risky driving behaviours at 19-20 years.

Substance use

Formation of groups
To investigate this question, groups of adolescents with differing across-time patterns of alcohol and marijuana use were identified 55. First, patterns of alcohol and marijuana use at each time point (13-14, 15-16 and 17-18 years) were examined and adolescents were classified as engaging in no/low 56 or moderate/high 57 substance use each time point. With regard to alcohol consumption, 6.8 per cent were classified as moderate/high alcohol users at 13-14 years, 22.6 per cent at 15-16 years and 38.1 per cent at 17-18 years. A total of 6.4 per cent were classified as marijuana users at 13-14 years, 14.0 per cent at 15-16 years and 19.9 per cent at 17-18 years.

Second, patterns of use across the three time points were inspected to identify groups with differing across-time trajectories of use. Based on adolescents' reported levels of alcohol and marijuana use at each time point, three groups were identified for each substance type (alcohol, marijuana). These were: stable low - these individuals had engaged in low/no use of the substance at all time points; experimental - these individuals engaged in moderate or high use of the substance during early to mid adolescence and then ceased this level of use; and stable high - these individuals engaged in moderate or high levels of use of the substance at two or more time points, including 17-18 years. Some individuals did not fit these across-time patterns and were therefore excluded. Further details relating to the formation of these groups are available in Appendix 4. Table 33 summarises the characteristics of these groups.

Characteristics of adolescent substance use groups

Findings
Adolescent alcohol use was significantly related to later risky driving behaviour 58. Young people who reported high levels of risky driving behaviour were more likely to have engaged in 'stable high' levels of alcohol use during adolescence (35 per cent) than those whose driving pattern was less risky (26 per cent of moderate risky drivers and 17 per cent of low risk drivers), as can be seen in Figure 32. Additionally, fewer high risky drivers engaged in 'stable low' levels of alcohol use during adolescence. Nevertheless, the majority of risky drivers (about two-thirds) had not been moderate/high users of alcohol over adolescence. The odds ratios indicated that high risky drivers were almost three times more likely to have engaged in stable high alcohol use over adolescence than low risky drivers, while moderate risky drivers were almost twice as likely to have done so 59.

Relationship between adolescent alcohol use and risky driving at 19-20 years

Connections between adolescent marijuana use and young adult risky driving behaviour were similar60, although less powerful and clear-cut (see Figure 33), perhaps because few adolescents were experimental or high marijuana users (as shown in Table 33). Only about one-third of high risky drivers had used marijuana during adolescence. While high risky drivers were more likely to report some marijuana use during adolescence this use tended to be 'experimental' (to have ceased by late adolescence) rather than stable. The low risky driving group had the lowest rates of adolescent marijuana use, with only 12 per cent of this group engaging in experimental or stable high marijuana use, compared with 19 per cent of moderate risky drivers and 37 per cent of high risky drivers. The odds ratios indicated that both high and moderate risky drivers were about twice as likely as low risky drivers to have engaged in stable high marijuana use over adolescence than low risky drivers61.

Relationship between adolescent marijuana use and risky driving at 19-20 years

Antisocial behaviour

Formation of groups
Groups of adolescents with differing across-time patterns of antisocial behaviour have previously been identified in ATP research (see Vassallo et al. 2002). Using a criterion of engagement in three or more different types of antisocial behaviour (such as property offences, violence, authority transgressions, or the sale or use of illegal drugs) within the previous 12 months to indicate high levels of antisocial behaviour, individuals were classified as highly antisocial or low/non antisocial, at three separate time points - early adolescence (13-14 years), mid adolescence (15-16 years) and late adolescence (17-18 years). Twelve per cent of adolescents were classified as highly antisocial at 13-14 years, 20 per cent at 15-16 years, and 20 per cent at 17-18 years.

Across-time patterns of antisocial behaviour were then mapped, leading to the formation of the following three groups: 62 low/non antisocial - these individuals displayed low/no antisocial behaviour at all time points; experimental - these individuals exhibited high antisocial behaviour during early to mid adolescence and then desisted; and persistent - these individuals engaged in high levels of antisocial behaviour at two or more time points, including 17-18 years. The three groups thus identified, and their characteristics, are shown in Table 34.

Characteristics of adolescent antisocial groups

Findings
Adolescent antisocial behaviour was significantly related to young adult risky driving behaviour. 63 Approximately 40 per cent of high risky drivers had been persistently antisocial adolescents, compared with only 13 per cent of moderate risky drivers and 8 per cent of low risky drivers (see Figure 34). Furthermore, odds ratios indicated that high risky drivers were eight times more likely than low risky drivers to have been persistently antisocial during adolescence, while moderate risky drivers were 1.8 times more likely to have been persistently antisocial during adolescence 64.

Relationship between adolescent antisocial behaviour and risky driving at 19-20 years

Summary

In summary, high risky drivers had displayed higher rates of all types of problem behaviours during adolescence. These trends were most apparent for antisocial behaviour, with 40 per cent of high risky drivers having engaged in persistent adolescent antisocial behaviour, and odds ratios showing that high risky drivers were eight times more likely to have been persistently antisocial adolescents than low risky drivers. High risky drivers had also more frequently consumed alcohol at moderate or high levels throughout adolescence, with one-third of high risky drivers having been consistently moderate/high alcohol users compared with 26 per cent of moderate risky drivers and 17 per cent of low risky drivers. High risky drivers were also significantly more likely to have used marijuana during adolescence, but this trend was less powerful, perhaps because few adolescents overall were involved in marijuana use. High risky drivers tended to engage in experimental rather than consistently high marijuana use.

These findings suggest that adolescent problem behaviours were powerful risks for later risky driving behaviour. Nevertheless, it should also be noted that many risky drivers had not engaged in problem behaviours during adolescence.

Profile of risks of single-problem and multiple-problem groups

The final issue addressed was whether distinct risk factors could be identified for groups with differing patterns of problem behaviours. To investigate this issue, single and multi-problem groups were identified, based upon participants' self reports at 19-20 years.

Three types of analyses were conducted in order to identify the correlates of different combinations of problem behaviours. Single and multi-problem groups were compared on aspects of personal functioning, relationships with parents and peers, current life circumstances, and attitudes and values, all measured at 19-20 years.

The first set of analyses compared three groups: a high risky driving group who were not high users of alcohol, a high alcohol use group who were not high risky drivers, and a dual problem group who were both high risky drivers and high alcohol users. The second set of analyses also involved three groups: a high risky driving group who were not high marijuana users, a high marijuana use group who were not risky drivers, and a dual problem group who were high risky drivers and high marijuana users. Similarly, three groups were used for the third set of analyses: a high risky driving group who were not highly antisocial, a high antisocial group who were not high risky drivers, and a dual problem group who were both high risky drivers and highly antisocial. Thus, three different high risky driving only and dual problem groups were used in these analyses.

As the number of individuals who met the criteria for some groups was quite small, these findings should be viewed as exploratory only, and interpreted with caution.

Correlates of risky driving and alcohol use

'High risky driving only' (n=36), 'high alcohol use only' (n=199), and 'dual problem' (high risky driving and high alcohol use) groups (n=20) were compared to identify correlates of these patterns on problem behaviours at 19-20 years. Table 35 summarises the significant findings from this analysis.

Significant differences between the high risky driving only (n=36), high alcohol use only (n=199), and dual problem (high risky driving and high alcohol use) (n=20) groups at 19-20 years

A consistent trend emerging from these analyses was the higher rate of emotional problems (depression, stress, shy (unsociable) temperament, low assertiveness) among the high risky driving only group, particularly in comparison with the high alcohol use only group. These findings do not necessarily mean that the high risky driving only group was highly problematic on these aspects (that is, that they were clinically depressed), just that they scored higher on these emotional problems than the groups to which they were compared.

The high alcohol use only group, on the other hand, tended to report less confidence in the police than the high risky driving only group. They also tended to participate in civic activities more than the high risky driving only group, although rates of civic engagement among all three groups were low.

Interestingly, only one significant difference was found between the dual problem group and the single problem groups: individuals who exhibited high levels of both risky driving and alcohol use tended to have more disagreements with parents than the high alcohol use only group. Hence, the dual problem group did not significantly differ from the single problem groups on any aspects of their personal functioning, their peer relationships, their life circumstances or their attitudes and values, during early adulthood.

While the comparisons of the high risky driving only group with the dual problem group did not reach significance (perhaps partly due to the lower power associated with the small size of these groups), the gap between these groups was often almost as large as found when comparing the high risky driving only group and the high alcohol use only group. In other words, the dual problem group was similar to the high alcohol use only group on many characteristics.

Correlates of risky driving and marijuana use

Few significant differences were found when comparing the 'high risky driving only' (n=53), 'high marijuana use only' (n=46), and the high risky driving and high marijuana use 'dual problem' (n=8) groups (see Table 36). However, it should be noted that the groups compared were very small (particularly the dual problem group), hence, the power of these analyses to detect statistically significant group differences would have been greatly limited.

Significant differences between the high risky driving only, (n=53) high marijuana use only (n=46), and dual problem (high risky driving and high marijuana use) (n=8) groups at 19-20 years

Those differences that were found pointed to greater difficulties on emotional control and persistence among the high marijuana use only group than the high risky driving only group. The dual problem group (high risky driving and high marijuana use), on the other hand, tended to be less responsible than the high risky driving only group.

Correlates of risky driving and antisocial behaviour

A number of significant group differences were found when comparing the 'high risky driving only' (n=47), the 'high antisocial only' (n=80), and the 'dual problem' high risky driving and high antisocial (n=27) groups. These are shown in Table 37.

Significant differences between the high risky driving only (n=47), high antisocial only (n=80), and dual problem (high risky driving and high antisocial) (n=27) groups at 19-20 years

Group comparisons consistently indicated greater difficulties among the dual problem (high risky driving and high antisocial) group than the single problem groups, especially the high risky driving only group. More specifically, the dual problem group displayed a more difficult temperament style, tended to have lower social skills, had considerably higher rates of illicit drug use, had more disagreements with parents, and were less involved in civic activities than individuals who only engaged in high levels of risky driving or antisocial behaviour. Hence, young adults who displayed a pattern of high antisocial behaviour and high risky driving appeared to experience substantially more difficulties than those who engaged in high risky driving behaviour alone.

Summary

These exploratory analyses revealed several significant differences between dual problem groups and single problem groups. For example, young people who engaged in high risky driving and alcohol use tended to have more disagreements with parents than those who only reported a single problem behaviour, while those who engaged in high risky driving and marijuana use were less responsible than those who only engaged in high risky driving.

However, the most extensive differences were between young people who engaged in both high risky driving and high antisocial behaviour and their counterparts who reported only one of these behaviours. Thus, the high risky driving and high antisocial behaviour group tended to display a more difficult temperament style, possess lower social skills, experience more conflict with parents, and participate less in civic endeavours than those who reported a single problem behaviour (particularly those who only engaged in high levels of risky driving). Interestingly, the high risky driving but no alcohol use group tended to report more emotional problems than the high alcohol use only and high risky driving and alcohol use groups. These findings suggest that there is substantial variability among individuals who engage in high risky driving. However, perhaps not surprisingly, high risky drivers who also engage in high levels of antisocial behaviour, high alcohol use or high marijuana use tend to experience more difficulties overall than those who engage in only one of these behaviours.

Nevertheless, while a number of group differences were found, there were many aspects on which the single and dual problem groups did not significantly differ. Thus, it seemed that there were considerable similarities between the single and multiple problem groups as well, and that they shared many risk factors. However, these findings should be viewed cautiously and as exploratory only, because the small group sizes employed limited the study's power to detect group differences.

  1. The first two reports from this collaborative project can be accessed from AIFS website at www.aifs.gov.au/atp/pubs or by phoning Crime Prevention Victoria on (03) 9651-6933. A third report is to be released in 2005.
  2. Three or more different antisocial acts in the past 12 months (or in the past month for illicit substance use).
  3. Multi-substance use was defined by the presence of at least four of the following six criteria at 15-16 years of age: (i) smoking tobacco on 3 or more occasions in the past month; (ii) drinking alcohol on three or more occasions in the past month; (iii) drinking to intoxication on one or more occasions in the past month; (iv) any marijuana use in the past month; (v) any substance sniffing; and (vi) any use of illicit drug such as heroin, cocaine, speed or designer drugs.
  4. For reader interest, the relationship between unsafe driving and anxiety and depression were also examined. However, no significant relationships were found between risky driving and these types of problems.
  5. Only 84 individuals (7.3 per cent) reported the recent use of one or more of such substances.
  6. x2 (4) = 23.05; p <.001.
  7. x2 (4) = 28.19; p <.001.
  8. The odds ratio obtained for a variable denotes the change in the odds of being in the outcome group (for example, marijuana use) for each change in the level of that variable (for example, risky driving). An odds ratio of 1 represents no change in risk (odds are the same at any level of the variable). Odds ratios significantly greater than 1 indicate an increased risk at increased levels of the variable, whilst odds ratios smaller than 1 indicate a decreased risk at higher levels of the variable. For example, with regard to marijuana use, the odds ratios suggest that as
    9. propensity to engage in risky driving increases, marijuana use increases.
  9. Odds ratio for the comparison of high and low risky driving groups on high alcohol use OR = 2.12, CI (1.18 - 3.79); and for the comparison of moderate and low risky driving groups OR = 1.81, CI (1.30 - 2.52).
  10. Odds ratio for the comparison of high and low risky driving groups on high marijuana use: OR=4.17, CI (1.77- 9.82); and for the comparison of moderate and low risky driving groups: OR = 2.60, CI (1.43-4.73).
  11. x2 (6) = 40.63; p <.001.
  12. Odds ratio for the comparison of high and low risky driving groups on moderate/high alcohol use but not moderate/high marijuana use OR = 2.12, CI (1.08 - 4.19); and for the comparison of moderate and low risky driving groups on this outcome OR = 1.89, CI (1.36 - 2.62).
  13. Odds ratio for the comparison of high and low risky driving groups on moderate/high alcohol use and moderate/high marijuana use OR = 6.71, CI (2.68 - 16.83); and for the comparison of moderate and low risky driving groups OR = 2.77, CI (1.49 - 5.12).
  14. In these analyses, illicit substance use was not included as an indicator of antisocial behaviour, in contrast to much other research into antisocial behaviour.
  15. The cutoff of three or more antisocial acts in the past year is consistent with the criteria for Conduct Disorder in the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV; American Psychiatric Association 1994).
  16. Odds ratio for the comparison of high and low risky driving groups on antisocial behaviour OR = 9.63, CI (5.42-17.12); and for the comparison of moderate and low risky driving groups OR=2.68, CI (1.69-4.25).
  17. Slightly different criteria were used to assess levels of substance use across the three adolescent survey waves (13-14 years, 15-16 years, and 17-18 years). The criteria were designed to take into account the normative increase in substance use that occurs across adolescence.
  18. For alcohol, low/no use was defined as consumption of alcohol on 0-3 days in the past month at the 13-14 and 15-16 year survey waves, and as consumption of alcohol on 0-4 days in the past month at 17-18 years. For marijuana, low/no use was defined as no lifetime use at the 13- 14 year survey wave; and as no use in the past month at the 15-16 and 17-18 year waves.
  19. For alcohol, moderate/high use was defined as consumption of alcohol on 4 or more days in the past month at 13-14 and 15-16 years, and as consumption of alcohol on 5 or more days in the past month at 17-18 years. For marijuana, moderate/high use was defined as any lifetime use at 13-14 years; and as any use in the past month at the 15-16 and 17-18 years survey waves.
  20. x2 (4) = 14.78; p <.05.
  21. Odds ratio for the comparison of high and low risky driving groups on stable high alcohol use over adolescence: OR= 2.70, CI (1.38-5.29, and for the comparison of moderate and low risky driving groups OR = 1.80, CI (1.21-2.68.
  22. x2 (4) = 29.49; p <.001.
  23. Odds ratio for the comparison of high and low risky driving groups on stable high marijuana use over adolescence: OR=2.47, (CI 0.96-6.32), and for the comparison of moderate and low risky driving groups OR=2.01, CI (1.15-3.53).
  24. Some individuals did not fit these across-time criteria, and were therefore excluded.
  25. x2 (2) = 75.78; p <.001.
  26. Odds ratio for the comparison of high and low risky driving groups on persistent antisocial behaviour during adolescence: OR = 8.44, CI (4.34-16.39); and for the comparison of moderate and low risky driving groups OR=1.82, CR (1.11-2.97).

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