Department of Psychiatry, College of Medicine, National Taiwan University and National Taiwan University Hospital, Taipei
Department of Psychiatry, Chang Gung Memorial Hospital, Kaohsiung
Department of Psychiatry, Kaohsiung Medical University, Kaohsiung, Taiwan
Division of Biostatistics and Bioinformatics, National Health Research Institutes, Taiwan and Department of Biostatistics, Johns Hopkins University, USA
Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan.
Correspondence: Professor Andrew T. A. Cheng, Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan. Fax: +88 62 2782 3047; email: bmandrew{at}gate.sinica.edu.tw
Declaration of interest None. Funding detailed in Acknowledgements.
* Presented in part at the Tenth International Congress of the International
Federation of Psychiatric Epidemiology, Bristol, UK, 1013 September,
2004. ![]()
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Aims To identify psychosocial and psychiatric predictors of substance use disorders in adolescence.
Method School children aged 12 years (s.d.=0.3) free from any substance use disorder at grade 7 (n=428) were assessed in three consecutive years, using a standardised psychiatric interview. Their baseline psychosocial information was also collected. The outcome was the onset age of a substance use disorder. The Cox regression model was used for data analysis.
Results The most significant predictive factors for adolescent substance use disorder included male gender, attention-deficit hyperactivity disorder, conduct disorder and sibling use of tobacco. Three protective factors against such morbidity included living in a household withtwo parents, a good academic grade atgrade 7 and objection to the use of substances.
Conclusions Early intervention for disruptive behaviour disorders and specific psychosocial risk factors might prevent substance use disorders in early adolescence.
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A two-stage case-finding strategy was employed. In the first year of the study (1995), 446 out of the 1070 students received a second-stage standardised psychiatric assessment conducted by staff child psychiatrists unaware of the first-stage screening results (Gau et al, 2005). This subsample included all of those who were screened positive (n=382) and every 1 in 10 randomly selected from those who screened negative (n=64) for any mental disorders; 6 students refused to undergo the follow-up assessments, and 12 developed a substance use disorder before grade 7. The remaining 428 students (215 boys and 213 girls) had formed the cohort for this study (Fig. 1). Their mean age at baseline was 12.5 years (s.d.=0.3). They were interviewed to provide information about psychosocial factors in the past year. The same standardised psychiatric interview was conducted among them in the following two consecutive years (grade 8 and grade 9).
![]() View larger version (15K): [in a new window] [as a PowerPoint slide] |
Fig. 1 Flow chart of recruitment and assessment (SUD, substance use disorder).
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Measures
Chinese KSADSE
The Chinese version of the Schedule for Affective Disorders and
Schizophrenia for School-Age Children Epidemiologic Version
(KSADSE) was developed by the Taiwan Child Psychiatry Research
Group (Gau & Soong, 1999)
and further revised to meet the DSMIV diagnostic criteria
(American Psychiatric Association,
1994) with an additional section regarding betel-nut use disorder
(Chong et al, 1999;
Gau et al, 2005). The
interrater reliability of this instrument was examined among nine staff child
psychiatrists in the research team in advance: generalised kappa coefficients
ranged from 0.73 to 0.96 for all mental disorders included
(Chong et al, 1999;
Gau et al, 2005).
In this study all the screening items in individual sections of the Chinese KSADSE were grouped together to form a separate screening version for use in the first stage of case-finding. Validity of this screening version was examined among 124 randomly selected grade 8 students, and the overall sensitivity (78%) and specificity (98%) against any Chinese KSADSE diagnosis made by the nine child psychiatrists were satisfactory (Gau et al, 2005).
Teacher Report Form and academic performance
Teachers reported on the Chinese version of the Teachers Report Form
(TRF; Achenbach, 1991). The
Chinese TRF has been reported to be a reliable and valid self-administered
instrument for measuring child behavioural problems based on teachers
ratings (Yang et al,
2000). Teachers were also interviewed to provide information about
the students classroom behaviours, academic performance and peer
relationships. School report cards of grade point average at primary school
were provided by schools, with the participants permission.
Interview for psychosocial variables
An interview was developed to obtain demographic and psychosocial
information for the year prior to the first assessment at grade 7. The kappa
statistics for a 4-week testretest reliability among 115 junior
high-school students regarding these variables were as follows: house-moving
at grade 6,
=0.41; parents and students expectation of
highest educational level,
=0.48 and
=0.72 respectively;
allowance at grade 6,
=0.54; after-school curricular cram courses,
=0.470.87; company during free time,
=0.76; spare-time
activities,
=0.460.71; and spending time in unsuitable places,
=0.680.86. The kappa statistics for reports of parents
and siblings regular use of any substance (tobacco, alcohol, betel nut,
glue, sedatives, amphetamine, central nervous system depressants or heroin)
ranged from 0.58 to 1.00 and from 0.49 to 1.00 respectively.
Attitudes towards substance use
Participants attitude towards the use of any substances was
investigated with three questions:
One question was designed to enquire about peer use of substances: What proportion of your friends use any substance? (0 none, 1 no more than one in four, 2 around half, 3 no more than three in four, 4 almost all).
The Cronbachs alpha coefficients for internal consistency of these
questions among a representative sample of 1291 junior-high-school students
ranged from 0.76 to 0.87. The intraclass correlation coefficients for the
4-week testretest reliability among 115 junior-high-school students
ranged from 0.45 to 0.71. The internal consistency of these four questions was
also satisfactory in this study (
=0.650.84).
Psychiatric diagnosis
Psychiatric diagnoses of the study participants were first made by the
child psychiatrists who conducted the Chinese KSADSE interview,
according to DSMIV criteria. All the diagnoses were then independently
reassessed by S.S.F.G. and A.T.A.C. through a systematic review of all the
interview records. Psychiatric diagnoses generated from this reassessment were
jointly discussed and the consensus diagnosis was taken as final. To minimise
the likely underreporting of externalised disorders by the participants,
information regarding behaviour syndromes gathered from the TRF data was
incorporated into our diagnostic consideration for the best estimation of
ADHD, oppositional defiant disorder, and conduct disorders. Diagnoses of
substance use disorders included substance abuse and substance dependence.
Statistical analysis
Survival analysis using the Cox proportional hazard regression analysis
with time-dependent variable was employed to examine the psychiatric
predictors and baseline psychosocial predictors for substance use disorders.
Psychiatric predictors included ADHD, conduct disorder, oppositional defiant
disorder, depressive disorders and anxiety disorders. Substance use disorders
included misuse of and dependence on nicotine, alcohol, betel nut and illicit
drugs.
The outcome (survival time) was age at onset of the substance use disorder. If the student was diagnosed with such a disorder, then an event was recorded and this participants data were not censored. If the participant had more than one substance use disorder, the earliest age at onset for any disorder was taken as the age at onset. Under this condition, the age at onset of the substance use disorder was the survival time for a non-censored case. In contrast, if the substance use disorder was not diagnosed by the end of the study, then no event was recorded and the participants data were censored; under this condition, the age at the last observation for this censored case was the survival time. Thus, censored individuals were those who either had no diagnosis of a substance use disorder by the end of the study, or were lost to follow-up during the course of the study with no prior diagnosis of a substance use disorder.
For survival analysis, participants with any psychiatric predictor (disorder) but who did not develop a substance use disorder by the end of the study, or with an onset of substance use disorder later than that of the predictor, belonged to the positive psychiatric group. Participants with a substance use disorder but without any psychiatric predictor, or with an onset of the disorder preceding that of the predictor, belonged to the negative psychiatric group. Psychosocial predictors included measures in family, school and peer domains in the year preceding the baseline psychiatric assessment.
Statistical analyses were performed using SAS version 9.1 (SAS Institute Inc., Cary, North Carolina, USA). The pre-selected alpha value was 0.05. The PROC PHREG procedure was used to create time-dependent variables in order to generate a Cox regression model with time-dependent variables. Hazard ratios and their 95% confidence intervals were computed using this model.
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Thirty-five (16.3%) boys and 7 (3.3%) girls were newly diagnosed with substance use disorders. Among them, there were 16 (38%) primary cases (individuals who had had no previous mental health disorders). All of them had nicotine use disorder (19 for nicotine abuse and 23 for nicotine dependence), and 18 (43%) and 13 (31%) also had betel use disorder (15 for betel abuse and 3 for betel dependence) and alcohol use disorder (12 for alcohol abuse and 1 for alcohol dependence) respectively. Only one participant misused amphetamines.
Socio-demographic predictors
Table 1 displays the effect
of socio-demographic factors assessed at baseline on the risk of substance use
disorder. Participants with such a disorder were more likely to be male and to
have fathers and mothers with lower educational attainments. There was no
significant difference in family structure, birth order or household status on
such risk.
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View this table: [in a new window] | Table 1 Socio-demographic predictors of substance use disorders among adolescents |
Psychosocial predictors
Table 2 presents the
individual effect of psychosocial factors on the risk of substance use
disorder. In family domains, participants who had a lower expectation of their
highest educational attainment had a significantly higher risk of subsequent
onset of substance use disorder. The same trend was observed for participants
whose parents had the same expectation. A higher risk of disorder was found
among participants whose siblings had regular use of tobacco or any substance
before the baseline assessment. No such trend was observed for parents
regular use of tobacco or any substance or for monthly allowances at grade 6.
In terms of school performance, those who had higher grades at primary school
and attended curriculum-related cram courses after school were less likely to
develop a substance use disorder.
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View this table: [in a new window] | Table 2 Psychosocial predictors of substance use disorders among adolescents |
Regarding peer influences, those who preferred to be with their friends rather than their family during their spare time and those who passed their time in unsuitable places were more likely to develop substance use disorders. An increased proportion of friends using substances and number of unsuitable places where participants spent time also increased the risk of disorder. In contrast, an increase in the variety of appropriate and healthy spare-time activities decreased the risk of disorder.
Regarding attitudes towards substance use, a response indicating that the student would use substances given the opportunity significantly predicted substance use disorder, whereas objection to substance use and recognising substance use as harmful to physical health significantly decreased the likelihood of developing this disorder.
Psychiatric predictors
Oppositional defiant disorder, ADHD and conduct disorder, but not
depressive disorders or anxiety disorders, significantly predicted the risk of
substance use disorder among study participants
(Table 3). The significant
predictive effect of ADHD on the risk of such disorder was maintained after
controlling for effects of other mental disorders, except that conduct
disorders partially explained the pathway from ADHD to substance use
disorders. Similarly, the significant predictive effect of conduct disorder on
the risk of substance use disorder remained after controlling for effects of
other mental disorders, except that ADHD partially explained the pathway from
conduct disorder to substance use disorder. Although the significant effect of
oppositional defiant disorder on the risk of substance use disorder remained
the same after controlling for depressive and anxiety disorders, such effect
disappeared after controlling for ADHD or conduct disorder, suggesting that
comorbidity of oppositional defiant disorder with ADHD and/or conduct disorder
might explain the prediction by oppositional defiant disorder of substance use
disorder.
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View this table: [in a new window] | Table 3 Psychiatric predictors of substance use disorders among adolescents |
Final model for the predictors of substance use disorders
Table 4 shows the final
model of predictors of substance use disorder using multivariate analysis with
stepwise selection. All the demographic, psychosocial and psychiatric
predictors (P<0.1 in univariate analysis) were included in the
model selection, except for five factors significantly associated with conduct
disorder. These included proportion of peers using substances, spending time
in unsuitable places, attempt to use a substance, grade point average at
primary school, and company during spare time. The final model shows that the
most predictive factors were male gender, ADHD, conduct disorder, and sibling
using tobacco. On the other hand, the risk of substance use disorder was
significantly lower for students with a household of two parents, better
academic grade at grade 7, and objection to use of a substance.
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View this table: [in a new window] | Table 4 Final model of predictors of substance use disorders among adolescents |
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Psychiatric predictors
Although earlier studies have reported that disruptive behaviour disorders
notably conduct disorder and ADHD were the most important
psychiatric predictors of adolescent substance use disorder, some differences
in their findings can be observed. Several studies have shown that conduct
disorder most strongly predicted substance use disorder (e.g.
Lynskey & Fergusson, 1995;
Clark & Cornelius, 2004),
and partially explained the predictive effect of ADHD on such disorders (e.g.
Flory & Lynam, 2003).
Other studies reported that the effect of ADHD remained significant after
controlling for other psychiatric comorbidity (e.g.
Biederman et al,
1998). However, the study by Lynskey & Fergusson
(1995) suggested that when due
allowance was made for early conduct problems, early attentional problems were
not related to later substance use. Findings in this study lend support to
independent effects of ADHD and conduct disorder on substance misuse.
Findings regarding the relationships between depression and anxiety disorders and substance use disorders have been inconsistent in previous studies (Miller-Johnson et al, 1998; Rao et al, 2000; Costello et al, 2003; Goodwin et al, 2004). Although our study did not find that depression or anxiety disorders predicted substance use disorders, the relatively short duration of follow-up did not allow us to confirm Goodwin et als (2004) finding that they strongly predicted substance use disorders in late adolescence or young adulthood. Nevertheless, the evidence gathered here tends to suggest that disruptive behaviour disorders (notably ADHD and conduct disorder) may act as psychiatric antecedents of substance misuse in early adolescence, and anxiety and depressive disorders might have such a role in late adolescence and adulthood.
Psychosocial predictors
Individual factors
As in earlier studies (Costello et
al, 1996; Chong et
al, 1999; Tot et
al, 2004), our cohort showed that the risk of substance use
disorders was greater in boys and in adolescents with academic
underachievement. However, our study was unable to assess the predictive role
of substance use disorders for poor academic achievement. It is likely that
school failure might cause an adolescent to be vulnerable to substance use,
which might in turn lead to further downgrading of academic performance. This
study is superior to most previous studies (e.g.
Tot et al, 2004) in
that participants grades were based on school report cards rather than
on self-perceived academic performance.
The duration of compulsory education in Taiwan is 9 years. Owing to the keen academic competition for senior high-school (Gau & Soong, 1995), it is common for junior-high-school students to take curriculum-related cram courses after school. These courses are related to the subjects included in the joint entrance examinations for senior high school. Taking these cram courses represents a higher expectation of future academic achievement held by both students and parents, which was found to have a significantly reduced risk of adolescents substance misuse in previous work (Chassin et al, 1992) and in this study. Such a higher academic expectation from adolescents and their parents also represents their shared values and philosophy of life, which has been reported to be one of the protective factors against adolescent substance use (Bogenschneider et al, 1998).
Familial factors
Our results have lent strong support to the notion that substance use
disorders are associated with low socio-economic status, indicated by low
parental educational attainment (Chassin
et al, 1992; Costello
et al, 1996; Chong
et al, 1999; Ho &
Gee, 2002), and with broken family, indicated by either a
single-parent or no-parent household
(Griffin et al,
2000). Although the educational attainments of both fathers and
mothers predicted adolescent substance use disorder in the univariate
analysis, only that of mothers remained in the multivariate model. This might
be explained by the fact that mothers in Taiwan play a major part in
child-rearing and child education. Our findings did not support the
association between family structure and the risk of adolescent substance
misuse previously reported (Farrington
& Loeber, 2000). Like other studies, we found no significant
association between birth order and the risk of adolescent substance use
disorder.
Parental use of substances has been documented to be one of the predictors of substance use disorder among adolescents in Western societies (e.g. Biederman et al, 2000). Our study supports this finding only for betel nut chewing, which was reported to have a family aggregation (Ho & Gee, 2002). As in some Western studies (e.g. Tot et al, 2004), tobacco and alcohol use in siblings predicted nicotine and alcohol use disorders among adolescents in our study. These findings partially support the notion of greater influence by siblings than by parents on the use of tobacco and alcohol among adolescents, and also suggest an important role of common environmental factors in the risk of substance use. Increased substance use among parents and siblings may imply not only a potential genetic contribution but also an environmental contribution to the problem, because parental substance use may create a relaxed environment for substance use by the children.
Peer influences
Consistent with other studies (e.g.
Distefan et al, 1998;
Beal et al, 2001;
Urberg et al, 2003;
Tot et al, 2004), our
study demonstrated that peer use of substances is a significant predictor of
adolescent substance use, with a stronger effect than that of use by siblings
and parents (e.g. Beal et al,
2001). Previous studies (e.g.
Distefan et al, 1998)
have shown that increased communication with parents about various serious
problems has a protective role in preventing adolescent use of tobacco and
alcohol. Our findings have shown that a preference for staying with friends
rather than parents increased the risk of substance use disorder. Moreover,
our finding also indicates that adolescents less interested in spending time
with their parents might be more apt than others to choose friends who smoke
cigarettes or use other substances
(Distefan et al,
1998). In general, the general, the less parents are involved in
their childrens daily life, the greater is the risk of their children
developing substance use disorders
(Griffin et al, 2000;
Borawski et al,
2003).
Like other researchers (e.g., Beal et al, 2001; Urberg et al, 2003), we found that adolescents who spent time in places considered inappropriate for students under grade 9 in Taiwan tended to have a higher access to substances through peers, leading to subsequent development of substance use disorders. Conversely, adolescents who often spent their free time in places considered suitable were less likely to develop such disorders. Visits to places such as libraries and bookshops may indicate that these adolescents were interested in study, had a good home and school connection, and had healthy leisure activities such as going to the gym, scenic resorts and parks.
Attitudes towards substance use
Our findings support the notion that a view of substance use as harmful to
health (Lambert et al,
2004) and an attitude of objection to substance use
(Lambert et al, 2004)
are preventive for adolescent substance use disorder. Our study also supports
the potential contribution of novelty- or stimulus-seeking behaviour (such as
attempting to use a substance whenever there is a chance or the substance is
present) to a higher risk of adolescent substance use disorder
(Gerra et al, 2004).
Hence, differential inner drives and values may lead an adolescent either to
initiate and maintain, or to stay away from, the use of a substance
(Gerra et al,
2004).
Strengths and limitations of the study
Strengths of our study include its longitudinal design; the conduct of the
psychiatric assessment by child mental health professionals, using a
standardised Chinese version of the well-recognised KSADSE with
cross-cultural validation and satisfactory interrater reliability; the use of
consensus psychiatric diagnoses from independent assessments, supplemented by
independent TRF reports; the use of structured interviews for psychosocial
factors with satisfactory psychometric properties; and the satisfactory
response rate.
Despite all these strengths, some limitations require careful consideration in the interpretation of the findings. First, owing to the purposeful sampling of study schools for this cohort, its external validity for the Taiwanese adolescent population needs to be examined. Second, psychiatric diagnoses were mainly based on student interviews and teachers reports, without an interviewing of the participants parents. Previous studies have shown low agreement among child, parent and teacher informants in reporting childrens emotional and behavioural problems (Mitsis et al, 2000), and the agreement between parent and child increased with age (Jensen et al, 1999). In general, adolescents are superior to the other two informants in reporting their internalising symptoms, but may under-report their externalising behaviours (Jensen et al, 1999). Since the literature has documented the importance of teachers contributions to the identification of externalising disorders (Mitsis et al, 2000), we have included the TRF assessment to make the best estimates of psychiatric diagnoses of ADHD, conduct disorder and oppositional defiant disorder. Third, despite the employment of a wealth of measures, this study did not include any biological measures for the prediction of substance use disorder. Fourth, we applied the DSMIV diagnostic criteria for substance use disorder in this study. It is likely that we have excluded some respondents with one or two symptoms for dependence not meeting the diagnostic criteria for abuse and dependence diagnostic orphans (e.g. Hasin & Paykin, 1998; Pollock & Martin, 1999). Lastly, the follow-up period was not long enough to have a greater incidence of cases of substance use disorders and other psychiatric disorders, enabling a more powerful examination of psychiatric and psychosocial predictors. A follow-up study of this cohort in young adulthood is in preparation.
Implications
Our findings imply that early intervention for specific psychosocial risk
factors and psychiatric disorders, particularly ADHD and conduct disorder, may
prevent substance misuse in adolescents through the creation of a protective
psychosocial environment. Such measures should include the attenuation of
factors contributing to the aggravation of cognitivebehavioural deficit
in ADHD. Further investigations may focus on the elucidation of pathways from
ADHD to substance misuse, so that specific targets for primary prevention
among different vulnerable groups can be identified.
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