1. Longitudinal trajectories of polydrug use among adolescents: Two-year follow-up
Martínez-Loredo, V. 1, De La Torre-Luque, A. 2, Grande- Gosende, A. 1, García-Perez, A. 1, & Fernández-Hermida, J.R. 1
1Addictive Behaviors Research Group. Department of Psychology. University of Oviedo, Spain
2Research Institute of Health Sciences, University of the Balearic Islands

2. Acknowledgements and Disclosure
This work was supported by the Ministry of Health Ref. MSSSI /131 and by a predoctoral grant from the Spanish Government Ref. BES
Conflict of interest: none

3. Introduction (I) The EMCDDA/PNSD estimates that…
48% of the adolescents had consumed alcohol during the last 30 days  67.65% Spain
21% of the adolescents had smoked cigarettes during the last 30 days  24.95% Spain
16% of the adolescents had smoked cannabis at least once in their lifetime 27,43% Spain

4. Introduction (II)
Age of onset of the main substances is between 13 and 15 years old  early substance use as risk factor for SUD
Some individuals develop risk patterns of use (substance abuse, binge drinking, polydrug use)  leads to problems, risk behaviors or dependence
Few studies have explored differential patterns of substance involvement among adolescents (mainly cross-sectional studies focused on single substances)
To identify risk trajectories of substance use is an important outcome for prevention and treatment
Goal  To empirically characterize patterns of polydrug use among a big sample of Spanish community-based adolescents

5. Sociodemographic characteristics
Method (I)
Participants 1,612 adolescents randomly recruited from 22 secondary schools in the Principality of Asturias and Valencia (Spain).
Sociodemographic characteristics
Gender
54.5% males
Mean age
13.06 years (SD = 0.52)
Country of birth
89.1% Spain
Wave 1
13 years old
Wave 2
14 years old
Wave 3
15 years old
≈12.71 % attrition

6. Variables & Instruments
Method (II)
Variables & Instruments
Substance use
Frequency of previous year alcohol, tobacco and cannabis use were assessed using items from the European School Survey Project on Alcohol and Drugs (ESPAD)
Age at first drink (AFD)
Heavy drinking
Frequency of intoxication episodes within the past month
Presence of alcohol-related problems using the Spanish validation of the Rutgers Alcohol Problem Index (RAPI) (López-Núñez et al. 2012) (α = )

7. Method (III) Data Analysis Growth Mixture Modelling (LCMM) based on ML
Goodness of fit criteria
Sample-adjusted Bayesian Information Criterion (SABIC)
Akaike Information Criterion (AIC)
Best growth solution defined by
The smallest SABIC & AIC
Means of posterior probabilities in each class higher than .80
Covering at least 5% of participants in each class

8. Results (I) T1 T2 T3 Tobacco use 268 (17.20) 281 (17.90) 448 (18.60)
N (%) T2 T3
Tobacco use
268 (17.20)
281 (17.90) 
448 (18.60) 
None
1,297 (82.9)
1,284 (82.0)
1,117 (71.4)
1-2 times
50 (3.2)
82 (5.2)
124 (7.9)
3 or more times
218 (14.0)
199 (12.7)
324 (10.7)
Alcohol use
708 (45.20)
833 (53.20)
1,126 (72.1)
857 (54.8)
732 (46.8)
439 (28.1)
317 (20.30)
328 (21.0)
303 (19.4)
391 (24.9)
505 (32.2)
823 (52.7)
Cannabis use
98 (6.30)
179 (11.50)
317 (20.60)
1,467 (93.7)
1,386 (88.6)
1,248 (79.7)
39 (2.5)
75 (4.8)
110 (7.0)
59 (3.8)
104 (6.7)
207 (13.6)
Intoxication episodes
65 (4.20)
113 (7.30)
238 (15.30)
1,500 (95.8)
1,452 (92.8)
1,327 (84.8)
43 (2.7)
84 (5.4)
170 (10.9)
22 (1.5)
29 (1.8)
68 (4.4)
RAPI
0.57 (3.47)
1.11 (4.38)
1.94 (5.58)

9. Results (I) 20.5% 61.3% 14.45% 14.90% T1 T2 T3 Tobacco use 268 (17.20)
N (%) T2 T3
Tobacco use
268 (17.20)
281 (17.90) 
448 (18.60) 
None
1,297 (82.9)
1,284 (82.0)
1,117 (71.4)
1-2 times
50 (3.2)
82 (5.2)
124 (7.9)
3 or more times
218 (14.0)
199 (12.7)
324 (10.7)
Alcohol use
708 (45.20)
833 (53.20)
1,126 (72.1)
857 (54.8)
732 (46.8)
439 (28.1)
317 (20.30)
328 (21.0)
303 (19.4)
391 (24.9)
505 (32.2)
823 (52.7)
Cannabis use
98 (6.30)
179 (11.50)
317 (20.60)
1,467 (93.7)
1,386 (88.6)
1,248 (79.7)
39 (2.5)
75 (4.8)
110 (7.0)
59 (3.8)
104 (6.7)
207 (13.6)
Intoxication episodes
65 (4.20)
113 (7.30)
238 (15.30)
1,500 (95.8)
1,452 (92.8)
1,327 (84.8)
43 (2.7)
84 (5.4)
170 (10.9)
22 (1.5)
29 (1.8)
68 (4.4)
RAPI
0.57 (3.47)
1.11 (4.38)
1.94 (5.58)
20.5%
61.3%
14.45%
14.90%

10. Results (II)
First trajectory (black line, 8.69% participants): early use and steep increase later on

11. Results (II)
Second trajectory (dashed line, 81.28% participants): stable low alcohol use (normative substance use) without any other substance use

12. Results (IV)
Third trajectory (grey line, 10.03% participants): low substance use up to T2 and an escalation in substance involvement between T2 and T3

13. Discussion
Early users are mainly smokers: increasing prevalence of tobacco and cannabis co-use (Webster, 2014)  preventive efforts for increasing the risk perception of cannabis
A large low-risk class of moderately alcohol users & no users was also previously reported (Dierker et al., 2007; Khurana et al., 2015; Lamont et al., 2014; Lanza et al., 2010; Shin, 2012): similarity in response patterns and absence of associated risks (Cranford, McCabe, & Boyd, 2013; Lamont et al., 2014; Shin, Hong, & Hazen, 2010)
The telescoping trajectory is a novel finding: to focus on specific patterns of use instead of isolated general indexes (i.e. prevalences)

14. Conclusions
First study finding different polydrug trajectories among early adolescents  three main trajectories: early users, normative users, telescopers
Special attention to the telescoping trajectory  finding associated specific risk factors is encouraged
The AFD did not differ between polydrug trajectories (too fuzzy measure)

15. Addictive Behaviors Research Group Department of Psychology
THANK YOU
OBRIGADO
Addictive Behaviors Research Group
Department of Psychology
University of Oviedo