Youth in transition: Addiction trajectories and profiles. A longitudinal study in a youth addiction treatment cohort

Substance use disorders (SUDs) are prevalent in the general population (De
Graaf, 2010), tend to follow a chronic course, are associated with many
individual and social problems, and - as most mental disorders - often have
their onset in adolescence (Copeland, 2009).
While most substance use in adolescents remains experimental, irregular or
modest, it tends to become more frequent, intensive and long-lasting, and,
hence, increase the risk of developing SUD, when first consumption takes place
in early adolescence and when the use of substances is part of multiple problem
behavior including comorbidity with mental health problems, social dysfunction,
and delinquency (Copeland, 2009; Hussong, 2004).

Our proposed study focuses on a subgroup that is particularly at risk for
chronicity: adolescents in addiction treatment. Although research on treatment
outcome of adolescents with SUD has expanded considerably in the past decade
(Tanner-Smith, 2013), there are remarkably few studies that investigated the
course of SUD in adolescents following addiction treatment prospectively for
longer than one year. Overall, addiction treatment research in adolescents
shows small to moderate effect-sizes of interventions aimed at reducing
substance use, but importantly, information is lacking about which adolescents
benefit most from which type(s) of treatment.
To conclude, the available data from prospective population surveys and
treatment-outcome studies on the long-term course of SUD in adolescents are
limited at best. Remission, continuation and progression rates are largely
unknown, and so are the risk and protective factors involved. While nearly
6,000 youth aged 22 years or younger come into treatment for addiction problems
annually in the Netherlands (Stichting IVZ, 2016), we have virtually no
information as to how these youth will fare moving from adolescence to early
adulthood. Our study will further our understanding of (1) the course of SUD,
(2) the relation of SUD with comorbid mental disorders and social functioning,
and (3) their determinants and consequences during the transition from
adolescence to young adulthood. In addition, we will investigate (4) the
long-term outcome of youth addiction treatment in a naturalistic, *real world*
treatment context, and (5) subgroups of treated youth at high risk for
developing chronic SUD and related problems, who should be the target of more
intensive or comprehensive interventions at an early stage. Finally, we will
investigate (6) bio-psycho-social, cognitive and treatment-related predictors
of long-term treatment response, thus providing a more solid basis for
generating specific hypotheses for patient-treatment matching, and hence, for
the development of personalized prevention and treatment of youth.

Primary research questions:
(1) What is the rate of persistent DSM-5 moderate to severe SUD from
adolescence to young adulthood among youth in addiction treatment?
(2) What is the prognostic value of a general population-based set of
predictors of persistent SUD from adolescence to young adulthood, derived from
a secondary analysis of data from the Tracking Adolescents' Individual Lives
Survey (TRAILS) study, for predicting persistent DSM-5 moderate to severe SUD
among youth in addiction treatment?
(3) Can we optimize the accuracy of predicting persistent DSM-5 moderate to
severe SUD among youth in addiction treatment by extending or modifying the
TRAILS general population-based set of predictors with baseline indicators from
our treatment sample?
(4) Which distinct longitudinal treatment outcome trajectories can be
identified from adolescence to young adulthood pertaining to SUD, comorbid
mental health problems, and social functioning among youth in addiction
treatment?
(5) Which treatment interventions - in terms of type, intensity and duration -
are associated with favorable or unfavorable long-term outcomes, in terms of
SUD, mental health problems and social functioning, for which youth in
addiction treatment?

In the present study, we will use a naturalistic, multi-center prospective
cohort design among youth in addiction treatment to investigate (a) the course
of SUD, comorbid mental disorders and social functioning from adolescence to
young adulthood; (b) the rate of persistent DSM-5 moderate to severe SUD and
its predictors; and (c) which treatment interventions for which youth are
associated with favorable or unfavorable long-term outcomes.
Youth aged 16 to 22 years (N=420) who enter addiction treatment at one of the
participating treatment organizations will be assessed on a range of measures
related to substance use and SUD, comorbid mental health problems and social
functioning at treatment-entry (baseline), and 2 and 4 years post-baseline.

There are no risks attached to participation in this study. The only burden
that participants can experience is having an interview and filling in
questionnaires, conducting a computer task, and submitting a hair sample at the
beginning of the treatment and 2 and 4 years post-treatment-entry. Participants
also have no direct benefits. Participation, however, will contribute to more
knowledge about the prognosis of youth in addiction treatment, including
knowledge about vulnerable subgroups of youth being at risk for persistent SUD.