Substance use disorders typically emerge after age 14 though the precursors can be seen before adolescence. The most prominent influences are the family (e.g. conflict; parent substance use), larger social-ecological context (e.g. drug availability) and the adolescents’ genetic vulnerability (e.g. poor impulse control). Substance use is common and substance abuse is prevalent at 8% for youth between the ages of 12 and 17 and 20% for youth aged 18 to 25.

Youth with substance use disorders often first use to pursuit specific pharmacological effects (e.g. managing negative emotions) but it is associated with high risk for long-term functional impairments (e.g. cognitive deficits).

Adolescents are vulnerable to the consequences of substance use because they have a fully functional reward-seeking and pain-avoidance system in place and less impulse control and judgement. Substance use disorders typically first appear during adolescence and is associated with susceptibility to comorbidity. Adolescents with SUD and a comorbid disorder often have behavioural skills deficits (1), limited coping strategies (2) and emotion dysregulation (3). A treatment should consider these properties and the unique pharmacological and addictive properties of different substances. Family-based interventions are associated with improvement.

Functional family therapy (FFT) is a family systems therapy which conceptualizes alcohol and drug abuse as behaviours that develop and are maintained in the context of maladaptive family relationships. Changing the family interactions and improved relationship functioning is thus key to reduce adolescent substance use. The locus of problem behaviour is relational. This treatment is able to target comorbid disorders as well. It links treatment strategies into a unity family-centred approach.

The treatment goals include reducing substance use and co-occurring problems (1), improving family relationships (2) and increase adolescents’ productive use of time. The treatment tries to make sure that the functions of substance use are met through other, more adaptive behaviours. The treatment consists of 14 weekly 1-hour sessions with more frequently or longer sessions initially to potentiate the initial change process. The sessions may be spaced farther apart near completion. Treatment follows five methods which are completed in order:

1. Engagement
   This focuses on maximizing initial positive expectations for change among family members. This is aimed at reducing attrition. The perceived credibility and characteristics of the therapist (1), the referral process (2), the reputation of the agency (3) and the friendliness of staff (4) influence treatment expectancies. Therapists can adopt the language system used by the family (1), normalize problems (2) and express confidence (3) to influence family expectations.
2. Motivation
   Youth with SUD often enter treatment with low motivation or readiness to change and parents often solely focus on the youths’ need to change. Strategies to motivate families includes emphasize strengths (1), develop a relational framework by interconnecting the thoughts, feelings and/or behaviours of family members (2), reframing or changing the meaning of behaviours and interactions that are perceived negatively to a more neutral understanding of them (3) and actively manage aversive interactions (4). The therapist needs to highlight the interactions between family members to increase awareness of how they affect one another. Reframing problem behaviour to change the meaning and value of negative emotions and behaviours in the family may be essential. Exploring and clarifying the meaning of substance use in families is an important task for the motivation phase of treatment.
3. Assessment
   This takes place at the level of what change is needed (i.e. behavioural targets of change) and how the behaviour change needs to occur to maintain the functions served by the behaviour (i.e. process of change). FFT relies on family report (1), in-session observations (2) and formal assessment instruments (3). The interpersonal function of behaviour for all relationships needs to be assessed (e.g. drug use elicits nurturance from the father but creates distance to the mom). The functions are not given a moral label (i.e. good or bad) but are assessed in terms of adaptive or maladaptive. The focus of treatment is changing maladaptive behaviours by which functions are achieved. The identification of the functions for each dyad in the family allows the therapist to develop a change plan to address maladaptive behaviour while ensuring that the functions are maintained.
4. Behaviour change
   This phase focuses on establishing and maintaining behaviour change at the individual and family level. The motivational framework that has been created and the assessment data from the engagement and motivation phase are used to guide the selection and implementation of specific behavioural techniques. The primary goal is to establish new behaviours and patterns of interaction that will replace old ones. It often includes a functional analysis of substance use. The techniques that are used should be tailored to each set of family relationships (i.e. take the functions into account).
5. Generalization and termination
   This phase aims to facilitate maintenance of behaviour change and the generalization of treatment gains to the natural environment. The therapist gradually takes a less active role as the therapist attempts to make sure the family is independent from therapy. Families should attempt to apply their new behavioural skills to novel situations. This can be aided by reviewing these attempts during the session. The family should learn to identify and control difficult situations and anticipate future problems and potential solutions.

FFT seems effective in reducing recidivism and improving family functioning. It is effective for delinquency and youth disruptive behaviour. It also seems to reduce substance use. FFT is a very good fit for Hispanic youth and this is especially the case when the therapist has a similar ethnic background. The results appear to be maintained over the long-term. The results can be sustained through brief telephone counselling calls to help families consolidate treatment gains. Telehealth strategies are promising. FFT is efficacious in reducing depression and substance use for youth with comorbid depressive disorders.