Chapter 1: Understanding the Risk Factors for Substance Abuse There are multiple developmental pathways to substance use disorders, with the risk factors that can start an individual down one of these pathways ranging from the genetic to the sociocultural. Because these factors tend to cluster and can vary with age, disentangling their unique contributions can be difficult. Consequently, a focus on the stages of development is key. This chapter looks at the latest research on the different risk factors at play during a person’s development, including: • Genetic factors (i.e., the fact that the risk for substance runs in families), which are estimated to contribute 40–60 percent of vulnerability to drug abuse; • Early brain development, looking particularly at how disruptions in the development of the brain’s fear processing and reward cue processing circuitry can predict later behaviour, including substance abuse; and • The role of the environment in shaping brain functioning, including maltreatment and severe early stress; parental factors such as prenatal exposure to drugs, anti-social behaviour, a non-intact family and maternal depression; the influence of peers, especially among youth with low self-efficacy; and the cultural and social structures that inadvertently channel people toward drug use. The chapter concludes with a brief look at how these factors contribute to the two major developmental pathways (characterized by external problems such as aggression or internal problems such as anxiety), both of which represent an increased risk for substance use disorders. For example, “externalizers” seem to be more responsive to drug activation of the brain’s reward cue system, while “internalizers” appear to use drugs in an attempt to control their hyper-responsive fear-anxiety system.
Chapter 2: The Externalizing Developmental Pathway to Substance Use Disorders Almost all young children are impulsive, inattentive and emotionally reactive, and many are aggressive and highly active. In most cases, these behaviours subside as a child matures. In about 25 percent of children, though, these behaviours are unusually elevated and persistent, expressing themselves as an enduring mixture of features that include social gregariousness, risky thrill-seeking, emotionality and irritability. These externalizing behaviours are predictive of various childand adolescent-onset disruptive behavioural disorders (DBDs), including oppositional defiant disorder in the preschool years, attention deficit/hyperactivity disorder in the elementary school years, and conduct disorder in middle childhood through adolescence. By adolescence, these DBDs increase the risk for substance use disorders: compared to those without DBDs, individuals with DBDs have double the risk of abusing tobacco, triple the risk of abusing alcohol, and five times the risk of abusing illicit drugs. Indeed, 75 percent of adolescents with a DBD become substance abusers in adulthood and 50 percent of adults with substance use disorders had a history of at least one DBD in childhood or adolescence. This chapter summarizes the various risk factors that predict the development of DBDs and substance use problems including genetic predispositions, chronic early maltreatment, parental antisocial behaviour and substance abuse, poor inhibitory control, and an early age of onset of drug and alcohol use.
Chapter 3: The Internalizing Developmental Pathway to Substance Use Disorders Youth and adults who abuse substances commonly experience co-occurring mental health problems, with mood and anxiety disorders among the most prevalent. Because internalizing personality traits are relatively stable over time and can be detected early in life, behavioural inhibition (i.e., a temperamental factor involving withdrawal, avoidance, over-arousal and fear of the unfamiliar) in infancy can be used to predict internalizingproblems into adulthood. While the rates of depressive disorders in males and females is relatively equal in childhood, this changes dramatically when youth reach adolescence, with females becoming three times more likely to develop mood disorders. Gender differences in anxiety are present from childhood, with females twice as likely as males to experience clinically relevant anxiety in their lifetimes. In most cases, mood and anxiety problems precede the onset of substance abuse, suggesting individuals self-medicate with alcohol or drugs to temporarily diminish their anxiety. As a corollary, this observation also implies that the shared risk for internalizing behaviours and substance use problems reflects an overlap of pre-existing vulnerabilities. This chapter presents evidence indicating there is indeed an overlap in genetic factors, neurobiological differences that influence personality, responses to drugs and alcohol, and early life experiences such as abuse and neglect. Once substance use begins, it can lead to worsened mood and more anxiety, further perpetuating the relationship between internalizing problems and substance use. Obtaining a better understanding of the factors that increase risk for substance use in people with anxiety/depression and influence their progress along this pathway is expected to improve our understanding of how addictions develop.
Chapter 4: A developmental approach to prevention and intervention The multiple risk factors influencing internalizing and externalizing behaviours are partly a function of the developmental stage of the individual. Each stage presents unique challenges that might increase vulnerability to substance abuse, as well as distinct opportunities for promoting resilience and detecting at-risk individuals. This chapter outlines the need to consider prevention within this developmental context, summarizing the key risk factors as well as several well-validated preventive interventions for each of the early childhood, school-age and adolescent stages. Such a framework not only highlights specific developmental pathways and milestones, it also underscores the need to implement personalized prevention strategies in a multidisciplinary manner, working across different social contexts and in developmentally appropriate ways. For example: • Exposure to parental substance abuse and psychopathology during early childhood increases the likelihood of poor outcomes later in life. Helping parents improve their ability to care for infants and toddlers can help counteract exposure to these risk factors by improving child–parent attachment and reducing behavioural and emotional dysregulation. • In school-age children, genetic predispositions, suboptimal parenting and exposure to uncontrollable stressful life events all affect the emergence of internalizing and externalizing behaviours. Multilevel preventive interventions implemented at the individual, family and school levels have proven to be most effective in targeting specific risk patterns while increasing social adaptation and self-efficacy. • Prevention programs targeted at adolescents are often ineffective, partly because of researchers’ inability to distinguish normal features of adolescence (e.g., novelty-seeking, reduced risk aversion, heightened reward salience) from causal mechanisms predicting substance abuse. For instance, internalizing and externalizing symptoms might be associated with specific motivations to use substances that, in turn, could be targeted through personalized interventions to prevent future substance abuse. Reflecting the increased importance of teens’ broader social environments, community-based interventions should be implemented alongside individual- and school-based initiatives.
Chapter 5: A Call to Action On the basis of the research findings presented in the previous chapters, this final section makes a series of recommendations for prevention research and interventions, and highlights future directions and developments in the field of substance abuse prevention. Given the inter-relationships between the risk factors for substance abuse and their potentially broad impact on a wide range of negative outcomes, this chapter reinforces the need to take a multidimensional, interdisciplinary approach to futureprevention research and interventions. It also looks at the need to develop a methodology for classifying the early warning signs of risk to help teachers and other childcare professionals identify at-risk youth as soon as possible, as well as the need to codify specific neurobiological and behavioural markers of substance abuse risk so that they can be better matched to specific interventions. Doing so would help streamline early detection efforts and improve the development and implementation of personalized prevention programs.