Substance Abuse Effects on Adolescent Brain Development

Introduction: Adolescent Substance Abuse as a Public Health Crisis

Directly or indirectly, adolescents are affected by substance abuse. Substance use is one of the United States' leading health problems. According to the National Institute on Drug Abuse, deaths associated with drug use have more than doubled since the early 1980s. Substance use addictions are costly to taxpayers, and substance abuse continues to grow as an overlooked problem. Although eliminating the use of alcohol, tobacco, and other drugs is impossible, it is important to create awareness about the health effects of substance abuse among teenagers.

To some degree, society has learned to accept the use of alcohol and tobacco for modifying mood and behavior through social drinking and smoking. Unfortunately, these substances often become daily activities for normal functioning. When this happens, the situation becomes one of substance abuse—a major concern for adolescents still experiencing physical maturation. An area of high concern is the developing brain. Wetherill and Tapert (2013) cite national survey data indicating that participation in the use of alcohol and other drugs grows exponentially from early to late adolescence. Research indicates that while substance use has become normalized in adolescent experiences, this period of development is particularly vulnerable; those who engage in substance use during adolescence are at heightened risk of developing substance use disorders.

Reasons for Adolescent Substance Abuse

A substantial number of adolescent youth have experimented with illegal drugs. Feldman (2011) reports that almost 50% of high school seniors and almost 20% of eighth graders have used marijuana within the past year. The reasons for using drugs vary widely. New technology and neuroscience research have revealed that the impulse control center of the brain—the prefrontal cortex—remains biologically immature during adolescence. Theorists now believe that this immaturity is a key factor in the impulsivity and risk-taking behavior commonly observed in adolescents. This neurological immaturity causes youth to become prone to impulsive behavior rather than logical thinking, leading them to indulge in substance abuse without comprehending the full consequences of their actions.

Other reasons for adolescent substance abuse include depression, trauma, low self-esteem, and peer pressure. In fact, peer substance use is identified as a key factor in adolescent substance abuse according to research by Rus-Makovec et al. (2010). While marijuana use among high school students has decreased since the 1990s, it remains a substantial problem among U.S. youth. Teenagers face social influences from friends, school, acquaintances, and the community. When a teenager's main peer group is involved in drug use, the presence and easy availability of drugs creates strong pressure to participate. Consequently, the teenager may try drugs to fit social norms.

Alcohol and drugs are accessible to anyone who develops an interest in them. For teenagers, hearing drug experiences from other students in school creates curiosity and interest in connecting with that experience. Young people often believe that first-time drug use is safe and that instant addiction is unlikely. At this developmental stage, teenagers lack the neural maturity to see long-term consequences of their experimentation with alcohol and drugs. They believe they are immune to the negative health effects experienced by others. Without intervention to stop experimentation, teenagers often develop a tendency toward more dangerous drugs.

Parent-Adolescent Interaction and Family Risk Factors

The primary reason for adolescent substance abuse is the lack of psychological stability during the teenage years. Young people often begin drinking and using drugs around age 13, when their psychology is unstable and their primary goal is self-assertion. Substance abuse makes teenagers feel free and independent, allowing them to engage in activities prohibited by parents and society. They long to break rules and social restrictions. A report on young people and alcohol shows that more than 10 million people between ages 12 and 20 in the United States struggle with alcohol abuse. Research also indicates that girls begin alcohol and drug abuse at an earlier age than boys, leading to more severe consequences and difficulty in treatment. Understanding the lack of psychological stability requires examining the stages of brain development among teenagers.

Research indicates that substance use during the adolescent development phase is directly related to parental use. Rus-Makovec et al. (2010) states that parental alcoholism and peer substance use are the most predictive factors for adolescent substance abuse. Additional research indicates that the lack of parental involvement with adolescent youth puts youth at risk of becoming involved with unhealthy activities, including drug use and abuse (Fauziah, Mohamad, Chong, and Manaf, 2012). Low-level parental monitoring, development of inappropriate discipline structures, and inadequate teenage support may lead to an increase in alcohol and other drug use over time. Despite evidence linking poor parenting to adolescent alcohol abuse, the mechanisms of this relationship are not fully characterized. Negative parenting and adolescent alcohol abuse can be explained by the adolescent's physical and emotional responses to family interaction (Chaplin et al., 2012). Adolescents often try to avoid family interactions, leading to decreased parental monitoring and increased risk of substance abuse.

Additional research shows that behavior problems and personality traits such as sensitivity, hopelessness, impulsivity, and anxiety in childhood lead to alcohol abuse in adolescence (Erath et al., 2009; Jaffee and D'Zurilla, 2009). Therefore, parenting should emphasize warmth and structure so that adolescents do not feel inadequate or defeated, as these emotions may create discomfort. Perceived discomfort may lead to decreased interactions between youth and parents, decreased monitoring, and increased involvement with deviant peers. The subsequent reduction in parental involvement and increase in negative peer interaction may lead to initiation of alcohol and other drug abuse.

Adolescent Brain Development and Neural Maturation

Experience sculpts the human brain. At birth, the brain contains many neural connections that are unspecialized and undeveloped. As children grow, connections strengthen while others are pruned away. This refinement and pruning process is continuous during childhood, adolescence, and early adulthood. The brain's frontal lobe and outer mantle undergo marked changes during adolescent development. The prefrontal cortex, located in the frontal lobe, performs executive functions including formulation of strategies, attention allocation, impulse control, and priority setting (Squeglia, Jacobus, and Tapert, 2009; Wetherill and Tapert, 2013).

Psychologist David Walsh provides an apt analogy to describe the effects of brain maturation during adolescence. Walsh states, "it is as if a teenager's brain has a fully functional car accelerator but the brakes have not been installed yet" (Walsh, 2004, p. 72). This explains the transparent behavioral changes accompanying adolescent development. Teenagers become obsessed with social interaction and social rules, including breaking those rules associated with social norms. The teenage brain at this period is ill-equipped to make concrete decisions and choices without assistance from trusted adults such as family members (Squeglia et al., 2009).

Teenage brains are designed to master social and intellectual challenges. Brain development toward maturity for complex thinking begins around age 11 or 12 and continues into the early twenties (Feldman, 2011). In the early twenties, the prefrontal cortex and brain's outer mantle continue developing. Additional neural wiring strengthens logical thought, connections become more robust, and nerve fibers become coated with a fatty layer called the myelin sheath (Baird and Furek, 2012). This layer assists nerve connections in faster processing, rational thinking, quick decision-making, and automaticity (Baird and Furek, 2012).

Inhalant Abuse and Neurological Consequences

Research conducted by Baird and Furek (2012) demonstrates that chemical exposures through inhalation lead to neurological and cognitive symptoms. The most prevalent inhalation exposure comes from intentional experimentation through huffing, sniffing, or bagging. Twenty-six percent of adolescents between ages 12 and 19 have experimented with neurotoxic substances to achieve a high. During adolescence, when the brain is undergoing critical development, chronic abuse of inhalants can damage the central nervous system and cause neurological disorders. The most commonly abused inhalants include organic compounds, aesthetic gases, and nitrites.

Once these chemicals enter the bloodstream, they affect the liver and brain. Much like alcohol, the effects include "initial excitation, followed by drowsiness, disinhibition, lightheadedness, and agitation." A report by the National Survey on Drug Use and Health shows that the most prevalent inhalants used during adolescence include glue, spray paints, aerosol sprays, gasoline, and shoe polish. These substances damage fatty tissue and the brain, leading to hearing loss due to nerve cell damage, slurred speech, neuropathy, and chronic limb spasms. Damage to axons leads to impaired movement and damage to cognitive activities such as language processing. Chemical inhalants damage the myelin sheath, disrupting and slowing communication between neurons. Most alarming is adolescents' willingness to inhale these compounds to achieve temporary euphoria. Given the critical neuro-maturational changes occurring during adolescence and the brain's heightened vulnerability, exposure to chemical inhalants poses a serious risk for long-term neurological damage.

Neurocognitive Damage from Substance Use

With ongoing brain changes during adolescence, neurotoxins such as alcohol and illicit drugs interrupt neural development and cognitive and behavioral functioning. Neuroimaging studies of white matter microstructure have shown adverse effects of substance abuse on adolescent brain development. Results demonstrate that heavy-drinking adolescents have smaller hippocampal and prefrontal volumes compared to non-drinking adolescents (De Bellis, 2008). Using functional magnetic resonance imaging (fMRI), researchers can measure brain activity and determine alcohol's effects on neural responses. With fMRI studies of adolescent heavy drinkers, researchers have detected aberrant frontal and parietal neural responses during spatial working memory, verbal coding, and inhibition tasks (Wetherill and Tapert, 2012).

Adolescent marijuana users, by contrast, show increased activation of the right frontal and parietal areas during attention control tasks compared to non-using controls. These results suggest that adolescent marijuana users exert considerable effort attempting to self-regulate. There is also disadvantaged attention due to adolescents' substance abuse. Adolescents participating in substance use may demonstrate preexisting deficiencies that become exacerbated by use (Squeglia et al., 2011).