More than three decades of research supported by the National Institute on Drug Abuse (NIDA) has proven that addiction is a complex brain disease characterized by compulsive, at times uncontrollable, drug craving, seeking, and use that persist despite potentially devastating consequences. Addiction is also a developmental disease; that is, it usually starts in adolescence or even childhood and can last a lifetime if untreated. Disagreements about the nature of addiction remain: namely, whether it reflects voluntary or involuntary behavior and whether it should be punished or treated as a health issue. Even though the first time a person takes a drug, it is often by choice—to achieve a pleasurable sensation or desired emotional state—we now know from a large body of research that this ability to choose can be affected by drugs. And when addiction takes hold in the brain, it disrupts a person’s ability to exert control over behavior— reflecting the compulsive nature of this disease.
The human brain is an extraordinarily complex and fine-tuned communications network made up of billions of cells that govern our thoughts, emotions, perceptions, and drives. Our brains reward certain behaviors such as eating or procreating—registering these as pleasurable activities that we want to repeat. Drug addiction taps into these vital mechanisms geared for our survival. And although not a life necessity, to an addicted person, drugs become life itself, driving the compulsive use of drugs—even in the face of dire life consequences—that is the essence of addiction.
The rewarding effects of drugs of abuse come from large and rapid upsurges in dopamine, a neurochemical critical to stimulating feelings of pleasure and to motivating behavior. The rapid dopamine “rush” from drugs of abuse mimics but greatly exceeds in intensity and duration the feelings that occur in response to such pleasurable stimuli as the sight or smell of food, for example. Repeated exposure to large, drug-induced dopamine surges has the insidious consequence of ultimately blunting the response of the dopamine system to everyday stimuli. Thus the drug disturbs a person’s normal hierarchy of needs and desires and substitutes new priorities concerned with procuring and using the drug.
Drug abuse also disrupts the brain circuits involved in memory and control over behavior. Memories of the drug experience can trigger craving as can exposure to people, places, or things associated with former drug use. Stress is also a powerful trigger for craving. Control over behavior is compromised because the affected frontal brain regions are what a person needs to exert inhibitory control over desires and emotions.
That is why addiction is a brain disease. As a person’s reward circuitry becomes increasingly dulled and desensitized by drugs, nothing else can compete with them—food, family, and friends lose their relative value, while the ability to curb the need to seek and use drugs evaporates. Ironically and cruelly, eventually even the drug loses its ability to reward, but the compromised brain leads addicted people to pursue it, anyway; the memory of the drug has become more powerful than the drug itself.
Like many other diseases, vulnerability to addiction is influenced by multiple factors, with genetic, environmental, and developmental factors all contributing. Genetics accounts for approximately half of an individual’s vulnerability to addiction, including the effects of the environment on gene function and expression. Elements of our social environments—culture, neighborhoods, schools, families, peer groups— can also greatly influence individual choices and decisions about behaviors related to substance abuse, which can in turn affect vulnerability. Indeed, addiction is a quintessential gene-byenvironment- interaction disease: a person must be exposed to drugs (environment) to become addicted, yet exposure alone does not determine whether that will happen—predisposing genes interact with this and other environmental factors to create vulnerability. In fact, environmental variables such as stress or drug exposure can cause lasting changes to genes and their function, known as epigenetic changes, which can result in long-term changes to brain circuits. Genes may also mitigate the effects of environment—which is why, for example, two substance-abusing individuals growing up in the same high-risk environment may have very different outcomes.
Adding to the complexity, the contributions of environmental and genetic risk factors may also vary during the different life stages of childhood, adolescence, and young adulthood. Adolescence is the period when addiction typically takes hold. Additionally, because their brains are still undergoing rapid development in areas that contribute to decision-making, judgment, and risk-taking, adolescents tend toward immediate gratification over long-term goals. This can lead to risk-taking, including experimenting with drugs. When coupled with their increased sensitivity to social or peer influences and decreased sensitivity to negative consequences of behavior, it is easy to see why adolescents are particularly vulnerable to drug abuse.
As with any other medical disorder that impairs the function of vital organs, repair and recovery of the addicted brain depends on targeted and effective treatments that must address the complexity of the disease. We continue to gain new insights into ways to optimize treatments to counteract addiction’s powerful disruptive effects on brain and behavior because we now know that with prolonged abstinence, our brains can recover at least some of their former functioning, enabling people to regain control of their lives.
That said, the chronic nature of the disease means that relapsing to drug abuse is not only possible but likely, with relapse rates similar to those for other well-characterized chronic medical illnesses such as diabetes, hypertension, and asthma. For all these diseases, including drug abuse, treatment involves changing deeply embedded behaviors, so lapses should not be considered failure but rather indicate that treatment needs to be reinstated or adjusted, or that alternate treatment is needed. But addicted individuals also need to do their part. Even though they are dealing with a compromised brain that affects decision-making and judgment, people with drug abuse or addiction must also take responsibility to get treatment and actively participate in it.
Although we have a range of effective addiction treatment options in our clinical toolbox, we still don’t have enough to address the many facets of this problem. Research continues to search for improved prevention and treatment options and to reveal promising new strategies to help people deal with their compulsive drug use.
Science-based approaches to tackling drug abuse and addiction will yield smart solutions that bring positive change. As a society, the success of our efforts to deal with the drug problem depends on having an accurate understanding of it. Education is key. Education can impart knowledge to equip parents to be effective interveners with their children. Knowledge will also help our youth make more informed choices and perhaps think twice before they make a decision.
More information on drug abuse and addiction can be found on the NIDA homepage. Free publications can be ordered online from NIDA DRUGPUBS, Research Dissemination Center or by calling 1-877-NIDA-NIH or 1-877-643-2644.