A 15-year-old high school student was brought to the emergency department after his parents found him in his room staring at the ceiling and visibly frightened. Earlier that evening, he attended a party but was depressed because his girlfriend just broke up with him. His parents are also worried about a change in his behavior over the last few months. He is failing this year at school and has stopped playing soccer. He has lost interest in school, at times seems depressed, and tells his parents that his pocket money is not sufficient.
When questioned by the intern, he reports that space-cookies were served at the party. He also says that smoking marijuana has become a habit (three to four joints a week) but denies consumption of alcohol and other drugs.
How do you explain the state he was found in? What is the difference between hashish and marijuana? What may be the link to his poor performance at school? Do all drug users necessarily use several drugs?
Drugs are abused (used in ways that are not medically approved) because they cause strong feelings of euphoria or alter perception. However, repetitive exposure induces widespread adaptive changes in the brain. As a consequence, drug use may become compulsive—the hallmark of addiction.
BASIC NEUROBIOLOGY OF DRUG ABUSE
DEPENDENCE VERSUS ADDICTION
There is a conceptual and mechanistic separation of “dependence” and “addiction.” The older term “physical dependence” is now denoted as dependence, whereas “psychological dependence” is more simply called addiction.
Every addictive drug causes its own characteristic spectrum of acute effects, but they all induce strong feelings of euphoria and reward. With repetitive exposure, addictive drugs induce adaptive changes such as tolerance (ie, escalation of dose to maintain effect). Once the abused drug is no longer available, signs of withdrawal become apparent. A combination of such signs, referred to as the withdrawal syndrome, defines dependence. Dependence is not always a correlate of drug abuse—it can also occur with many classes of nonpsychoactive drugs, eg, sympathomimetic vasoconstrictors and bronchodilators, and organic nitrate vasodilators. Addiction, on the other hand, consists of compulsive, relapsing drug use despite negative consequences, at times triggered by cravings that occur in response to contextual cues (see Box: Animal Models in Addiction Research). Although dependence invariably occurs with chronic exposure, only a small percentage of subjects develop a compulsion, lose control, and become addicted. For example, very few patients who receive opioids as analgesics desire the drug after withdrawal. And only one person out of six becomes addicted within 10 years of first use of cocaine. Conversely, relapse is very common in addicts after a successful withdrawal when, by definition, they are no longer dependent.
ADDICTIVE DRUGS INCREASE THE LEVEL OF DOPAMINE (DA): REINFORCEMENT
To understand the long-term changes induced ...