It doesn’t have to go this far addiction can be eradicated if you avoid substance abuse, be it stimulant or otherwise.
Over the last several decades, research on substances of abuse has vastly improved our understanding of human behavior and physiology and the nature of substance abuse and dependence. Basic neurobiological research has enhanced our understanding of the biological and genetic causes of addiction. These discoveries have helped establish addiction as a biological brain disease that is chronic and relapsing in nature. By mapping the neural pathways of pleasure and pain through the human brain, investigators are beginning to understand how abused psychoactive substances, including stimulants, interact with various cells and chemicals in the brain.
For the purpose of this article I will tell you the effects of cocaine and methamphetamine (MA) use, have on the user’s brain and behavior, which in turn leads to the stimulant user’s unique needs. Understanding these effects provides the foundation for stimulant-specific treatment approaches and gives treatment providers greater insight into stimulant users and why certain treatment approaches are more effective.
The fundamental problem in dealing with any substance of abuse is to understand “the target” (the user). Therefore, to understand why people take drugs such as cocaine and MA and why some people become addicted, we must first understand what these drugs are doing to their target; that is to say, how stimulants affect the user.
Proper engagement of substance abuse and dependence often involve some discussion of the root causes–the societal and risk factors that lead to these conditions. To date, investigators have identified as many as 72 risk factors for substance use and dependence. Among them are poverty, racism, social dysfunction, weak families, poor education, poor upbringing, and substance-abusing peer groups. These risk factors–as well as other environmental and genetic factors–only influence an individual’s initial decision to use substances of abuse. But after initial use, an individual continues to use a substance because she likes its effects: Use modifies mood, perception, and emotional state. All of these effects are modulated through the brain; basic understanding of neuroscience will help us understand this phenomenon.
For substances of abuse to exert their effects, they must first get to the brain. The four most common routes of administering psychoactive (mood-changing) substances are:
Oral consumption (i.e., swallowing)
A swallowed substance goes to the stomach and on to the intestinal tract. Some substances easily pass through the digestive tract into the bloodstream. Other substances are broken down into their chemical components (i.e., metabolized) in the digestive system, thereby destroying the substance.
Intranasal consumption (i.e., snorting)
Inhalation into the lungs (generally by smoking)
Substances that are inhaled into the lungs adhere to the lining of the nasal passages (the nasal mucosa) through which they enter directly into the bloodstream. Inhaled substances are usually first changed into a gaseous form by igniting (e.g., marijuana) or volatilizing by intense heat (e.g., crack cocaine, the ice form of MA). The lungs offer a large surface area through which the gaseous form may quickly pass directly into the bloodstream.
Injected substances obviously enter the bloodstream directly, although at a somewhat regulated rate. In these last three routes of administration, substances enter the bloodstream in none metabolized form.
Once a substance enters the bloodstream, it is transported throughout the body to various organs and organ systems, including the brain. Substances that enter the liver may be metabolized there. Substances that enter the kidney may be excreted. If a female substance user is pregnant, and the substance is able to cross the placenta, then the substance will enter the fetus’ bloodstream. Nursing babies may ingest some substances from breast milk.
To enter the brain, a substance’s molecules must first get through its chemical protection system, which consists mainly of the blood-brain barrier. Tight cell-wall junctions and a layer of cells around the blood vessels keep large or electrically charged molecules from entering the brain. However, small neutral molecules like those of cocaine and MA easily pass through the blood-brain barrier and enter the brain. Once inside the brain, substances of abuse begin to exert their psychoactive effects.
The human nervous system is an elaborately wired communication system, and the brain is the control center. The brain processes sensory information from throughout the body, guides muscle movement and locomotion, regulates a multitude of bodily functions, forms thoughts and feelings, modulates perception and moods, and essentially controls all behavior.
The brain is organized into lobes, which are responsible for specialized functions like cognitive and sensory processes and motor coordination. These lobes are made up of far more complex units called circuits, which involve direct connections among the billions of specialized cells that the various substances of abuse may affect.
The fundamental functional unit of the brain’s circuits is a specialized cell called a neuron, which conveys information both electrically and chemically. The function of the neuron is to transmit information: It receives signals from other neurons, integrates and interprets these signals, and in turn, transmits signals on to other, adjacent neurons.
The brain circuit that is considered essential to the neurological reinforcement system is called the limbic reward system (also called the dopamine reward system or the brain reward system). This neural circuit spans between the ventral tegmental area (VTA) and the nucleus accumbens. Every substance of abuse–alcohol, cocaine, MA, heroin, marijuana and nicotine–has some effect on the limbic reward system. Substances of abuse also affect the nucleus accumbens by increasing the release of the neurotransmitter dopamine, which helps to regulate the feelings of pleasure (euphoria and satisfaction).
Dopamine also plays an important role in the control of movement, cognition, motivation, and reward. High levels of free dopamine in the brain generally enhance mood and increase body movement but too much dopamine may produce nervousness, irritability, aggressiveness, and paranoia that approximates schizophrenia, as well as the hallucinations and bizarre thoughts of schizophrenia. While too little dopamine in certain areas of the brain results in the tremors and paralysis of Parkinson’s disease.
Natural activities such as eating, drinking, and sex activate the nucleus accumbens, inducing considerable communication among this structure’s neurons. This internal communication leads to the release of dopamine. The released dopamine produces immediate, but ephemeral, feelings of pleasure and elation. As dopamine levels subside, so do the feelings of pleasure. But if the activity is repeated, then dopamine is again released, and more feelings of pleasure and euphoria are produced. The release of dopamine and the resulting pleasurable feelings positively reinforce such activities in both humans and animals and motivate the repetition of these activities.
Dopamine is believed to play an important role in the reinforcement of and motivation for repetitive actions and there is an increasing amount of scientific evidence suggesting that the limbic reward system and levels of free dopamine provide the common link in the abuse and addiction of all substances. Dopamine has even been labeled “the master molecule of addiction.”
