Understanding the Addicted Brain

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It’s All In Your Head: Understanding the Addicted Brain Drugs and alcohol interfere with the exchange of information in your brain, producing changes that promote repeated drug use. If you’re one of the 24 million Americans who suffer from alcohol or drug addiction, just seeing a drug or its paraphernalia can bring you anticipatory pleasure. Then, with the fix, comes the real rush. For a brief period, everything feels right.

But something happens after repeated exposure to drugs — whether it be heroin or cocaine, beer or speed: Your brain becomes accustomed to the chemical changes caused by the drug and begins altering its normal production and release of neurotransmitters. As a result, you begin losing control and having difficulty limiting your drug intake. Your need to consume drugs now becomes compulsive because the drug has affected the regions in your brain controlling impulse, craving and behavior.

How does this happen? Information transmission in the brain occurs through communication from one nerve cell (neuron) to another. Science’s understanding of how the brain functions shows that drugs interfere with this information pathway and produce changes that promote repeated drug use.

Science tells us that the euphoria induced by drugs occurs because drugs boost the activity of our brain's reward system. This reward system makes us feel satisfied after eating a good meal or having great sex — things we need to do to survive and pass along our genes. At least initially, interfering with this system by using drugs or alcohol makes us feel good, which then encourages us to repeat whatever activity gave us that pleasure.

But chronic drug use induces changes in the structure and function of neurons that can last for years after you’re clean. These adaptations reduce the pleasurable effects of a drug that you chronically abuse, yet also increase the cravings that trap you in the destructive spiral of escalating use.

THE BRAIN AND DRUG INTERFERENCE

Your nervous system includes vast circuits of cells called neurons that are interconnected. Neurons connect one area of your brain to another area via pathways.

Your brain contains more than 100 billion neurons. One neuron can reach over 1,000 other neurons. These pathways and the natural release of the chemicals that enable the transmission allow your body to maintain a healthy mental balance. Every time you feel something — including the effects of a drug — millions of neurons are "firing" messages to and from one another.

But this delicate balance is upset by the use of drugs.

Neurons receive messages, process messages and send out the results as new messages to other cells. The message consists of chemicals that interact with the outer surface of the cell membrane, and this chemical interaction with the cell membrane causes chemical changes within the receiving neuron.

This constant exchange of chemical messages between neurons is called neurotransmission: Neurons release neurotransmitters, neurotransmitters bind to receptors and binding passes on the neurotransmitter’s message.

What science has shown is that drugs interfere with the message transmission. Each receptor is designed to bind only a particular neurotransmitter. A drug that’s structured similarly to a neurotransmitter can block nerve impulses, preventing neurotransmitters from getting where they’re supposed to be or causing the brain to produce too many or too little neurotransmitters. As a result, neurons may be overstimulated or understimulated, hindering the nervous system from carrying out its functions.

NEUROTRANSMITTERS AFFECTED BY DRUG USE

The following are a few of the neurotransmitters affected by drug abuse and their primary role:

Dopamine — role: mood, pleasure and motivation. Dopamine plays a major role in addiction. It affects brain processes that control movement, emotional response and the ability to experience pleasure and pain, playing a crucial role in our mental and physical health. Cocaine and other drugs can alter dopamine function. Such drugs may have a different action depending on which dopamine receptors they stimulate or block, and how well they mimic dopamine. Ultimately, however, what happens is that addicts end up with a reduced supply of dopamine, resulting in increased stress, lack of motivation and depression. These feelings create a craving for more drugs or alcohol and for substances such as carbohydrates and nicotine, which all stimulate the release of dopamine and bring temporary relief.

Serotonin (5-HTP) — role: mood, appetite, sex and aggression. Serotonin plays a major role in emotional disorders such as depression, suicide, impulsive behavior and aggression. Decreases in serotonin increase impulsive behavior. Drugs that affect serotonin receptors include LSD and some antidepressant drugs.

Norepinephrine — role: mood, attention, concentration. Norepinephrine, also called noradrenaline, is a neurotransmitter that doubles part-time as a hormone. As a neurotransmitter, it helps to regulate arousal, dreaming and moods. As a hormone, it acts to increase blood pressure, constrict blood vessels and increase heart rate — responses that occur when we feel stress.

Endorphins — role: blood pressure, body temperature, mood, pain suppression. Endorphins act as opiates in the brain. They’re always present but are released in greater amounts when you’re in pain or under stress.

Acetylcholine — role: mood, memory, movement. Acetylcholine is released where nerves meet muscles and is responsible for muscle contraction. After acetylcholine stimulates its receptors, it’s quickly inactivated and destroyed by an enzyme.

Glutamate and Gamma Amino Butyric Acid (GABA) — role: sedation, inhibitions, learning, memory. Glutamate and GABA are amino acids that act as neurotransmitters. Glutamate is the precursor to GABA and is the second most prevalent neurotransmitter in the brain. GABA is the first. Glutamate is the primary excitatory neurotransmitter in the brain and excites virtually every neuron within the central nervous system. The majority of synapses in the brain (the gaps between neurons) use glutamate or GABA. The fact that GABA and glutamate are so widely present makes it likely that they’ll be affected by drug abuse.

DRUGS AND THE BRAIN

What happens in your brain depends on the drug you abuse and the neurotransmitters that drug hinders or stimulates. Here are some of the ways specific drugs may contribute to addiction:

• Alcohol addiction — Physical dependence on alcohol occurs gradually as drinking alters the balance of some chemicals in your brain, such as GABA, which inhibits impulsiveness, and glutamate, which excites the nervous system. Alcohol also raises dopamine levels in the brain, which is why you then associate drinking with pleasure. Excessive, long-term drinking can deplete or increase the levels of some of these chemicals, causing your body to crave alcohol to restore good feelings or to avoid negative ones, such as withdrawal.

• Cannabis compounds — The main active agent in cannabis compounds such as marijuana is delta-9-tetrahydrocannabinol (THC), which affects the neurotransmitter communication process. Some people perceive the effects of THC as enjoyable, and this sensation reinforces use of the drug. For others, THC causes uncomfortable feelings or anxiety, which doesn't reinforce use of the drug.

▪ Central nervous system depressants — Benzodiazepines and barbiturates produce long-term cellular changes partly by enhancing the actions of the inhibitory neurotransmitter GABA. When GABA is released into the synapses (the gaps between neurons), it binds to receptors and lowers cell excitability, which slows brain activity.

▪ Central nervous system stimulants — These drugs raise the levels of dopamine and serotonin in the synapses (the gaps between neurons), causing overstimulation and, over time, altering the normal production and release of these neurotransmitters. Neurons release dopamine as part of the reward system through which you learn to seek pleasurable stimuli. Stimulants block the reabsorption of dopamine after its release and can physically alter the sensitivities of some dopamine and serotonin receptors.

For example, cocaine acts as a local anesthetic by blocking the reuptake of dopamine, norepinephrine and serotonin by the nerve terminal, so they’re not reabsorbed by the sending neuron and are left swimming in the synaptic gap — to continue stimulating the neighboring neurons over and over.

Another stimulant, methamphetamine has a structure that’s similar enough to norepinephrine and dopamine that it tricks the receiving neuron into thinking it’s being stimulated.

But the net effect of cocaine, methamphetamine and other stimulants on neurons is the same: over-stimulation.

▪ Opiates — Opiates such as heroin and morphine stimulate the "pleasure system" in the brain, much like stimulants, affecting dopamine and producing pleasurable effects and positive reinforcement for continuing the use of these drugs. Opiates also affect other neurotransmitter systems, such as those related to endorphins. Opiates have a chemical structure similar to endorphins, which are naturally manufactured in the brain to provide relief when the body experiences pain or stress (like from exercise) by flooding the synapses (the gaps between neurons) in the brain. When you take an opiate, the morphine molecule binds to the endorphin-receptor sites on neurons and mimics the function of natural endorphins.

THE ADDICTED BRAIN

The impact of a drug — an artificial stimulus — on your brain’s chemical balance produces long-term changes in the reward circuitry of your brain.

Drugs alter the amount of neurotransmitters in the mesocorticolimbic pathway (MCLP), which is the route to our major pleasure/reward centers. Natural rewards such as a great meal or a great kiss result in a large spike in the dopamine level in your brain —allowing you to feel pleasure — and these pleasurable feelings you experience then reinforce the behavior so that you’ll repeat it. After this “natural” event, your dopamine level quickly returns to normal so your body is ready to enjoy another pleasurable event.

But unnatural rewards, like drugs, also stimulate this pleasure pathway and cause the release of dopamine. The result: increased pleasure.

When you experience your first drug high, your dopamine level rises even higher than during a natural reward, is even more intense and lasts longer. But your dopamine level doesn’t return to the normal baseline after that. It plunges to 0 — no dopamine – and stays there.

Your first high then becomes an emotional memory, made and stored in the section of your brain called the amygdala. In the brain of an addict, the intense high created by drugs or alcohol creates a "snapshot" of the moment that’s etched in the amygdala. And you’re only "rewarded" upon recreation of that snapshot.

The snapshots of the euphoric highs form emotional memories and are triggered by exposure to "people,” "places" or "things.” You can be listening to a certain song or particular band, which triggers memories of when you were using, producing a craving for that drug. You could be getting together with an old drinking buddy, which triggers memories of when you two used to go on all-night benders, stimulating a craving for a drink. You could be driving to grandma’s, which triggers memories of the time you used before going to her house, stimulating a craving for that drug.

“Triggers” are everywhere. And despite what many people think, it’s not a lack of will power. It’s neurochemistry.

Central nervous system (CNS) stimulants, CNS depressants, certain hallucinogens and opiates all target our brain’s MCLP reward center. These drugs have an increased potential for addiction because you need to continue taking them to achieve an acceptable level of pleasure.

This constant stimulation of your reward pathway due to drug use causes your brain to adapt and to expect this heightened feeling as “normal.” But with each time you use drugs, you have to use more and more to get less and less of an effect (tolerance). This continues until you’re using not to get high, but just to get normal.

What happens is that as your brain becomes accustomed to the drug-induced chemical changes, it changes its normal production and release of natural neurotransmitters. In the case of dopamine in particular, drug abuse can alter the number and functioning of dopamine receptors and transporters in the brain, and these changes can continue for many months after abstinence.

Because of all these changes, when you stop taking the drug, your brain creates an intense craving in order to bring back the pleasurable feeling, and it’s this repeated intense craving that results in addiction. Unlike in the normal brain, there’s no satiation with pleasure. Dopamine levels crash quickly and stimulate "cravings.” Your neurons have adapted to the repeated drug exposure, so now you can only function normally when you’re using the drug. Without it, you’ll crash and go into withdrawal.

GETTING HELP

People dependent on drugs or alcohol may have one or all of the following problems at the time they enter treatment:

Induced chemical imbalance
Genetic chemical imbalance
Social and psychological problems
Inhibited life and/or coping skills

With one or more of these factors present, it’s easy to see why different treatments work for some people but not others and why many addicts end up having to go through rehab multiple times before staying clean (if they ever stay clean).

There’s ongoing research into the ability of brain cells to recover from damage caused by drugs, and many recovering addicts certainly learn to live happy, productive lives drug-free – giving hope that the brain possesses some ability to return to a state that allows normal experience of pleasure.

There are a variety of approaches to the treatment of addiction. Regardless of what route you choose, a comprehensive drug treatment program needs to address biological, psychological and sociological factors.

The roots of addiction lie in the regions of the brain connected to the pleasure/reward pathway and the change in brain chemistry that relays information from one section of the brain to another. Once addicted, it’s important that you find a treatment program that addresses how to begin to undo the damage caused by drug or alcohol abuse.

by Alex Robboy