Multiple Addictions

Why isn’t one drug enough?

The newer views of addiction as an organic brain disorder have cast strong doubt on the longstanding assumption that different kinds of people become addicted to different kinds of drugs. As far back as 1998, the Archives of General Psychiatry flatly stated: “There is no definitive evidence indicating that individuals who habitually and preferentially use one substance are fundamentally different from those who use another.” This quiet but highly influential breakthrough in the addiction paradigm has paid enormous dividends ever since.

The behaviors known as pan-addiction, substitute addiction, multiple addiction, and cross-addiction demonstrate that some addicts are vulnerable in an overall way to other addictive drugs as well. If it was one addiction at a time, that was known as substitute addiction. If it was many addictions simultaneously, researchers called it pan-addiction. The fact that a striking number of alcoholics also had cigarette addictions, and were heavy coffee drinkers, or had been addicted sequentially or simultaneously to various illegal addictive drugs—this was no great secret in the addiction therapy community. Indeed, it was clear that many addicts preferred the mix of two or more addictive drugs. And the phenomenon has serious social and economic ramifications.

Addicts show a remarkable ability to shift addictions, or to multiply them. Many addicts seem to be able to use whatever was readily at hand—alcoholics turning to cough syrup or doctor-prescribed morphine; pill poppers switching to alcohol; cocaine addicts turning to pot. If addiction was really, at bottom, a metabolic tendency rather than a sociological aberration, then it could conceivably express itself as a propensity to become seriously hooked on any drug that afforded enough pleasurable reinforcement to be considered addictive.

One leading school of thought views the metabolic disorder we call addiction as a manifestation of an “impaired reward cascade response.” This fact matters more than the differing details of addictive drugs themselves. This is where and how addiction happens. It is understood that addiction has its cognitive and environmental aspects as well, but the scientific mystery of how normal people become uncontrollable addicts has been substantially explained. Addictive drugs are a way of triggering the reward cascade. Cocaine, cocktails, and carbo-loading were all short-term methods of either supplying artificial amounts of these neurotransmitters, or sensitizing their receptors, in a way that produced short-term contentment in people whose reward pathway did not operate normally.

Naturally, you have to allow for environmental and social factors, but no matter how you add it up, a certain number of people are going to get into trouble with drugs and alcohol—it doesn’t really matter which drugs or what kind of alcohol. And a percentage of that percentage was going to get into trouble very quickly. These were the people who were hard to treat, and seriously prone to relapse. They would get into trouble because drugs did not have the same effect on them that they had on other people. Like a virus infecting a suitable host, drugs—any addictive drug--went to work on those kinds of addicts in a hurry.

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What’s a Neurotransmitter, Anyway?

A brief guide for the perplexed.

A neurotransmitter is a chemical substance that carries impulses from one nerve cell to another. Neurotransmitters are manufactured by the body and are released from storage sacs in the nerve cells. A tiny junction, called the synaptic gap, lies between brain cells. (Think of Michelangelo’s Sistine Chapel, with the finger of Adam and the finger of God not quite touching, yet conveying energy and information.)

Neurotransmitters squirt across the synaptic gap, and this shower of chemical messengers lands on a field of tiny bumps attached to the surface of the nerve cell on the other side of the synaptic gap. These bumps are receptors, and they have distinctive shapes. Picture these receptors, brain researcher Candace Pert has suggested, as a field of lily pads floating on the outer oily surface of the cell.

Neurotransmitter molecules bind themselves tightly to these receptors. The fact that certain drugs of abuse also lock tightly into existing receptors, and send messages to nerve cells in the brain, is the key to the mystery of addiction.

The fact that certain drugs essentially “fool” receptors into receiving them is one of the most important and far-reaching discoveries in the history of modern science. It is the reason why even minute amounts of certain drugs can have such powerful effects on the human nervous system. The lock-and-key arrangement of neurotransmitters and their receptors is the fundamental architecture of action in the brain. Glandular cells are studded with receptors, and many of the hormones have their own receptors as well. If the drug fits the receptor and elicits a response, it is called an agonist. If it simply blocks the receptor site without stimulating a response, it is an antagonist. Still other neurotransmitters have only a secondary effect, causing the target cell to release other kinds of neurotransmitters and hormones.

Two of the most important neurotransmitters are serotonin and dopamine. The unfolding story of addiction science, at bottom, is the story of what has been learned about the nature and function of such chemicals, and the many and varied ways they effect the pleasure and reward centers in our brains.

In 1948, three researchers—Maurice Rapport, Arda Green, and Irvine Page—were looking for a better blood pressure medication. Instead, they managed to isolate a naturally occurring compound in beef blood called serotonin (pronounced sarah-tóne-in), and known chemically as 5-hydroxytryptamine, or simply 5-HT. The researchers determined that serotonin was involved in vasoconstriction, or narrowing of the blood vessels, and in that respect resembled another important chemical messenger in the brain—epinephrine, better known as adrenaline.

Even though there is at most 10 milligrams of the substance in our bodies, serotonin turned out to be one of nature’s signature chemicals—a chemical of thought, movement and behavior, as well as digestion, ejaculation, and evacuation. The body’s all-purpose neurotransmitter, involved in sleep, mood, appetite, among dozens of other functions. The cortex, the limbic system, the brain stem, the gut, the genitals, the bowels: serotonin is a key chemical messenger in all of it.

Another key neurotransmitter—dopamine—is considered to be one of the brain’s primary “pleasure chemicals,” and is found in areas of the brain linked to experiences of joy and reward.

Dopamine pathways play a role in carrying signals related to attention, movement, problem solving, pleasure, and the anticipation of rewarding experiences. Dopamine is one of the reasons why, after you have a pleasurable experience with food, drink, sex, or certain drugs, you are likely to feel a desire to repeat the experience. Dopamine is implicated in not just the drug high, but in the craving that accompanies withdrawal as well.

Feelings of pleasure, or joy, are natural drug highs. The fact that they are produced by chemical alterations in brain state does not make the fear or the pleasure feel any less real.

Excerpted from The Chemical Carousel: What Science Tells Us About Beating Addiction by Dirk Hanson © 2008


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Neuroaddiction and the Reward Pathway

How addictive drugs fool Mother Nature

"The addicted brain is distinctly different from the nonaddicted brain,” writes Alan Leshner, the former director of the National Institute of Drug Abuse (NIDA). “Changes in brain structure and function is what makes it, fundamentally, a brain disease. A metaphorical switch in the brain seems to be thrown as a result of prolonged drug use.”

Addiction is both a cause and a consequence of these fundamental alterations in brain function. If physical abnormalities in the brain are at the root of the problem, then any treatment program worth its weight ought to be dealing—directly or indirectly--with these differences in brain state. Writing in Lancet, researcher Charles O’Brien has suggested a similar orientation: “Addiction must be approached more like other chronic illnesses--such as diabetes and chronic hypertension--than like an acute illness, such as a bacterial infection or a broken bone."

All of this suggests that we are not likely to win a war on drugs, achieve zero tolerance, or become chemical-free any time soon. The drug problem is an artifact of the basic design of the mammalian brain. Humankind is extraordinarily susceptible to drug abuse anywhere and everywhere certain drugs are widely available—and all because of a “design quirk” in the reward pathways of the central nervous system.

Any sufficiently powerful receptor-active drug is, in its way, fooling Mother Nature. This deceit means, in a sense, that all such drugs are illicit. They are not natural, however organic they may be. Yet, the human drive to use them is all-pervasive. We have no real built-in immunity to drugs that directly target specific receptors in the limbic and cortical pleasure pathways. The act of “liking” something is controlled by the forebrain and brain stem. If you receive a pleasant reward, your reaction is to “like” it.

If, however, you are anticipating a reward, and are, in fact, engaging in behaviors motivated by that anticipation, it can be said that you “want” it. The wholly different act of wanting something strongly is a mesolimbic dopamine-serotonin phenomenon. We like to receive gifts, for example, but we want food, sex, and drugs. As Nesse and Berridge put it, “The ‘liking’ system is activated by receiving the reward, while the ‘wanting’ system anticipates reward and motivates instrumental behaviors. When these two systems are exposed to drugs, the “wanting” system motivates persistent pursuit of drugs that no longer give pleasure, thus offering an explanation for a core paradox in addiction."

Under the biochemical paradigm, a runaway appetite for non-stop stimulation of the reward pathway is a prescription for disaster. The harm is physical, behavioral, and psychological--as are the symptoms. Peer pressure, disciplinary difficulties, contempt for authority--none of these conditions is necessary for drug addiction to blossom. What the drug itself does to people who are biologically vulnerable is enough. No further inducements are required.

Even this brief summation of the ways in which addictive drugs alter neurotransmission should serve to demonstrate that these substances have more in common than we ordinarily assume. All these drugs are of course rewarding, so it is perhaps not too surprising, for all their differences, that they work the limbic reward pathways. All these drugs share common mechanisms of action, which is why they are addictive.

--Excerpted from The Chemical Carousel: What Science Tells Us About Beating Addiction © Dirk Hanson 2008, 2009.


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