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← In the Realm of Hungry Ghosts Close Encounters with Addiction

In the Realm of Hungry Ghosts Close Encounters with Addiction Chapter 17. Their Brains Never Had a Chance

Author: Gabor Mate Publisher: Berkeley, CA: North Atlantic Books. Publish Date: 2010-1-5 Review Date: Status:📚

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In Scattered Minds, I had laid out some well-established research evidence showing that the mammalian brain develops largely under the influence of the environment, rather than according to strict genetic predetermination—and that this is especially the case with the human brain. These findings were relatively recent but by then wholly uncontroversial, at least in brain-science circles. They were not obscure academic secrets but had been the subjects of cover articles in both Time and Newsweek.

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That a TV producer, or any layperson for that matter, would have trouble accepting the new brain science is understandable, given the mind-body separation prevalent in our culture, and given, too, how long we’ve been taught that genes determine almost everything about a human being: personality traits, behavior, eating patterns, and all manner of disease. Much more perplexing is the fact that this new knowledge is virtually unfamiliar to the medical community. Despite the thousands of research papers published in leading scientific and medical journals, countless monographs and conference documents, and several outstanding academic books on the subject, the role of the environment in brain development isn’t taught in many medical schools.1 It’s not incorporated into our work with children or adults. Not only is brain development ignored in medical training, but so is human psychological development as well. “It is astonishing to realize,” remarks neurologist Antonio Damasio, “that [medical] students learn about psychopathology without ever being taught normal psychology.”2

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Brain development in the uterus and during childhood is the single most important biological factor in determining whether or not a person will be predisposed to substance dependence and to addictive behaviors of any sort, whether drug-related or not. Startling as this view may appear to be at first sight, it is amply supported by recent research. Dr. Vincent Felitti was chief investigator in a landmark study of over seventeen thousand middle-class Americans for Kaiser Permanente and the U.S. Centers for Disease Control. “The basic cause of addiction is predominantly experience-dependent during childhood, and not substance-dependent,” Dr. Felitti has written. “The current concept of addiction is ill-founded.”3

  1. V. J. Felitti, “Ursprünge des Suchtverhaltens: Evidenzen aus einer Studie zu belaststenden Kindheitserfahrungen” (“The Origins of Addiction: Evidence from the Adverse Childhood Experiences Study”), Praxis der Kinderpsychologie und Kinderpsychiatrie 52 (2003): 547–59.

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To state that childhood brain development has the greatest impact on addiction is not to rule out genetic factors. However, the emphasis placed on genetic influences in addiction medicine—and in many other areas of medicine—is an impediment to our understanding. The view that genes play a decisive role in the way a person’s brain develops has been replaced by a radically different notion: the expression of genetic potentials is, for the most part, contingent on the environment. Genes do dictate the basic organization, developmental schedule, and anatomical structure of the human central nervous system, but it’s left to the environment to sculpt and fine-tune the chemistry, connections, circuits, networks, and systems that determine how well we function.

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Of all the mammals, we humans have the least mature brain at birth. Early in their infancy other newborn animals perform tasks far beyond the capabilities of human babies. A horse, for example, can run on its first day of life. Not for a year and a half or more can most humans muster the muscle strength, visual acuity, and neurological control skills—perception, balance, orientation in space, coordination—to perform that activity. In other words, the horse’s brain development at birth is at least a year and a half ahead of our own—probably even more, in horse years. Why are we saddled with such a disadvantage in comparison to a horse? We can think of it as a compromise imposed by Nature. Our evolutionary predecessors were permitted to walk upright, which freed fore-limbs to evolve into arms and hands capable of many delicate and complicated activities. Those advances in manual versatility and dexterity required a tremendous enlargement of the brain, especially of its frontal areas. Our frontal lobes, which coordinate the movement of our hands, are much larger even than those of our closest evolutionary relative, the chimpanzee. These lobes, particularly their prefrontal areas, are also responsible for the problem solving, social, and language skills that have allowed humankind to thrive. As we became a two-legged species, the human pelvis had to narrow to accommodate our upright stance. At the end of the nine months of human gestation the head forms the largest diameter of the body, the one most likely to get stuck in our journey through the birth canal. It’s simple engineering: any further brain growth in the uterus and we couldn’t be born.

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To ensure that babies can make their way out of the birth canal, the bargain forced upon our ancestors was that the human brain would be relatively small and immature at birth. On the other hand, it would undergo tremendous growth outside the mother’s body. In the period following birth, the human brain, unlike that of the chimpanzee, continues to grow at the same rate as in the womb. There are times in the first year of life when, every second, multiple millions of nerve connections, or synapses, are established. Three-quarters of our brain growth takes place outside the womb, most of it in the early years. By three years of age, the brain has reached 90 percent of adult size, whereas the body is only 18 percent of adult size.4 This explosion in growth outside the womb gives us a far higher potential for learning and adaptability than is granted to other mammals. Were we born with our brain development rigidly predetermined by heredity, the frontal lobes would be limited in their capacity to help us learn and adapt to the many different environments and social situations we humans now inhabit.

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Greater reward demands greater risk. Outside the relatively safe environment of the womb, our brains-in-progress are highly vulnerable to potentially adverse circumstances. Addiction is one of the possible negative outcomes—although, as we will see when we discuss genetic influences, the brain can already be negatively affected in the uterus in ways that increase vulnerability to addiction and to many other chronic conditions that threaten health.

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The dynamic process by which 90 percent of the human brain’s circuitry is wired after birth has been called neural Darwinism because it involves the selection of those nerve cells (neurons), synapses, and circuits that help the brain adapt to its particular environment, and the discarding of others. In the early stages of life, the infant’s brain has many more neurons and connections than necessary—billions of neurons in excess of what will eventually be required. This overgrown, chaotic synaptic tangle needs to be trimmed to shape the brain into an organ that can govern action, thought, learning, and relationships and carry out its multiple and varied other tasks—and to coordinate them all in our best interests. Which connections survive depends largely on input from the environment. Connections and circuits used frequently are strengthened, while unused ones are pruned out: indeed, scientists call this aspect of neural Darwinism synaptic pruning. “Both neurons and neural connections compete to survive and grow,” write two researchers. “Experience causes some neurons and synapses (and not others) to survive and grow.”5 Through this weeding out of unutilized cells and synapses, the selection of useful connections, and the formation of new ones, the specialized circuits of the maturing human brain emerge. The process is highly specific to each individual person—so much so that not even the brains of identical twins have the same nerve branching, connections, and circuitry. In large part, an infant’s early years define how well her brain structures will develop and how the neurological networks that control human behavior will mature. “Developmental experiences determine the organizational and functional status of the mature brain,” writes child psychiatrist and researcher Bruce Perry.6 Or in the words of Dr. Robert Post, chief of the Biological Psychiatry Branch of the U.S. National Institute of Mental Health: “At any point in this process you have all these potentials for either good or bad stimulation to get in there and set the microstructure of the brain.”7 And it is precisely here where the problem arises for young children who will, in adolescence and beyond, become chronically hooked on hard drugs: too much of what Dr. Post called bad stimulation. This is true of the hard-core intravenous drug users such as the ones I deal with in the Downtown Eastside. In many other cases it’s not a question of “bad stimulation” but of a lack of sufficient “good stimulation.” Our genetic capacity for brain development can find its full expression only if circumstances are favorable. To illustrate this, just imagine a baby who was cared for in every way but kept in a dark room. After a year of such sensory deprivation the brain of this infant would not be comparable to those of others, no matter what his inherited potential. Despite perfectly good eyes at birth, without the stimulation of light waves, the thirty or so neurological units that together make up our visual sense would not develop. The neural components of vision already present at birth would atrophy and become useless if this child did not see light for about five years. Why? Neural Darwinism. Without the requisite stimulation during the critical period allotted by Nature for the visual system’s development, the child’s brain would never have received the information that being able to see is needed for survival. Irreversible blindness would be the result.

  1. Kurt W. Dawson and Geraldine Fischer, eds., Human Behavior and the Developing Brain (New York: Guildford Press, 1994), 9.

  2. Bruce D. Perry et al., “Childhood Trauma, the Neurobiology of Adaptation, and ‘Use-dependent’ Development of the Brain: How ‘States’ Become ‘Traits,’ ” Infant Mental Health Journal 16(4) (1995): 271–91.

  3. R. Kotulak, Inside the Brain: Revolutionary Discoveries of How the Mind Works (Kansas City: Andrews and McMeel, 1996).

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What is true for vision is also true for the dopamine circuits of incentive motivation and the opioid circuitry of attachment reward, as well as for the regulatory centers in the prefrontal cortex, such as the orbitofrontal cortex (OFC)—in other words, for all the major brain systems implicated in addiction that we surveyed in the previous three chapters. In the case of these circuits, which process emotions and govern behavior, it is the emotional environment that is decisive. By far the dominant aspect of this environment is the role of the nurturing adults in the child’s life, especially in the early years.

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The three environmental conditions absolutely essential to optimal human brain development are nutrition, physical security, and consistent emotional nurturing. In the industrialized world, except in cases of severe neglect or dire poverty, the baseline nutritional and shelter needs of children are usually satisfied. The third prime necessity—emotional nurture—is the one most likely to be disrupted in Western societies. The importance of this point cannot be overstated: emotional nurturance is an absolute requirement for healthy neurobiological brain development. “Human connections create neuronal connections”—in the succinct phrase of child psychiatrist Daniel Siegel, a founding member of the University of California, Los Angeles’s Center for Culture, Brain, and Development.8 As we will soon see, this is particularly so for the brain systems involved in addiction. The child needs to be in an attachment relationship with at least one reliably available, protective, psychologically present, and reasonably nonstressed adult. Attachment, as we’ve already learned, is the drive to pursue and preserve closeness and contact with others; an attachment relationship exists when that state has been achieved. It’s an instinctual drive programmed into the mammalian brain, owing to the absolute helplessness and dependency of infant mammals—particularly infant humans. Without attachment he cannot survive; without safe, secure, and nonstressed attachment, his brain cannot develop optimally. Although that dependency wanes as we mature, attachment relationships remain important throughout our lifetime.

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For the infant and young child, attachment relationships are the major environmental factors that shape the development of the brain during its period of maximal growth.… Attachment establishes an interpersonal relationship that helps the immature brain use the mature functions of the parent’s brain to organize its own processes.9 Infants require more than the physical presence and attention of the parent. Just as the visual circuits need light waves for their development, the emotional centers of the infant brain, in particular the all-important OFC, require healthy emotional input from the parenting adults. Infants read, react to, and are developmentally influenced by the psychological states of the parents. They are affected by body language: tension in the arms that hold them, tone of voice, joyful or despondent facial expressions, and, yes, the size of the pupils. In a very real sense, the parent’s brain programs the infant’s, and this is why stressed parents will often rear children whose stress apparatus also runs in high gear, no matter how much they love their child and no matter that they strive to do their best.

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The electrical activity of the infant’s brain is exquisitely sensitive to that of the nurturing adult. A study at the University of Washington in Seattle compared the brain-wave patterns of two groups of six-month-old infants: one group whose mothers were suffering postpartum depression and one group whose mothers were in normal good spirits. Electroencephalograms (EEGs) showed consistent, marked differences between the two groups: the babies of the depressed mothers had EEG patterns characteristic of depression even during interactions with their mothers that were meant to elicit a joyful response. Significantly, these effects were noted only in the frontal areas of the brain, where the centers for the self-regulation of emotion are located.10 How does this pertain to brain development? Repeatedly firing nerve patterns become wired into the brain and will form part of a person’s habitual responses to the world. In the words of the great Canadian neuroscientist Donald Hebb, “cells that fire together, wire together.” The infants of stressed or depressed parents are likely to encode negative emotional patterns in their brains. The long-term effect of parental mood on the biology of the child’s brain is illustrated by several studies showing that concentrations of the stress hormone cortisol are elevated in the children of clinically depressed mothers. At age three, the highest cortisol levels were found in those children whose mothers had been depressed during the child’s first year of life, rather than later.11 Thus we see that the brain is “experience-dependent.” Good experiences lead to healthy brain development, while the absence of good experiences or the presence of bad ones distorts development in essential brain structures. Dr. Rhawn Joseph, a scientist at the Brain Research Laboratory in San Jose, California, explains it this way: {An} abnormal or impoverished rearing environment can decrease a thousand fold the number of synapses per axon {the long extension from the cell body that conducts electrical impulses toward another neuron}, retard growth and eliminate billions if not trillions of synapses per brain, and result in the preservation of abnormal interconnections which are normally discarded over the course of development.12

  1. Dawson and Fischer, Human Behavior, 367.

  2. M. R. Gunnar and B. Donzella, “Social Regulation of the Cortisol Levels in Early Human Development,” Psychoneuroendocrinology 27(1–2) (January–February 2002): 199–220. Such information ought to increase our respect for, and social and cultural support for, the parenting task. No one becomes depressed on purpose, and in my observation depression in a new mother often reflects a lack of sufficient support in her own environment.

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