Water-Fleas, Caterpillars and People with ADHD

Water-Fleas, Caterpillars and People with ADHD

Sam Goldstein, Ph.D.
May, 2005
Copyright - 2005

There was a time not more than 100 years ago when children were thought to be born "tabla rasa" or as blank slates. It was believed all that children were and became was determined by their day in and day out experiences. Behavioral psychologists believed strongly that given any child they could, through controlling the child's experiences, lead that child to become a beggar, thief, scholar or even an artist. Then the pendulum swung towards the concept of human beings as "homunculus." All that someone was and would become came with them on their day of birth. It was simply a matter of "unfolding" and opening the master blueprint as children grew. This comprised exactly the opposite belief about development. We have now come to understand that it is even more complex than either of these, nor simply an interaction of the two. In this month's article, Dr. Goldstein reviews recent research dealing with the fascinating interaction of genes and environment. He raises the question as to whether this emerging research has applicability in our understanding and treatment of Attention Deficit Hyperactivity Disorder.

One of the most memorable and influential experiences shaping my understanding of children and parents occurred a number of years ago in a pub in London. I often speak of this experience during my presentations. I was having lunch with a friend when a young couple came in with an eight month old child. They sat at an adjacent table. Within a few moments this young child had caught everyone's attention. When you looked at him he smiled. Waitresses were stopping and patting him on the head. He pleasantly played with some crackers his parents had brought along while they ordered lunch. It was as if he was announcing to the world "Look what wonderful parents I have. Look what a great job they are doing raising me." I engaged this young couple in conversation and they informed me that they were going to have numerous children since parenting was "so easy." About half way through our meal, a young couple came in with a baby about the same age. They sat a number of tables away. Perhaps this child was having a bad day or many days were bad days. The child was whining and clearly unhappy at the prospect of sitting down to lunch. As his father attempted to position a high chair and his mother wrestled with him and a diaper bag he extended his leg and knocked over a large pitcher of beer on an adjacent table. Needless to say this young couple's luncheon experience went downhill from that point forward. These parents equally loved, cared for and worried about their young children. They equally hoped for happiness and life satisfaction for their children as they transitioned over the coming twenty years into adulthood. Given their temperament and style, children appear at a young age much more powerful in shaping the behavior, beliefs and attitudes of their parents than vice versa. At least that is how it appears. Yet, if we take a "helicopter view" as my colleague Dr. Robert Brooks points out and realize that the transition through childhood is a long process, perhaps we have underestimated the impact parents can truly have on their children's emerging development, personality, behavior and ultimate adult outcome.

In a recent science article in the April 25th issue of the Wall Street Journal, reporter Sharon Begley eloquently described the markedly different traits that can be elicited from the same DNA based upon the environment in which they are expressed. She wrote of two genetically equal groups of fleas developing very different predatory defenses based upon where they were raised. One group raised in a fish tank with the chemical scent of fish, the fleas main predator, developed a particular body quality that made it difficult for predators to swallow them. The other fleas with the same DNA - clones in fact - developed no such body armor when raised in a fish tank absent the scent of fish. Thus, a given genotype can unfold in multiple ways leading to very different development, physical structure and behavior. Ms. Begley in her article also writes about oak tree caterpillars. Those that hatch in the spring eat oak blossoms and grow up to look a bit like the flowers they consume. The very same caterpillars hatching in the summer eat leaves and grow up to look like twigs. As Eric Turkheimer at the University of Georgia points out, the effects of genes depends on the environment in which they are expressed. He notes, "Anything that looks genetic because people with that gene always turn out a certain way, might not really be a genetic effect but an artifact of how few environments people with that gene have been exposed to. Once a new environment comes along it can change everything. So what you thought was a fixed gene effect isn't."

This phenomena has been demonstrated in human beings as well. At one time it was thought that lack of a certain enzyme in the brain linked to a single gene contributed to aggression and violence. However, further study has demonstrated that many individuals with low amounts of this enzyme do not grow up to be antisocial or violent unless they have been exposed to violence growing up. A similar profile has been found with depression. Though certain genetic variations, particularly related to the neurotransmitter, Serotonin, have been found in a higher incidence in individuals with depression, longitudinal research has now demonstrated that other individuals with similar vulnerability never develop depression unless exposed to deeply stressful events. The understanding that different environments can produce different endophenotypes (outcomes) from the same genotype (gene) is increasingly accepted. I am not suggesting that biology does not play an important role but rather as child psychiatrist John Werry has pointed out, biology is not destiny. To this I would add, but it does affect probability. I believe these probabilities can be best altered through environmental and psychosocial interventions for children at risk for emotional, developmental and behavioral problems.

In describing the work of Michael Meaney and colleagues of Magill University in Montreal, Ms. Begley brings us closer to the issue of modifying behavioral outcome. She reports that a gene that shapes how fearful, jumpy and neurotic a rat typically behaves can be altered by how regularly it's mother licks and grooms it. Maternal care changes the chemistry of this gene and these rat pups given their mother's attention grow up to be mellow and curious. The genetic trait of neuroticism at first suggested to be innate because scientists found a gene that contributes to it has been demonstrated to be reversible by environmental experience. Based upon her fifty year longitudinal study of resilience in Hawaii, Dr. Emmy Werner has pointed out that except in the most extreme cases, such as autism or retardation, environmental experience trumps biology every time. In her analysis of a number of longitudinal projects examining adult outcome, Dr. Werner notes that an early history of positive adaptation engendered by consistent and supportive care served as a powerful and enduring influence on children's adaptation increasing the likelihood that they would transition adequately into adult life.

Researchers have demonstrated that children with early histories of secure attachment at infancy and generally supportive care in the first two years of life demonstrate a greater capacity to rebound from a period of poor adaptation in the elementary school years compared to those with less supportive histories. Likewise, children who exhibit positive transitions for maladaptation in middle childhood to competence in adolescence were able to draw on a positive foundation of early support and positive adaptation. In her Kauai longitudinal study, Dr. Werner reports that the majority of high risk children, those who had become troubled teenagers, were recovered in the third and fourth decades of life and became responsible partners, parents and citizens in their communities. Individuals who had availed themselves of informal sources of support in the community and whose lives then took a positive turn, differed in significant ways from those who did not make use of such resources. They had also been exposed to more positive interactions with their primary caregivers in the first two years of life. Dr. Werner suggests that their early rearing conditions fostered a sense of trust which served them well much later in life.

When gene-environment interactions are examined, these longitudinal studies suggest that adverse environments, including serious pre and perinatal stress and other significant adversities throughout childhood have the most negative impact on individuals who are themselves genetically vulnerable. In a recent chapter authored for our new textbook, Dr. Werner concluded, "The frequency with which the same predictors of resilience emerge from longitudinal studies conducted with different ethnic groups and in different geographic settings is impressive. In most cases, the factors that mitigated the negative effects of childhood adversity also benefitted children who lived in stable and secure homes but they appear to have particular importance when adversity levels are high" (pg. 103).

Does environmental power to moderate genetic outcome operate only for single gene phenomena? Might the same be true of emotional, behavioral and developmental outcomes that are influenced by multiple genes? The mounting evidence concerning gene-environment interactions for complex phenomena such as behavior is impressive and argues for the affirmative. Genes don't work in isolation. A child may possess all of the genes necessary to learn to speak but if never exposed to a speaking model will never speak. In contrast, a child may struggle with the basic genetic blue print to learn speech effectively yet with early identification and careful, consistent intervention, can and will learn to communicate effectively. Even skeptics of therapeutic interventions for speech, motor skills or other developmental disabilities acknowledge that intervention accelerates the process of development.

Where does this leave us in our understanding and appreciation of the psychosocial effects of parenting, education, home and classroom environments in ultimately shaping the behavior and life outcome of children with ADHD? In a number of my recent articles I have argued based on scientific and ethical grounds for the importance of psychosocial phenomena in ultimately shaping the life outcome of children with ADHD. Though it is certainly premature to suggest that environmental manipulation alone has been demonstrated to dramatically alter the phenotype and life course of carefully diagnosed children with ADHD, it can and does play an important role. Developmental psychologists such as Alan Sroufe and Myrna Shure have and continue to generate well-respected research demonstrating the powerful effect parents have upon the behavior and development of their children. It is not all in the genes. The complexity of the human brain leads us to appreciate, yet not fully understand, the means by which millions of interactions children have with caregivers and educators during their lives ultimately shapes their personality, behavior and development. Those who carry a banner of evidenced based treatment for ADHD only based upon short term, symptom relief focused studies, primarily with medications, are myopic in their views and limited in their understanding of the complexities of raising children. I am not advocating unproven treatments but suggesting we take a broader perspective in raising all children, especially those with vulnerabilities, developmental or otherwise.

This past month, Dr. Robert Brooks and I celebrated the publication of our seventh book together, The Handbook of Resilience in Children (Springer Publishers). We believe the contributions in this edited volume stand as a testament to the complex biological and environmental processes that ultimately shape each and every life. There remains much work to be done to systematically evaluate the myriad of variables within children, their families and the environment contributes to, mediates and moderates adult outcome. Much additional research remains to be completed to understand how to best disseminate and promote this knowledge so it becomes an integral part of raising children and fostering everyone's mental health. As our appreciation of our genome grows, so too does our understanding of the evolutionary relationship between genes and the environments in which they have been expressed over millions of years. As author and anthropologist, Dean Falk has written, this reciprocity has created "a brain dance" of exquisite complexity, allowing our brains and bodies to evolve at a dramatically accelerated pace over the past 200,000 years. If we hope to walk upon this earth for another 200,000 years we have much to learn from water-fleas and caterpillars.