Scientific papers tend to be loaded with statistics and jargon, so it's always a delightful surprise to stumble on a nugget of poetry in an otherwise technical report. So it was with a 2005 paper in the journal Development and Psychopathology, drily titled "Biological sensitivity to context." The authors of the research paper, human development specialists Bruce Ellis of the University of Arizona and W. Thomas Boyce of Berkeley, borrowed a bit of Swedish idiom to name a startling new concept in genetics and child development: orkidebarn.
Orkidebarn means "orchid child," and it stands in contrast to maskrosbarn, or "dandelion child." As Ellis and Boyce explained in their 2005 paper, dandelion children seem to have the capacity to survive -- even thrive -- in whatever circumstances they encounter. They are psychologically resilient. Orchid children, by contrast, are highly sensitive to their environment, especially to the quality of parenting they receive. If neglected, orchid children promptly wither -- but if they are nurtured, they not only survive but flourish. In the authors' poetic language, an orchid child becomes "a flower of unusual delicacy and beauty."
Inside the small world of scientists who study genetics and child development, the notion of the orchid child was stunning. The idea of resilient children was hardly new, nor was the related idea that some kids are especially vulnerable to the stresses of their world. What was novel here was the idea that some of the vulnerable, highly reactive children -- the orchid children -- had the capacity for both withering and thriving. It appeared these children were highly sensitive to home and family life, for better or worse. Is it possible, scientists wondered, that there are genes underlying this double-edged childhood sensitivity?
The 2005 paper launched a search for those genes -- and for the risk pathways that might lead to bad outcomes like delinquency, substance abuse and mental illness. Most of the work initially focused on what behavioral geneticists call the "usual suspects" -- and it paid off. Studies soon showed that genes linked to a particular enzyme or brain chemical receptor, if combined with family stress or maltreatment, can lead to a slew of behavioral problems or mood disorders. These links have now been verified again and again, and scientists are searching for additional genes that might play a role in this exquisite childhood sensitivity.
But where to look? Well, if one is looking for genes that might be linked to unhappy lives, why not consider heavy drinking? That was the reasoning of behavioral geneticist Danielle Dick of Virginia Commonwealth University, who, with 13 other scientists from around the world, has been exploring a gene called CHRM2. CHRM2 has already been implicated in alcohol dependence, which is in the same family of disruptive behaviors as childhood conduct disorders and antisocial behavior. What's more, the gene codes for a chemical receptor involved in many brain functions, like learning and memory, so it's plausible that the gene might play a role in behavioral disorders. Dick and her colleagues decided to test the idea.
They took DNA samples from a group of more than 400 boys and girls who have been part of a larger child development study since before kindergarten, and analyzed variations in their CHRM2 gene. These kids did not have behavioral problems at the start; they were a representative sample from communities in three U.S. cities. The kids have been studied every year since kindergarten and were around age 17 at the time of this study. The scientists collected information on the teenagers' misbehavior -- delinquency, aggression, drug abuse -- from both the mothers and the kids themselves. They also asked the kids how much their parents knew about their lives -- their whereabouts, whom they hung out with, what they did with their time, how they spent their money and so forth. They wanted to get a general idea of how closely these kids were monitored by their parents in their daily comings and goings -- as a way of measuring nurturance or indifference or neglect.
As reported online in the journal Psychological Science, the genetic and behavioral data are consistent with the orchid child model of susceptibility. That is, there appears to be an interaction between variations in children's CHRM2 gene and lack of parental vigilance in producing the most undesirable teenage behavior. But the nature of that interaction is what's most important: The genetic variant that combined with lousy parenting to produce the worst aggression and delinquency -- that variant also combined with the most attentive parenting to produce the best teenage outcomes. Put another way, the kids at highest risk in bad homes were at lowest risk in healthy, nurturing homes.
Although the scientists studied parental monitoring -- or parental awareness -- this measure is most likely a proxy for the teenage world more generally. That is, adolescents who scored low on parental involvement are probably more likely to live in unsafe neighborhoods and hang out with friends who are in trouble. Some kids might do okay in such a world, but these stresses may be enough to tank the genetically sensitive orchid children.
If CHRM2 does turn out to be an orchid child gene, this might explain some earlier findings. For example, the gene has also been linked to serious depression in some studies, and to cognitive ability in others. But it does not appear that the gene codes for these outcomes directly, nor do all of these outcomes necessarily show up in all genetically at-risk teenagers. Indeed, it looks like CHRM2 may not be a gene "for" anything -- other than the tendency to follow life's fortunes or misfortunes.