My former SciBling David Dobbs regularly posts on the SciAm Blog, usually bringing in guest contributors highlighting novel research in neuroscience. Today, he invited Charles Glatt to review an interesting study on the interaction between genes and environment in development of depression. David writes:
This week reviewer Charles Glatt reviews a study that takes this investigation a level deeper, examining how two different gene variants show their power -- or not -- depending on whether a child is abused, nurtured, or both. As Glatt describes, this study, despite its grim subject, suggests promising things about the power of nurture to magnify nature's gifts or lift its burdens.
In the study, two candidate genes identified as potentially predisposing people to depression were checked in two different environments - a nurturing one and an abusive one. Charles concludes:
As with any behavioral genetic study, one must be careful not to overinterpret these findings, because virtually no study in behavioral genetics is consistently or completely replicated. Nonetheless, some additional points about this paper can help inform us on the nature-nurture debate. First, depression scores and categorical diagnoses of depression were significantly higher in children with a history of maltreatment versus controls even before any genetic analysis was factored in. In a similar vein, the highest average depression score of any genotype category in the unabused control children was lower than the average depression score for any genotype category in the maltreated children; genes alone weren't likely to make the child depressed, but maltreatment alone could.These findings suggest that, at least regarding these specific polymorphisms, nurture beats nature. This conclusion will come as a relief to believers in human free will. It also argues strongly for the identification of children at risk for maltreatment and strong actions to reverse the negative effects of this experience.
Read the whole thing for details.
Life Science
Medicine & Health
Comments
That's interesting, but the question of free will has nothing to do with the innatist vs environmentalist debate. In either extreme - or any model along the continuum - human behavior could be totally dependent on factors other than some hypothetical independent agent incompatible with free will.
In addition to the innatist vs environmentalist debate, the issue of free will is also sometimes confused with the determinism vs chance debate. While pure (Laplacian) determinism is obviously incompatible with free will, a model that includes unpredictable (in principle) chance factors can also preclude free will. The important variable in the free will debate is the postulated existence of a truly autonomous agent, wholly independent of both genetic or environmental determinism as well as any purely chance events.
I suspect that free will is a functionally inevitable illusion of the brain-mind. In addition, social models of free will influence behavioral choices, so whether or not free will actually exists, views about free will are behaviorally relevant.
Posted by: Colugo | October 9, 2007 2:56 PM
Sorry - I made a typo in my haste. My second sentence should read: "and hence incompatible with free will."
Posted by: Colugo | October 9, 2007 2:58 PM
Colugo, I don't think that phrase means what you want it to mean.
Coturnix, I haven't read the whole essay, but I do have to ask. Did they consider situations where the overall environment is abusive, but the upbringing, at worst, can be typified as uninformed? That is, parents who do not know what is going on, and thus prone to exploitation by frauds and huxters. And furthermore, the environment can only be considered abusive by the effect it has upon the subject.
(I have a talent for skewing results. :) )
Posted by: Alan Kellogg | October 9, 2007 8:46 PM
There is actually quite a lot of literature on the effects of upbringing styles on outcomes, but this is the first time anyone introduced genes into the equation, and the upbringing trumped the effects of genes.
Posted by: coturnix | October 9, 2007 8:51 PM
As far as I can tell, the study reviewed by Glatt in this Mind Matters post did NOT break down the abusive environments in any systematic or detailed way; rather, they studied a large group of children (106) who had in common that they had all been removed from their homes because of repeated or severe abuse. Thus the abuse in question doubtless varied in intensity, frequency, and type.
Counterbalancing that, in some, was the presence of reliable nurturing adults.
So there are your two 'nurture' (i.e., experience/environment) variables. Crossed against them were variations in two genes often implicated in depression risk, 5-HTPLLR (which appears to influence serotonin uptake) and another gene influencing the level of brain-derived neurotrophic factor (BDNF), a hormone-like substance that seems to be friendly to neuronal growth and mental health.
The take-home of the various crosses of these variables was that a) carrying a "bad" variant of either gene didn't heighten risk for depression unless the child was abused and b) a high level of nurturing could essentially negate even the triple-whammy of 2 bad gene variants and abusive parents.
Free will or not ... I see the point of the complaint. Yet I believe Glatt's broader point is that to the extent that the idea of free will is incompatible with the idea that genes trump experience, the strong and encouraging role that nurturing plays here argues in favor of free will. That argument is strengthened, if in roundabout fashion, if you recognize that gene-environment effects don't merely flick genes on and off but also create a dynamic in which the changing person (changed, i.e., by genetic response to environment) may change in a way that better enables him or her to behave differently, thus changing the environment. A nurturing presence gives me some resilience, increasing my ability to behave constructively.
It gets a bit slippery -- indeed, it starts to erase the fate v. free-will distinction.
Posted by: David Dobbs | October 9, 2007 10:32 PM