Berkeleyan

Hinshaw on environment, genes, and risk

| 12 February 2009

Recent findings about the causes of mental illness helped shape Stephen Hinshaw’s thinking about the pressures facing today’s adolescent girls. Berkeleyan Editor Jonathan King talked with him as he was preparing for a round of national-media interviews to publicize The Triple Bind.

Berkeleyan: In your book, you note that the last 50 years have seen a shift in thinking about the etiology of depression — from the notion, popular in the 1950s, that “bad parenting” is the cause, to a more recent “new orthodoxy” that puts the blame on genetics and brain chemistry. And neither perspective, you say, is sufficient unto itself.

Hinshaw: The scientific and clinical fields get themselves into hot water when reductionist thinking takes hold. In this area, reductionism can take the form of, on the one hand, statements such as “All mental disorder is related to trauma or inadequate parenting,” or, on the other hand, “All mental disorder is related to faulty genes or aberrant biology.”

First, genes explain some of the risk for certain people to become depressed, but environments actually matter more. For other conditions, like bipolar disorder or autism, genes explain most of the risk.

But it’s not a matter of genes versus environments. In fact, genes and experience work together in intriguing ways. For example, the genetically mediated tenden-cies that I may have to be shy and withdrawn will lead me to seek environments that perpetuate my isolation, or may actually pull for protective responses from others.

Furthermore, there is no single gene for any form of mental illness. It undoubtedly takes several, or even many, genes, working together, to create the strongest risk. The genes we know about create tendencies to behave in a certain way; but only when those tendencies are molded by experience does disorder emerge.

Berkeleyan: You maintain that a person’s life experiences play a significant role in determining whether she or he will experience depression, because the genes that make a person vulnerable to that disorder must be activated by external forces before they switch on.

Hinshaw: The crucial concept here is one of “gene by environment interaction.” This means that neither genes alone, nor environments and settings alone, predict high rates of mental disorders like depression. But the risk goes way up when a person with a certain form of a particular gene has certain negative life experiences.

You can say it two ways: Genes matter when certain life experiences occur; or life experiences make a difference primarily for the sub-population with high genetic risk factors.

Finally, even for traits or conditions with a strong genetic risk, the overall levels can rise or fall through the environment alone. Height is under strong genetic control, but we’re all taller, on average, than our grandparents. This is explainable by changes in diet, not gene mutations in a couple of generations.

Berkeleyan: Taking all of this into consideration, then, has brought you to the conclusion that for today’s adolescent girls, the risk for depression and self-destructive behavior is even greater than before.

Hinshaw: The unrelenting pressures placed on girls by today’s society — to be both nurturing and competitive, and effortlessly perfect in achieving both of these contradictory aims — makes it more likely that all girls will experience distress, and even depression. This is especially so for those girls with underlying genetic vulnerabilities or other risk factors, like maltreatment.

Berkeleyan: This is an era of medication-as-therapy for many mental disorders. Does psychobiology hold out the prospect of a “magic bullet” that might counteract these pressures on our girls?

Hinshaw: Treating clinical depression with both medication and therapy has been shown to work best for most individuals. But at a deeper, preventive level, we need to change the conditions under which our girls are struggling. That’s something that will require changes in the messages that parents, and society at large, convey to girls about what’s expected of them … especially when those messages now contain such impossible contradictions, and such an early press toward sexualization. Indeed, relieving our girls of the unrelenting pressures they now experience — and linking them with a wider sense of community and belonging — may be the most helpful thing we can do across our entire culture.