Depression: Nature or Nurture?

My pathophysiology professor at college participated in gene-oncogene cancer research. She looked at the inflammation cascade and genetic markers for cancer. The tentative findings of her research at that point was this: A person can have the genes for cancer, but something environmentally had to switch it on. That is good news, because many people live with cancer genes and lifestyle choices will play a big part in whether they ever suffer the disease.

The debate over nature verses nurture has raged on for decades. Plenty of people have reasons to want point to bad genes as the cause of mental and physical problems, aka it's-not-my-fault-I-was-born-this-way. Other people insist that environment trumps everything. If-society-were-more-supportive-he-would-never-have-been-a-rapist, goes the thinking in some corners. In both cases, the desire for either outcome is political not scientific. Everyone wants to know why bad, weird, and wrong people happen.

New research finds that both nature and nurture contribute to depression, at least, but that the environment trumps genetics. The findings are quite similar to the cancer research:

The researchers studied 109 children who had been removed from their parents' care due to reports of abuse or neglect and 87 control children with no reports of abuse or maltreatment. They scored all the children for depressive symptoms such as irritability, crying and reluctance to see friends. High scores on this scale indicate greater depression. They then compared the distribution of these scores in children with different combinations of the 5-HTTLPR and BDNF polymorphisms described above.

They found that children with the "bad" form of 5-HTTLPR had higher depressive symptom scores -- but only if they had a history of maltreatment. Bad 5-HTTLPR made it more likely (but not certain) that an abused child would develop depression. But it created no effect on depression scores in children without a history of maltreatment. It was like a seed that had to be watered by abuse. This replicates similar findings in studies by Caspi and Moffit and other groups.

Finally, Kaufman and colleagues looked at the effects of social support. They asked the children about people in their lives whom they could talk to about personal things, count on to buy them things they needed and other, similar signs of supportive relationships, and from the answers derived a social support score. Children were then characterized as having high or low support. The researchers found that high levels of such nurturing counteracted the effects of the genetic risk factors almost completely.

This research comes down squarely on the side of nurture. That is, genes won't express themselves if the environment doesn't force the expression. Usually, stressors cause bad gene expression. Emotional stressors are the worst of all. That's why a guy who smokes and drinks but has a loving, supportive marriage will end up not having a heart-attack while the marathon runner with a miserable married life may be more at risk.

My next question for the researchers would be this: How do children without the depression genes end up mentally in these situations? That is, do children with no genetic predisposition to depression have higher rates of depression when they're in a non-supportive, abusive environment? My guess would be yes. Conversely, what are the rates of depression among children with supportive environments?

I have a theory: There are a small percentage of children, for whom a parent with a supportive nature and the patience of Mother Theresa, would still not be enough to bring them into adulthood depression-free and happy. There are a small percentage of children who manage to find happiness even with the depression genes and abusive parents. In between, there are a lot of children who are responsive to their environment. A genetically predisposed kid, with depressive issues, but happy, well-adjusted parents who exhibit excellent coping skills and conflict resolution management will end up fine. A genetically neutral kid with abusive parents will take on what he's learned and be more depressive.

There has been a fair amount of political opinions masquerading as scientific research that have made it seem that parenting is almost irrelevant to how a kid turns out. On the face of it, the notion is preposterous. But many people deeply desire absolution for how their kids end up or want their current choices minimized. They hope it doesn't matter what's going on in the kid's environment. They hope that the home dynamics don't matter. What a relief that would be!

Except in rare cases, how a kid is nurtured matters. My guess is that it will trump genes nearly every time.