Lots of genes could be important -- genes that determine how you absorb a drug, variations in one gene involved in breaking down the drugs, variations in the way that you excrete a drug.

Genes tend to have a very broad effect and it is often more than one gene that determines the interests a child will learn toward. Environment tends to act as the specialist. Reading to children can increase their interest in books but because of the genetic factor, they may never take to the love of books that a parent may have no matter how hard a parent tries to teach it.

Up until now we have chronically underestimated the very substantial differences in the way individuals respond to the same dose of the same drug.

One of the surprises in this study, where we put some of the people through the same protocol five times, is that there is substantial variation with a person on how they respond day to day. That can be due to a lot of potential sources, including environmental factors, that we don't understand.

I think aspirin would do exactly what you might expect -- attenuate, but not abolish the risk.

Although these results are in mice, not people, they raise an exciting possibility which can be tested in humans.