03/22/2012 11:57 am ET Updated May 22, 2012

Genetics as Rohrshachs: Pondering Genes and Fate

"I always knew I shouldn't have stayed in that job and that apartment," a social worker with breast cancer and a mutation for the disease recently told me.

"Why is that?" I asked.

"Because that's why I got the cancer."

"But you have the mutation," I reminded her.

"Yes, but it was the stress of that job and the mildew in that apartment that triggered the illness."

At first, her answer surprised me -- it did not seem very scientific. But as I thought about it more, it made far more sense.

Genes are hard to understand. And she may not be wrong.

Many scientists predict that genetics will revolutionize medicine. The price of decoding a person's DNA has plummeted from $1 billion, and is expected to soon be less than $1,000. Soon, all of our complete genomes -- the chains of 3 billion molecules that make up each of us -- will be sequenced. But to understand this information will be difficult.

Most physicians feel uncomfortable with genetic tests, and many have never ordered one. Doctors trained more than 10 years ago often have little knowledge about these new assays, and either over- or under-order these tests.

Hence, patients are often left on their own to fathom complex genetics that scientists do not fully grasp.

To understand these challenges, I recently interviewed a group of men and women confronting a variety of diseases for which genetic tests exist. While researchers and physicians see genetic tests as bare objective facts -- black and white -- patients turn out to view DNA results as a kind of Rorschach test, interpreting and responding to the information in a wide range of ways, based on their prior beliefs about themselves and the world and their beliefs about metaphysics and fate. They struggle to incorporate these results into their understandings and stories about themselves.

For many relatively rare diseases, fairly predictive tests exist. But for most common ailments -- from diabetes to depression -- numerous genes no doubt interact in complex ways with environmental and behavioral factors. For many common conditions, ongoing stress and genetic predispositions can play key roles.

These combinations may not surprise many people, but the amount of genetic testing is skyrocketing, and most of us will soon have to struggle with fathoming how much to blame on genes vs. other factors.

Already, patients may have a sample of their blood taken and saved in a biobank, where their genes will eventually be mapped and kept. Patients are also increasingly getting tested through direct-to-consumer companies such as 23andMe and through their doctors, who every month receive advertisements for new tests. Soon, no doubt, all of our genes will be sequenced.

At first, scientists thought that most diseases (and many behaviors) would each result from a single gene. But many tests offer only small amounts of useful information. Nonetheless, scientists still search for the "fat gene," "gay gene," "alcoholism gene," "schizophrenia gene" and countless others. But predicting most disorders turns out to be more like forecasting the weather. We face vague probabilities. There may be a 35 percent chance of rain -- or of illness.

Increasingly, the results are murky. Only 5 to 10 percent of all breast cancer is genetic. A mutation gives a person about a 60 percent chance of getting the disease. Hence, people both with and without mutations can get sick. Still, women with many affected relatives and a mutation often choose to undergo prophylactic surgery as a result -- removing breasts and ovaries -- though these decisions can be excruciating.

But these tests also raise profound existential issues. "I know I have Huntington's disease because of the mutation," one man recently told me. "But why do I have the mutation, while my sister does not?" Randomness is hard to accept. Even Einstein argued that "God does not roll dice."

"I thought the test would give me answers," the social worker above, facing breast cancer, told me. "But it's just left me with a lot of questions."

For most of us, genes will confront us with many quandaries, which we should begin to ponder.

Clearly, our DNA plays crucial roles in making us who we are physically, but to what degree "are" we our genes? The answers are complex, and in many ways up to each of us.

In making sense of our DNA, and of who we are, our stories about our genes -- how we each understand them -- will be as important as our genes themselves.

For more by Robert Klitzman, M.D., click here.

For more on genetic testing, click here.