This is the third time there has been a major negative study for a genetic basis of Schizophrenia. The first occurred when almost 100% of the population with Schizophrenia were committed to State Mental Hospitals. There was relatively no reproduction among Schizophrenic people...yet the disease persisted at the same rate, if not higher in the US

When the study with the twins came out they seem to have forgot the prior study. They thought once the human genome has been de-coded we could find the Schizophrenia gene! Well, that didn't work either.

So instead of looking for a specific gene, they though they would look for a mutated gene that would lead to Schizophrenia. If you wanted to describe the first method it's like looking for the Toyota in a row of Fords. The second method is like looking for the red Ford in a row of blue fords.

This is the nature of science though. I really don't want them to stop looking for a genetic cause but this does put a damper on things.

There are many other theories of Schizophrenia. I'm not sure where I stand on most of them.