Heres what the results of that study actually mean.
For every 100 people in the general population, about 1 has schizophrenia.
For every 100 people who've smoked pot (as defined by the survey), 2 are schizophrenic.
Saying 1% of the general population comes down with schizophrenia is not the same thing as saying the average person has a 1% chance of getting the disease. The risk factor isn't evenly distrubuted through the population, and some people have a much higher risk than others. Many people who develop the disease show warning signs in early childhood, long before they ever get the chance to do any sort of drug.
Also, its well known from self reports of people going through treatment for schizophrenia that many of them use drugs and alcohol to help them cope with their symptoms.
So no, smoking a J every now and then won't make you go crazy. They're also very little evidence that it increases your risk of lung cancer.
And if your worried about that, get a vaporizor, or make some brownies.
And FYI, I hate the effects of weed, but its about the most benign recreational drug you can do.