Well like shoi said, they just described symptoms that can apply to many different mental disorders, and effects from different mind altering substances.

For instances, a symptom of TB is coughing, weed makes you cough too, so if they said "This weed, one puff causes TB", they might as well have said that, because their schizo argument is just as lame.

Unless it's a really potent psychedelic sativa, and only new smokers took a hit, and then had a bad reaction, and searched their symptoms on google, and found schizophrenia listed.