Having tried both pot and spice, I can testify that spice is much, much worse. It felt like a seizure! Extreme panic, paranoia and a feeling that my body had been poisoned. That crap is marketed with a "not meant for human consumption" sticker so the manufacturers are clear. Very little is known about the production of the synthetic cannabanoids and 2 close friends of mine have vomited while using it. Slowly, in my state, it is being banned by county. As well it SHOULD! Pot and synthetic versions of cannabanoids are extremely powerful psychoactive compounds that have been shown to mimic schizophrenic brain activity and should NOT BE USED by people who are already prone to that disorder or who suffer from general anxiety and paranoia. I hate the way I feel everytime I use pot or spice and vowed last summer never to do either again. You son is taking a huge risk to his mental health and spice is TOTALLY unresearched, especially as far as any long-term effects go.
I'm sorry to hear this... does he respond well to common sense or logical reasoning? Perhaps show him (in a "non-worried mother" sort of way) the harmful effects things like this have on his body, his mindset and his overall behavior. Weed is much more "healthy" than alcohol, tobacco and synthetic crap and he will probably throw that common argument in your face. However, the smoke inhaled, even through bongs, is much more sticky and tar -filled than cigs. My biggest question is, if he is exhibiting schizo/paranoia traits anyway, WHY ON EARTH does he enjoy taking substances that make it worse??? Has he ever had a total panic meltdown on it? Maybe that's what it will take--that's what got me to swear to never play with that stuff--or anything else--ever again!
good luck!