Its all about the THC man.
There has never been a documented human fatality from marijuana.[9] Information about THC's toxicity is derived from animal studies. The toxicity depends on the route of administration and the laboratory animal. Absorption is limited by serum lipids, which can become saturated with THC, mitigating toxicity.[10] According to the Merck Index, 12th edition, THC has a LD50 (dose killing half of the research subjects) value of 1270 mg/kg (male rats) and 730 mg/kg (female rats) administered orally dissolved in sesame oil.[11] The LD50 value for rats by inhalation of THC is 42 mg/kg of body weight.[11] One estimate of Cannabis's LD50 for humans indicates that about 1500 pounds of marijuana would have to be smoked within 15 minutes.[12] This estimate is supported by studies which indicate that the effective dose of THC is at least 1000 times lower than the estimated lethal dose (a "safety ratio" of 1000:1). This is much higher than alcohol (safety ratio of 10), cocaine (15), or heroin (6).[13]
skunk, hash, chronic as long as you aren't smoking 1500 pounds of pot in 15 minutes then you're fine.
No real (or proven) long lasting psychological effects.
What I was saying before, those kids you mentioned were probably either on something that actually was dangerous and did fuck them up, or they already had psychological problems to begin with. It wasn't the weed and it shouldn't be weed that you're worried about.
synthetic or not its still THC and unless they're putting some dangerous ass chemical in it when growing or afterward then it doesn't matter its just more concentrated THC and less money spent to get high!
http://en.wikipedia.org/wiki/THC It does say something about increased psychosis in already psychotic patients, but that has been refuted and studies aren't certain on it. Also increased Cognitive function on schizophrenic patients but I don't' see how that could be bad...