A decade after first appearing in the United States, synthetic marijuana is seen as a growing health danger. Some marijuana smokers turned to it because it is relatively cheap and not detected in routine drug testing. Dozens of people in New Haven, Connecticut, went to the hospital this week after overdosing on a batch of synthetic pot. A look at the issue:WHAT IS IT?While states have moved to legalize traditional marijuana, synthetic marijuana has become a public health threat. Synthetic pot...