(Live Science, March 15) The chemical tetrahydrocannabinol (THC) in marijuana is known to trigger responses in brain regions related to thinking, perception, coordination and memory, and to have a lasting impact on users when taken frequently over time. 
 
But much less is known about how a growing brain responds to its first introduction to marijuana. An upcoming, long-term study, however, could shed light on the ways that marijuana and other substances and experiences affect a teenager's developing brain. Read more.