Scientists Are Learning How Weed Causes Paranoia:
By injecting small amounts of the marijuana-derived drug into different parts of a rat’s brain and then watching for behavioral cues, they learned that THC works wonders in the prefrontal cortex and ventral hippocampus, but causes anxious behavior when dribbled into the basolateral amygdala.German biochemists had an even better story to tell: Beat Lutz and his colleagues at Johannes Gutenberg-University studied an enzyme that is partially responsible for anxiety. Make a drug that can slow it down and you may be able to prevent paranoia.
They proved their point in two ways: Knockout mice, animals lacking the genetic recipe for that protein, were resistant to nervous behavior. Also, unusually nervous lab mice were calmed by an experimental chemical that inactivates the same molecule.
(Hat tip to Mike.)