Exposing rats to THC increases the likelihood that the animals will later self-administer nicotine. THC-exposed rats are also willing to work harder to obtain nicotine. When extrapolated to people, the findings suggest that THC’s pharmacological impact on the brain may make a person who uses marijuana more vulnerable to developing nicotine addiction, an underappreciated health consequence of marijuana use.
Methamphetamine alters brain structures involved in decision-making and impairs the ability to suppress habitual behaviors that have become useless or counterproductive. The two effects were correlated, indicating that the structural change underlies the decline in mental flexibility.
November 2011 In a new series of studies tracing the molecular events that occur in the brain as memories are formed and preserved, researchers find that certain epigenetic changes may promote vulnerability to relapse.