In an article in the journal Biological Psychiatry, researchers Eun-Kyung Hwang and Carl R. Lupica reported that in rats, long-term use of THC (tetrahydrocannabinol) weakens input from the cortex to the reward area of the brain, the nucleus accumbens (NAc). Long-term THC use also strengthens connections to the NAc from emotional control (limbic) regions, such as the basolateral amygdala and ventral hippocampus. Hwang and Lupica reason that this shift from cortical control of the NAc to limbic control likely contributes to the cognitive and psychiatric symptoms associated with cannabis use.

Editor’s Note: Street marijuana largely contains THC rather than CBD, the beneficial, anxiety-reducing component of cannabis. Cannabis products are being decriminalized, but it is important to remember that those with THC are linked to cannabis use disorder and increased susceptibility to psychiatric illness. Patients with bipolar disorder who use marijuana also have a more adverse course of illness than those who do not use it.

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