• Marijuana usage disrupts short-term memory, working memory, and attentional skills. (1)
• Marijuana induces problems mathematical skills, verbal expression, and memory retrieval. (2)
• Cannabis may long produce long lasting problems in short-term memory (3) and residual neuropsychological effects (4) persist even after abstinence.
• THC changes the way in which sensory information gets into and is processed by the hippocampus. The hippocampus is a component of the brain's limbic system that is crucial for learning, memory, and the integration of sensory experiences with emotions and motivations". (5)
  

Chronic marijuana usage can cause free radical damage, neurotransmitter disturbances and impairments to nerves in the hippocampus region of the brain.

• A 1998 study by Chan showed that THC (main psychoactive component in marijuana) causes the shrinkage of cell bodies and nuclei of hippocambal neurons as well as genomic DNA strands to break. (6)
• Brain imaging measurements of cerebral blood flow found localized changes temporal lobe brain activity from chronic marijuana use. (7)
• Psyhometric tests of memory functions between marijuana intoxicated subjects and hippocambal damaged subjects showed similar deficits in memory. (8)
• THC may damage neurons by inceasing cyclooxygenase (COX) tthat catalyzes the formation of reactive oxygen species (ROS). This can cause cell death by stimulating the oxidation of lipids, proteins, and nucleic acids. (6)
• THC reduces the release of the neurotransmitter acetylcholine from the hippocampus. (9)
• THC alters arachidonic acid metabolism and increases the production of lipoxygenase products that are prooxidants. (6)
• THC is a potent source of cellular oxidative stress that could contribute to cell injury, metabolic impairments and lung dysfunction. THC generates harmful free radical molecules and lowers GSH oxidative defenses. (10)

Taking antioxidant supplements may protect hippocampus neurons and brain cells against oxidative stress damage and the harmful effects of marijuana smoke.

• Vitamin E administration prevents THC from causing hippocampus neuron damage. (6)
• Glutathione provides the cell with multiple defenses not only against ROS but also against their toxic products. (11)
• Carnosine is a endogenous antioxidant neuroprotector against molecular and cellular damage from free radical molecules .(12)
• Astaxanthin is significantly stronger than vitamin E at protecting cell membranes against free radical damage. (13)
• Lipoic acid protects the brain and neural tissue against damage from oxidative stress. (14)
• R-Lipoic Acid prevents the depletion of glutathione and the formation of free radical molecules that cause neuron death. (15)
• Quercetin prevent the consumption of lipophilic alpha-tocopherol (Vitamin E) and the peroxidation of neuronal membranes. (16, 17)
• Schizandra Extract increases glutathione, a major component of the endogenous antioxidant protective shield against THC-induced oxidative stress. (18,19,20)
• Selenium is an essential neuroprotective antioxidant mineral and works synergistically with vitamin E at preventing lipid peroxidation damage in brain tissues. (21,22)

References

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2. Block RI, Ghoneim MM (1993) Effects of chronic marijuana use on human cognition. Psychopharmacology 110:219 -228.
   
3. Schwartz RH, Gruenewald PJ, Klitzner M, Fedio P (1989) Short-term memory impairment in cannabis-dependent adolescents. Am J Dis Child 143:1214 -1219.
4. Pope HG, Yurgelun-Todd D (1996) The residual cognitive effects of heavy marijuana use in college students. J Am Med Assoc 275:521-527.
5. Zickler P (1999) Evidence Accumulates That Long-Term marijuana Users Experience Withdrawal. NIDA Notes, Marijuana Research
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19. Recent Advances in Chinese Herbal Drugs-Actions and Uses Beijing:Sci Press 1991 pp 100-101
20. Nutrition Science News: The Journal of Natural Products Research and Innovation Jan 2001 Vol 6 No 1 pp 16-18
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22. Chen J, Berry MJ. (2003) Selenium and selenoproteins in the brain and brain diseases. Neurochem. 2003 Jun; 86(1):1-12.