In the most recently published study, rhesus monkeys were exposed through face-mask inhalation to the smoke equivalent of four to five joints per day for one year. When sacrificed seven months later, there was no observed alteration of hippocampal architecture, cell size, cell number, or synaptic configuration. The authors conclude:
"while behavioral and neuroendocrinal effects are observed during marijuana smoke exposure in the monkey, residual neuropathological and neurochemical effects of marijuana exposure were not observed seven months after the year-long marijuana smoke regimen." 53
Thus, 20 years after the first report of brain damage in two marijuana-exposed monkeys, the claim of damage to brain cells has been effectively disproven.
No postmortem examinations of the brains of human marijuana users have ever been conducted. However, numerous studies have explored marijuana effect on brain-related cognitive functions. Many employ an experimental design - in which subjects are given marijuana in a laboratory setting, and then compared to controls on a variety of measures involving attention, learning and memory.
In a number of studies, no significant differences were detected. 54 In fact, there is substantial research demonstrating that that marijuana intoxication does not impair the retrieval of information learned previously. 55 However, there is evidence that marijuana, particularly in high doses, may interfere with users' ability to transfer new information into longterm memory. 56
Stop spreading bunk ass information for fuck's sake.