Everything can be toxic....but there is a ton of data that has failed to show any evidence of brain toxicity either in chronic human cannabis users or in animals treated with very high doses of cannabis extract or THC. Doses up to 1,000 x's higher than those needed to produce a "high" in man were given to rats and monkeys every day for up to 90 days without causing serious adverse effects on the brain. I doubt the same could be said for ethanol, JMO.