imo mephedrone is absolute toxic shit. That said... Claim: Abstract of citation: They apparently tested the mephedrone users while high and then some unknown amount of time later while they were no longer intoxicated. The only conclusion they came to was that it caused an acute impairment in working memory. In summary versus Unless the cited study goes into more detail than the conclusion of the abstract, the claim of lasting rather than acute cognitive impairment is not an accurate summary of the citation provided. At least if you take the word 'lasting' to be different from 'acute', which I certainly do.