ant ▁use ▁to ▁lower ▁recall ▁rates ▁in ▁humans ▁after ▁prolong ed ▁usage . ▁The ▁ax ons , ▁d end rit es , ▁and ▁neur ons ▁wear ▁out ▁in ▁many ▁cases . ▁Current ▁research ▁illustr ates ▁a ▁par ado x ical ▁effect . ▁The ▁few ▁exceptions ▁under go ▁mental ▁hy pert ro phy . ▁▁ ▁M eth y len ed io x ym eth am ph et am ine ▁( MD MA ) ▁users ▁are ▁found ▁to ▁exhib it ▁difficulties ▁encoding ▁information ▁into ▁long - term ▁memory , ▁display ▁imp a ired ▁ver bal ▁learning , ▁are ▁more ▁easily ▁dist ract ed , ▁and ▁are ▁less ▁efficient ▁at ▁foc using ▁attention ▁on ▁complex ▁tasks . ▁The ▁degree ▁of ▁executive ▁imp air ment ▁increases ▁with ▁the ▁sever ity ▁of ▁use , ▁and ▁the ▁imp air ments ▁are ▁relatively ▁long - last ing . ▁Chron ic ▁c oca ine ▁users ▁display ▁imp a ired ▁attention , ▁learning , ▁memory , ▁reaction ▁time ▁and ▁cogn itive ▁flex ibility . ▁Whether ▁or ▁not ▁stim ul ants ▁have ▁a ▁positive ▁or ▁negative ▁effect ▁on ▁recall ▁depends ▁on ▁how ▁much ▁is ▁used ▁and ▁for ▁how ▁long . ▁ ▁G ender ▁Cons ist ently , ▁females ▁perform ▁better ▁than ▁males ▁on ▁epis od ic ▁memory ▁tasks ▁including ▁delayed ▁recall ▁and ▁recognition . ▁However , ▁ ▁males ▁and ▁females ▁do ▁not ▁differ ▁on ▁working , ▁immediate ▁and ▁semantic ▁memory ▁tasks . ▁Ne uro - ps ych ological ▁observations ▁suggest ▁that , ▁in ▁general , ▁previous ▁inj uries ▁cause ▁greater ▁def ic its