Drug abuse

New research chal­lenges tradi­tional accounts of why we wallow in chemical gratification
March 21, 2008World Science staff
Why do peo­ple abuse drugs? It’s not only a ques­tion wor­ried par­ents ask their way­ward, sub­stance-dab­bling teenagers. It’s al­so a deeper ques­tion asked by bi­ol­o­gists.In gen­er­al, na­ture has de­signed all crea­tures as ex­quis­ite machines for their own pro­tec­tion and propaga­t­ion. Yet we’re easily and of­ten drawn in­to self-destruction by noth­ing more than life­less chem­i­cal lures. This weak­ness seems such a jar­ring ex­cep­tion, such a dis­mal Achilles’ heel, that it seems to de­mand ex­plana­t­ion.
A new study pro­poses that hu­mans and other animals have a long ev­o­lu­tion­ary re­la­tion­ship with brain-in­flu­enc­ing drugs. Shown above is the plant Can­na­bis sativa, which pro­duces the psy­cho­ac­tive in­gre­di­ent in ma­ri­jua­na. (Im­age cour­te­sy Mis­souri Dept. of Trans­por­ta­tion)
Sci­en­tists typ­ic­ally of­fer the fol­low­ing one. Drugs are chem­i­cals that in­ap­pro­pri­ate­ly trig­ger ac­ti­vity in brain cir­cuits de­signed for very dif­fer­ent pur­poses: to pro­vide a sense of re­ward for hav­ing sat­is­fied or­di­nary needs, health­fully. The brain has few de­fenses against this chem­i­cal de­cep­tion, the stand­ard account goes, be­cause drugs were un­known in the nat­u­ral en­vi­ron­ment that shaped hu­man ev­o­lu­tion.