Scant ev­i­dence med­i­cal pot helps many ill­nesses: study


Med­i­cal mar­i­juana has not been proven to work for many ill­nesses that state laws have ap­proved it for, ac­cord­ing to the first com­pre­hen­sive anal­y­sis of re­search on its po­ten­tial ben­e­fits.

The strong­est ev­i­dence is for chronic pain and for mus­cle stiff­ness in mul­ti­ple scle­ro­sis, ac­cord­ing to the re­view, which eval­u­ated 79 stud­ies in­volv­ing more than 6,000 pa­tients. Ev­i­dence was weak for many other con­di­tions, in­clud­ing anx­i­ety, sleep dis­or­ders, and Tourette’s syn­drome and the au­thors rec­om­mend more re­search.

The anal­y­sis is among sev­eral med­i­cal mar­i­juana ar­ti­cles pub­lished Tues­day in the Jour­nal of the Amer­i­can Med­i­cal As­so­cia- tion. They in­clude a small study sug­gest­ing that many brand la­bels for ed­i­ble mar­i­juana prod­ucts list in­ac­cu­rate amounts of ac­tive in­gre­di­ents. More than half of brands tested had much lower amounts than la­beled, mean­ing users might get no ef­fect.

High­lights from the jour­nal:

The Anal­y­sis

The re­searchers pooled re­sults from stud­ies that tested mar­i­juana against place­bos, usual care or no treat­ment. That’s the most rig­or­ous kind of re­search but many stud­ies found no con­clu­sive ev­i­dence of any ben­e­fit. Side ef­fects were com­mon and in­cluded dizzi­ness, dry mouth and sleepi­ness. A less ex­ten­sive re­search re­view in the jour­nal found sim­i­lar re­sults.

It’s pos­si­ble med­i­cal mar­i­juana could have wide­spread ben­e­fits, but strong ev­i­dence from high­qual­ity stud­ies is lack­ing, au­thors of both ar­ti­cles say.

“It’s not a won­der drug but it cer­tainly has some po­ten­tial,” said Dr. Robert Wolff, a co-au­thor and re­searcher with Klei­j­nen Sys­tem­atic Re­views Ltd., a re­search com­pany in York, Eng­land.

Ed­i­ble Prod­ucts

Re­searchers eval­u­ated 47 brands of med­i­cal mar­i­juana prod­ucts, in­clud­ing candy, baked goods and drinks, bought at dis­pen­saries in Los An­ge­les, San Fran­cisco and Seat­tle.

In­de­pen­dent lab­o­ra­tory test­ing for THC, mar­i­juana’s lead­ing ac­tive in­gre­di­ent, found ac­cu­rate amounts listed on la­bels for just 13 of 75 prod­ucts. Al­most 1 in 4 had higher amounts than la­beled, which could cause ill ef­fects. Most had lower- than- listed amounts. There were sim­i­lar find­ings for another ac­tive in­gre­di­ent. Prod­ucts were not iden­ti­fied by name.

Johns Hop­kins Univer­sity re­searcher Ryan Van­drey, the lead au­thor, said he was sur­prised so many la­bels were in­ac­cu­rate. The re­searchers note, how­ever, that the re­sults may not be the same in other lo­ca­tions.

Mar­i­juana Laws

Twenty-three U.S. states and Washington, D.C. have laws per­mit­ting med­i­cal mar­i­juana use. Ap­proved con­di­tions vary but in­clude Alzheimer’s dis­ease, epilepsy, glau­coma, kid­ney dis­ease, lu­pus and Parkin­son’s dis­ease.

An ed­i­to­rial in the jour­nal says ap­proval in many states has been based on poor qual­ity stud­ies, pa­tients’ tes­ti­mo­ni­als or other non­sci­en­tific ev­i­dence.

Mar­i­juana is illegal un­der fed­eral law and some sci­en­tists say re­search has been stymied by gov­ern­ment hur­dles in­clud­ing a dec­la­ra­tion that mar­i­juana is a con­trolled sub­stance with no ac­cepted med­i­cal use.

But in a no­tice pub­lished Tues­day in the Fed­eral Register, the Depart­ment of Health and Hu­man Ser­vices made it a lit­tle eas­ier for pri­vately funded med­i­cal mar­i­juana re­search to get ap­proved. The depart­ment said that a fed­eral Public Health Ser­vice re­view of re­search pro­pos­als is no longer nec­es­sary be­cause it du­pli­cates a re­quired re­view by the Food and

Drug Ad­min­is­tra­tion.

The Fu­ture

Colorado, one of a few states where recre­ational mar­i­juana use is le­gal, has pledged more than US$ 8 mil­lion in state funds for sev­eral stud­ies on the drug’s po­ten­tial med­i­cal ben­e­fits, in­clud­ing whether it can re­duce vet­er­ans’ symp­toms of post- trau­matic stress dis­or­der. That study may be­gin re­cruit­ing par­tic­i­pants later this year, said Van­drey, one of that study’s lead­ers.

Van­drey said there’s a feel­ing of op­ti­mism in the re­search com­mu­nity that “we’ll start to get a good science base” for the po­ten­tial med­i­cal uses of mar­i­juana.

The Rec­om­men­da­tions

The ed­i­to­rial by two Yale Univer­sity psy­chi­a­trists sug­gests en­thu­si­asm for med­i­cal mar­i­juana has out­paced rig­or­ous re­search and says wide­spread use should wait for bet­ter ev­i­dence.

Fed­eral and state gov­ern­ments should sup­port and en­cour­age such re­search, the ed­i­to­rial says.

“Per­haps it is time to place the horse back in front of the cart,” Drs. Deepak Cyril D’Souza and Mo­hini Ran­ganathan wrote in the ed­i­to­rial.

They note that re­peated recre­ational mar­i­juana use can be ad­dic­tive and say unan­swered ques­tions in­clude what are the long- term health ef­fects of med­i­cal mar­i­juana use and whether its use is jus­ti­fied in chil­dren whose de­vel­op­ing brains may be more vul­ner­a­ble to its ef­fects.

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