In1970,marijuanawasclassifiedasaschedule1drugintheUnitedStates:thestrictestdesignationpossible,meaningitwascompletelyillegalandhadnorecognizedmedicaluses.Today,marijuana'stherapeuticbenefitsarewidelyacknowledged,butagrowingrecognitionforitsmedicalvaluedoesn'tanswerthequestion:isrecreationalmarijuanausebadforyourbrainAneesBahjiinvestigates.
美国于1970年将大麻被列为一级管制药物：这是最严格的分类，意即，大麻完全不合法，没有被认可的医疗用途。现今，大麻的治疗助益已经被广为认可。但大麻的医疗价值越来越被认可，仍然无法回答这个问题：将大麻用在娱乐用途上，对大脑会有不良影响吗？亚内斯·巴吉带大家来探讨这个议题。
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英文文稿
In1970,marijuanawasclassifiedasaschedule1drugintheUnitedStates:
thestrictestdesignationpossible,
meaningitwascompletelyillegalandhadnorecognizedmedicaluses.
Fordecades,thisviewpersisted
andsetbackresearchonthedrug'smechanismsandeffects.
Today,marijuana’stherapeuticbenefitsarewidelyacknowledged,
andsomenationshavelegalizedmedicaluseoraremovinginthatdirection.
Butagrowingrecognitionformarijuana’smedicalvaluedoesn’tanswerthequestion:
isrecreationalmarijuanausebadforyourbrain
Marijuanaactsonthebody’scannabinoidsystem,
whichhasreceptorsalloverthebrainandbody.
Moleculesnativetothebody,calledendocannabinoids,
alsoactonthesereceptors.
Wedon’ttotallyunderstandthecannabinoidsystem,
butithasonefeaturethatprovidesabigcluetoitsfunction.
Mostneurotransmitterstravelfromoneneurontothenext
throughasynapsetopropagateamessage.
Butendocannabinoidstravelintheoppositedirection.
Whenamessagepassesfromtheoneneurontothenext,
thereceivingneuronreleasesendocannabinoids.
Thoseendocannabinoidstravelbackwardtoinfluencethesendingneuron—
essentiallygivingitfeedbackfromthereceivingneuron.
Thisleadsscientiststobelievethattheendocannabinoidsystem
servesprimarilytomodulateotherkindsofsignals—
amplifyingsomeanddiminishingothers.
Feedbackfromendocannabinoidsslowsdownratesofneuralsignaling.
Thatdoesn’tnecessarilymeanitslowsdownbehaviororperception,though.
Forexample,slowingdownasignalthatinhibitssmell
couldactuallymakesmellsmoreintense.
Marijuanacontainstwomainactivecompounds,
tetrahydrocannabinolorTHC,andcannabidiol,orCBD.
THCisthoughttobeprimarilyresponsibleformarijuana’spsychoactiveeffects
onbehavior,cognition,andperception,
whileCBDisresponsibleforthenon-psychoactiveeffects.
Likeendocannabinoids,
THCslowsdownsignalingbybindingtocannabinoidreceptors.
Butitbindstoreceptorsalloverthissprawling,diffusesystematonce,
whereasendocannabinoidsarereleasedinaspecificplace
inresponsetoaspecificstimulus.
Thiswidespreadactivitycoupledwiththefactthatthecannabinoidsystem
indirectlyaffectsmanyothersystems
meansthateachperson’sparticularbrainchemistry,genetics,
andpreviouslifeexperiencelargelydeterminehowtheyexperiencethedrug.
That’struemuchmoresowithmarijuanathanwithotherdrugs
thatproducetheireffectsthroughoneorafewspecificpathways.
Sotheharmfuleffects,ifany,varyconsiderablyfrompersontoperson.
Andwhilewedon’tknowhowexactlyhowmarijuana
producesspecificharmfuleffects,
thereareclearriskfactorsthatcanincreasepeoples’likelihoodofexperiencingthem.
Theclearestriskfactorisage.
Inpeopleyoungerthan25,cannabinoidreceptorsaremoreconcentrated
inthewhitematterthaninpeopleover25.
Thewhitematterisinvolvedincommunication,
learning,memory,andemotions.
Frequentmarijuanausecandisruptthedevelopmentofwhitemattertracts,
andalsoaffectthebrain’sabilitytogrownewconnections.
Thismaydamagelong-termlearningabilityandproblemsolving.
Fornow,it’sunclearhowseverethisdamagecanbeorwhetherit’sreversible.
Andevenamongyoungpeople,theriskishighertheyoungersomeoneis—
muchhigherfora15yearoldthana22yearold,forinstance.
Marijuanacanalsocausehallucinationsorparanoiddelusions.
Knownasmarijuana-inducedpsychosis,
thesesymptomsusuallysubsidewhenapersonstopsusingmarijuana.
Butinrarecases,psychosisdoesn’tsubside,
insteadunmaskingapersistentpsychoticdisorder.
Afamilyhistoryofpsychoticdisorderslikeschizophreniaistheclearest,
thoughnottheonly,riskfactorforthiseffect.
Marijuana-inducedpsychosisisalsomorecommonamongyoungadults,
thoughit’sworthnotingthatpsychoticdisorders
usuallysurfaceinthisagerangeanyway.
What’sunclearinthesecasesiswhetherthepsychoticdisorder
wouldhaveappearedwithoutmarijuanause—
whethermarijuanausetriggersitearly,
isacatalystforatippingpointthatwouldn’thavebeencrossedotherwise,
orwhetherthereactiontomarijuanaismerelyanindication
ofanunderlyingdisorder.
Inalllikelihood,marijuana’srolevariesfrompersontoperson.
Atanyage,aswithmanyotherdrugs,
thebrainandbodybecomelesssensitivetomarijuanaafterrepeateduses,
meaningittakesmoretoachievethesameeffects.
Fortunately,unlikemanyotherdrugs,
there’snoriskoffataloverdosefrommarijuana,
andevenheavyusedoesn’tleadtodebilitating
orlife-threateningwithdrawalsymptomsifusestops.
Therearemoresubtleformsofmarijuanawithdrawal,though,
includingsleepdisturbances,irritability,anddepressedmood,
whichpasswithinafewweeksofstoppinguse.
Soismarijuanabadforyourbrain
Itdependswhoyouare.
Butwhilesomeriskfactorsareeasytoidentify,othersaren’twellunderstood—
whichmeansthere’sstillsomepossibilityofexperiencingnegativeeffects,