1 National Institute on Drug Abuse (NIDA) Marijuana Last Updated June 2018 https://www.drugabuse.gov
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NationalInstituteonDrugAbuse(NIDA)
Marijuana
LastUpdatedJune2018
https://www.drugabuse.gov
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TableofContents
Marijuana
LetterFromtheDirector
Whatismarijuana?
WhatisthescopeofmarijuanauseintheUnitedStates?
Whataremarijuanaeffects?
Howdoesmarijuanaproduceitseffects?
Doesmarijuanauseaffectdriving?
Ismarijuanaaddictive?
Whataremarijuana'slong-termeffectsonthebrain?
Ismarijuanaagatewaydrug?
Howdoesmarijuanauseaffectschool,work,andsociallife?
Istherealinkbetweenmarijuanauseandpsychiatricdisorders?
Whataremarijuana'seffectsonlunghealth?
Whataremarijuana’seffectsonotheraspectsofphysicalhealth?
Ismarijuanasafeandeffectiveasmedicine?
Whataretheeffectsofsecondhandexposuretomarijuanasmoke?
Canmarijuanauseduringandafterpregnancyharmthebaby?
AvailableTreatmentsforMarijuanaUseDisorders
WherecanIgetfurtherinformationaboutmarijuana?
References
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LetterFromtheDirector
Changesinmarijuanapoliciesacrossstateslegalizingmarijuanaformedical
and/orrecreationalusesuggestthatmarijuanaisgaininggreateracceptancein
oursociety.Thus,itisparticularlyimportantforpeopletounderstandwhatis
knownaboutboththeadversehealtheffectsandthepotentialtherapeutic
benefitslinkedtomarijuana.
Becausemarijuanaimpairsshort-termmemoryandjudgmentanddistorts
perception,itcanimpairperformanceinschooloratworkandmakeit
dangeroustodrive.Italsoaffectsbrainsystemsthatarestillmaturingthrough
youngadulthood,soregularusebyteensmayhavenegativeandlong-lasting
effectsontheircognitivedevelopment,puttingthematacompetitive
disadvantageandpossiblyinterferingwiththeirwell-beinginotherways.Also,
contrarytopopularbelief,marijuanacanbeaddictive,anditsuseduring
adolescencemaymakeotherformsofproblemuseoraddictionmorelikely.
PhotobytheNIDA
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Whethersmokingorotherwiseconsumingmarijuanahastherapeuticbenefits
thatoutweighitshealthrisksisstillanopenquestionthatsciencehasnot
resolved.Althoughmanystatesnowpermitdispensingmarijuanaformedicinal
purposesandthereismountinganecdotalevidencefortheefficacyof
marijuana-derivedcompounds,theU.S.FoodandDrugAdministrationhasnot
approved"medicalmarijuana."However,safemedicinesbasedoncannabinoid
chemicalsderivedfromthemarijuanaplanthavebeenavailablefordecades
andmorearebeingdeveloped.
ThisResearchReportisintendedasausefulsummaryofwhatthemostup-to-
datesciencehastosayaboutmarijuanaanditseffectsonthosewhouseitat
anyage.
NoraD.Volkow,M.D.
Director
NationalInstituteonDrugAbuse
SeeAlso:
MessagefromtheNIDADirector-Marijuana’sLastingEffectsontheBrain,
(March2013)
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Whatismarijuana?
Marijuana—alsocalledweed,herb,pot,grass,bud,ganja,MaryJane,anda
vastnumberofotherslangterms—isagreenish-graymixtureofthe
driedflowersofCannabissativa.Somepeoplesmokemarijuanainhand-rolled
cigarettescalledjoints;inpipes,waterpipes(sometimescalledbongs),or
inblunts(marijuanarolledincigarwraps). Marijuanacanalsobeusedtobrew
teaand,particularlywhenitissoldorconsumedformedicinalpurposes,is
frequentlymixedintofoods(edibles)suchasbrownies,cookies,orcandies.
Vaporizersarealsoincreasinglyusedtoconsumemarijuana.Strongerformsof
marijuanaincludesinsemilla(fromspeciallytendedfemaleplants)and
concentratedresinscontaininghighdosesofmarijuana’sactiveingredients,
includinghoneylikehashoil,waxybudder,andhardamberlikeshatter.These
resinsareincreasinglypopularamongthosewhousethembothrecreationally
andmedically.
Themainpsychoactive(mind-altering)chemicalinmarijuana,responsiblefor
Imageby©iStock.com/nicoolay
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mostoftheintoxicatingeffectsthatpeopleseek,isdelta-9-tetrahydrocannabinol
(THC).Thechemicalisfoundinresinproducedbytheleavesandbuds
primarilyofthefemalecannabisplant.Theplantalsocontainsmorethan500
otherchemicals,includingmorethan100compoundsthatarechemically
relatedtoTHC,calledcannabinoids.2
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Whatisthescopeofmarijuanausein
theUnitedStates?
Marijuanaisthemostcommonlyusedillicitdrug(22.2millionpeoplehaveused
itinthepastmonth)accordingtothe2015NationalSurveyonDrugUseand
Health. Itsuseismoreprevalentamongmenthanwomen—agendergapthat
widenedintheyears2007to2014.
Marijuanauseiswidespreadamongadolescentsandyoungadults.According
totheMonitoringtheFuturesurvey—anannualsurveyofdruguseandattitudes
amongtheNation’smiddleandhighschoolstudents—mostmeasuresof
marijuanauseby8th,10th,and12thgraderspeakedinthemid-to-late1990s
andthenbeganaperiodofgradualdeclinethroughthemid-2000sbefore
levellingoff.Mostmeasuresshowedsomedeclineagaininthepast5years.
Teens’perceptionsoftherisksofmarijuanausehavesteadilydeclinedoverthe
pastdecade,possiblyrelatedtoincreasingpublicdebateaboutlegalizingor
looseningrestrictionsonmarijuanaformedicinalandrecreationaluse.In2016,
9.4percentof8thgradersreportedmarijuanauseinthepastyearand5.4
percentinthepastmonth(currentuse).Among10thgraders,23.9percenthad
usedmarijuanainthepastyearand14.0percentinthepastmonth.Ratesof
useamong12thgraderswerehigherstill:35.6percenthadusedmarijuana
duringtheyearpriortothesurveyand22.5percentusedinthepastmonth;6.0
percentsaidtheyusedmarijuanadailyornear-daily.
Medicalemergenciespossiblyrelatedtomarijuanausehavealsoincreased.
TheDrugAbuseWarningNetwork(DAWN),asystemformonitoringthehealth
impactofdrugs,estimatedthatin2011,therewerenearly456,000drug-related
emergencydepartmentvisitsintheUnitedStatesinwhichmarijuanausewas
mentionedinthemedicalrecord(a21percentincreaseover2009).Abouttwo-
thirdsofpatientsweremaleand13percentwerebetweentheagesof12and
17. Itisunknownwhetherthisincreaseisduetoincreaseduse,
increasedpotencyofmarijuana(amountofTHCitcontains),orotherfactors.It
shouldbenoted,however,thatmentionsofmarijuanainmedicalrecordsdonot
necessarilyindicatethattheseemergenciesweredirectlyrelatedtomarijuana
intoxication.
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Whataremarijuanaeffects?
Whenmarijuanaissmoked,THCandotherchemicalsintheplantpassfromthe
lungsintothebloodstream,whichrapidlycarriesthemthroughoutthebodyto
thebrain.Thepersonbeginstoexperienceeffectsalmostimmediately(see
"Howdoesmarijuanaproduceitseffects?").Manypeopleexperiencea
pleasanteuphoriaandsenseofrelaxation.Othercommoneffects,whichmay
varydramaticallyamongdifferentpeople,includeheightenedsensory
perception(e.g.,brightercolors),laughter,alteredperceptionoftime,and
increasedappetite.
Ifmarijuanaisconsumedinfoodsorbeverages,theseeffectsaresomewhat
delayed—usuallyappearingafter30minutesto1hour—becausethedrugmust
firstpassthroughthedigestivesystem.Eatingordrinkingmarijuanadelivers
significantlylessTHCintothebloodstreamthansmokinganequivalentamount
oftheplant.Becauseofthedelayedeffects,peoplemayinadvertentlyconsume
moreTHCthantheyintendto.
Pleasantexperienceswithmarijuanaarebynomeansuniversal.Insteadof
relaxationandeuphoria,somepeopleexperienceanxiety,fear,distrust,or
panic.Theseeffectsaremorecommonwhenapersontakestoomuch,the
marijuanahasanunexpectedlyhighpotency,orthepersonisinexperienced.
Peoplewhohavetakenlargedosesofmarijuanamayexperienceanacute
psychosis,whichincludeshallucinations,delusions,andalossofthesenseof
personalidentity.Theseunpleasantbuttemporaryreactionsaredistinctfrom
longer-lastingpsychoticdisorders,suchasschizophrenia,thatmaybe
associatedwiththeuseofmarijuanainvulnerableindividuals.(See"Istherea
linkbetweenmarijuanauseandpsychiatricdisorders?")
AlthoughdetectableamountsofTHCmayremaininthebodyfordaysoreven
weeksafteruse,thenoticeableeffectsofsmokedmarijuanagenerallylastfrom
1to3hours,andthoseofmarijuanaconsumedinfoodordrinkmaylastfor
manyhours.
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Howdoesmarijuanaproduceits
effects?
THC’schemicalstructureissimilartothebrainchemicalanandamide.Similarity
instructureallowsthebodytorecognizeTHCandtoalternormalbrain
communication.
Endogenouscannabinoidssuchasanandamide(seefigure)functionas
neurotransmittersbecausetheysendchemicalmessagesbetweennervecells
(neurons)throughoutthenervoussystem.Theyaffectbrainareasthatinfluence
pleasure,memory,thinking,concentration,movement,coordination,and
sensoryandtimeperception.Becauseofthissimilarity,THCisabletoattachto
moleculescalledcannabinoidreceptorsonneuronsinthesebrainareasand
activatethem,disruptingvariousmentalandphysicalfunctionsandcausingthe
effectsdescribedearlier.Theneuralcommunicationnetworkthatusesthese
cannabinoidneurotransmitters,knownastheendocannabinoidsystem,playsa
ImagebytheNIDA
THC’schemicalstructureissimilartothebrainchemicalanandamide.Similarityin
structureallowsdrugstoberecognizedbythebodyandtoalternormalbrain
communication.
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criticalroleinthenervoussystem’snormalfunctioning,sointerferingwithitcan
haveprofoundeffects.
Forexample,THCisabletoalterthefunctioningofthehippocampus(see
"Marijuana,Memory,andtheHippocampus")andorbitofrontalcortex,brain
areasthatenableapersontoformnewmemoriesandshifthisorherattentional
focus.Asaresult,usingmarijuanacausesimpairedthinkingandinterfereswith
aperson’sabilitytolearnandperformcomplicatedtasks.THCalsodisrupts
functioningofthecerebellumandbasalganglia,brainareasthatregulate
balance,posture,coordination,andreactiontime.Thisisthereasonpeople
whohaveusedmarijuanamaynotbeabletodrivesafely(see"Doesmarijuana
useaffectdriving?")andmayhaveproblemsplayingsportsorengagingin
otherphysicalactivities.
Peoplewhohavetakenlargedosesofthedrugmayexperienceanacute
psychosis,whichincludeshallucinations,delusions,andalossofthe
senseofpersonalidentity.
THC,actingthroughcannabinoidreceptors,alsoactivatesthebrain’sreward
system,whichincludesregionsthatgoverntheresponsetohealthypleasurable
behaviorssuchassexandeating.Likemostotherdrugsthatpeoplemisuse,
THCstimulatesneuronsintherewardsystemtoreleasethesignalingchemical
dopamineatlevelshigherthantypicallyobservedinresponsetonaturalstimuli.
Thisfloodofdopaminecontributestothepleasurable"high"thatthoseusewho
recreationalmarijuanaseek.
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Diagramshowingdifferentpartsofthebrainanddescribingmarijuana'seffectsonthe
brain
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Doesmarijuanauseaffectdriving?
Marijuanasignificantlyimpairsjudgment,motorcoordination,andreactiontime,
andstudieshavefoundadirectrelationshipbetweenbloodTHCconcentration
andimpaireddrivingability.
Marijuanaistheillicitdrugmostfrequentlyfoundinthebloodofdriverswho
havebeeninvolvedinvehiclecrashes,includingfatalones. Twolarge
EuropeanstudiesfoundthatdriverswithTHCintheirbloodwereroughlytwice
aslikelytobeculpableforafatalcrashthandriverswhohadnotuseddrugsor
alcohol. However,theroleplayedbymarijuanaincrashesisoftenunclear
becauseitcanbedetectedinbodyfluidsfordaysorevenweeksafter
intoxicationandbecausepeoplefrequentlycombineitwithalcohol.Those
involvedinvehiclecrasheswithTHCintheirblood,particularlyhigherlevels,
arethreetoseventimesmorelikelytoberesponsiblefortheincidentthan
driverswhohadnotuseddrugsoralcohol.Theriskassociatedwithmarijuana
incombinationwithalcoholappearstobegreaterthanthatforeitherdrugby
itself.
Photoby©iStock.com/MadCircles
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Severalmeta-analysesofmultiplestudiesfoundthattheriskofbeinginvolved
inacrashsignificantlyincreasedaftermarijuanause —inafewcases,therisk
doubledormorethandoubled. However,alargecase-controlstudy
conductedbytheNationalHighwayTrafficSafetyAdministrationfoundno
significantincreasedcrashriskattributabletocannabisaftercontrollingfor
drivers’age,gender,race,andpresenceofalcohol.
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Ismarijuanaaddictive?
Marijuanausecanleadtothedevelopmentofproblemuse,knownasa
marijuanausedisorder,whichtakestheformofaddictioninseverecases.
Recentdatasuggestthat30percentofthosewhousemarijuanamayhave
somedegreeofmarijuanausedisorder. Peoplewhobeginusingmarijuana
beforetheageof18arefourtoseventimesmorelikelytodevelopamarijuana
usedisorderthanadults.
Marijuanausedisordersareoftenassociatedwithdependence—inwhicha
personfeelswithdrawalsymptomswhennottakingthedrug.Peoplewhouse
marijuanafrequentlyoftenreportirritability,moodandsleepdifficulties,
decreasedappetite,cravings,restlessness,and/orvariousformsofphysical
discomfortthatpeakwithinthefirstweekafterquittingandlastupto2
weeks. Marijuanadependenceoccurswhenthebrainadaptstolarge
amountsofthedrugbyreducingproductionofandsensitivitytoitsown
endocannabinoidneurotransmitters.
Marijuanausedisorderbecomesaddictionwhenthepersoncannotstopusing
thedrugeventhoughitinterfereswithmanyaspectsofhisorherlife.Estimates
ofthenumberofpeopleaddictedtomarijuanaarecontroversial,inpart
becauseepidemiologicalstudiesofsubstanceuseoftenusedependenceasa
proxyforaddictioneventhoughitispossibletobedependentwithoutbeing
addicted.Thosestudiessuggestthat9percentofpeoplewhousemarijuana
willbecomedependentonit, risingtoabout17percentinthosewhostart
usingintheirteens.
In2015,about4.0millionpeopleintheUnitedStatesmetthediagnosticcriteria
foramarijuanausedisorder; 138,000voluntarilysoughttreatmentfortheir
marijuanause.
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RisingPotency
Marijuanapotency,asdetectedinconfiscatedsamples,hassteadily
increasedoverthepastfewdecades. Intheearly1990s,theaverageTHC
contentinconfiscatedmarijuanasampleswasroughly3.8percent.In
2014,itwas12.2percent.Theaveragemarijuanaextractcontainsmore
than50percentTHC,withsomesamplesexceeding80percent.These
trendsraiseconcernsthattheconsequencesofmarijuanausecouldbe
worsethaninthepast,particularlyamongthosewhoarenewtomarijuana
useorinyoungpeople,whosebrainsarestilldeveloping(see"Whatare
marijuana’slong-termeffectsonthebrain?").
Researchersdonotyetknowthefullextentoftheconsequenceswhenthe
bodyandbrain(especiallythedevelopingbrain)areexposedtohigh
concentrationsofTHCorwhethertherecentincreasesinemergency
departmentvisitsbypeopletestingpositiveformarijuanaarerelatedto
risingpotency.Theextenttowhichpeopleadjustforincreasedpotencyby
usinglessorbysmokingitdifferentlyisalsounknown.Recentstudies
suggestthatexperiencedpeoplemayadjusttheamounttheysmokeand
howmuchtheyinhalebasedonthebelievedstrengthofthemarijuana
theyareusing,buttheyarenotabletofullycompensateforvariationsin
potency.
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Whataremarijuana'slong-term
effectsonthebrain?
Substantialevidencefromanimalresearchandagrowingnumberofstudiesin
humansindicatethatmarijuanaexposureduringdevelopmentcancauselong-
termorpossiblypermanentadversechangesinthebrain.RatsexposedtoTHC
beforebirth,soonafterbirth,orduringadolescenceshownotableproblemswith
specificlearningandmemorytaskslaterinlife. Cognitiveimpairmentsin
adultratsexposedtoTHCduringadolescenceareassociatedwithstructural
andfunctionalchangesinthehippocampus. Studiesinratsalsoshowthat
adolescentexposuretoTHCisassociatedwithanalteredrewardsystem,
increasingthelikelihoodthatananimalwillself-administerotherdrugs(e.g.,
heroin)whengivenanopportunity(see"Ismarijuanaagatewaydrug?").
Imagingstudiesofmarijuana’simpactonbrainstructureinhumanshaveshown
conflictingresults.Somestudiessuggestregularmarijuanauseinadolescence
isassociatedwithalteredconnectivityandreducedvolumeofspecificbrain
regionsinvolvedinabroadrangeofexecutivefunctionssuchasmemory,
learning,andimpulsecontrolcomparedtopeoplewhodonotuse. Other
studieshavenotfoundsignificantstructuraldifferencesbetweenthebrainsof
peoplewhodoanddonotusethedrug.
Severalstudies,includingtwolargelongitudinalstudies,suggestthatmarijuana
usecancausefunctionalimpairmentincognitiveabilitiesbutthatthedegree
and/ordurationoftheimpairmentdependsontheagewhenapersonbegan
usingandhowmuchandhowlongheorsheused.
Amongnearly4,000youngadultsintheCoronaryArteryRiskDevelopmentin
YoungAdultsstudytrackedovera25-yearperioduntilmid-adulthood,
cumulativelifetimeexposuretomarijuanawasassociatedwithlowerscoreson
atestofverbalmemorybutdidnotaffectothercognitiveabilitiessuchas
processingspeedorexecutivefunction.Theeffectwassizeableandsignificant
evenaftereliminatingthoseinvolvedwithcurrentuseandafteradjustingfor
confoundingfactorssuchasdemographicfactors,otherdrugandalcoholuse,
andotherpsychiatricconditionssuchasdepression.
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AlargelongitudinalstudyinNewZealandfoundthatpersistentmarijuanause
disorderwithfrequentusestartinginadolescencewasassociatedwithalossof
anaverageof6orupto8IQpointsmeasuredinmid-adulthood. Significantly,
inthatstudy,thosewhousedmarijuanaheavilyasteenagersandquitusingas
adultsdidnotrecoverthelostIQpoints.Peoplewhoonlybeganusing
marijuanaheavilyinadulthooddidnotloseIQpoints.Theseresultssuggest
thatmarijuanahasitsstrongestlong-termimpactonyoungpeoplewhose
brainsarestillbusybuildingnewconnectionsandmaturinginotherways.The
endocannabinoidsystemisknowntoplayanimportantroleintheproper
formationofsynapses(theconnectionsbetweenneurons)duringearlybrain
development,andasimilarrolehasbeenproposedfortherefinementofneural
connectionsduringadolescence.Ifthelong-termeffectsofmarijuanauseon
cognitivefunctioningorIQareupheldbyfutureresearch,thismaybeone
avenuebywhichmarijuanauseduringadolescenceproducesitslong-term
effects.
However,recentresultsfromtwoprospectivelongitudinaltwinstudiesdidnot
supportacausalrelationshipbetweenmarijuanauseandIQloss.Thosewho
usedmarijuanadidshowasignificantdeclineinverbalability(equivalentto4
IQpoints)andingeneralknowledgebetweenthepreteenyears(ages9to12,
beforeuse)andlateadolescence/earlyadulthood(ages17to20).However,at
thestartofthestudy,thosewhowoulduseinthefuturealreadyhadlower
scoresonthesemeasuresthanthosewhowouldnotuseinthefuture,andno
predictabledifferencewasfoundbetweentwinswhenoneusedmarijuanaand
onedidnot.ThissuggeststhatobservedIQdeclines,atleastacross
adolescence,maybecausedbysharedfamilialfactors(e.g.,genetics,family
environment),notbymarijuanauseitself. Itshouldbenoted,though,that
thesestudieswereshorterindurationthantheNewZealandstudyanddidnot
exploretheimpactofthedoseofmarijuana(i.e.,heavyuse)orthedevelopment
ofacannabisusedisorder;thismayhavemaskedadose-ordiagnosis-
dependenteffect.
Theabilitytodrawdefinitiveconclusionsaboutmarijuana’slong-termimpacton
thehumanbrainfrompaststudiesisoftenlimitedbythefactthatstudy
participantsusemultiplesubstances,andthereisoftenlimiteddataaboutthe
participants’healthormentalfunctioningpriortothestudy.Overthenext
decade,theNationalInstitutesofHealthisfundingtheAdolescentBrain
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CognitiveDevelopment(ABCD)study—amajorlongitudinalstudythatwilltrack
alargesampleofyoungAmericansfromlatechildhood(beforefirstuseof
drugs)toearlyadulthood.Thestudywilluseneuroimagingandotheradvanced
toolstoclarifypreciselyhowandtowhatextentmarijuanaandother
substances,aloneandincombination,affectadolescentbraindevelopment.
Marijuana,Memory,andtheHippocampus
Distributionofcannabinoidreceptorsintheratbrain.Brainimagerevealshigh
levels(showninorangeandyellow)ofcannabinoidreceptorsinmanyareas,
includingthecortex,hippocampus,cerebellum,andnucleusaccumbens
(ventralstriatum).
MemoryimpairmentfrommarijuanauseoccursbecauseTHCaltershowthe
hippocampus,abrainarearesponsibleformemoryformation,processes
information.Mostoftheevidencesupportingthisassertioncomesfromanimal
studies.Forexample,ratsexposedtoTHCinutero,soonafterbirth,orduring
adolescence,shownotableproblemswithspecificlearning/memorytaskslater
inlife.Moreover,cognitiveimpairmentinadultratsisassociatedwithstructural
andfunctionalchangesinthehippocampusfromTHCexposureduring
adolescence.
ImagebytheNIDA
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Aspeopleage,theyloseneuronsinthehippocampus,whichdecreasestheir
abilitytolearnnewinformation.ChronicTHCexposuremayhastenage-related
lossofhippocampalneurons.Inonestudy,ratsexposedtoTHCeverydayfor8
months(approximately30percentoftheirlifespan)showedalevelofnervecell
lossat11to12monthsofagethatequaledthatofunexposedanimalstwice
theirage.
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Ismarijuanaagatewaydrug?
Someresearchsuggeststhatmarijuanauseislikelytoprecedeuseofotherlicit
andillicitsubstances andthedevelopmentofaddictiontoothersubstances.
Forinstance,astudyusinglongitudinaldatafromtheNationalEpidemiological
StudyofAlcoholUseandRelatedDisordersfoundthatadultswhoreported
marijuanauseduringthefirstwaveofthesurveyweremorelikelythanadults
whodidnotusemarijuanatodevelopanalcoholusedisorderwithin3years;
peoplewhousedmarijuanaandalreadyhadanalcoholusedisorderatthe
outsetwereatgreaterriskoftheiralcoholusedisorderworsening. Marijuana
useisalsolinkedtoothersubstanceusedisordersincludingnicotineaddiction.
Earlyexposuretocannabinoidsinadolescentrodentsdecreasesthereactivity
ofbraindopaminerewardcenterslaterinadulthood. Totheextentthatthese
findingsgeneralizetohumans,thiscouldhelpexplaintheincreased
vulnerabilityforaddictiontoothersubstancesofmisuselaterinlifethatmost
epidemiologicalstudieshavereportedforpeoplewhobeginmarijuanause
earlyinlife. ItisalsoconsistentwithanimalexperimentsshowingTHC’s
abilityto"prime"thebrainforenhancedresponsestootherdrugs. For
example,ratspreviouslyadministeredTHCshowheightenedbehavioral
responsenotonlywhenfurtherexposedtoTHCbutalsowhenexposedtoother
drugssuchasmorphine—aphenomenoncalledcross-sensitization.
Thesefindingsareconsistentwiththeideaofmarijuanaasa"gatewaydrug."
However,themajorityofpeoplewhousemarijuanadonotgoontouseother,
"harder"substances.Also,cross-sensitizationisnotuniquetomarijuana.
Alcoholandnicotinealsoprimethebrainforaheightenedresponsetoother
drugs andare,likemarijuana,alsotypicallyusedbeforeapersonprogresses
toother,moreharmfulsubstances.
Itisimportanttonotethatotherfactorsbesidesbiologicalmechanisms,suchas
aperson’ssocialenvironment,arealsocriticalinaperson’sriskfordruguse.
Analternativetothegateway-drughypothesisisthatpeoplewhoaremore
vulnerabletodrug-takingaresimplymorelikelytostartwithreadilyavailable
substancessuchasmarijuana,tobacco,oralcohol,andtheirsubsequentsocial
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interactionswithotherswhousedrugsincreasestheirchancesoftryingother
drugs.Furtherresearchisneededtoexplorethisquestion.
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Howdoesmarijuanauseaffect
school,work,andsociallife?
Researchhasshownthatmarijuana’snegativeeffectsonattention,memory,
andlearningcanlastfordaysorweeksaftertheacuteeffectsofthedrugwear
off,dependingontheperson’shistorywiththedrug. Consequently,someone
whosmokesmarijuanadailymaybefunctioningatareducedintellectuallevel
mostorallofthetime.Considerableevidencesuggeststhatstudentswho
smokemarijuanahavepoorereducationaloutcomesthantheirnonsmoking
peers.Forexample,areviewof48relevantstudiesfoundmarijuanausetobe
associatedwithreducededucationalattainment(i.e.,reducedchancesof
graduating). ArecentanalysisusingdatafromthreelargestudiesinAustralia
andNewZealandfoundthatadolescentswhousedmarijuanaregularlywere
significantlylesslikelythantheirnon-usingpeerstofinishhighschoolorobtain
adegree.Theyalsohadamuchhigherchanceofdevelopingdependence,
usingotherdrugs,andattemptingsuicide. Severalstudieshavealsolinked
heavymarijuanausetolowerincome,greaterwelfaredependence,
unemployment,criminalbehavior,andlowerlifesatisfaction.
Imageby©iStock.com/AntonioGuillem
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Towhatdegreemarijuanauseisdirectlycausalintheseassociationsremains
anopenquestionrequiringfurtherresearch.Itispossiblethatotherfactors
independentlypredisposepeopletobothmarijuanauseandvariousnegative
lifeoutcomessuchasschooldropout. Thatsaid,peoplereportaperceived
influenceoftheirmarijuanauseonpooroutcomesonavarietyoflife
satisfactionandachievementmeasures.Onestudy,forexample,compared
peopleinvolvedwithcurrentandformerlong-term,heavyuseofmarijuanawith
acontrolgroupwhoreportedsmokingmarijuanaatleastonceintheirlivesbut
notmorethan50times. Allparticipantshadsimilareducationandincome
backgrounds,butsignificantdifferenceswerefoundintheireducational
attainment:Fewerofthosewhoengagedinheavycannabisusecompleted
college,andmorehadyearlyhouseholdincomesoflessthan$30,000.When
askedhowmarijuanaaffectedtheircognitiveabilities,careerachievements,
sociallives,andphysicalandmentalhealth,themajorityofthosewhoused
heavilyreportedthatmarijuanahadnegativeeffectsinalltheseareasoftheir
lives.
Studieshavealsosuggestedspecificlinksbetweenmarijuanauseandadverse
consequencesintheworkplace,suchasincreasedriskforinjuryor
accidents. Onestudyamongpostalworkersfoundthatemployeeswhotested
positiveformarijuanaonapre-employmenturinedrugtesthad55percent
moreindustrialaccidents,85percentmoreinjuries,and75percentgreater
absenteeismcomparedwiththosewhotestednegativeformarijuanause.
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Istherealinkbetweenmarijuanause
andpsychiatricdisorders?
Severalstudieshavelinkedmarijuanausetoincreasedriskforpsychiatric
disorders,includingpsychosis(schizophrenia),depression,anxiety,and
substanceusedisorders,butwhetherandtowhatextentitactuallycauses
theseconditionsisnotalwayseasytodetermine. Theamountofdrugused,
theageatfirstuse,andgeneticvulnerabilityhaveallbeenshowntoinfluence
thisrelationship.Thestrongestevidencetodateconcernslinksbetween
marijuanauseandsubstanceusedisordersandbetweenmarijuanauseand
psychiatricdisordersinthosewithapreexistinggeneticorothervulnerability.
ResearchusinglongitudinaldatafromtheNationalEpidemiologicalSurveyon
AlcoholandRelatedConditionsexaminedassociationsbetweenmarijuana
use,moodandanxietydisorders,andsubstanceusedisorders.Afteradjusting
forvariousconfoundingfactors,noassociationbetweenmarijuanauseand
moodandanxietydisorderswasfound.Theonlysignificantassociationswere
increasedriskofalcoholusedisorders,nicotinedependence,marijuanause
disorder,andotherdrugusedisorders.
Recentresearch(see"AKT1GeneVariationsandPsychosis")hasfoundthat
peoplewhousemarijuanaandcarryaspecificvariantoftheAKT1gene,which
codesforanenzymethataffectsdopaminesignalinginthestriatum,areat
increasedriskofdevelopingpsychosis.Thestriatumisanareaofthebrainthat
becomesactivatedandfloodedwithdopaminewhencertainstimuliarepresent.
Onestudyfoundthattheriskofpsychosisamongthosewiththisvariantwas
seventimeshigherforthosewhousedmarijuanadailycomparedwiththose
whouseditinfrequentlyorusednoneatall.
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Anotherstudyfoundanincreasedriskofpsychosisamongadultswhohadused
marijuanainadolescenceandalsocarriedaspecificvariantofthegenefor
catechol-O-methyltransferase(COMT),anenzymethatdegrades
neurotransmitterssuchasdopamineandnorepinephrine (see"Genetic
VariationsinCOMTInfluencestheHarmfulEffectsofAbusedDrugs").
Marijuanausehasalsobeenshowntoworsenthecourseofillnessinpatients
whoalreadyhaveschizophrenia.Asmentionedpreviously,marijuanacan
produceanacutepsychoticreactioninnon-schizophrenicpeoplewhouse
marijuana,especiallyathighdoses,althoughthisfadesasthedrugwearsoff.
Whetheradolescentmarijuanausecancontributetodevelopingpsychosislaterin
adulthoodappearstodependonwhetherapersonalreadyhasageneticallybased
vulnerabilitytothedisorder.TheAKT1genegovernsanenzymethataffectsbrain
signalinginvolvingtheneurotransmitterdopamine.Altereddopaminesignalingis
knowntobeinvolvedinschizophrenia.AKT1cantakeoneofthreeformsinaspecific
regionofthegeneimplicatedinsusceptibilitytoschizophrenia:T/T,C/T,andC/C.
Thosewhousemarijuanadaily(greenbars)withtheC/Cvarianthaveaseventimes
higherriskofdevelopingpsychosisthanthosewhouseitinfrequentlyorusenoneat
all.TheriskforpsychosisamongthosewiththeT/Tvariantwasunaffectedby
whethertheyusedmarijuana.
Source:DiFortietal.BiolPsychiatry.2012.
65
26
Inconsistentandmodestassociationshavebeenreportedbetweenmarijuana
useandsuicidalthoughtsandattemptedsuicideamongteens. Marijuana
hasalsobeenassociatedwithanamotivationalsyndrome,definedasa
diminishedorabsentdrivetoengageintypicallyrewardingactivities.Because
oftheroleoftheendocannabinoidsysteminregulatingmoodandreward,ithas
beenhypothesizedthatbrainchangesresultingfromearlyuseofmarijuana
mayunderlietheseassociations,butmoreresearchisneededtoverifythat
suchlinksexistandbetterunderstandthem.
Theinfluenceofadolescentmarijuanauseonadultpsychosisisaffectedbygenetic
variables.Thisfigureshowsthatvariationsinagenecanaffectthelikelihoodof
developingpsychosisinadulthoodfollowingexposuretocannabisinadolescence.
TheCOMTgenegovernsanenzymethatbreaksdowndopamine,abrainchemical
involvedinschizophrenia.Itcomesintwoforms:"Met"and"Val."Individualswithone
ortwocopiesoftheValvarianthaveahigherriskofdevelopingschizophrenic-type
disordersiftheyusedcannabisduringadolescence(darkbars).Thosewithonlythe
Metvariantwereunaffectedbycannabisuse.
Source:Caspietal.BiolPsychiatry.2005.
66,67
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AdverseConsequencesofMarijuanaUse
Acute(presentduringintoxication)
Impairedshort-termmemory
Impairedattention,judgment,andothercognitivefunctions
Impairedcoordinationandbalance
Increasedheartrate
Anxiety,paranoia
Psychosis(uncommon)
Persistent(lastinglongerthanintoxication,butmaynotbe
permanent)
Impairedlearningandcoordination
Photoby©getttyimages.com/Fuse
28
Sleepproblems
Long-term(cumulativeeffectsofrepeateduse)
Potentialformarijuanaaddiction
ImpairmentsinlearningandmemorywithpotentiallossofIQ*
Increasedriskofchroniccough,bronchitis
Increasedriskofotherdrugandalcoholusedisorders
Increasedriskofschizophreniainpeoplewithgeneticvulnerability**
*LossofIQamongindividualswithpersistentmarijuanausedisorderwho
beganusingheavilyduringadolescence
**Theseareoftenreportedco-occurringsymptoms/disorderswithchronic
marijuanause.However,researchhasnotyetdeterminedwhether
marijuanaiscausalorjustassociatedwiththesementalproblems.
29
Whataremarijuana'seffectsonlung
health?
Liketobaccosmoke,marijuanasmokeisanirritanttothethroatandlungsand
cancauseaheavycoughduringuse.Italsocontainslevelsofvolatile
chemicalsandtarthataresimilartotobaccosmoke,raisingconcernsaboutrisk
forcancerandlungdisease.
Marijuanasmokingisassociatedwithlargeairwayinflammation,increased
airwayresistance,andlunghyperinflation,andthosewhosmokemarijuana
regularlyreportmoresymptomsofchronicbronchitisthanthosewhodonot
smoke. Onestudyfoundthatpeoplewhofrequentlysmokemarijuanahad
moreoutpatientmedicalvisitsforrespiratoryproblemsthanthosewhodonot
smoke. Somecasestudieshavesuggestedthat,becauseofTHC’simmune-
suppressingeffects,smokingmarijuanamightincreasesusceptibilitytolung
infections,suchaspneumonia,inpeoplewithimmunedeficiencies;however,a
largeAIDScohortstudydidnotconfirmsuchanassociation. Smoking
marijuanamayalsoreducetherespiratorysystem’simmuneresponse,
increasingthelikelihoodofthepersonacquiringrespiratoryinfections,
includingpneumonia. Animalandhumanstudieshavenotfoundthat
marijuanaincreasesriskforemphysema.
Whethersmokingmarijuanacauseslungcancer,ascigarettesmokingdoes,
remainsanopenquestion. Marijuanasmokecontainscarcinogenic
combustionproducts,includingabout50percentmorebenzopreneand75
percentmorebenzanthracene(andmorephenols,vinylchlorides,
nitrosamines,reactiveoxygenspecies)thancigarettesmoke. Becauseofhow
itistypicallysmoked(deeperinhale,heldforlonger),marijuanasmokingleads
tofourtimesthedepositionoftarcomparedtocigarettesmoking. However,
whileafewsmall,uncontrolledstudieshavesuggestedthatheavy,regular
marijuanasmokingcouldincreaseriskforrespiratorycancers,well-designed
populationstudieshavefailedtofindanincreasedriskoflungcancer
associatedwithmarijuanause.
Onecomplexityincomparingthelung-healthrisksofmarijuanaandtobacco
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68
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68
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68
30
concernstheverydifferentwaysthetwosubstancesareused.Whilepeople
whosmokemarijuanaofteninhalemoredeeplyandholdthesmokeintheir
lungsforalongerdurationthanistypicalwithcigarettes,marijuana’seffectslast
longer,sopeoplewhousemarijuanamaysmokelessfrequentlythanthose
whosmokecigarettes.
Additionally,thefactthatmanypeopleusebothmarijuanaandtobaccomakes
determiningmarijuana’sprecisecontributiontolungcancerrisk,ifany,difficult
toestablish.CellcultureandanimalstudieshavealsosuggestedTHCand
CBDmayhaveantitumoreffects,andthishasbeenproposedasonereason
whystrongerexpectedassociationsarenotseenbetweenmarijuanauseand
lungcancer,butmoreresearchisneededonthisquestion.68
31
Whataremarijuana’seffectsonother
aspectsofphysicalhealth?
Withinafewminutesafterinhalingmarijuanasmoke,aperson’sheartrate
speedsup,thebreathingpassagesrelaxandbecomeenlarged,andblood
vesselsintheeyesexpand,makingtheeyeslookbloodshot.Theheartrate—
normally70to80beatsperminute—mayincreaseby20to50beatsperminute
ormayevendoubleinsomecases.Takingotherdrugswithmarijuanacan
amplifythiseffect.
Limitedevidencesuggeststhataperson’sriskofheartattackduringthefirst
houraftersmokingmarijuanaisnearlyfivetimeshisorherusualrisk. This
observationcouldbepartlyexplainedbymarijuanaraisingbloodpressure(in
somecases)andheartrateandreducingtheblood’scapacitytocarry
oxygen. Marijuanamayalsocauseorthostatichypotension(headrushor
dizzinessonstandingup),possiblyraisingdangerfromfaintingandfalls.
Tolerancetosomecardiovasculareffectsoftendevelopswithrepeated
exposure. Thesehealtheffectsneedtobeexaminedmoreclosely,particularly
giventheincreasinguseof"medicalmarijuana"bypeoplewithhealthissues
andolderadultswhomayhaveincreasedbaselinevulnerabilityduetoage-
relatedcardiovascularriskfactors(see"Ismarijuanasafeandeffectiveas
medicine?").
Afewstudieshaveshownaclearlinkbetweenmarijuanauseinadolescence
andincreasedriskforanaggressiveformoftesticularcancer
(nonseminomatoustesticulargermcelltumor)thatpredominantlystrikesyoung
adultmales. Theearlyonsetoftesticularcancerscomparedtolungand
mostothercancersindicatesthat,whateverthenatureofmarijuana’s
contribution,itmayaccumulateoverjustafewyearsofuse.
Studieshaveshownthatinrarecases,chronicuseofmarijuanacanleadto
CannabinoidHyperemesisSyndrome—aconditionmarkedbyrecurrentbouts
ofseverenausea,vomiting,anddehydration.Thissyndromehasbeenfoundto
occurinpersonsunder50yearsofageandwithalonghistoryofmarijuana
use.CannabinoidHyperemesisSyndromecanleadsuffererstomakefrequent
73
74
75
76,77
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tripstotheemergencyroom,butmayberesolvedwhenapersonstopsusing
marijuana.78
33
Ismarijuanasafeandeffectiveas
medicine?
Thepotentialmedicinalpropertiesofmarijuanaanditscomponentshavebeen
thesubjectofresearchandheateddebatefordecades.THCitselfhasproven
medicalbenefitsinparticularformulations.TheU.S.FoodandDrug
Administration(FDA)hasapprovedTHC-basedmedications,dronabinol
(Marinol )andnabilone(Cesamet ),prescribedinpillformforthetreatmentof
nauseainpatientsundergoingcancerchemotherapyandtostimulateappetite
inpatientswithwastingsyndromeduetoAIDS.TheFDAalsoapprovedaCBD-
basedliquidmedicationcalledEpidiolex forthetreatmentoftwoformsof
severechildhoodepilepsy,DravetsyndromeandLennox-Gastautsyndrome.
It’sbeingdeliveredtopatientsinareliabledosageformandthrougha
reproduciblerouteofdeliverytoensurethatpatientsderivetheanticipated
benefits.CBDdoesnothavetherewardingpropertiesofTHC.
Inaddition,severalothermarijuana-basedmedicationshavebeenapprovedor
areundergoingclinicaltrials.Nabiximols(Sativex ),amouthspraythatis
currentlyavailableintheUnitedKingdom,Canada,andseveralEuropean
countriesfortreatingthespasticityandneuropathicpainthatmayaccompany
multiplesclerosis,combinesTHCwithanotherchemicalfoundinmarijuana
calledcannabidiol(CBD).
Researchersgenerallyconsidermedicationslikethese,whichusepurified
chemicalsderivedfromorbasedonthoseinthemarijuanaplant,tobemore
promisingtherapeuticallythanuseofthewholemarijuanaplantoritscrude
extracts.Developmentofdrugsfrombotanicalssuchasthemarijuanaplant
posesnumerouschallenges.Botanicalsmaycontainhundredsofunknown,
activechemicals,anditcanbedifficulttodevelopaproductwithaccurateand
consistentdosesofthesechemicals.Useofmarijuanaasmedicinealsoposes
otherproblemssuchastheadversehealtheffectsofsmokingandTHC-induced
cognitiveimpairment.Nevertheless,agrowingnumberofstateshavelegalized
dispensingofmarijuanaoritsextractstopeoplewitharangeofmedical
conditions.
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Anadditionalconcernwith"medicalmarijuana"isthatlittleisknownaboutthe
long-termimpactofitsusebypeoplewithhealth-and/orage-related
vulnerabilities—suchasolderadultsorpeoplewithcancer,AIDS,
cardiovasculardisease,multiplesclerosis,orotherneurodegenerative
diseases.Furtherresearchwillbeneededtodeterminewhetherpeoplewhose
healthhasbeencompromisedbydiseaseoritstreatment(e.g.,chemotherapy)
areatgreaterriskforadversehealthoutcomesfrommarijuanause.
MedicalMarijuanaLegalizationandPrescriptionOpioid
UseOutcomes
TworecentstudiesinJAMAInternalMedicinereportanassociation
betweennotonlymedicalmarijuanalaws(MML)butalsoprotectedaccess
todispensariesandtheirassociationwithopioidprescriptionpatterns
basedonMedicaidorMedicarePartDprescriptiondata.Thefirststudy
foundthatMedicarePartDprescriptionsfilledforallopioidsdecreasedin
stateswithMMLby2.11milliondailydosesperyearperstate.Instates
withmedicalcannabisdispensaries,prescriptionsdecreasedby3.742
milliondailydosesperyearperstate. Similarly,thesecondstudy
examinedMedicaidprescriptiondataandfoundthatMMLsandadult-use
marijuanalawswereassociatedwithloweropioidprescribingrates(5.88%
and6.38%lower,respectively).
Additionally,NIDAfundedtwostudiesthatexploredtherelationship
betweenmarijuanalegalizationandadverseoutcomesassociatedwith
prescriptionopioids.Thefirststudyfoundanassociationbetweenmedical
marijuanalegalizationandareductioninoverdosedeathsfromopioid
painrelievers;aneffectthatstrengthenedineachyearfollowingthe
implementationoflegislation. ThesecondNIDA-fundedstudywasa
moredetailedanalysisbytheRANDCorporationthatshowedlegally
protectedaccesstomedicalmarijuanadispensariesisassociatedwith
lowerlevelsofopioidprescribing,lowerself-reportofnonmedical
prescriptionopioiduse,lowertreatmentadmissionsforprescriptionopioid
usedisorders,andreductioninprescriptionopioidoverdosedeaths.
Notably,thereductionindeathswaspresentonlyinstateswith
dispensaries(notjustmedicalmarijuanalaws)andwasgreaterinstates
withactivedispensaries.Itshouldbenotedthatthepopulation-based
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80
81
82
35
natureofthesestudies,andthetwoabove,donotestablishacausal
relationshiporgiveevidenceforchangesinindividualpainpatient
behaviorandcautionshouldbeusedwheninterpretingtheirresults.
Todate,researchintotheeffectsofcannabisonopioiduseinpainpatients
ismixed.Somedatasuggestthatmedicalcannabistreatmentmayreduce
thedoseofopioidsrequiredforpainrelief, whileanotherNIH-funded
studyfoundthatcannabisuseappearstoincreasetheriskofdeveloping
nonmedicalprescriptionopioiduseandopioidusedisorder. Thoughno
singlestudyisdefinitive,theycumulativelysuggestthatmedicalmarijuana
productsmayplayaroleinreducingtheuseofopioidsneededtocontrol
painbutthattheseproductsdon’tcomewithoutrisk.Moreresearchis
neededtoinvestigatethepotentialtherapeuticroleofmarijuanaincluding
itsroleasatreatmentoptionforopioidusedisorderanditsabilitytoreduce
specifictypesofpain.
83,84
85
36
Whataretheeffectsofsecondhand
exposuretomarijuanasmoke?
Peopleoftenaskaboutthepossiblepsychoactiveeffectofexposureto
secondhandmarijuanasmokeandwhetherapersonwhohasinhaled
secondhandmarijuanasmokecouldfailadrugtest.Researchersmeasuredthe
amountofTHCinthebloodofpeoplewhodonotsmokemarijuanaandhad
spent3hoursinawell-ventilatedspacewithpeoplecasuallysmoking
marijuana;THCwaspresentinthebloodofthenonsmokingparticipants,but
theamountwaswellbelowthelevelneededtofailadrugtest.Anotherstudy
thatvariedthelevelsofventilationandthepotencyofthemarijuanafoundthat
somenonsmokingparticipantsexposedforanhourtohigh-THCmarijuana
(11.3percentTHCconcentration)inanunventilatedroomshowedpositive
urineassaysinthehoursdirectlyfollowingexposure ;afollow-upstudy
showedthatnonsmokingpeopleinaconfinedspacewithpeoplesmokinghigh-
THCmarijuanareportedmildsubjectiveeffectsofthedrug—a"contacthigh"—
anddisplayedmildimpairmentsonperformanceinmotortasks.
Theknownhealthrisksofsecondhandexposuretocigarettesmoke—tothe
heartorlungs,forinstance—raisequestionsaboutwhethersecondhand
exposuretomarijuanasmokeposessimilarhealthrisks.Atthispoint,verylittle
researchonthisquestionhasbeenconducted.A2016studyinratsfoundthat
secondhandexposuretomarijuanasmokeaffectedameasureofbloodvessel
functionasmuchassecondhandtobaccosmoke,andtheeffectslasted
longer. Oneminuteofexposuretosecondhandmarijuanasmokeimpaired
flow-mediateddilation(theextenttowhicharteriesenlargeinresponseto
increasedbloodflow)ofthefemoralarterythatlastedforatleast90minutes;
impairmentfrom1minuteofsecondhandtobaccoexposurewasrecovered
within30minutes.TheeffectsofmarijuanasmokewereindependentofTHC
concentration;i.e.,whenTHCwasremoved,theimpairmentwasstillpresent.
Thisresearchhasnotyetbeenconductedwithhumansubjects,butthetoxins
andtarlevelsknowntobepresentinmarijuanasmoke(see“Whatare
marijuana’seffectsonlunghealth?”)raiseconcernsaboutexposureamong
vulnerablepopulations,suchaschildrenandpeoplewithasthma.
86
87
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Canmarijuanauseduringandafter
pregnancyharmthebaby?
Moreresearchisneededonhowmarijuanauseduringpregnancycouldimpact
thehealthanddevelopmentofinfants,givenchangingpoliciesaboutaccessto
marijuana,aswellassignificantincreasesoverthelastdecadeinthenumber
ofpregnantwomenseekingsubstanceusedisordertreatmentformarijuana
use. Onestudyfoundthatabout20%ofpregnantwomen24-years-oldand
youngerscreenedpositiveformarijuana.However,thisstudyalsofoundthat
womenwereabouttwiceaslikelytoscreenpositiveformarijuanauseviaa
drugtestthantheystateinself-reportedmeasures.Thissuggeststhatself-
reportedratesofmarijuanauseinpregnantfemalesmaynotbeanaccurate
measureofmarijuanause. Additionally,inonestudyofdispensaries,
nonmedicalpersonnelatmarijuanadispensarieswererecommending
marijuanatopregnantwomenfornausea,butmedicalexpertswarnagainstit.
Photoby©Thinkstock.com/CreatasImages
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Thereisnohumanresearchconnectingmarijuanausetothechanceof
miscarriage, althoughanimalstudiesindicatethattheriskformiscarriage
increasesifmarijuanaisusedearlyinpregnancy. Someassociationshave
beenfoundbetweenmarijuanauseduringpregnancyandfuture
developmentalandhyperactivitydisordersinchildren. Evidenceismixed
astowhethermarijuanausebypregnantwomenisassociatedwithlowbirth
weight orprematurebirth, althoughlong-termusemayelevatethese
risks. Researchhasshownthatpregnantwomenwhousemarijuanahavea
2.3timesgreaterriskofstillbirth. Giventhepotentialofmarijuanato
negativelyimpactthedevelopingbrain,theAmericanCollegeofObstetricians
andGynecologistsrecommendsthatobstetrician-gynecologistscounselwomen
againstusingmarijuanawhiletryingtogetpregnant,duringpregnancy,and
whiletheyarebreastfeeding.
Somewomenreportusingmarijuanatotreatseverenauseaassociatedwith
theirpregnancy; however,thereisnoresearchconfirmingthatthisisa
safepractice,anditisgenerallynotrecommended.Womenconsideringusing
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98–102 101
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104
RecentTrendsinTreatmentAdmissionsforMarijuanaUseDuringPregnancy
Source:Martinetal.,2015
105,106
39
medicalmarijuanawhilepregnantshouldnotdosowithoutcheckingwiththeir
healthcareproviders.Animalstudieshaveshownthatmoderateconcentrations
ofTHC,whenadministeredtomotherswhilepregnantornursing,couldhave
long-lastingeffectsonthechild,includingincreasingstressresponsivityand
abnormalpatternsofsocialinteractions. Animalstudiesalsoshowlearning
deficitsinprenatallyexposedindividuals.
Humanresearchhasshownthatsomebabiesborntowomenwhoused
marijuanaduringtheirpregnanciesdisplayalteredresponsestovisualstimuli,
increasedtrembling,andahigh-pitchedcry, whichcouldindicateproblems
withneurologicaldevelopment. Inschool,marijuana-exposedchildrenare
morelikelytoshowgapsinproblem-solvingskills,memory, andtheabilityto
remainattentive. Moreresearchisneeded,however,todisentangle
marijuana-specificeffectsfromthoseofotherenvironmentalfactorsthatcould
beassociatedwithamother'smarijuanause,suchasanimpoverishedhome
environmentorthemother'suseofotherdrugs. Prenatalmarijuanaexposure
isalsoassociatedwithanincreasedlikelihoodofapersonusingmarijuanaas
ayoungadult,evenwhenotherfactorsthatinfluencedruguseare
considered. Moreinformationonmarijuanauseduringpregnancycanbe
foundintheNIDA'sSubstanceUseinWomenResearchReport.
Verylittleisknownaboutmarijuanauseandbreastfeeding.Onestudysuggests
thatmoderateamountsofTHCfindtheirwayintobreastmilkwhenanursing
motherusesmarijuana. SomeevidenceshowsthatexposuretoTHCthrough
breastmilkinthefirstmonthoflifecouldresultindecreasedmotordevelopment
at1yearofage. TherehavebeennostudiestodetermineifexposuretoTHC
duringnursingislinkedtoeffectslaterinthechild'slife.Withregularuse,THC
canaccumulateinhumanbreastmilktohighconcentrations. Becausea
baby'sbrainisstillforming,THCconsumedinbreastmilkcouldaffectbrain
development.Givenalltheseuncertainties,nursingmothersarediscouraged
fromusingmarijuana. Newmothersusingmedicalmarijuanashouldbe
vigilantaboutcoordinatingcarebetweenthedoctorrecommendingtheir
marijuanauseandthepediatriciancaringfortheirbaby.
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AvailableTreatmentsforMarijuana
UseDisorders
Marijuanausedisordersappeartobeverysimilartoothersubstanceuse
disorders,althoughthelong-termclinicaloutcomesmaybelesssevere.On
average,adultsseekingtreatmentformarijuanausedisordershaveused
marijuananearlyeverydayformorethan10yearsandhaveattemptedtoquit
morethansixtimes. Peoplewithmarijuanausedisorders,especially
adolescents,oftenalsosufferfromotherpsychiatricdisorders
(comorbidity). Theymayalsouseorbeaddictedtoothersubstances,suchas
cocaineoralcohol.Availablestudiesindicatethateffectivelytreatingthemental
healthdisorderwithstandardtreatmentsinvolvingmedicationsandbehavioral
therapiesmayhelpreducemarijuanause,particularlyamongthoseinvolved
withheavyuseandthosewithmorechronicmentaldisorders.Thefollowing
behavioraltreatmentshaveshownpromise:
Cognitive-behavioraltherapy:Aformofpsychotherapythatteachespeople
strategiestoidentifyandcorrectproblematicbehaviorsinordertoenhance
self-control,stopdruguse,andaddressarangeofotherproblemsthatoften
co-occurwiththem.
Contingencymanagement:Atherapeuticmanagementapproachbasedon
frequentmonitoringofthetargetbehaviorandtheprovision(orremoval)of
tangible,positiverewardswhenthetargetbehavioroccurs(ordoesnot).
Motivationalenhancementtherapy:Asystematicformofintervention
designedtoproducerapid,internallymotivatedchange;thetherapydoes
notattempttotreattheperson,butrathermobilizehisorherowninternal
resourcesforchangeandengagementintreatment.
Currently,theFDAhasnotapprovedanymedicationsforthetreatmentof
marijuanausedisorder,butresearchisactiveinthisarea.Becausesleep
problemsfeatureprominentlyinmarijuanawithdrawal,somestudiesare
examiningtheeffectivenessofmedicationsthataidinsleep.Medicationsthat
haveshownpromiseinearlystudiesorsmallclinicaltrialsincludethesleepaid
zolpidem(Ambien ),ananti-anxiety/anti-stressmedicationcalledbuspirone
117
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(BuSpar ),andananti-epilepticdrugcalledgabapentin
(Horizant ,Neurontin )thatmayimprovesleepand,possibly,executive
function.OtheragentsbeingstudiedincludethenutritionalsupplementN-
acetylcysteineandchemicalscalledFAAHinhibitors,whichmayreduce
withdrawalbyinhibitingthebreakdownofthebody’sowncannabinoids.Future
directionsincludethestudyofsubstancescalledallostericmodulatorsthat
interactwithcannabinoidreceptorstoinhibitTHC’srewardingeffects.
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WherecanIgetfurtherinformation
aboutmarijuana?
Tolearnmoreaboutmarijuanaandotherdrugs,visittheNIDAwebsiteat
drugabuse.govorcontacttheDrugPubsResearchDisseminationCenterat
877-NIDA-NIH(877-643-2644;TTY/TDD:240-645-0228).
TheNIDAwebsiteincludes:
informationaboutdrugsandrelatedhealthconsequences
NIDApublications,news,andevents
resourcesforhealthcareprofessionals
fundinginformation(includingprogramannouncementsanddeadlines)
internationalactivities
linkstorelatedwebsites(accesstowebsitesofmanyotherorganizationsin
thefield)
informationinSpanish(enespañol)
NIDAwebsitesandwebpages
drugabuse.gov
teens.drugabuse.gov
easyread.drugabuse.gov
drugabuse.gov/drugs-abuse/marijuana
drugabuse.gov/related-topics/hivaids
researchstudies.drugabuse.gov
irp.drugabuse.gov
43
Forphysicianinformation
NIDAMED:drugabuse.gov/nidamed
Otherwebsites
Informationaboutmarijuanaisalsoavailablethroughthefollowingwebsites:
SubstanceAbuseandMentalHealthServicesAdministration:samhsa.gov
DrugEnforcementAdministration:dea.gov
MonitoringtheFuture:monitoringthefuture.org/
PartnershipforDrug-FreeKids:drugfree.org/drug-guide
Thispublicationisavailableforyouruseandmaybereproducedinits
entiretywithoutpermissionfromtheNIDA.Citationofthesourceis
appreciated,usingthefollowinglanguage:Source:NationalInstituteon
DrugAbuse;NationalInstitutesofHealth;U.S.DepartmentofHealthand
HumanServices.
44
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