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NationalInstituteonDrugAbuse(NIDA)

Marijuana

LastUpdatedMay2018

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

Changesinmarijuanapoliciesacrossstateslegalizingmarijuanaformedicaland/orrecreationalusesuggestthatmarijuanaisgaininggreateracceptanceinoursociety.Thus,itisparticularlyimportantforpeopletounderstandwhatisknownaboutboththeadversehealtheffectsandthepotentialtherapeuticbenefitslinkedtomarijuana.

Becausemarijuanaimpairsshort-termmemoryandjudgmentanddistortsperception,itcanimpairperformanceinschooloratworkandmakeitdangeroustodrive.Italsoaffectsbrainsystemsthatarestillmaturingthroughyoungadulthood,soregularusebyteensmayhavenegativeandlong-lastingeffectsontheircognitivedevelopment,puttingthematacompetitivedisadvantageandpossiblyinterferingwiththeirwell-beinginotherways.Also,contrarytopopularbelief,marijuanacanbeaddictive,anditsuseduringadolescencemaymakeotherformsofproblemuseoraddictionmorelikely.

PhotobytheNIDA

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Whethersmokingorotherwiseconsumingmarijuanahastherapeuticbenefitsthatoutweighitshealthrisksisstillanopenquestionthatsciencehasnotresolved.Althoughmanystatesnowpermitdispensingmarijuanaformedicinalpurposesandthereismountinganecdotalevidencefortheefficacyofmarijuana-derivedcompounds,theU.S.FoodandDrugAdministrationhasnotapproved"medicalmarijuana."However,safemedicinesbasedoncannabinoidchemicalsderivedfromthemarijuanaplanthavebeenavailablefordecadesandmorearebeingdeveloped.

ThisResearchReportisintendedasausefulsummaryofwhatthemostup-to-datesciencehastosayaboutmarijuanaanditseffectsonthosewhouseitatanyage.

NoraD.Volkow,M.D.DirectorNationalInstituteonDrugAbuse

SeeAlso:

MessagefromtheNIDADirector-Marijuana’sLastingEffectsontheBrain,(March2013)

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Whatismarijuana?

Marijuana—alsocalledweed,herb,pot,grass,bud,ganja,MaryJane,andavastnumberofotherslangterms—isagreenish-graymixtureofthedriedflowersofCannabissativa.Somepeoplesmokemarijuanainhand-rolledcigarettescalledjoints;inpipes,waterpipes(sometimescalledbongs),orinblunts(marijuanarolledincigarwraps). Marijuanacanalsobeusedtobrewteaand,particularlywhenitissoldorconsumedformedicinalpurposes,isfrequentlymixedintofoods(edibles)suchasbrownies,cookies,orcandies.Vaporizersarealsoincreasinglyusedtoconsumemarijuana.Strongerformsofmarijuanaincludesinsemilla(fromspeciallytendedfemaleplants)andconcentratedresinscontaininghighdosesofmarijuana’sactiveingredients,includinghoneylikehashoil,waxybudder,andhardamberlikeshatter.Theseresinsareincreasinglypopularamongthosewhousethembothrecreationallyandmedically.

Themainpsychoactive(mind-altering)chemicalinmarijuana,responsiblefor

Imageby©iStock.com/nicoolay

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mostoftheintoxicatingeffectsthatpeopleseek,isdelta-9-tetrahydrocannabinol(THC).Thechemicalisfoundinresinproducedbytheleavesandbudsprimarilyofthefemalecannabisplant.Theplantalsocontainsmorethan500otherchemicals,includingmorethan100compoundsthatarechemicallyrelatedtoTHC,calledcannabinoids.2

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WhatisthescopeofmarijuanauseintheUnitedStates?

Marijuanaisthemostcommonlyusedillicitdrug(22.2millionpeoplehaveuseditinthepastmonth)accordingtothe2015NationalSurveyonDrugUseandHealth. Itsuseismoreprevalentamongmenthanwomen—agendergapthatwidenedintheyears2007to2014.

Marijuanauseiswidespreadamongadolescentsandyoungadults.AccordingtotheMonitoringtheFuturesurvey—anannualsurveyofdruguseandattitudesamongtheNation’smiddleandhighschoolstudents—mostmeasuresofmarijuanauseby8th,10th,and12thgraderspeakedinthemid-to-late1990sandthenbeganaperiodofgradualdeclinethroughthemid-2000sbeforelevellingoff.Mostmeasuresshowedsomedeclineagaininthepast5years.Teens’perceptionsoftherisksofmarijuanausehavesteadilydeclinedoverthepastdecade,possiblyrelatedtoincreasingpublicdebateaboutlegalizingorlooseningrestrictionsonmarijuanaformedicinalandrecreationaluse.In2016,9.4percentof8thgradersreportedmarijuanauseinthepastyearand5.4percentinthepastmonth(currentuse).Among10thgraders,23.9percenthadusedmarijuanainthepastyearand14.0percentinthepastmonth.Ratesofuseamong12thgraderswerehigherstill:35.6percenthadusedmarijuanaduringtheyearpriortothesurveyand22.5percentusedinthepastmonth;6.0percentsaidtheyusedmarijuanadailyornear-daily.

Medicalemergenciespossiblyrelatedtomarijuanausehavealsoincreased.TheDrugAbuseWarningNetwork(DAWN),asystemformonitoringthehealthimpactofdrugs,estimatedthatin2011,therewerenearly456,000drug-relatedemergencydepartmentvisitsintheUnitedStatesinwhichmarijuanausewasmentionedinthemedicalrecord(a21percentincreaseover2009).Abouttwo-thirdsofpatientsweremaleand13percentwerebetweentheagesof12and17. Itisunknownwhetherthisincreaseisduetoincreaseduse,increasedpotencyofmarijuana(amountofTHCitcontains),orotherfactors.Itshouldbenoted,however,thatmentionsofmarijuanainmedicalrecordsdonotnecessarilyindicatethattheseemergenciesweredirectlyrelatedtomarijuanaintoxication.

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Whataremarijuanaeffects?

Whenmarijuanaissmoked,THCandotherchemicalsintheplantpassfromthelungsintothebloodstream,whichrapidlycarriesthemthroughoutthebodytothebrain.Thepersonbeginstoexperienceeffectsalmostimmediately(see"Howdoesmarijuanaproduceitseffects?").Manypeopleexperienceapleasanteuphoriaandsenseofrelaxation.Othercommoneffects,whichmayvarydramaticallyamongdifferentpeople,includeheightenedsensoryperception(e.g.,brightercolors),laughter,alteredperceptionoftime,andincreasedappetite.

Ifmarijuanaisconsumedinfoodsorbeverages,theseeffectsaresomewhatdelayed—usuallyappearingafter30minutesto1hour—becausethedrugmustfirstpassthroughthedigestivesystem.EatingordrinkingmarijuanadeliverssignificantlylessTHCintothebloodstreamthansmokinganequivalentamountoftheplant.Becauseofthedelayedeffects,peoplemayinadvertentlyconsumemoreTHCthantheyintendto.

Pleasantexperienceswithmarijuanaarebynomeansuniversal.Insteadofrelaxationandeuphoria,somepeopleexperienceanxiety,fear,distrust,orpanic.Theseeffectsaremorecommonwhenapersontakestoomuch,themarijuanahasanunexpectedlyhighpotency,orthepersonisinexperienced.Peoplewhohavetakenlargedosesofmarijuanamayexperienceanacutepsychosis,whichincludeshallucinations,delusions,andalossofthesenseofpersonalidentity.Theseunpleasantbuttemporaryreactionsaredistinctfromlonger-lastingpsychoticdisorders,suchasschizophrenia,thatmaybeassociatedwiththeuseofmarijuanainvulnerableindividuals.(See"Istherealinkbetweenmarijuanauseandpsychiatricdisorders?")

AlthoughdetectableamountsofTHCmayremaininthebodyfordaysorevenweeksafteruse,thenoticeableeffectsofsmokedmarijuanagenerallylastfrom1to3hours,andthoseofmarijuanaconsumedinfoodordrinkmaylastformanyhours.

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Howdoesmarijuanaproduceitseffects?

THC’schemicalstructureissimilartothebrainchemicalanandamide.SimilarityinstructureallowsthebodytorecognizeTHCandtoalternormalbraincommunication.

Endogenouscannabinoidssuchasanandamide(seefigure)functionasneurotransmittersbecausetheysendchemicalmessagesbetweennervecells(neurons)throughoutthenervoussystem.Theyaffectbrainareasthatinfluencepleasure,memory,thinking,concentration,movement,coordination,andsensoryandtimeperception.Becauseofthissimilarity,THCisabletoattachtomoleculescalledcannabinoidreceptorsonneuronsinthesebrainareasandactivatethem,disruptingvariousmentalandphysicalfunctionsandcausingtheeffectsdescribedearlier.Theneuralcommunicationnetworkthatusesthesecannabinoidneurotransmitters,knownastheendocannabinoidsystem,playsa

ImagebytheNIDA

THC’schemicalstructureissimilartothebrainchemicalanandamide.Similarityinstructureallowsdrugstoberecognizedbythebodyandtoalternormalbraincommunication.

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criticalroleinthenervoussystem’snormalfunctioning,sointerferingwithitcanhaveprofoundeffects.

Forexample,THCisabletoalterthefunctioningofthehippocampus(see"Marijuana,Memory,andtheHippocampus")andorbitofrontalcortex,brainareasthatenableapersontoformnewmemoriesandshifthisorherattentionalfocus.Asaresult,usingmarijuanacausesimpairedthinkingandinterfereswithaperson’sabilitytolearnandperformcomplicatedtasks.THCalsodisruptsfunctioningofthecerebellumandbasalganglia,brainareasthatregulatebalance,posture,coordination,andreactiontime.Thisisthereasonpeoplewhohaveusedmarijuanamaynotbeabletodrivesafely(see"Doesmarijuanauseaffectdriving?")andmayhaveproblemsplayingsportsorengaginginotherphysicalactivities.

Peoplewhohavetakenlargedosesofthedrugmayexperienceanacutepsychosis,whichincludeshallucinations,delusions,andalossofthesenseofpersonalidentity.

THC,actingthroughcannabinoidreceptors,alsoactivatesthebrain’srewardsystem,whichincludesregionsthatgoverntheresponsetohealthypleasurablebehaviorssuchassexandeating.Likemostotherdrugsthatpeoplemisuse,THCstimulatesneuronsintherewardsystemtoreleasethesignalingchemicaldopamineatlevelshigherthantypicallyobservedinresponsetonaturalstimuli.Thisfloodofdopaminecontributestothepleasurable"high"thatthoseusewhorecreationalmarijuanaseek.

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Diagramshowingdifferentpartsofthebrainanddescribingmarijuana'seffectsonthebrain

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Doesmarijuanauseaffectdriving?

Marijuanasignificantlyimpairsjudgment,motorcoordination,andreactiontime,andstudieshavefoundadirectrelationshipbetweenbloodTHCconcentrationandimpaireddrivingability.

Marijuanaistheillicitdrugmostfrequentlyfoundinthebloodofdriverswhohavebeeninvolvedinvehiclecrashes,includingfatalones. TwolargeEuropeanstudiesfoundthatdriverswithTHCintheirbloodwereroughlytwiceaslikelytobeculpableforafatalcrashthandriverswhohadnotuseddrugsoralcohol. However,theroleplayedbymarijuanaincrashesisoftenunclearbecauseitcanbedetectedinbodyfluidsfordaysorevenweeksafterintoxicationandbecausepeoplefrequentlycombineitwithalcohol.ThoseinvolvedinvehiclecrasheswithTHCintheirblood,particularlyhigherlevels,arethreetoseventimesmorelikelytoberesponsiblefortheincidentthandriverswhohadnotuseddrugsoralcohol.Theriskassociatedwithmarijuanaincombinationwithalcoholappearstobegreaterthanthatforeitherdrugbyitself.

Photoby©iStock.com/MadCircles

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Severalmeta-analysesofmultiplestudiesfoundthattheriskofbeinginvolvedinacrashsignificantlyincreasedaftermarijuanause —inafewcases,theriskdoubledormorethandoubled. However,alargecase-controlstudyconductedbytheNationalHighwayTrafficSafetyAdministrationfoundnosignificantincreasedcrashriskattributabletocannabisaftercontrollingfordrivers’age,gender,race,andpresenceofalcohol.

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Ismarijuanaaddictive?

Marijuanausecanleadtothedevelopmentofproblemuse,knownasamarijuanausedisorder,whichtakestheformofaddictioninseverecases.Recentdatasuggestthat30percentofthosewhousemarijuanamayhavesomedegreeofmarijuanausedisorder. Peoplewhobeginusingmarijuanabeforetheageof18arefourtoseventimesmorelikelytodevelopamarijuanausedisorderthanadults.

Marijuanausedisordersareoftenassociatedwithdependence—inwhichapersonfeelswithdrawalsymptomswhennottakingthedrug.Peoplewhousemarijuanafrequentlyoftenreportirritability,moodandsleepdifficulties,decreasedappetite,cravings,restlessness,and/orvariousformsofphysicaldiscomfortthatpeakwithinthefirstweekafterquittingandlastupto2weeks. Marijuanadependenceoccurswhenthebrainadaptstolargeamountsofthedrugbyreducingproductionofandsensitivitytoitsownendocannabinoidneurotransmitters.

Marijuanausedisorderbecomesaddictionwhenthepersoncannotstopusingthedrugeventhoughitinterfereswithmanyaspectsofhisorherlife.Estimatesofthenumberofpeopleaddictedtomarijuanaarecontroversial,inpartbecauseepidemiologicalstudiesofsubstanceuseoftenusedependenceasaproxyforaddictioneventhoughitispossibletobedependentwithoutbeingaddicted.Thosestudiessuggestthat9percentofpeoplewhousemarijuanawillbecomedependentonit, risingtoabout17percentinthosewhostartusingintheirteens.

In2015,about4.0millionpeopleintheUnitedStatesmetthediagnosticcriteriaforamarijuanausedisorder; 138,000voluntarilysoughttreatmentfortheirmarijuanause.

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RisingPotency

Marijuanapotency,asdetectedinconfiscatedsamples,hassteadilyincreasedoverthepastfewdecades. Intheearly1990s,theaverageTHCcontentinconfiscatedmarijuanasampleswasroughly3.8percent.In2014,itwas12.2percent.Theaveragemarijuanaextractcontainsmorethan50percentTHC,withsomesamplesexceeding80percent.Thesetrendsraiseconcernsthattheconsequencesofmarijuanausecouldbeworsethaninthepast,particularlyamongthosewhoarenewtomarijuanauseorinyoungpeople,whosebrainsarestilldeveloping(see"Whataremarijuana’slong-termeffectsonthebrain?").

Researchersdonotyetknowthefullextentoftheconsequenceswhenthebodyandbrain(especiallythedevelopingbrain)areexposedtohighconcentrationsofTHCorwhethertherecentincreasesinemergencydepartmentvisitsbypeopletestingpositiveformarijuanaarerelatedtorisingpotency.Theextenttowhichpeopleadjustforincreasedpotencybyusinglessorbysmokingitdifferentlyisalsounknown.Recentstudiessuggestthatexperiencedpeoplemayadjusttheamounttheysmokeandhowmuchtheyinhalebasedonthebelievedstrengthofthemarijuanatheyareusing,buttheyarenotabletofullycompensateforvariationsinpotency.

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Whataremarijuana'slong-termeffectsonthebrain?

Substantialevidencefromanimalresearchandagrowingnumberofstudiesinhumansindicatethatmarijuanaexposureduringdevelopmentcancauselong-termorpossiblypermanentadversechangesinthebrain.RatsexposedtoTHCbeforebirth,soonafterbirth,orduringadolescenceshownotableproblemswithspecificlearningandmemorytaskslaterinlife. CognitiveimpairmentsinadultratsexposedtoTHCduringadolescenceareassociatedwithstructuralandfunctionalchangesinthehippocampus. StudiesinratsalsoshowthatadolescentexposuretoTHCisassociatedwithanalteredrewardsystem,increasingthelikelihoodthatananimalwillself-administerotherdrugs(e.g.,heroin)whengivenanopportunity(see"Ismarijuanaagatewaydrug?").

Imagingstudiesofmarijuana’simpactonbrainstructureinhumanshaveshownconflictingresults.Somestudiessuggestregularmarijuanauseinadolescenceisassociatedwithalteredconnectivityandreducedvolumeofspecificbrainregionsinvolvedinabroadrangeofexecutivefunctionssuchasmemory,learning,andimpulsecontrolcomparedtopeoplewhodonotuse. Otherstudieshavenotfoundsignificantstructuraldifferencesbetweenthebrainsofpeoplewhodoanddonotusethedrug.

Severalstudies,includingtwolargelongitudinalstudies,suggestthatmarijuanausecancausefunctionalimpairmentincognitiveabilitiesbutthatthedegreeand/ordurationoftheimpairmentdependsontheagewhenapersonbeganusingandhowmuchandhowlongheorsheused.

Amongnearly4,000youngadultsintheCoronaryArteryRiskDevelopmentinYoungAdultsstudytrackedovera25-yearperioduntilmid-adulthood,cumulativelifetimeexposuretomarijuanawasassociatedwithlowerscoresonatestofverbalmemorybutdidnotaffectothercognitiveabilitiessuchasprocessingspeedorexecutivefunction.Theeffectwassizeableandsignificantevenaftereliminatingthoseinvolvedwithcurrentuseandafteradjustingforconfoundingfactorssuchasdemographicfactors,otherdrugandalcoholuse,andotherpsychiatricconditionssuchasdepression.

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AlargelongitudinalstudyinNewZealandfoundthatpersistentmarijuanausedisorderwithfrequentusestartinginadolescencewasassociatedwithalossofanaverageof6orupto8IQpointsmeasuredinmid-adulthood. Significantly,inthatstudy,thosewhousedmarijuanaheavilyasteenagersandquitusingasadultsdidnotrecoverthelostIQpoints.PeoplewhoonlybeganusingmarijuanaheavilyinadulthooddidnotloseIQpoints.Theseresultssuggestthatmarijuanahasitsstrongestlong-termimpactonyoungpeoplewhosebrainsarestillbusybuildingnewconnectionsandmaturinginotherways.Theendocannabinoidsystemisknowntoplayanimportantroleintheproperformationofsynapses(theconnectionsbetweenneurons)duringearlybraindevelopment,andasimilarrolehasbeenproposedfortherefinementofneuralconnectionsduringadolescence.Ifthelong-termeffectsofmarijuanauseoncognitivefunctioningorIQareupheldbyfutureresearch,thismaybeoneavenuebywhichmarijuanauseduringadolescenceproducesitslong-termeffects.

However,recentresultsfromtwoprospectivelongitudinaltwinstudiesdidnotsupportacausalrelationshipbetweenmarijuanauseandIQloss.Thosewhousedmarijuanadidshowasignificantdeclineinverbalability(equivalentto4IQpoints)andingeneralknowledgebetweenthepreteenyears(ages9to12,beforeuse)andlateadolescence/earlyadulthood(ages17to20).However,atthestartofthestudy,thosewhowoulduseinthefuturealreadyhadlowerscoresonthesemeasuresthanthosewhowouldnotuseinthefuture,andnopredictabledifferencewasfoundbetweentwinswhenoneusedmarijuanaandonedidnot.ThissuggeststhatobservedIQdeclines,atleastacrossadolescence,maybecausedbysharedfamilialfactors(e.g.,genetics,familyenvironment),notbymarijuanauseitself. Itshouldbenoted,though,thatthesestudieswereshorterindurationthantheNewZealandstudyanddidnotexploretheimpactofthedoseofmarijuana(i.e.,heavyuse)orthedevelopmentofacannabisusedisorder;thismayhavemaskedadose-ordiagnosis-dependenteffect.

Theabilitytodrawdefinitiveconclusionsaboutmarijuana’slong-termimpactonthehumanbrainfrompaststudiesisoftenlimitedbythefactthatstudyparticipantsusemultiplesubstances,andthereisoftenlimiteddataabouttheparticipants’healthormentalfunctioningpriortothestudy.Overthenextdecade,theNationalInstitutesofHealthisfundingtheAdolescentBrain

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CognitiveDevelopment(ABCD)study—amajorlongitudinalstudythatwilltrackalargesampleofyoungAmericansfromlatechildhood(beforefirstuseofdrugs)toearlyadulthood.Thestudywilluseneuroimagingandotheradvancedtoolstoclarifypreciselyhowandtowhatextentmarijuanaandothersubstances,aloneandincombination,affectadolescentbraindevelopment.

Marijuana,Memory,andtheHippocampus

Distributionofcannabinoidreceptorsintheratbrain.Brainimagerevealshighlevels(showninorangeandyellow)ofcannabinoidreceptorsinmanyareas,includingthecortex,hippocampus,cerebellum,andnucleusaccumbens(ventralstriatum).

MemoryimpairmentfrommarijuanauseoccursbecauseTHCaltershowthehippocampus,abrainarearesponsibleformemoryformation,processesinformation.Mostoftheevidencesupportingthisassertioncomesfromanimalstudies.Forexample,ratsexposedtoTHCinutero,soonafterbirth,orduringadolescence,shownotableproblemswithspecificlearning/memorytaskslaterinlife.Moreover,cognitiveimpairmentinadultratsisassociatedwithstructuralandfunctionalchangesinthehippocampusfromTHCexposureduringadolescence.

ImagebytheNIDA

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Aspeopleage,theyloseneuronsinthehippocampus,whichdecreasestheirabilitytolearnnewinformation.ChronicTHCexposuremayhastenage-relatedlossofhippocampalneurons.Inonestudy,ratsexposedtoTHCeverydayfor8months(approximately30percentoftheirlifespan)showedalevelofnervecelllossat11to12monthsofagethatequaledthatofunexposedanimalstwicetheirage.

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Ismarijuanaagatewaydrug?

Someresearchsuggeststhatmarijuanauseislikelytoprecedeuseofotherlicitandillicitsubstances andthedevelopmentofaddictiontoothersubstances.Forinstance,astudyusinglongitudinaldatafromtheNationalEpidemiologicalStudyofAlcoholUseandRelatedDisordersfoundthatadultswhoreportedmarijuanauseduringthefirstwaveofthesurveyweremorelikelythanadultswhodidnotusemarijuanatodevelopanalcoholusedisorderwithin3years;peoplewhousedmarijuanaandalreadyhadanalcoholusedisorderattheoutsetwereatgreaterriskoftheiralcoholusedisorderworsening. Marijuanauseisalsolinkedtoothersubstanceusedisordersincludingnicotineaddiction.

Earlyexposuretocannabinoidsinadolescentrodentsdecreasesthereactivityofbraindopaminerewardcenterslaterinadulthood. Totheextentthatthesefindingsgeneralizetohumans,thiscouldhelpexplaintheincreasedvulnerabilityforaddictiontoothersubstancesofmisuselaterinlifethatmostepidemiologicalstudieshavereportedforpeoplewhobeginmarijuanauseearlyinlife. ItisalsoconsistentwithanimalexperimentsshowingTHC’sabilityto"prime"thebrainforenhancedresponsestootherdrugs. Forexample,ratspreviouslyadministeredTHCshowheightenedbehavioralresponsenotonlywhenfurtherexposedtoTHCbutalsowhenexposedtootherdrugssuchasmorphine—aphenomenoncalledcross-sensitization.

Thesefindingsareconsistentwiththeideaofmarijuanaasa"gatewaydrug."However,themajorityofpeoplewhousemarijuanadonotgoontouseother,"harder"substances.Also,cross-sensitizationisnotuniquetomarijuana.Alcoholandnicotinealsoprimethebrainforaheightenedresponsetootherdrugs andare,likemarijuana,alsotypicallyusedbeforeapersonprogressestoother,moreharmfulsubstances.

Itisimportanttonotethatotherfactorsbesidesbiologicalmechanisms,suchasaperson’ssocialenvironment,arealsocriticalinaperson’sriskfordruguse.Analternativetothegateway-drughypothesisisthatpeoplewhoaremorevulnerabletodrug-takingaresimplymorelikelytostartwithreadilyavailablesubstancessuchasmarijuana,tobacco,oralcohol,andtheirsubsequentsocial

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interactionswithotherswhousedrugsincreasestheirchancesoftryingotherdrugs.Furtherresearchisneededtoexplorethisquestion.

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Howdoesmarijuanauseaffectschool,work,andsociallife?

Researchhasshownthatmarijuana’snegativeeffectsonattention,memory,andlearningcanlastfordaysorweeksaftertheacuteeffectsofthedrugwearoff,dependingontheperson’shistorywiththedrug. Consequently,someonewhosmokesmarijuanadailymaybefunctioningatareducedintellectuallevelmostorallofthetime.Considerableevidencesuggeststhatstudentswhosmokemarijuanahavepoorereducationaloutcomesthantheirnonsmokingpeers.Forexample,areviewof48relevantstudiesfoundmarijuanausetobeassociatedwithreducededucationalattainment(i.e.,reducedchancesofgraduating). ArecentanalysisusingdatafromthreelargestudiesinAustraliaandNewZealandfoundthatadolescentswhousedmarijuanaregularlyweresignificantlylesslikelythantheirnon-usingpeerstofinishhighschoolorobtainadegree.Theyalsohadamuchhigherchanceofdevelopingdependence,usingotherdrugs,andattemptingsuicide. Severalstudieshavealsolinkedheavymarijuanausetolowerincome,greaterwelfaredependence,unemployment,criminalbehavior,andlowerlifesatisfaction.

Imageby©iStock.com/AntonioGuillem

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Towhatdegreemarijuanauseisdirectlycausalintheseassociationsremainsanopenquestionrequiringfurtherresearch.Itispossiblethatotherfactorsindependentlypredisposepeopletobothmarijuanauseandvariousnegativelifeoutcomessuchasschooldropout. Thatsaid,peoplereportaperceivedinfluenceoftheirmarijuanauseonpooroutcomesonavarietyoflifesatisfactionandachievementmeasures.Onestudy,forexample,comparedpeopleinvolvedwithcurrentandformerlong-term,heavyuseofmarijuanawithacontrolgroupwhoreportedsmokingmarijuanaatleastonceintheirlivesbutnotmorethan50times. Allparticipantshadsimilareducationandincomebackgrounds,butsignificantdifferenceswerefoundintheireducationalattainment:Fewerofthosewhoengagedinheavycannabisusecompletedcollege,andmorehadyearlyhouseholdincomesoflessthan$30,000.Whenaskedhowmarijuanaaffectedtheircognitiveabilities,careerachievements,sociallives,andphysicalandmentalhealth,themajorityofthosewhousedheavilyreportedthatmarijuanahadnegativeeffectsinalltheseareasoftheirlives.

Studieshavealsosuggestedspecificlinksbetweenmarijuanauseandadverseconsequencesintheworkplace,suchasincreasedriskforinjuryoraccidents. Onestudyamongpostalworkersfoundthatemployeeswhotestedpositiveformarijuanaonapre-employmenturinedrugtesthad55percentmoreindustrialaccidents,85percentmoreinjuries,and75percentgreaterabsenteeismcomparedwiththosewhotestednegativeformarijuanause.

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Istherealinkbetweenmarijuanauseandpsychiatricdisorders?

Severalstudieshavelinkedmarijuanausetoincreasedriskforpsychiatricdisorders,includingpsychosis(schizophrenia),depression,anxiety,andsubstanceusedisorders,butwhetherandtowhatextentitactuallycausestheseconditionsisnotalwayseasytodetermine. Theamountofdrugused,theageatfirstuse,andgeneticvulnerabilityhaveallbeenshowntoinfluencethisrelationship.Thestrongestevidencetodateconcernslinksbetweenmarijuanauseandsubstanceusedisordersandbetweenmarijuanauseandpsychiatricdisordersinthosewithapreexistinggeneticorothervulnerability.

ResearchusinglongitudinaldatafromtheNationalEpidemiologicalSurveyonAlcoholandRelatedConditionsexaminedassociationsbetweenmarijuanause,moodandanxietydisorders,andsubstanceusedisorders.Afteradjustingforvariousconfoundingfactors,noassociationbetweenmarijuanauseandmoodandanxietydisorderswasfound.Theonlysignificantassociationswereincreasedriskofalcoholusedisorders,nicotinedependence,marijuanausedisorder,andotherdrugusedisorders.

Recentresearch(see"AKT1GeneVariationsandPsychosis")hasfoundthatpeoplewhousemarijuanaandcarryaspecificvariantoftheAKT1gene,whichcodesforanenzymethataffectsdopaminesignalinginthestriatum,areatincreasedriskofdevelopingpsychosis.Thestriatumisanareaofthebrainthatbecomesactivatedandfloodedwithdopaminewhencertainstimuliarepresent.Onestudyfoundthattheriskofpsychosisamongthosewiththisvariantwasseventimeshigherforthosewhousedmarijuanadailycomparedwiththosewhouseditinfrequentlyorusednoneatall.

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Anotherstudyfoundanincreasedriskofpsychosisamongadultswhohadusedmarijuanainadolescenceandalsocarriedaspecificvariantofthegeneforcatechol-O-methyltransferase(COMT),anenzymethatdegradesneurotransmitterssuchasdopamineandnorepinephrine (see"GeneticVariationsinCOMTInfluencestheHarmfulEffectsofAbusedDrugs").Marijuanausehasalsobeenshowntoworsenthecourseofillnessinpatientswhoalreadyhaveschizophrenia.Asmentionedpreviously,marijuanacanproduceanacutepsychoticreactioninnon-schizophrenicpeoplewhousemarijuana,especiallyathighdoses,althoughthisfadesasthedrugwearsoff.

Whetheradolescentmarijuanausecancontributetodevelopingpsychosislaterinadulthoodappearstodependonwhetherapersonalreadyhasageneticallybasedvulnerabilitytothedisorder.TheAKT1genegovernsanenzymethataffectsbrainsignalinginvolvingtheneurotransmitterdopamine.Altereddopaminesignalingisknowntobeinvolvedinschizophrenia.AKT1cantakeoneofthreeformsinaspecificregionofthegeneimplicatedinsusceptibilitytoschizophrenia:T/T,C/T,andC/C.Thosewhousemarijuanadaily(greenbars)withtheC/Cvarianthaveaseventimeshigherriskofdevelopingpsychosisthanthosewhouseitinfrequentlyorusenoneatall.TheriskforpsychosisamongthosewiththeT/Tvariantwasunaffectedbywhethertheyusedmarijuana.

Source:DiFortietal.BiolPsychiatry.2012.

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Inconsistentandmodestassociationshavebeenreportedbetweenmarijuanauseandsuicidalthoughtsandattemptedsuicideamongteens. Marijuanahasalsobeenassociatedwithanamotivationalsyndrome,definedasadiminishedorabsentdrivetoengageintypicallyrewardingactivities.Becauseoftheroleoftheendocannabinoidsysteminregulatingmoodandreward,ithasbeenhypothesizedthatbrainchangesresultingfromearlyuseofmarijuanamayunderlietheseassociations,butmoreresearchisneededtoverifythatsuchlinksexistandbetterunderstandthem.

Theinfluenceofadolescentmarijuanauseonadultpsychosisisaffectedbygeneticvariables.Thisfigureshowsthatvariationsinagenecanaffectthelikelihoodofdevelopingpsychosisinadulthoodfollowingexposuretocannabisinadolescence.TheCOMTgenegovernsanenzymethatbreaksdowndopamine,abrainchemicalinvolvedinschizophrenia.Itcomesintwoforms:"Met"and"Val."IndividualswithoneortwocopiesoftheValvarianthaveahigherriskofdevelopingschizophrenic-typedisordersiftheyusedcannabisduringadolescence(darkbars).ThosewithonlytheMetvariantwereunaffectedbycannabisuse.

Source:Caspietal.BiolPsychiatry.2005.

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AdverseConsequencesofMarijuanaUse

Acute(presentduringintoxication)

Impairedshort-termmemory

Impairedattention,judgment,andothercognitivefunctions

Impairedcoordinationandbalance

Increasedheartrate

Anxiety,paranoia

Psychosis(uncommon)

Persistent(lastinglongerthanintoxication,butmaynotbepermanent)

Impairedlearningandcoordination

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Sleepproblems

Long-term(cumulativeeffectsofrepeateduse)

Potentialformarijuanaaddiction

ImpairmentsinlearningandmemorywithpotentiallossofIQ*

Increasedriskofchroniccough,bronchitis

Increasedriskofotherdrugandalcoholusedisorders

Increasedriskofschizophreniainpeoplewithgeneticvulnerability**

*LossofIQamongindividualswithpersistentmarijuanausedisorderwhobeganusingheavilyduringadolescence

**Theseareoftenreportedco-occurringsymptoms/disorderswithchronicmarijuanause.However,researchhasnotyetdeterminedwhethermarijuanaiscausalorjustassociatedwiththesementalproblems.

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Whataremarijuana'seffectsonlunghealth?

Liketobaccosmoke,marijuanasmokeisanirritanttothethroatandlungsandcancauseaheavycoughduringuse.Italsocontainslevelsofvolatilechemicalsandtarthataresimilartotobaccosmoke,raisingconcernsaboutriskforcancerandlungdisease.

Marijuanasmokingisassociatedwithlargeairwayinflammation,increasedairwayresistance,andlunghyperinflation,andthosewhosmokemarijuanaregularlyreportmoresymptomsofchronicbronchitisthanthosewhodonotsmoke. Onestudyfoundthatpeoplewhofrequentlysmokemarijuanahadmoreoutpatientmedicalvisitsforrespiratoryproblemsthanthosewhodonotsmoke. Somecasestudieshavesuggestedthat,becauseofTHC’simmune-suppressingeffects,smokingmarijuanamightincreasesusceptibilitytolunginfections,suchaspneumonia,inpeoplewithimmunedeficiencies;however,alargeAIDScohortstudydidnotconfirmsuchanassociation. Smokingmarijuanamayalsoreducetherespiratorysystem’simmuneresponse,increasingthelikelihoodofthepersonacquiringrespiratoryinfections,includingpneumonia. Animalandhumanstudieshavenotfoundthatmarijuanaincreasesriskforemphysema.

Whethersmokingmarijuanacauseslungcancer,ascigarettesmokingdoes,remainsanopenquestion. Marijuanasmokecontainscarcinogeniccombustionproducts,includingabout50percentmorebenzopreneand75percentmorebenzanthracene(andmorephenols,vinylchlorides,nitrosamines,reactiveoxygenspecies)thancigarettesmoke. Becauseofhowitistypicallysmoked(deeperinhale,heldforlonger),marijuanasmokingleadstofourtimesthedepositionoftarcomparedtocigarettesmoking. However,whileafewsmall,uncontrolledstudieshavesuggestedthatheavy,regularmarijuanasmokingcouldincreaseriskforrespiratorycancers,well-designedpopulationstudieshavefailedtofindanincreasedriskoflungcancerassociatedwithmarijuanause.

Onecomplexityincomparingthelung-healthrisksofmarijuanaandtobacco

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concernstheverydifferentwaysthetwosubstancesareused.Whilepeoplewhosmokemarijuanaofteninhalemoredeeplyandholdthesmokeintheirlungsforalongerdurationthanistypicalwithcigarettes,marijuana’seffectslastlonger,sopeoplewhousemarijuanamaysmokelessfrequentlythanthosewhosmokecigarettes.

Additionally,thefactthatmanypeopleusebothmarijuanaandtobaccomakesdeterminingmarijuana’sprecisecontributiontolungcancerrisk,ifany,difficulttoestablish.CellcultureandanimalstudieshavealsosuggestedTHCandCBDmayhaveantitumoreffects,andthishasbeenproposedasonereasonwhystrongerexpectedassociationsarenotseenbetweenmarijuanauseandlungcancer,butmoreresearchisneededonthisquestion.68

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Whataremarijuana’seffectsonotheraspectsofphysicalhealth?

Withinafewminutesafterinhalingmarijuanasmoke,aperson’sheartratespeedsup,thebreathingpassagesrelaxandbecomeenlarged,andbloodvesselsintheeyesexpand,makingtheeyeslookbloodshot.Theheartrate—normally70to80beatsperminute—mayincreaseby20to50beatsperminuteormayevendoubleinsomecases.Takingotherdrugswithmarijuanacanamplifythiseffect.

Limitedevidencesuggeststhataperson’sriskofheartattackduringthefirsthouraftersmokingmarijuanaisnearlyfivetimeshisorherusualrisk. Thisobservationcouldbepartlyexplainedbymarijuanaraisingbloodpressure(insomecases)andheartrateandreducingtheblood’scapacitytocarryoxygen. Marijuanamayalsocauseorthostatichypotension(headrushordizzinessonstandingup),possiblyraisingdangerfromfaintingandfalls.Tolerancetosomecardiovasculareffectsoftendevelopswithrepeatedexposure. Thesehealtheffectsneedtobeexaminedmoreclosely,particularlygiventheincreasinguseof"medicalmarijuana"bypeoplewithhealthissuesandolderadultswhomayhaveincreasedbaselinevulnerabilityduetoage-relatedcardiovascularriskfactors(see"Ismarijuanasafeandeffectiveasmedicine?").

Afewstudieshaveshownaclearlinkbetweenmarijuanauseinadolescenceandincreasedriskforanaggressiveformoftesticularcancer(nonseminomatoustesticulargermcelltumor)thatpredominantlystrikesyoungadultmales. Theearlyonsetoftesticularcancerscomparedtolungandmostothercancersindicatesthat,whateverthenatureofmarijuana’scontribution,itmayaccumulateoverjustafewyearsofuse.

Studieshaveshownthatinrarecases,chronicuseofmarijuanacanleadtoCannabinoidHyperemesisSyndrome—aconditionmarkedbyrecurrentboutsofseverenausea,vomiting,anddehydration.Thissyndromehasbeenfoundtooccurinpersonsunder50yearsofageandwithalonghistoryofmarijuanause.CannabinoidHyperemesisSyndromecanleadsuffererstomakefrequent

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tripstotheemergencyroom,butmayberesolvedwhenapersonstopsusingmarijuana.78

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Ismarijuanasafeandeffectiveasmedicine?

Thepotentialmedicinalpropertiesofmarijuanaanditscomponentshavebeenthesubjectofresearchandheateddebatefordecades.THCitselfhasprovenmedicalbenefitsinparticularformulations.TheU.S.FoodandDrugAdministrationhasapprovedTHC-basedmedications,dronabinol(Marinol )andnabilone(Cesamet ),prescribedinpillformforthetreatmentofnauseainpatientsundergoingcancerchemotherapyandtostimulateappetiteinpatientswithwastingsyndromeduetoAIDS.

Inaddition,severalothermarijuana-basedmedicationshavebeenapprovedorareundergoingclinicaltrials.Nabiximols(Sativex ),amouthspraythatiscurrentlyavailableintheUnitedKingdom,Canada,andseveralEuropeancountriesfortreatingthespasticityandneuropathicpainthatmayaccompanymultiplesclerosis,combinesTHCwithanotherchemicalfoundinmarijuanacalledcannabidiol(CBD).CBDdoesnothavetherewardingpropertiesofTHC,andanecdotalreportsindicateitmayhavepromiseforthetreatmentofseizuredisorders,amongotherconditions.ACBD-basedliquidmedicationcalledEpidiolexiscurrentlybeingtestedintheUnitedStatesforthetreatmentoftwoformsofseverechildhoodepilepsy,DravetsyndromeandLennox-Gastautsyndrome.

Researchersgenerallyconsidermedicationslikethese,whichusepurifiedchemicalsderivedfromorbasedonthoseinthemarijuanaplant,tobemorepromisingtherapeuticallythanuseofthewholemarijuanaplantoritscrudeextracts.Developmentofdrugsfrombotanicalssuchasthemarijuanaplantposesnumerouschallenges.Botanicalsmaycontainhundredsofunknown,activechemicals,anditcanbedifficulttodevelopaproductwithaccurateandconsistentdosesofthesechemicals.UseofmarijuanaasmedicinealsoposesotherproblemssuchastheadversehealtheffectsofsmokingandTHC-inducedcognitiveimpairment.Nevertheless,agrowingnumberofstateshavelegalizeddispensingofmarijuanaoritsextractstopeoplewitharangeofmedicalconditions.

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Anadditionalconcernwith"medicalmarijuana"isthatlittleisknownaboutthelong-termimpactofitsusebypeoplewithhealth-and/orage-relatedvulnerabilities—suchasolderadultsorpeoplewithcancer,AIDS,cardiovasculardisease,multiplesclerosis,orotherneurodegenerativediseases.Furtherresearchwillbeneededtodeterminewhetherpeoplewhosehealthhasbeencompromisedbydiseaseoritstreatment(e.g.,chemotherapy)areatgreaterriskforadversehealthoutcomesfrommarijuanause.

MedicalMarijuanaLegalizationandPrescriptionOpioidUseOutcomes

TworecentstudiesinJAMAInternalMedicinereportanassociationbetweennotonlymedicalmarijuanalaws(MML)butalsoprotectedaccesstodispensariesandtheirassociationwithopioidprescriptionpatternsbasedonMedicaidorMedicarePartDprescriptiondata.ThefirststudyfoundthatMedicarePartDprescriptionsfilledforallopioidsdecreasedinstateswithMMLby2.11milliondailydosesperyearperstate.Instateswithmedicalcannabisdispensaries,prescriptionsdecreasedby3.742milliondailydosesperyearperstate. Similarly,thesecondstudyexaminedMedicaidprescriptiondataandfoundthatMMLsandadult-usemarijuanalawswereassociatedwithloweropioidprescribingrates(5.88%and6.38%lower,respectively).

Additionally,NIDAfundedtwostudiesthatexploredtherelationshipbetweenmarijuanalegalizationandadverseoutcomesassociatedwithprescriptionopioids.Thefirststudyfoundanassociationbetweenmedicalmarijuanalegalizationandareductioninoverdosedeathsfromopioidpainrelievers;aneffectthatstrengthenedineachyearfollowingtheimplementationoflegislation. ThesecondNIDA-fundedstudywasamoredetailedanalysisbytheRANDCorporationthatshowedlegallyprotectedaccesstomedicalmarijuanadispensariesisassociatedwithlowerlevelsofopioidprescribing,lowerself-reportofnonmedicalprescriptionopioiduse,lowertreatmentadmissionsforprescriptionopioidusedisorders,andreductioninprescriptionopioidoverdosedeaths.Notably,thereductionindeathswaspresentonlyinstateswithdispensaries(notjustmedicalmarijuanalaws)andwasgreaterinstateswithactivedispensaries.Itshouldbenotedthatthepopulation-based

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natureofthesestudies,andthetwoabove,donotestablishacausalrelationshiporgiveevidenceforchangesinindividualpainpatientbehaviorandcautionshouldbeusedwheninterpretingtheirresults.

Todate,researchintotheeffectsofcannabisonopioiduseinpainpatientsismixed.Somedatasuggestthatmedicalcannabistreatmentmayreducethedoseofopioidsrequiredforpainrelief, whileanotherNIH-fundedstudyfoundthatcannabisuseappearstoincreasetheriskofdevelopingnonmedicalprescriptionopioiduseandopioidusedisorder. Thoughnosinglestudyisdefinitive,theycumulativelysuggestthatmedicalmarijuanaproductsmayplayaroleinreducingtheuseofopioidsneededtocontrolpainbutthattheseproductsdon’tcomewithoutrisk.Moreresearchisneededtoinvestigatethepotentialtherapeuticroleofmarijuanaincludingitsroleasatreatmentoptionforopioidusedisorderanditsabilitytoreducespecifictypesofpain

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Whataretheeffectsofsecondhandexposuretomarijuanasmoke?

Peopleoftenaskaboutthepossiblepsychoactiveeffectofexposuretosecondhandmarijuanasmokeandwhetherapersonwhohasinhaledsecondhandmarijuanasmokecouldfailadrugtest.ResearchersmeasuredtheamountofTHCinthebloodofpeoplewhodonotsmokemarijuanaandhadspent3hoursinawell-ventilatedspacewithpeoplecasuallysmokingmarijuana;THCwaspresentinthebloodofthenonsmokingparticipants,buttheamountwaswellbelowthelevelneededtofailadrugtest.Anotherstudythatvariedthelevelsofventilationandthepotencyofthemarijuanafoundthatsomenonsmokingparticipantsexposedforanhourtohigh-THCmarijuana(11.3percentTHCconcentration)inanunventilatedroomshowedpositiveurineassaysinthehoursdirectlyfollowingexposure ;afollow-upstudyshowedthatnonsmokingpeopleinaconfinedspacewithpeoplesmokinghigh-THCmarijuanareportedmildsubjectiveeffectsofthedrug—a"contacthigh"—anddisplayedmildimpairmentsonperformanceinmotortasks.

Theknownhealthrisksofsecondhandexposuretocigarettesmoke—totheheartorlungs,forinstance—raisequestionsaboutwhethersecondhandexposuretomarijuanasmokeposessimilarhealthrisks.Atthispoint,verylittleresearchonthisquestionhasbeenconducted.A2016studyinratsfoundthatsecondhandexposuretomarijuanasmokeaffectedameasureofbloodvesselfunctionasmuchassecondhandtobaccosmoke,andtheeffectslastedlonger. Oneminuteofexposuretosecondhandmarijuanasmokeimpairedflow-mediateddilation(theextenttowhicharteriesenlargeinresponsetoincreasedbloodflow)ofthefemoralarterythatlastedforatleast90minutes;impairmentfrom1minuteofsecondhandtobaccoexposurewasrecoveredwithin30minutes.TheeffectsofmarijuanasmokewereindependentofTHCconcentration;i.e.,whenTHCwasremoved,theimpairmentwasstillpresent.Thisresearchhasnotyetbeenconductedwithhumansubjects,butthetoxinsandtarlevelsknowntobepresentinmarijuanasmoke(see“Whataremarijuana’seffectsonlunghealth?”)raiseconcernsaboutexposureamongvulnerablepopulations,suchaschildrenandpeoplewithasthma.

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Canmarijuanauseduringandafterpregnancyharmthebaby?

Moreresearchisneededonhowmarijuanauseduringpregnancycouldimpactthehealthanddevelopmentofinfants,givenchangingpoliciesaboutaccesstomarijuana,aswellassignificantincreasesoverthelastdecadeinthenumberofpregnantwomenseekingsubstanceusedisordertreatmentformarijuanause. Onestudyfoundthatabout20%ofpregnantwomen24-years-oldandyoungerscreenedpositiveformarijuana.However,thisstudyalsofoundthatwomenwereabouttwiceaslikelytoscreenpositiveformarijuanauseviaadrugtestthantheystateinself-reportedmeasures.Thissuggeststhatself-reportedratesofmarijuanauseinpregnantfemalesmaynotbeanaccuratemeasureofmarijuanause.

Thereisnohumanresearchconnectingmarijuanausetothechanceofmiscarriage, althoughanimalstudiesindicatethattheriskformiscarriage

Photoby©Thinkstock.com/CreatasImages

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increasesifmarijuanaisusedearlyinpregnancy. Someassociationshavebeenfoundbetweenmarijuanauseduringpregnancyandfuturedevelopmentalandhyperactivitydisordersinchildren. Evidenceismixedastowhethermarijuanausebypregnantwomenisassociatedwithlowbirthrate orprematurebirth, althoughlong-termusemayelevatetheserisks. Researchhasshownthatpregnantwomenwhousemarijuanahavea2.3timesgreaterriskofstillbirth. Giventhepotentialofmarijuanatonegativelyimpactthedevelopingbrain,theAmericanCollegeofObstetriciansandGynecologistsrecommendsthatobstetrician-gynecologistscounselwomenagainstusingmarijuanawhiletryingtogetpregnant,duringpregnancy,andwhiletheyarebreastfeeding.

Somewomenreportusingmarijuanatotreatseverenauseaassociatedwiththeirpregnancy; however,thereisnoresearchconfirmingthatthisisasafepractice,anditisgenerallynotrecommended.Womenconsideringusingmedicalmarijuanawhilepregnantshouldnotdosowithoutcheckingwiththeirhealthcareproviders.Animalstudieshaveshownthatmoderateconcentrations

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RecentTrendsinTreatmentAdmissionsforMarijuanaUseDuringPregnancySource:Martinetal.,2015

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ofTHC,whenadministeredtomotherswhilepregnantornursing,couldhavelong-lastingeffectsonthechild,includingincreasingstressresponsivityandabnormalpatternsofsocialinteractions. Animalstudiesalsoshowlearningdeficitsinprenatallyexposedindividuals.

Humanresearchhasshownthatsomebabiesborntowomenwhousedmarijuanaduringtheirpregnanciesdisplayalteredresponsestovisualstimuli,increasedtrembling,andahigh-pitchedcry, whichcouldindicateproblemswithneurologicaldevelopment. Inschool,marijuana-exposedchildrenaremorelikelytoshowgapsinproblem-solvingskills,memory, andtheabilitytoremainattentive. Moreresearchisneeded,however,todisentanglemarijuana-specificeffectsfromthoseofotherenvironmentalfactorsthatcouldbeassociatedwithamother'smarijuanause,suchasanimpoverishedhomeenvironmentorthemother'suseofotherdrugs. Prenatalmarijuanaexposureisalsoassociatedwithanincreasedlikelihoodofapersonusingmarijuanaasayoungadult,evenwhenotherfactorsthatinfluencedruguseareconsidered. MoreinformationonmarijuanauseduringpregnancycanbefoundintheNIDA'sSubstanceUseinWomenResearchReport.

Verylittleisknownaboutmarijuanauseandbreastfeeding.OnestudysuggeststhatmoderateamountsofTHCfindtheirwayintobreastmilkwhenanursingmotherusesmarijuana. SomeevidenceshowsthatexposuretoTHCthroughbreastmilkinthefirstmonthoflifecouldresultindecreasedmotordevelopmentat1yearofage. TherehavebeennostudiestodetermineifexposuretoTHCduringnursingislinkedtoeffectslaterinthechild'slife.Withregularuse,THCcanaccumulateinhumanbreastmilktohighconcentrations. Becauseababy'sbrainisstillforming,THCconsumedinbreastmilkcouldaffectbraindevelopment.Givenalltheseuncertainties,nursingmothersarediscouragedfromusingmarijuana. Newmothersusingmedicalmarijuanashouldbevigilantaboutcoordinatingcarebetweenthedoctorrecommendingtheirmarijuanauseandthepediatriciancaringfortheirbaby.

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AvailableTreatmentsforMarijuanaUseDisorders

Marijuanausedisordersappeartobeverysimilartoothersubstanceusedisorders,althoughthelong-termclinicaloutcomesmaybelesssevere.Onaverage,adultsseekingtreatmentformarijuanausedisordershaveusedmarijuananearlyeverydayformorethan10yearsandhaveattemptedtoquitmorethansixtimes. Peoplewithmarijuanausedisorders,especiallyadolescents,oftenalsosufferfromotherpsychiatricdisorders(comorbidity). Theymayalsouseorbeaddictedtoothersubstances,suchascocaineoralcohol.Availablestudiesindicatethateffectivelytreatingthementalhealthdisorderwithstandardtreatmentsinvolvingmedicationsandbehavioraltherapiesmayhelpreducemarijuanause,particularlyamongthoseinvolvedwithheavyuseandthosewithmorechronicmentaldisorders.Thefollowingbehavioraltreatmentshaveshownpromise:

Cognitive-behavioraltherapy:Aformofpsychotherapythatteachespeoplestrategiestoidentifyandcorrectproblematicbehaviorsinordertoenhanceself-control,stopdruguse,andaddressarangeofotherproblemsthatoftenco-occurwiththem.

Contingencymanagement:Atherapeuticmanagementapproachbasedonfrequentmonitoringofthetargetbehaviorandtheprovision(orremoval)oftangible,positiverewardswhenthetargetbehavioroccurs(ordoesnot).

Motivationalenhancementtherapy:Asystematicformofinterventiondesignedtoproducerapid,internallymotivatedchange;thetherapydoesnotattempttotreattheperson,butrathermobilizehisorherowninternalresourcesforchangeandengagementintreatment.

Currently,theFDAhasnotapprovedanymedicationsforthetreatmentofmarijuanausedisorder,butresearchisactiveinthisarea.Becausesleepproblemsfeatureprominentlyinmarijuanawithdrawal,somestudiesareexaminingtheeffectivenessofmedicationsthataidinsleep.Medicationsthathaveshownpromiseinearlystudiesorsmallclinicaltrialsincludethesleepaidzolpidem(Ambien ),ananti-anxiety/anti-stressmedicationcalledbuspirone

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(BuSpar ),andananti-epilepticdrugcalledgabapentin(Horizant ,Neurontin )thatmayimprovesleepand,possibly,executivefunction.OtheragentsbeingstudiedincludethenutritionalsupplementN-acetylcysteineandchemicalscalledFAAHinhibitors,whichmayreducewithdrawalbyinhibitingthebreakdownofthebody’sowncannabinoids.FuturedirectionsincludethestudyofsubstancescalledallostericmodulatorsthatinteractwithcannabinoidreceptorstoinhibitTHC’srewardingeffects.

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WherecanIgetfurtherinformationaboutmarijuana?

Tolearnmoreaboutmarijuanaandotherdrugs,visittheNIDAwebsiteatdrugabuse.govorcontacttheDrugPubsResearchDisseminationCenterat877-NIDA-NIH(877-643-2644;TTY/TDD:240-645-0228).

TheNIDAwebsiteincludes:

informationaboutdrugsandrelatedhealthconsequences

NIDApublications,news,andevents

resourcesforhealthcareprofessionals

fundinginformation(includingprogramannouncementsanddeadlines)

internationalactivities

linkstorelatedwebsites(accesstowebsitesofmanyotherorganizationsinthefield)

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

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Forphysicianinformation

NIDAMED:drugabuse.gov/nidamed

Otherwebsites

Informationaboutmarijuanaisalsoavailablethroughthefollowingwebsites:

SubstanceAbuseandMentalHealthServicesAdministration:samhsa.gov

DrugEnforcementAdministration:dea.gov

MonitoringtheFuture:monitoringthefuture.org/

PartnershipforDrug-FreeKids:drugfree.org/drug-guide

ThispublicationisavailableforyouruseandmaybereproducedinitsentiretywithoutpermissionfromtheNIDA.Citationofthesourceisappreciated,usingthefollowinglanguage:Source:NationalInstituteonDrugAbuse;NationalInstitutesofHealth;U.S.DepartmentofHealthandHumanServices.

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