Climate Change and Risk of Completed Suicide by articles

ClimateChangeandRiskofCompletedSuicide

CarolineDumont,MD,*ElizabethHaase,MD,†‡ TrygveDolber,MD,§ JanetLewis,MD,||andJohnCoverdale,MD,MEd¶

Downloaded from http://journals.lww.com/jonmd by l8lgcFOoAXHnR5xSF7ruXMe506TYY7hR/WNmVOPTtsP6dMh/y7HuQRbUzljMSdFvOF5UR/ntk6KWm4Sipsk55QZoiTWELaiEK016Pj9yaHM= on

Abstract: Climatechangeisincreasinglyrecognizedashavingmultipleadversementalhealtheffects,manyofwhicharejustbeginningtobeunderstood. Theelevatedratesofsuicidesobservedinsomecommunitiesaffectedbyclimate changeandrisingratesofsuicideintheUnitedStatesasclimatechangeintensifieshavesuggestedthetwomaybeassociated.WesearchedPubMedand PsycInfousingthetermsclimatechangeandsuicide,andprovidehereareview ofthecurrentliteratureonclimatechangeandsuicidethatexplorespossibleassociationsandmethodologicalissuesandchallengesinthisresearch.

KeyWords: Climate,suicide,mentalhealth,psychiatry,environment,disasters (JNervMentDis 2020;208:559 565)

Eachyearandthroughouttheworld,morethan900,000peopledieby suicide.IntheUnitedStatesalone,14ofevery100,000peopledied bysuicidein2017,makingsuicidethe10thleadingcauseofdeathin theUnitedStates(Murphyetal.,2018).Thisratehasincreasedby 33%since1999(CurtinandHedegaard,2019),andsignificantlyincreasedfrom2016to2017(Murphyetal.,2018).Ithasincreasedfor bothmalesandfemalesandforallages10through74(Curtinand Hedegaard,2017).Particulargroupsofconcernincludeadolescents andyoungadults(Mironetal.,2019).

Althoughamyriadofpsychiatric,psychological,andculturalfactorsmaybeinvolvedintheincreasingratesofsuicide,onelessappreciatedfactoristheroleofclimatechange.Climatechangeisincreasingly recognizedashavingaprofoundimpactonmentalhealth.Populations especiallyvulnerabletoclimatechangeincludethepoorandhomeless, children,theelderly,andthementallyill(Berryetal.,2018;Bourqueand CunsoloWillox,2014;Coverdaleetal.,2018;Masson-Delmotteetal., 2018).Elevatedratesofsuicidehavebeenobservedinsomecommunitiesaffectedbyclimatechange(Haniganetal.,2012).Wesearched PubMedandPsycInfousingthetermsclimatechangeandsuicide,and foundnooverviewofthedifferentcontributingfactorsthathavelinked climatechangetosuicidetodate.

Inthisarticle,therefore,weaimtoexplorethepotentialroleof climatechangeinsuicideratesandtodescribethemethodologicalissuesandchallengesinthisresearch.Thereissignificantvalueincorrelatingsuiciderateswithclimatechange,asitmaybeoneindicatorof psychicdistressamongthosestrugglingatthefrontlinesofachanging planet.Asthequalityofsuicidedatabeingreportedimprovesglobally (Bachmann,2018),theoutcomesofsuicidepreventionmeasuresand climateadaptationeffortscanbemoreaccuratelyassessed.Weadvocateforanincreasedfocusofattentionandresearchonthisimportant publichealthconcern,becausetheprioritizationofactiononclimate changebythepsychiatricfieldrequiresgoodscienceandevidence.

*YaleSchoolofMedicine,NewHaven,Connecticut; †UniversityofNevadaSchoolof Medicine,Reno; ‡OutpatientBehavioralHealth,CarsonTahoeRegionalMedical Center,CarsonCity,Nevada;§EmoryUniversitySchoolofMedicine,Atlanta, Georgia;||UniversityofRochester,FingerLakesHealth,Geneva,NewYork; and¶MeningerDepartmentofPsychiatryandCenterforEthics,BaylorSchool ofMedicine,Houston,Texas.

SendreprintrequeststoElizabethHaase,MD,UniversityofNevadaSchoolof Medicine,5190NeilRd,Reno,NV89502.E mail:ehaase@me.com.

Thisreviewaddressesfouraspectsofanthropogenicclimate changeandassociatedfindingsonsuiciderates:1)airpollutionfrom theburningoffossilfuels,firesmoke,andozoneproduction;2)higher temperatures,includingambienttemperatureandincreasedfrequency ofheatwaves;3)habitatchangeslinkedtorisingglobaltemperature,includingchangesinlandscape,foodsource,plantandanimallife,and drought;and4)impactsofoceanwarming,includingmorefrequent naturaldisasters,sealevelrise,andassociatedpredictedmassmigration.Wealsoincludesuicidethatappearstohavearisendirectlyfrom apsychologicalreactiontotheseclimaterealities.Forthepurposesof thisreview,wedonotincludechangesinsuicideassociatedwiththe changingepidemiologyofinfectiousdiseasesandsoil-basedchanges innutrition.Althoughchangesinthegeographicaldistributionand prevalenceofnutritionalandinfectiousdisorderswilllikelyinfluence theratesofsuicidalbehaviorassociatedwiththeseillnesses,thesenovel habitat-illnessinteractionshavenotyetbeenstudied.Ourdescription hereoftheliteratureisnotexhaustivebuthighlightsarangeofstudies withbothpositiveandnegativefindingstodemonstratethestateofthe fieldandsuggestareasforfurtherresearch.

ASSOCIATIONOFSUICIDERATESWITH AIRPOLLUTION

AirpollutionisdefinedbytheEPAintermsofsixcriteriapollutants:lead,ozone,carbonmonoxide,nitrogenoxide,particulatematter, andsulfurdioxide.Theburningoffossilfuelsisconsideredtobethe sourceof81%(Philipetal.,2014)ofthesepollutants.Particulatematter airpollution,definedbasedonparticlesizesof2.5 μm(PM2.5),10 μm (PM10),andultrafineparticles(UFPs),nowhasarobustliteratureofassociationwithadversehealthandmentalhealtheffects.Particulateair pollutionhasbeenshowntotranslocatetothebrainviaolfactoryandpulmonarynervesaswellasthevascularsystem,whereitcausesmultiple pathologicalchangesinneuronsandglia(WrightandDing,2016).

Aswithanyclimatevariable,studyingtheeffectsofaparticular elementofairpollutiononthebrainiscomplex,andscientistsmustdelineateeachfromothertypesofairpollutionandfromotherairfactors, suchasseasonalvariationsinwindflow,fires,dust,pollen,temperature,moisture,andsunshine.

Particulatematterandthecriteriapollutantsozone,sulfurdioxide,andnitrogenoxidehavebeenthemoststudiedfortheirmental healthimpacts.Allhavebeenassociatedeitherwithadirectincrease insuicideriskorwithneuropsychiatricconditionsknowntoincrease suicidality:autism(Volketal.,2013),dementia(Cacciottoloetal., 2017),depression(Guetal.,2019;Kioumourtzoglouetal.,2017), andbipolardisorder(Khanetal.,2019).Increasedsuicideriskandincreasedratesofneuropsychiatricdisordersassociatedwithsuicidehave alsobeenfoundunderavarietyofspatialandtemporalconditions,includingproximitytocoalplants,traffic,andfreeways,andchronic andacuteairpollutionevents(Cacciottoloetal.,2017;Guetal., 2019;Khanetal.,2019;Perera,2017;Volketal.,2013).

Overall,studieshaverevealedincreasedsuicideratesof1%to 2%perdayofpoor-qualityair.Itisimportant,however,forpsychiatrists tofeelsecurewiththedepthandbreadthofthesciencesupportingalink ofairpollutiontomentaldisorders(reviewedinBuolietal.,2018),asit

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isfrequentlyatargetforcritiqueandhassignificantimportforourpatients.Therefore,wepresentthisliteratureingreaterdetail.

Oneofthemostcomprehensivestudies(Kimetal.,2018)examined10citiesinAsia,eachwithapopulationofover2million,fortime spansof10to30years.Thisstudycontrolledforsunshine,temperature, barometricpressure,andprecipitation,andusedatime-controlledcasecrossoverdesigntocontrolfortrendsinairpollutionandsuicideover time.Allcriteriapollutantswerestudiedindividuallyandinassociation witheachother.Thestudyassessedrelationshipsbetween9-dayaveragepollutionandsuiciderates0to5dayslater.Anassociationwas foundforrelativerisksofsuicideperworsequartileairqualityfollowingthese9daysrangingfrom1.016(PM1)to1.019(nitrogenoxide, PM10 2.5),to1.02(sulfurdioxide).NoassociationwasfoundforPM2.5.

Similardesignshavebeenusedtostudycardiovascularpatients inSouthKorea(Kimetal.,2015),thecityofGuangzhou,China(Lin etal.,2016),Tokyo(Ngetal.,2016),andSaltLakeCity,Utah (Bakianetal.,2015).Eachstudyspanned10years.Inthesestudies,associationsofairpollutionandsuicidewerefoundforPM2.5(10%increase)andPM10(9%increase)(Kimetal.,2015),forNO2(7% increase)andPM2.5andSO2(11%increase)(Linetal.,2016),and PM2.5(oddsratio,1.05)andNO2(oddsratio,1.20)(Bakianetal., 2015).Takentogether,thesestudiesdemonstrateanincreaseintherate ofsuicidethatrangesfrom2%to20%dependingonthepollutantstudied,timeframe,andotherfactors.

Thepathophysiologyofairpollutionassociatedsuicideriskishypothesizedtobeneuroinflammatory,withairparticulatesactingasirritantsthatgeneratesystemicandlocalinflammatoryresponses(Costa etal.,2014).Thehypothesisthatpollutiontriggersaneuroinflammatory responseissupportedbyfindingsofincreasedratesofinflammatory vascularandpulmonarydisorders,includingasthma,strokes,andheart attacks,inassociationwithpoorqualityair(WrightandDing,2016).

ThishypothesisisalsosupportedbyMinetal.(2018)whoseresultsstratifiedtheriskofsuicidewithworseairpollutionbyusinganationalhealthsurveysamplethatidentifiedthepresenceorabsenceofa physicalormentaldisorder.Minfoundalargeincreaseinsuiciderisk associatedwithPM10(hazardsratio[HR],3.09),NO2(HR,1.33), andSO2(HR,1.15).Illnessfurtherincreasedthissuiciderisk.Inthe topquartileofairpollution,PM10andNO2pollutantswereassociated withanHRof4.35,particularlyinmetropolitanareas(HR,4.93for PM10,1.89forNO2).Althoughunfortunatelythisstudycouldnotisolatethosewithmentaldisordersfromotherillnesses,itdemonstratesthe profoundimpactofairpollutiononsuicideratesinthosealreadyvulnerabletoairpollutionhealthimpactsbecauseofpreexistingmedical illnesses,includingthoseassociatedwithinflammatoryresponses.

ASSOCIATIONOFSUICIDERATESWITH RISINGTEMPERATURES

Globaltemperaturesareprojectedtoincreasebetween2.6°Cand 8.5°Cbytheendofthiscentury,dependingonthetotalgreenhousegases emittedundereitherstringentorhighemissionsscenarios(MassonDelmotteetal.,2018).Presentestimates,withimplementationofcurrently endorsedunconditionalpoliciesaroundtheworld,projectatwo-thirds probabilityoftemperaturesrisingapproximately2.9°Cto3.2°C(Climate ActionTracker:WarmingProjectionsGlobalUpdate,2019).Theoverall increaseinheat-relatedsuicidesthatwouldbepredictedbysucha3°C increaseisintherangeof2.1%to6.3%(Burkeetal.,2018).

Sincebeforethe19thcentury,aseasonalpatterntosuiciderates hasbeenobserved,withratestendingtoincreaseinlatespringandearly summercomparedwiththefallandwinter.Althoughtheetiologyof thesefluctuationshasbeendifficulttoelucidate,theseseasonalpatterns ofsuicidehavebeenreportedintheliteraturefromanarrayofcountries andgeographicareas(Galvãoetal.,2018;Likhvaretal.,2011),and likelyrepresentaheterogeneousphenomenonrelatedtovariationsin temperature,daylightexposure,chronobiologicalaspectsofmooddisorders,

andsocioeconomicfactors(Ajdacic-Grossetal.,2010;Kevan,1980). Historicaldatasuggestadecreasingtrendinseasonalvariabilityofsuiciderates,particularlyinWesterncountries,whichmaybedueinpart tochangeinaccesstoviolentsuicidemethods(Ajdacic-Grossetal., 2010).Thiswillbeimportanttokeepinmindandtoelucidatefurther whenanalyzingsuicidedataalongsiderisingglobaltemperatures.Since climatechangeisdefinedoverlongerperiods,researchingclimate-related suicidesoverlargepopulationsandlongerperiodsismorelikelytocapture trendsandminimizeconfoundingfactors,suchasseasonalvariation. Recentstudiestakingthisapproachhaveindeedfoundsuicideratesincreasewithhottertemperatures(Bandoetal.,2017;Burkeetal.,2018; Carleton,2017;Fountoulakisetal.,2016;Luanetal.,2019).Thisassociationholdstrueforbothofthemainimpactsofclimatechangeon ambienttemperature:agreatertotalnumberofhotterdaysandmore frequentacuteheatwaves.

Asignificantstudy(Burkeetal.,2018)examinedtheeffectof localambienttemperatureintheUnitedStatesandMexicoonsuicide byusingvitalstatisticsoverlargegeographicareas,largerpopulations thanotherstudies(UnitedStatesN=851,000;MexicoN=611,366), andlongerperiods(decades).Theyfoundthat,between1990and 2010,suicideratesincreased0.7%inUnitedStatesand2.1%inMexico forevery1°Cincreaseinmonthlyaveragetemperature.Theyconcluded thatifclimatechangeproceedsunmitigatedunderthe “businessasusual” scenariothattheIPCCtechnicallyreferstoas “RepresentationConcentrationPathway(RPC)8.5,” itwilladdanestimated9,000to40,000additionalsuicidedeathsby2050.Theirdataindicatearelativelylinear responseofsuicideratestomonthlyaveragetemperatures.Unlikethe effectoftemperatureonotherall-causemortality,therewasnoincreased riskasthetemperaturegrewcolder,andtheeffectsdidnotdiminishin thosewithhigherincomesandmoreprevalentairconditioning.Furthermore,theydidnotfindevidenceofdecreasedsensitivitytotemperatureinpopulationsmorefrequentlyexposedtohightemperatures.

Linkagesbetweensuicideratesandelevatedtemperatureshave alsobeenobservedinlargeurbanpopulations.InChina,therelative riskforsuicidedeaths,measuredfrom2009to2013in31capitalcities amountingtoapopulationof300million,was1.37(95%confidence interval)forhightemperatures,definedasthe95thpercentileofambienttemperature(Luanetal.,2019).Atime-stratifiedcase-crossover studyofmultiplecitiesinthreeEastAsiancountriesfoundapositive associationbetweentemperatureandsuiciderates,rangingfrom3.9% to7.8%forapproximatelya4°Cincreaseintemperature(Kimetal., 2016).Anotedlimitationwasthatairpollutionwasnotaccountedfor inthedataanalysis.Atime-seriesstudyinSanPaolo,Brazil,revealed a2.28%increaseinsuicideswitheach1°Cincreaseinweeklyaverages ofminimumtemperature.Thesefindingsweresignificantformenonly (Bandoetal.,2017).Studyingannualratesofsuicideattemptsandsuicidesper100,000inhabitantsinThessaloniki,Greece,between2000 and2012(Fountoulakisetal.,2016),itwasfoundthatmalesuicide ratescorrelatesignificantlywithhighmeanannualtemperatureand accountedfor51%ofthevarianceofmalesuiciderates.

Carleton(2017)exploredtheeffectsofexposuretotemperature andrainfallinIndia,adevelopingcountrythataccountsforoverone quarterofsuicidesworldwide,andwheresuicidesrateshavedoubled since1980.Thecausesoftheincreasedrateshavebeenasource ofdebate,asfactorssuchaslowercropyieldsfromhighertemperaturescausingeconomicstraincouldalsoleadtohigherratesofsuicide.Thisstudyfoundthatfluctuationsinclimate,inparticular,high temperaturesduringthegrowingseason,correlatepositivelywith suiciderates.Ondaysabove20°C,aday'sincreaseof1°Cduringthe growingseasonadded0.008suicidesper100,000personsannually, amountingtoatotalof59,300additionaldeathsbysuicidesince1980. Therewasnoassociationbetweentemperatureandsuicideratesinthe nongrowingseason.Thesefindingsaresignificantgiventheextentto whichrisingglobaltemperatureswillimpactagriculturalcommunities indevelopingcountries.

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2020 Wolters Kluwer Health,

ASSOCIATIONOFDROUGHTANDSUICIDE

AsthestudybyCarletonhighlights,increasedtemperaturescontributetodrought,resultinginlowercropyields.Thelikelihoodthatanthropogenicclimatechangeisincreasingdroughtisveryhighacrossall continents(Masson-Delmotteetal.,2018).Itisthereforeimportantto considerwhetherdroughtisaseparateriskfactorforclimatechange suicide,andhowtemperature,drought,andsocialfactorssuchasagriculturalincomestogethermayincreasesuiciderates.

Droughtisdefinedasaperiodofabnormallydryweatherthat depleteswaterresources,includinglake,reservoir,andgroundwater.The resultantlowersoilmoistureandstreamflowleadtoerosion,habitat degradation,morewildfires,andwaterqualitydecline(Yusaetal.,2015). Droughtshaveaslow,vagueonset,indirectmanifestations,certainbut unpredictablerecurrence,andaseverityofimpactdeterminedpartly bythebehaviorsofpeoplenearby.Alloftheseparametersbothincrease thetotalmentalstressofadroughtandmakeitmoredifficulttoisolate theelementsofthiscomplexdrought-associatedpsychologythatimpact mentalwell-being.

Moststudiesoftheimpactofdroughtonmentalhealthhave beenconductedinAustralia,acountrywiththeworld'swidestclimatic fluctuationandalargeruralandindigenouspopulation.Studieshave generallyshownanincreaseinpsychicdistressoverall(OBrienetal., 2014)andsuicidespecifically,althoughonlyunderspecificdrought conditionsandamongruralfarmers.

Anecdotalreportsofcompletedsuicideinassociationwith droughtexistatleastbefore1915(Alpinoetal.,2016).Oneearlystudy ofsuicideinAustraliathatspanned1901to1998showedthatdrought wasageneralriskfactorforsuicideoverthese100yearsatthepopulationlevel,withRRof1.07(Pageetal.,2002).

Amorerecentstudyofdrought-relatedsuicidesinNewSouth Wales,Australia,foundthatsuicideratesfrom1970to2007roseinruralmalesaged30to49by15%whenthedroughtindexincreasedfrom thefirsttothirdquartile(Haniganetal.,2012).Thisstudyalsodemonstratedanadditionalseparatesuiciderateincreaseof3%inthegeneral populationwitheach1.6°Cincreaseoveraverageannualtemperature duringthisdroughtperiod.Thisincreaseinsuicidewithtemperature issimilartotheothertemperature-relatedsuicidestudiescited.Female suicidesdidnotincreaseinassociationwithdrought.Anotherstudyby thisgrouplookedatthesameregionfrom1964to2001,bothduring andnotduringlongdroughts.Theydemonstratedan8%increased riskofsuicideforevery300-mmdecreaseinrainfall,ameasuresimilartothatofwaterresourcestrain(Nichollsetal.,2006),butdifferent inthatthereisbothdroughtandanawarenessofchangesinweather. Bothofthesestudiescontrolledforoveralltrendsinsuicideratesduring theyearsinquestion.Anotherstudy(Guiney,2012)didnotdemonstrateanincreaseinfrequencyofsuicideoverthedroughtyearsof2001 to2007inVictoria,Australia.However,itdidnotadjustfordownward trendsinsuicideratesinAustraliaovertheyearsin question,andincludedemploymentgroupslesslikelytohavesuffereddrought-related economiclosses.

ASSOCIATIONOFINDIGENOUSPOPULATIONS

ANDSUICIDE

Proportionallyhigherratesofsuicidehavelongbeenrecognized inindigenouspopulationscomparedwithnonindigenouspopulations (CunsoloWilloxetal.,2014;Qietal.,2009).Arecentmeta-analysisaffirmsthisfinding,althoughnotinghighvariabilitybetweendifferentindigenousgroupsindependentofclimateconditions.Thisvariability, alongwithextremesintheclimateconditionsthatwillbeexperienced byindigenousgroupsaroundtheworld,willmakeconclusionsabout generalclimateeffectsdifficult(Pollocketal.,2018).

Aqualitativestudy(CunsoloWilloxetal.,2014)ofanInuitpopulationfoundthatchangesintheenvironmentandclimate,whencombinedwithotherstressors,wereimplicatedinincreasedsuicidalideation,

asdidastudyofsuicidalthoughtsinSwedishgroupofreindeerherders (Ommaetal.,2013).Furthermore,preservationofcommunityinstitutionsandpracticeswasfoundtoberoughlyinverselyassociatedwith suicideratesandgroupdistressinastudyofCanada'sindigenous groups(ChandlerandLalonde,1998).However,thereisnotyetmore directevidenceofclimatechangeimpactsoncompletedsuicideitself withinindigenouspopulations.

ASSOCIATIONOFNATURALDISASTERSANDSUICIDE

Althoughhurricanesandotherdisasterscanhaveseverehealth consequences(Beagleholeetal.,2018;Laneetal.,2013),adirectrelationshipbetweenadisasteranditsimpactonmentalhealthisdifficultto establish,asmanyotherfactorsalsocontributetotheseverityofits impactonanindividualorgroup(Hammer,2018).Thereisalsonota consensusthatclimatechangehasinfluencedhurricanefrequency (Landseaetal.,2006;PatricolaandWehner,2018).Ithas,however, beenamplydemonstratedthatclimatechangehasincreasedtheaverage andextremerainfallofhurricanes,andwill,inthefuture,increasewind speed(PatricolaandWehner,2018).

Onesystematicallyconductedreviewidentified14articlesof varyingdesignsthatassessedtherelationshipbetweenhurricanesand otherformsofdisastersonsuicidalbehaviors(Kõlvesetal.,2013).This reviewfoundvariabilityinoutcomesacrossallstudies,inpartbecause ofthevaryingmethodologiesemployedandlengthsoffollow-up.Only twoofthearticlesconcerningtheimpactofhurricanesaddressedsuicidemortality(Castellanosetal.,2003;LewandWetli,1996)butsamplesizesweresmall.Thesefindingsincludedaninsignificantincrease inyouthsuicideratesandasmallincreaseinhomicide-suicidesafter hurricaneAndrew.

Inanotherstudyprehurricaneandposthurricane,annualaverage suicideratesin24countiesaffectedbyasingleseverehurricaneinthe UnitedStatesincreased,butnotsignificantlyso(Krugetal.,2002).We foundnostudiesconcerningsuicideratesafterwildfires.

SUICIDALITYAMONGREFUGEESANDIMMIGRANTS

The1951UnitedNationsConventionontheStatusofRefugees definesa “refugee” asadisplacedpersonwhomusthave “awellfoundedfearofpersecutionbecauseoftheirrace,religion,nationality, membershipofasocialgrouporpoliticalopinion;andbeunableorunwillingtoreturntothecountryforfearofpersecution” (McColletal., 2008).Somecountriesalsodesignateacategoryof “asylum-seeker” tosomeonewhohasappliedforrefugeestatus.Thosewholeavetheir homebecauseithasbecomeuninhabitableduetoglobalwarmingdo notfiteasilyunderthisdefinition.Forthisreason,andbecausethere arerelativelyfewstudiesonsuicideinrefugeesandasylumseekers, weinclude “immigrants” inourliteraturesearch,tobetterassesssuicide ratesassociatedwithmovingfromonehomecountrytoanotherorleavingone'shomeunderdiversesituationsofthreat.

Accordingtoa2017UnitedNationDevelopmentProgramme report,projectedestimatesofclimate-relateddisplacedpersonsby 2050rangefrom25millionto1billionpeopleperyear.Incomparison, therearecurrentlyanestimated70.8milliondisplacedpersonsfromall causesworldwide(OpitzStapletonetal.,2017).Reasonsfordisplacementfromone'shomecountryduetoclimatechangewillincludeboth directclimateimpactssuchasfloodingandindirectclimateimpacts suchaspoliticaloreconomicinstability,violence,ordisease.

Theearlieststudiesonimmigrantsuicideby(Sainsburyand Barraclough,1968)establishedastatisticallyrobustcorrelationbetween suicideincountryoforiginandcountryofemigrationacrossmultiple nations,establishingboththatone'sculturalpredispositiontosuicide holdstrueregardlessoflocationandthatmethodsofrecordingsuicide aresufficientlyconsistentacrossnationalboundariestostudythistopic. Thesewereuncontrolledstudiesthatshowedwidelyvariabledifferences inratesofsuicidewithimmigration.

TheJournalofNervousandMentalDisease • Volume208,Number7,July2020 ClimateChangeandRiskofSuicide

Stack(1981)assessedthepopulationrateofsuicidecompared withtherateofimmigrationin34countriesintheyear1970andfound a0.13%increaseinnationalsuicidesforevery1%increaseinimmigration.Stackcontrolledforageolderthan65yearsandpercentageof womenintheworkforce,whichhetooktobeconfoundingvariables forpopulationisolationandroleconflictthatmightinfluencesuicide ratesinasimilarwaytoimmigrationstress.

MorerecentstudiesonsuicidalityamongrefugeesandimmigrantscomemostlyfromNorthernEurope.AstudyofimmigrantsuicidesinSwedenfrom1987to1991(Ferrada-Noli,1997)foundthat immigrantsfrom60%oforigincountrieswere,onaverage,50%more likelytocompletesuicidethannativeSwedishresidents.Immigrants from90%ofthoseorigincountriesweremorelikelytocompletesuicidethanthosefromtheirhomecountry.Astudyofasylum-seekers intheNetherlandsfrom2002to2007(Goosenetal.,2011)foundthat meninthisgroupweretwiceaslikelytocompletesuicideandhadarelativeriskof1.42forhospital-treatedsuicidalbehaviorcomparedwith Dutchnatives.InanegativestudybasedondatafromtheDanishImmigrationServicefrom1993to1999,refugeeshadalowersuiciderate thannative-bornDanes,butthisresultwaslow-powered(29completed suicides)(Norredametal.,2013).NeitherGoosennorNorredamcontrolledforsuiciderateincountryoforigin.

Twomuchlargerstudiesofsuicidesinimmigrants,however,show similarlycontrastingresults.ThefirstwasconductedusingWHOdata from1989to2003forallofEurope.Itrevealedthatsuicideattemptrates weresignificantlyhigherinimmigrantsthanintheirhostcountrycounterpartsfor27of56countriesoforigin.Suicideattemptratesinthenew countrycorrelatedpositivelywithsuicidecompletionratesinthecountry oforiginfor14of19countries.Fourimmigrantgroups thosefrom Chile,Iran,Morocco,andTurkey hadahighsuicideattemptratedespite relativelylowhomecountrysuicidecompletionrate(Lipsicasetal.,2012).

Thesecondstudy(Ikrametal.,2016)usesdatafromtheMigrant andEthnicHealthObservatoryProject,adatabaseofcountriesinthe EuropeanUnion,andcontrolledforsuiciderisksincountryoforigin withameasureweightedforlengthofemigration.Thisstudyshowed lowerriskofsuicide(mortalityrateratio,0.36 0.60)inallgroupsstudied withtheexceptionofthosefromNorthAfrica(mortalityrateratio,1.42).

Takentogether,theconsistencyofthefindingsthatsuicideattemptsandcompletionscorrelatewiththoseincountryoforiginaswell asthefactthatcertainimmigrantgroupssurpasstheirexpectedsuicide andsuicideattemptratesuggestthatculturalnormsincountryoforigin andrisksembeddedintheimmigrationexperienceallcontributetovariabilityinsuiciderisk.

Uncoveringtheseriskfactorswithsomanypotentialvariables andarelativelysmallnumberofcompletedsuicidesischallenging. Oneattempt(Hagamanetal.,2016)involvedperformingpsychological autopsiesof14completedsuicidesbetween2009and2012among BhutaneserefugeestotheUnitedStates.Thesuiciderateamongthese refugeesisroughlytwicethatoftheUSpopulationoverall.Mostofthe 14examinedweremarriedmenwithoutaregularincome,somewith poorhealth.Mosthadnotpreviouslyattemptedsuicide,andabouthalf seemedtohavesymptomsofamooddisorderorPTSD.Focusgroups inasubsequentanalysis(Brownetal.,2019)involving83Bhutanese refugees,includingchildren,revealedcommonthemesoflossandisolation,aswellasatabooagainstcommunicatingsuicidalthoughtsto eachother.

Manypopulationsdisplacedbyclimatechangecanbeexpected tofleefromonedevelopingcountrytoanother,withlittleaccesstoinfrastructureandmentalhealthsupportwhentheyarriveandthroughout theimmigrationexperience.Thisalreadyoccursthroughouttheworld, amongpopulationsfleeingviolenceandpoliticalinstability.Thirty-six percentof297mothersinterviewedatanAfghanrefugeecampin nearbyPakistanscreenedpositiveforamentaldisorderin2002,and 91%ofthatgroupendorsedsuicidalthoughtsinthepreviousmonth (RahmanandHafeez,2003).InaNigerianrefugeecampcomposed

mostlyofLiberiansstudiedin2012,27%ofresidentsendorsedatleast passivesuicidalideationinthepreviousmonth,comparedwith17%ofthe hostpopulation.Suicidalthoughtscorrelatedmoststronglywithapoor qualityoflifeandbeingunskilledorunemployed(Akinyemietal.,2015).

Muchremainsunanswered.Itisreasonabletosuspect,however, thatpopulationsdisplacedbyclimatechangewillfaceanevenhigher burdenofmentaldistressandsuicidalitythanothermigrantgroups,given thepredictedincreaseintheirnumbersandlackofresourcesavailable.

CLIMATECHANGEASANEXISTENTIALTHREAT

Ithasbeenrecognizedthatclimatechangenegativelyinfluences mentalhealththroughanarrayofinterwovenpathways(Berryetal., 2010)andthatdistressoverclimatechangecancontributetononsuicidal, self-destructivebehavior(Bodnar,2008).Bodnardetailspsychoanalytic casesofself-destructivebehaviorbyyoungadultsrelatedtoenvironmentaldistress,arguingthatthenaturalworldisanattachmentfigure indevelopmentandspeculatingthatsuchbehaviorexpressesinvulnerableindividualsourchangedrelationshipwiththenaturalworld.The high-profilesuicidein2018ofenvironmentaladvocateandattorney DavidBuckelviaimmolation(Conroy,2019;Mays,2018)istheonly reportofexistentialconcernoverclimatechangeasacontributionto completedsuicide.HeemailedtheNewYorkTimesofhisintent, “Mosthumansontheplanetnowbreatheairmadeunhealthybyfossil fuels,andmanydieearlydeathsasaresult myearlydeathbyfossil fuelreflectswhatwearedoingtoourselves.” Hisstatement, “[My]privilege” is “feelingheavierthanresponsibilitymet,” issuggestiveofthe “ecologicaldebt” experiencedescribedinpsychoanalyticliterature (Randall,2013).Therewasnotaformalpsychologicalautopsyinthis case.Althoughthereisagrowingliteratureaboutclimateanxiety,there isnotyetevidencebeyondtheincompleteknowledgeoftheBuckelcase ofaclimatechangecontributiontocompletedsuicideviaguiltordistress overclimatechangeitself.

DISCUSSION

Thereisconvincingevidencethattheimpactsofthegreenhouse gases,airpollution,andhigherglobaltemperaturesdirectlyincrease suiciderisk,makingthisanissueofglobalconcernforpsychiatry.

Existingstudiessuggestapopulation-wideincreasedriskofsuicideofupto3%2to3daysafterepisodesofsignificantlyworsenedair quality.Thedatasofaralsoshowthattheriskofsuicideissignificantly worsewhentheairisparticularlypolluted,as,forexample,inthethree studiesthatshowathreefoldtofourfoldincreaseinsuicidesforthe worstquartileaircomparedwithacceptableaverages(Kimetal., 2015;Linetal.,2016;Ngetal.,2016).Offurtherconcern,thesestudies mayhaveunderestimatedtherisksofpollutedair.Ithasonlyrecently beenpossibletomeasureUFPsatairqualitystationsandinthebrain, yettheyarethemostcommonparticletype.UFPsmaythereforeplay animportantrolethathasyettobemeasured(Donaldsonetal.,2005) intheneuroinflammatorychangesthatarehypothesizedtocontribute toriskofsuicide.

Theconsistencyoftheassociationbetweentemperaturesabove 37°Candsuicideacrossbothmiddle-incomeanddevelopedcountries andacrossdifferentclimatetypessuggestsasimilarpossibleunifying neurobiology(Burkeetal.,2018;Dixonetal.,2014).TheuseofdepressivelanguageonUnitedStatesinsocialmediaposts,whichalsoincreaseswithrisingtemperatures,suggestsadirecteffectoftemperature onmentalwellbeing.Linkagesbetweentemperatureandviolentconflicthavebeenobservedfordecades,whereheatincreasesratesofinterpersonalaswellasintergroupconflict(Hsiangetal.,2013).More violentmethodsofsuicideformalargerproportionofsuicidesmethods connectedtorisingtemperatures,comparedwithsuicidesnotstratified bytemperature(Bandoetal.,2017;Linetal.,2008).Thesefindings suggestthatheat-drivenbiologicalpathwaysleadtoincreasedhuman aggression,bothagainsttheselfandagainstothers,andunderscore

Dumontetal. TheJournalofNervousandMentalDisease • Volume208,Number7,July2020 562 www.jonmd.com

Wolters Kluwer Health,

theneedforongoingresearchintotheunderlyingcausalpathwaysof temperature-linkedsuicides.Burkeetal.(2018)notethattheirpredictedincreaseinsuicideduetoheatinthiscenturywillneutralize thegainsofallcurrentsuicide-reductionprogramsintheUnitedStates, highlightingthesignificanceofthisimpactforpsychiatry.

Althoughnopopulationsubgroupisimmunefromglobalclimate impacts,climatechangedisproportionatelyincreasesthepsychosocial stressorsthatcontributetosuicideinvulnerablepopulations:indigenous people,whosewayoflifeistiedtonaturalresources;refugeesfleeing countriesimpactedbysea-levelrise,resourcedepletion,andclimaterelatedconflict;socioeconomicallydisadvantagedpopulationslessableto adapttoheat,food,andwatershortages;aswellaschildren,women, theelderly,andthementallyillwillbeparticularlyvulnerabletomental healthissues.TheinterplayoffactorslinkingdroughttosuicideinAustralianstudiesisagoodexampleofcomplexityoftheseclimatestresses (BhiseandBehere,2016;EllisandAlbrecht,2017;Kundeetal.,2017). Thesepsychologicalautopsystudiessupportthehypothesisthat ecoterraticdistress,suchassolastalgia,lossofcherishedlandandanimals,socioeconomicstressfromdrought-relateddebtandbankruptcy, andfeelingsofpersonalfailureincreasethelikelihoodofsuicide.These vulnerablegroupsdeserveimminentattentiontotheirmentalhealthneeds.

Muchoftheriskofclimatesuicide,however,islikelytotranscendsocialclass,andhasyettobeexplored.Intenseemotionalreactionsincludinghopelessnessaboutthefuture,shame,guilt,andgrief, aswellaspanicaboutpersonalsurvivalamidstinterpersonalhostility andgeopoliticalconflicts,willincreasinglycontributetosuiciderisk, astheydoelsewhere.ExistentialanxietyasWesternlifestylescomeunderthreat,andasenseofbetrayalbyoldergenerationsmayfurthercontributetosuiciderisk.Giventheunexplainedriseinsuicideratesin today'syouthandtheevidencethatenvironmentalfactorsmaybethe mostimportantriskforsuicideinsomestudies,itisincumbentonfuturesuicideresearchtotakeclimaticfactorsintoaccount.

Althoughwefocusmostlyonsuicideasaharddatapointthatis moreeasilymeasuredatthisglobalscale,thebiological,intrapsychic, andpsychosocialinfluencesthatcontributetoclimatesuicidewillalso contributetooverallmentalmorbidity.Climateeffectsontheincidence andvulnerabilitiesassociatedwithmajorpsychiatricdiseasessuchas schizophrenia,autism,anddementiawillbeofgreateroverallimpactthan completedsuicideitself.Itbehoovespsychiatriststobecomefamiliarwith theclimatementalhealthliteratureandtoimplementpreventativemeasuresforallclimatementalhealthrisksintheirlivesandpractices.

ACKNOWLEDGMENT

TheauthorswishtoacknowledgeDrsDavidAdler,Ludmila BarbosadeFaria,ChristopherMcIntosh,andJosephMerlinoandthe GAPPublicationCommitteefortheirkindreviewofthismanuscript.

DISCLOSURE

Theauthorsdeclarenoconflictofinterest.

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