Cannabis Report 08

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CANNABIS AND MENTAL HEALTH:

RESPONSES TO THE EMERGINGEVIDENCE

THE BECKLEY FOUNDATION

DRUG POLICY PROGRAMME

A KCA REPORT

REPORT EIGHT

Neil Hunt, Simon Lenton, John Witton

APRIL 2006





1eport 8

CANNABIS AND MENTAL HEALTH:

Responses to the Emerging Evidence

SUMMARY

e unt , mon enton at ona rug esearc nst tute, ustra a o n tton at ona ct on entre, on on

e ec ey oun at on rug o cy rogramme s a new n t at ve e cate to prov ng a r gorous, n epen ent

review of the effectiveness of national and international drug policies. The aim of this programme of research and analysis is to

assemble and disseminate material that supports the rational consideration of complex drug policy issues, and leads to a more

effective management of the widespread use of psychoactive substances in the future.

According to United Nations figures, cannabis is the most widely used of the psychoactive substances that are prohibited under the UN Drug

ontro onvent ons. n e ero n an coca ne, w c are pro uce n re at ve y concentrate areas o t e wor , an w ose eve s o con-

sumpt on vary w e y across erent countr es an reg ons, canna s s now w e y cu t vate an consume across a cont nents. urt ermore,

t e use o canna s or ts er vat ves s em e e w t n many tra t ona cu tures, or as ecome cu tura y accepte as a rug o c o ce y a

significant proportion of the population in many countries. Not readily associated with the most visible harms arising from drug use, cannabis is

seen by many as a relatively benign drug. Indeed, many use it for its medical, therapeutic, social and spiritual benefits. However, there is increas-

ing apprehension about its possible role in triggering or exacerbating mental health problems, or of inhibiting young people’s emotional or social

eve opment. anna s t ere ore presents un que c a enges to t e nternat ona contro system t at nee to e con ronte y po cy ma ers –

n ee , t e rugs ontro e nton o ar a osta ac now e ge , n s c os ng speec at t e omm ss on on arcot c rugs, t at

canna s represents t e ma n wea po nt n t e system t at e oversees.

INTRODUCTION

cute e ects

e major acute a verse psyc o ogica an ea t e ects o canna is intoxication are:

- anxiety, dysphoria, panic and paranoia, especially in naive users;- cognitive impairment, especially of attention and memory;

- psychomotor impairment, and possibly an increased risk of accident if an intoxicated person attempts to drive a motor vehicle;

- an increase ris o experiencing psyc otic symptoms among t ose w o are vu nera e ecause o persona or ami y istory o psyc osis; an ,

- an increase ris o ow irt weig t a ies i canna is is use uring pregnancy.

ron c e ects

The most probable health and psychological effects of chronic heavy cannabis use appear to be:

- respiratory diseases associated with smoking as the method of administration, such as chronic bronchitis, and the occurrence of

histopathological changes that may be precursors to the development of malignancy;

- an increase ris o cancers o t e aero igestive tract, i.e. ora cavity, p arynx, an oesop agus; an ,

- eve opment o a canna is epen ence syn rome, c aracterise y an ina i ity to a stain rom or to contro canna is use.

The following oss e adverse effects of chronic, heavy cannabis use remain to be confirmed by further research:

- a decline in occupational performance marked by underachievement in adults in occupations requiring high level cognitive skills, and

impaire e ucationa attainment in a o escents; an ,

- su t e orms o cognitive impairment, most particu ar y o attention an memory, w ic persist w i e t e user remains c ronica y intoxicate ,

and may or may not be reversed by prolonged abstinence from cannabis.

e n te at ons recent y est mate t at . m on peop e age - use canna s ur ng t e year n te at ons ce on

Drugs and Crime 2005). In most countries, cannabis is both the most commonly reported illicit drug and the earliest that people use. Such

widespread use is important because our understanding of the risks and harms that can accompany its use are progressively improving and,

ecause ear y use o any rug across t e e-course ten s to e assoc ate w t g er r s s.

e acute s ort-term) an c ron c ong-term) e ects o canna s ave een summar se y a t a . : ) as o ows:





3

Europe

n est urope, t ere s cons era e var at on n rates o canna s

use: among - year-o s, et me preva ence ranges rom

countries with comparatively low rates in Portugal (8%), Sweden

(8%), Greece (9%), and Finland (10%) to others with relatively high

rates: pa n ), re an ), rance ) an t e ).

oman a s anot er nota e except on, as on y o young peop e

report av ng tr e canna s ut ave tr e ero n.

Australia and New Zealand

ates o c t rug use among young peop e n ustra a an ew

ea an are roa y s m ar to t ose n ort mer ca, w t t e

et me preva ence o c t rugs e ng g est or canna s an

lowest for heroin.

Considering the wide extent of its use, very few harms are reported

among t e m ons o exper menta an occas ona canna s users.

owever, ev ence t at r s s ncrease w t more requent, eavy

use s accumu at ng; w t n cat ons t at requent eavy use s as-

sociated with cannabis dependence (Coffey et al. 2002), depression

and anxiety (Patton t al. 2002) and later development of psychosisergusson t a . ). mong t e many peop e report ng et me

use, sma er num ers o regu ar a y users are cons stent y oun

an t s t s popu at on t at s expose to t e greatest r s o arm.

wo ypes of cannabis are generally available: a herbal preparation

(commonly known as marijuana, grass, weed etc.) and a resin

(hashish). Concentrated oil is also available, but rarely encounteredan not cons ere urt er or t s reason.

ype as some ear ng on t e way t at canna s s consume

and factors that relate to risk including: the mix of psychoactive

ingredients, the speed and efficiency with which these get to the

ra n, t e nature an extent o contam nants an t e mpact o a ts

const tuents on t e gut or ungs.

Cannabis is most commonly smoked; either on its own or with

tobacco in hand-rolled cigarettes or, in a variety of pipes, bongs and

s m ar ev ces. t may a so e use n a vapor ser. s s genera yregar e as sa er ecause t e act ve ngre ents are re ease at a

ower temperature t an w t smo ng, w c avo s t e n a at on o

smoke particles, with the additional risks these pose.

ust as a u terants, contam nants an uents may ave a ear ng

on ea t w t ot er rugs, t ere are anec ota suggest ons t at

ow-grade resin - known as ‘soap bar’ in places such as the UK

– may have contents that are hazardous to health such as toluene

n enzene. owever, t ere as een tt e researc on t e extent to

w c t s occurs an any accompany ng r s s.

inally, cannabis is sometimes eaten: a less popular method that

voids smoke-related hazards but has a slow onset that makes dose

regu at on ar er. anna s s not n ecte .

anna s s ma n psyc oact ve compoun s e ta tetra y rocan-

nabinol (THC) - for which there are several isomers and closely

related compounds. Other cannabinoids, notably cannabidiol (CBD),

can moderate the effects of THC and there is suggestive evidence

at may even exert an ant psyc ot c e ect ong et a . ).

e rat o s t ere ore a potent a y mportant area o

stu y w t n quest ons o t e mpact o canna s on menta ea t .

owever, to date, studies of cannabis potency have mainly focused

on THC content and it is premature to draw conclusions as to wheth-er some orms o canna s are more or ess arm u t an ot ers as a

resu t o t e r erent a : rat o.

The potency of cannabis has recently been reviewed by the European

onitoring Centre on Drugs and Drug Addiction (EMCDDA 2004a).

ey conc us ons were t at:

ere are a num er o mportant met o o og ca m tat ons

to t e qua ty o ex st ng ata.

Whereas cannabis resin is commonly consumed in many

uropean countries it is rarely seen in the USA - where

herbal cannabis dominates the market. This limits theircompara ty.

atura var at on n content etween an w t n

samp es at any one t me an p ace excee s any ong term

changes that have happened in Europe or the USA.

Intensive indoor cultivation of herbal cannabis usually

resu ts n a more potent up to - t mes) pro uct t an

mporte er a canna s. owever, t e potency ranges o

ntens ve y grown an mporte canna s over ap.

The overall increases in potency observed in some countries

e.g. the Netherlands) are largely attributable to increased use

o ome-grown canna s. ere s no mar e upwar tren n t e potency o er a

canna s or canna s res n mporte nto urope.

Country/Year Source Age group Nearly daily/Daily

Austra a 2004 Austra an Inst tute o Hea t an We are 2005 14-19 1.6%

USA 2003 o nston et a . 2004 17-18 6.0%

Spain 2002 EMCDDA (2004b:89) 14-18 3.6%

France 2002 EMCDDA 2004 :89 17-19 9.2% oys 3.3% g r s

VARIATIONS IN CANNABIS TYPE

AND POTENCY



4

Its final conclusion states that:

“there have been modest changes in THC levels that are

arge y con ne to t e re ative y recent appearance on

e mar et o intensive y cu tivate omestica y pro uce

annabis. Cannabis of this type is typically more potent,

lthough it is also clear that the THC content of cannabis

roducts in general is extremely variable and that there are

some samp es t at ave a ways a a ig potency… n

mportant point to note is t at t e possi i ity o a itiona

u ic ea t pro ems cause y t e use o ig potency

annabis as compared to cannabis products in general

emains poorly understood.”

er aps t e most mportant po nt s t at t e systems or mon tor ng

c ang ng potency are poor y eve ope an , at present, arge y

opportunistic, as they rely on cannabis seizures rather than more

systematic sampling from cannabis markets. Considerable work

s yet nee e to ensure t at t e met o o og es use or assess ng

potency - a ong w t ot er potent a y s gn cant compoun s

- generate proper y compara e ata etween p aces an across t me.

Cannabis production

he 2005 World Drug Report reports that 114 cannabis producer

countries have been identified, with significant exporter states

ex st ng on every cont nent ot er t an ntarct ca. ort mer ca

s thought to produce more cannabis than any other region and

global production is currently rising. Furthermore, increases in

HC potency have been reported within the USA, Netherlands

and Canada (United Nations Office on Drugs and Crime 2005).

eyond reliance on traditional cannabis exporters, there are

ndications that domestic cultivation is increasingly meeting

demand. For example, marijuana was the 8th most important

agricultural commodity grown in Washington State, USA in 2005

CBS 2006). The development of stronger strains of cannabis

grown hydroponically by widely-dispersed, small-scale producers

may also be altering some cannabis markets (for example, Hough

t al . 2003).

s sect on escr es w at s current y nown a out t e re at ons p

etween canna s an psyc os s - t e most ser ous, an o ten

en ur ng, orm o menta ness: symptoms o w c may nc u e

conditions which affect the mind and where there is some loss

of contact with reality. Some of the characteristic symptoms of

psyc os s are con use t n ng, sor entat on, e us on, a see e s, a uc nat ons an c ange ee ngs an e av our.

c izop renia s a psyc ot c ness n w c t e c anges n

behaviour and other symptoms occur in individuals for periods

of six months or more, with at least one month in this disturbed

per o mar e y two or more psyc ot c symptoms. eop e w t

sc zop ren a n t cu t to unct on n a y e.

A schizophreniform disorder is similar to schizophrenia but the

symptoms last for less than six months and it is not marked by a

decline in functioning.

epressive episo es may e m , mo erate an severe an

agnos s o an ep so e requ res symptoms to ave aste or at

east 2 weeks. Symptoms of depression include lack of energy,

mpairment of sleep, problems with concentration or appetite and

su c a t oug ts. ese symptoms are requent y com ne w t

symptoms o anx ety suc as nsomn a, tens on an rr ta ty.

Understanding the links between cannabis and psychosis has been a

challenge for scientific study, its methods and interpretation, which

as e t an ongo ng e ate a out t e s gn cance o t e researc

n ngs or pu c ea t ac eo t a . ).

isk factors for mental illnessThe reasons why some people develop psychosis and schizophrenia

re not fully understood. Schizophrenia is now considered to develop

s a resu t o an nteract on etween o og ca pre spos t on to

e sease an t e n v ua s env ronment. esearc as s own

at t ere s a strong genet c contr ut on to sc zop ren a an

hose with close relatives with a history of schizophrenia and

other psychiatric illnesses have an increased risk of developing thesease over t at o t e genera popu at on. owever, o t ose

w t sc zop ren a ave no c ose re at ve w t t e sease an a

range o env ronmenta actors ave een pos te as contr ut ng

o the susceptibility to schizophrenia, with a gene-environment

nteraction coming into play. For example, living in an urban

env ronment can ncrease t e r s o eve op ng sc zop ren a

y one- t r ra en am an s ). am y r s actors

nc u e materna n ect ons an u ur ng pregnancy or use o

painkillers by the pregnant mother, although the majority of the

factors have been found to have a modest effect. Other possible

risk factors identified by research include disturbances in earlyeve opment, ur an zat on an m grat on a t a . ).

he relationship between cannabis andsychological harm

There are four main views on the nature of the association between

canna s an ater menta sor ers. rst y t at t e n may e

ue to soc o emograp c, econom c or genet c actors common to

ot canna s use an t e sor er. econ y, t e se -me cat on

hypothesis suggests that patients with mental health problems may

be using cannabis and other drugs as a form of self-treatment for

e r con t on. r y t at canna s rect y causes new cases oe menta sor er. na y, t e vu nera ty ypot es s proposes

at t e use o canna s can ncrease t e r s o menta ea t

problems for some at-risk people (Hall t al. 2001).

CANNABIS AND PSYCHOSIS



5

Acute, short-lived psychotic episodesere s a un ant researc ev ence t at canna s can cause s ort-

ve psyc ot c ep so es. e ca case reports ave ent e a

num er o symptoms nc u ng m mpa rment o consc ousness,

distortion of time sense, a dream-like euphoric state, fragmentation

of thought processes, and auditory and visual hallucinations.

Episodes are brief and the person soon recovers. The precipitating

ro e o canna s n t ese ep so es s con rme y ts use

mme ate y prece ng t e onset o t ese attac s an t e ep so es

rem tt ng on cessat on o canna s use a egen ar t ).

Prevalence of cannabis use among people withschizophrenia

ere s ev ence rom a range o nat ona an oca stu es t at

rates o canna s use are g er approx mate y two- o ) among

people with schizophrenia than in the general population. For

example, the US National Epidemiological Catchment Area study

o ns eg er ) n cate t at o t ose ent e w t

sc zop ren a a so a a agnos s o su stance use sor er a use

or epen ence), compare w t o t e genera popu at on

(Regier et al.1990). People who used cannabis on a daily basis were

2.4 times more likely to report psychotic experiences than non-

daily cannabis users, after controlling for a variety of confounding

var a es nc u ng soc o emograp c actors, soc a ro e, an ot er

psyc atr c con t ons en nt ony ). m ar n ngs

ave emerge rom surveys n ustra a an t e et er an s a

& Degenhardt 2000; Van Os t al . 2002). Rates of cannabis use have

also tended to be twice as high among patients with psychosis inoca osp ta stu es t an n commun ty contro s, regar ess o t e

treatment sett ng rec et a . ).

Cannabis and the development of schizophreniaand psychosis

e stu es ave oun e evate rates o canna s use

amongst t ose w t sc zop ren a an psyc os s, a num er o

care u y es gne prospect ve stu es ave e pe to assess

the nature of the relationship involved and whether cannabis

use precede schizophrenia. The studies have used a variety of

different populations to chart the role of a range of risk factors,o w c canna s s ust one. e n ngs rom t ese stu es

ave een summar se n a num er o rev ews rseneau t t a .

; m t t a . ), one systemat c rev ew paper emp e

et al . 2005) and one meta-analysis (Henquet t al. 2005).

What is the relationship between cannabis and

psychosis?e t ese var ous stu es use a range o met o o og es,

measurements of cannabis use and psychosis and, in some cases like

the Dunedin birth cohort study and the Dutch NEMESIS study of

menta ea t n t e genera popu at on, were mar e y sma samp es zes, t ere was some cons stency n t e r s o eve op ng psyc os s

a ter canna s use across a t e popu at ons stu e . egu ar

cannabis use increased the chances of developing later schizophrenia

or schizophrenia-like psychotic illness by approximately two to

ree o rseneau t et a . ; emp e et a . ). n t e une n

stu y t ose w o starte t e r canna s use y age years a a

g er r s o eve op ng sc zop ren orm sor er y age

han those who started at age 18, suggesting that early cannabis use

ay provide higher risk of psychosis outcomes (Arseneault t al.

2002). The analysis from a birth cohort study in Christchurch New

ea an as gone t e urt est n terms o contro ng or a w e

range o poss e con oun ng emograp c, soc a an n v ua

actors n t e r ana ys s an suggeste t at t e assoc at on etween

cannabis use and psychosis in the study population is unlikely to

be due to confounding factors (Fergusson et al . 2005). The analysis

so suggeste t at t e rect on o causa ty was rom canna s to

psyc os s, un erm n ng t e se -me cat on ypot es s.

owever, the increased rates of cannabis use in the last thirty years

have not been accompanied by a corresponding increase in the

rates o psyc os s n t e popu at on egen ar t t a . a). e

stu es rev ewe ere suggest t at canna s s a mo est stat st ca

r s actor an t e vast ma or ty o young canna s smo ers o

not develop psychosis, supporting the hypothesis that a small

inority of users may be vulnerable to the effects of cannabis. The

vulnerability hypothesis has received some support from a study

at exp ore su stance use an psyc ot c exper ences n a y e.

e acute e ects o canna s were stronger among part c pants w t

g vu nera ty or psyc os s exper enc ng at east one zarre

psychotic symptom or at least two non-bizarre symptoms over the

rst month). Those vulnerable participants reported increased levelo perce ve ost ty an unusua percept ons, an a so ecrease

eve o p easure assoc ate w t t e exper ence o us ng canna s

er oux et a . ). tu es o t e am y stor es o users an

non users add further support to this model. The Edinburgh High

isk study found that frequent cannabis use, among young people

w t a am y story o psyc os s was assoc ate w t a s x- o

ncrease n t e r s o psyc os s compare w t contro s er e

. ) ng urt er we g t to t e strengt o t e vu nera ty

hypothesis is a recent study, awaiting replication, that examined

gene-environment interaction in the Dunedin study population,

nding that a gene called COMT moderated the influence ofo escent canna s use on eve op ng a u t psyc os s n t e

une n samp e asp et a . ).

Cannabis and the course of schizophreniaThe results from a number of studies suggest that cannabis use

can ma e t e symptoms an treatment outcomes o t ose w t t e

ness worse. n one prospect ve stu y canna s-us ng pat ents were

compare to pat ents w o not use canna s n an outpat ent

setting in Holland. The patients’ psychiatric health was tracked each

onth for a year. The cannabis users had more and earlier psychotic

re apses or exacer at on o symptoms, w c was s gn cant y morenot cea e among t e eavy users. ese e ects pers ste a ter

contro ng or ot er rug an a co o , use, ant psyc ot c me cat on

dherence and dosage (Linszen et al . 1994).



6

More recent prospective studies have had longer follow-up studies.

or examp e, one ong-term case-contro stu y o owe rst

ep so e pat ents w t s x assessments over a ve year per o . ow-

ever, t s stu y on y a canna s users n t e samp e w o were

combined with the conjoint alcohol and alcohol users only in the

group for analysis. The substance misusers fared worse than the non-

users, with poorer treatment adherence, lower use of rehabilitation

serv ces an s owe g er pos t ve symptoms at eac assessment.

owever, not a stu es ave oun t at canna s use as a negat ve

effect on the course and outcome of schizophrenia. Two commu-

nity studies, one in America and one in Scotland, found that past or

present su stance m suse ma n y canna s) a tt e a verse mpact

on symptoms, course o ness or serv ce use soo et a . ;

antwe ). e m xe resu ts rom t ese stu es may re ect

the difference in the samples studied and the research designs used.

Some studies did not control for the effect of medication, possibly

con oun ng t e resu ts. e strongest ev ence ava a e current y

suggests t at canna s oes worsen t e prognos s or t e ma or ty o

t ose w t sc zop ren a w o a so smo e canna s; ut, t at t ere

may be a subgroup who finds its use beneficial in coping with side

effects of their medication or dealing with the negative symptoms of

their illness.

Cannabis, anxiety and depressionanna s an ts re at ons p w t anx ety an epress on as rece ve

less research attention in comparison to schizophrenia and psychosis.

National population studies have found evidence for a link betweencanna s use an epress on. stu y o a nat ona y representat ve

samp e o a u ts age to n t e , oun a sma n-

crease r s o epress on among t e current users o canna s en

et al . 2002). Another study of a nationally representative sample of

40-50 year olds in the USA found an small increased risk, but one that

was assoc ate w t ear er onset o canna s use rat er t an current

use reen tter ). nat ona popu at on stu y n ustra a

oun t at canna s users were etween two to t ree t mes more e y

to meet criteria for a mood disorder than non-users. Prevalence of

mood disorders increased from 6% in non-users to 14% of those who

met criteria for cannabis dependence (Degenhardt et al. 2001).

n a ong tu na stu y o a representat ve samp e o secon -

ary sc oo stu ents n t e ustra an state o ctor a, wee y or

more frequent use led to a doubling of the risk for later anxiety or

depression by the age of 20 years, while female daily users had a

ve o ncrease n ater epress on an anx ety. atton et a . ).

epress on an anx ety n t e stu ents not pre ct ater canna s

use n t e ana ys s, suggest ng t at canna s was not use or se -

medication. However, findings from the smaller New Zealand Dun-

edin sample reported above indicated that those in the sample using

canna s y age not ave a s gn cant y g er r s o aterepress on y t e age o years t an non-users , a t oug t e

samp e s ze may prevente t e ent cat on o a re at ons p n t e

statistical analysis (Arseneault et al . 2002). The Dunedin study, how-

ever, did find that using cannabis three or more times by age 18 was

mo erate pre ctor o epress on y age a ter contro ng or a

range o var a es n t e stat st ca ana ys s. meta-ana ys s o co-

ort stu es oun a mo est ut s gn cant assoc at on etween ear y

onset heavy use of cannabis use and later depression (Degenhardt e

l . 2003b). In a follow-up study of the New Zealand Christchurch

sample, the analysis controlled for a range of confounding factors

at m g t exp a n t e assoc at on etween canna s an a range o

psyc osoc a outcomes nc u ng epress on an su c e attempts.

e n etween canna s an t ese outcomes an eavy at east

weekly) cannabis use still persisted, suggesting that cannabis was

contributing directly to these outcomes (Fergusson t al. 2002).

e epress on an sc zop ren a, anx ety sor ers are oun at

g er rates among requent users o canna s t an non-users. ere

have been a number of case reports of panic reactions after cannabis

use. In a survey of 1000 young adults in New Zealand, acute anxiety

n pan c was t e most common psyc atr c pro em reporte

y canna s smo ers n t e stu y omas ). s n cate

ove, t e ctor an ong tu na stu y oun an ncrease r s o

ixed anxiety and depression after daily cannabis use (Patton et al.

2002). However, the few other longitudinal studies in this area have

generally tended to fail to find a relationship between anxiety and

canna s use or oun t at ot er actors account or t e re at ons p.

or examp e t e r stc urc stu y oun t at a t oug su stance

ma n y canna s) a use an epen ence was g er among t ose

with an anxiety disorder, the association could largely be the results

of a range of factors such as childhood and family factors, peerat ons an co-mor epress on oo w n et a . ).

ConclusionTaken as a whole, the available epidemiological evidence suggests

hat cannabis can exacerbate the symptoms of schizophrenia. The

est ava a e ev ence rom t e ex st ng range o prospect ve

ep em o og ca stu es n cates t at canna s can prec p tate

sc zop ren a n peop e w o are a rea y vu nera e or n v ua

or family reasons. Those with a psychosis vulnerability may also

be at an increased risk of experiencing psychotic symptoms,

particularly if their cannabis use is regular. The evidence for anssoc at on etween canna s use an epress on or anx ety s

xe , w t ong tu na researc suggest ng t at canna s s a

o erate r s actor or ater epress on ut t at t e re at ons p

between cannabis and anxiety is likely to be the result of other

ediating factors such as childhood and family factors.

t oug more researc wor s nee e to un erstan t e pat ways

nvo ve , t s mp es t at a precaut onary approac s ou e a opt-

ed, which aims to minimise any contribution cannabis makes to the

development or exacerbation of psychotic illness. For prevention,

s mp es:e a opt on o strateg es to re uce canna s use, w t a

spec c o ect ve o m n m s ng regu ar an eavy patterns

of consumption.







9

(Henderson & Bennett 1999). This is therefore an area that is worthy

o eve opment. e o ow ng st s n cat ve o some areas t at

cou potent a y e a resse :

Mental health – Promoting awareness of a) the general risks of

adverse acute reactions to cannabis and possible triggering of

psychotic illness; b) heightened risks for people with family history

o sor er persona story o a verse e ects; c) t e es ra ty o

a st nence, part cu ar y or peop e w t e g tene r s .

Dependence – Public campaigns that a) reinforce awareness of the

risk of cannabis dependence; b) promote self-control strategies;

c) pu c se awareness o treatment an pat ways or e p-see ng.

ega arms – u c s ng t e r s o arm t at can ar se t roug

criminal/civil consequences of conviction such as a) impacts on free-

dom to travel, b) exclusion from employment/education and other

orms o sen ranc sement e.g. t e oss o ent t ement to vote n t e

.

TreatmentAlthough the great majority of cannabis use does not appear to

become problematic, use of cannabis already makes an important

contr ut on to t e overa eman or rug treatment. s t e n te

at ons ce on rugs an r me : ) conc u es:

espite its wi esprea use, canna is oes not generate

emand for treatment at the rate of other street drugs,

ut more than 60% of treatment admissions in Africa are

anna is-re ate , compare to in ort merica an

in t e ceania region.

Within Europe, demand for cannabis treatment is also climbing, with

indications that cannabis is the ‘primary drug’ in 12% of treatment

ep so es - secon on y to ero n a: ). oug t

s ou e note t at suc stat st cs are, to some extent, arte acts o

t e var ous mon tor ng systems t at are e ng use .

It is not yet clear how the effectiveness of treatment can be optimised

but there is growing evidence that it may fulfil a useful role (Loxleyet a . ). e recent v sory ounc on t e suse o

rugs report exp c t y ent es treatment or canna s epen ence

as an area requ r ng eve opment, a ong w t a para e programme

to enhance the evidence-base for practice (Advisory Council on the

Misuse of Drugs 2005).

reatment opt ons nc u e treatment or epen ence an r e nter-

vent ons raw ng on pr nc p es suc as mot vat ona nterv ew ng.

To date, cannabis/youth drug use treatment approaches have largely

derived from existing work in the alcohol field and with other illicit

rugs; us ng approac es arge y groun e n cogn t ve e av ourwor , a ong w t se - e p manua ase approac es w t ot

a st nence an non-a st nence arm re uct on goa s. ome recent

evidence points to the utility of a single motivational interviewing

session for reducing consumption, though again complete cessation

o canna s use was ess common: a nota e stu y ecause ts e ect

seeme most pronounce on more vu nera e an g r s yout

c am r ge trang ). uc wor requ res rep cat on an

further development.

Similar problems similarly limit what can be said about the

e ect veness o rug treatment or young peop e n genera .

evert e ess, one systemat c rev ew po nts to eve op ng ev ence

– arge y ort mer can – t at assorte counse ng an am y-

focused approaches can sometimes a) reduce drug use b) improve

well-being, and c) improve family and social relations (Elliot

. ). ga n, urt er eve opment an eva uat on s requ re

o un erstan to w at extent suc resu ts are repro uc e n ot er

contexts an are app ca e spec ca y to canna s.

ith specific regard to cannabis and mental health problems,

t seems e y t at en anc ng systems a son etween yout

serv ces, rug treatment agenc es an a o escent a u t psyc atr c

serv ces cou e ene c a . t s, as yet, unc ear to w at extent

wider, general health services might contribute to the reduction of

cannabis-related harm, but it seems noteworthy that the ACMD have

recently highlighted the importance of addressing cannabis use and

prevent on or pat ents w t sc zop ren a ).

na y, scann ng t e or zon w t n treatment ea t responses, t e

very early evidence (Caspi et al. 2005) that part of the population

ay be more susceptible to problems with cannabis due in some parto genet c actors suggests t at, n t me, genet c screen ng may ave

some ro e to p ay as a too or prov ng peop e w t n v ua se

ea t n ormat on a out e g tene r s s vu nera ty. owever,

he contribution of any such genetic factors requires further

clarification before any such measure could become feasible.

Structural interventionsere s ncreas ng recogn t on o t e ways t at pro em rug use

re determined by structural factors at the global, national and

community-level including: socioeconomic deprivation, income

nequalities, social inclusion, social cohesion and the cultural capitalva a e w t n commun t es pooner et a . ). s strong y

suggests t at ntervent ons ocus ng on t e n v ua are pro oun y

constra ne structura eterm nants o pro em canna s use, as

component of problem drug use in general, are ignored. Such

pproaches typically focus on enhancing protective factors nd

re uc ng t e ris actors to w c young peop e n genera , a ong

w t t ose rom spec c vu nera e groups e.g. young o en ers,

c ren w t n care systems, street c ren, sc oo exc u ees an

some ethnic minority groups) often have multiple exposure (The

ealth Advisory Service 2001; Benson et al. 2004).

e terature c te a ove revea s t at many suc actors are

ent a e. ome are suscept e to more mme ate, programmat c

pproaches. For example:



10

e uc ng g su stance ava a ty w t n part cu ar

ne g our oo s;

rogrammes to re uce sc oo exc us on; an ,

Tailored work targeting vulnerable groups such as young

offenders or street children/youth homeless.

t ers are eep y em e e w t n soc a an econom c con t ons,

o ten ntersect ng an un e y to e amena e to c ange w t n t e

s ort to me um term suc as:

Endemic, trans-generational socio-economic deprivation;

Racism and the social exclusion of ethnic minorities such as

Roma within Europe and indigenous peoples in Australia,ew ea an , t e an ana a; an ,

e g tene ava a ty ar s ng rom emerg ng an

esta s e patterns o rug pro uct on an t e r assoc ate

trafficking transit routes.

The use of cannabis raises a number of distinct challenges for policy

makers that, in several respects, set it out from other illicit substances.

anna s s asi y cu tivate . ven or rugs t at o ten ave to cross

nat ona or ers, w t t e r correspon ng contro s – suc as coca ne

or heroin – the difficulties in reducing supply are well known. By

contrast, canna s s rea y cu t vate n a most any country; as t e

now e ge, see s an tec no ogy to grow t are rea y ava a e.

upp y re uct on strateg es t ere ore ave even poorer prospects o

success than for other illicit drugs; pointing towards the need for a

strong emphasis in other areas of our response.

anna s use s among t e east visi y pro ematic orms o c t

rug use. resent ev ence suggests t at concern ng t e most

serious drug-related harm - death - the role of cannabis is negligible

compared to other legal, prescribed and illicit drugs (Blakemore

2003). Although it is increasingly clear that cannabis use incursr s s, nc u ng menta ea t pro ems, m ons o peop e use t e

rug w t out o v ous -e ects. egar ng ts potent a to cause

ser ous menta ea t pro ems, t s a so o note t at a co o as t e

potential to cause a psychosis – Korsakoff’s Syndrome; so in this

sense, the hazards of cannabis use are not unique.

ere are some n cat ons t at canna s potency s ncreas ng,

ut ev ence to ate suggests t at t s e ect s re at ve y mo est

nd uneven and has been overstated in the media. However, our

understanding of cannabis markets remains far from adequate and

ere s an urgent nee or etter mon tor ng o canna s ava a tyw t n ex st ng supp y systems w t regar to a) ts potency ) ts

ccess ty – espec a y to young peop e. evert e ess, we now

hat in most countries cannabis is the most widely used illicit drug,

CONCLUSIONS

.

The United Nations Conventions on drugs classify narcotic drugs and psychotropic substances by virtue of their danger to health, risk of abuse and therapeutic

alue. The 1961 Single Convention on Narcotic drugs is the bedrock of the current international system. While there is a certain degree of flexibility within the

extant treat es , , , t e pro t ve et os o t e system s c ear. rt c e c o t e ng e onvent on o ges s gnatory nat ons, su ect to t e

prov s ons o t e onvent on, to m t exc us ve y to me ca an sc ent c purposes t e pro uct on, manu acture, export, mport, str ut on o , tra e n, use

and possession of drugs listed. The Single Convention classifies narcotic drugs in four schedules. Cannabis is listed twice. It is in Schedule I, as a substance

w ose propert es g ve r se to epen ence an w c presents a ser ous r s o a use. t s a so n c e u e , among t e most angerous su stances, y v rtue

o t e assoc ate r s s o a use, ts part cu ar y arm u c aracter st cs an ts extreme y m te me ca or t erapeut c va ue , .

anna s rst came un er a m te orm o nternat ona contro at t e eneva on erence n , on t e ns stence o t e gypt an e egat on. s was

accepte esp te t e act t at t e ssue was not on t e agen a an accor ng to t e r t s e egate was yet n an unprepare state. ur ng t e s

the implementation of international controls was pushed for by the US, which was troubled by the use of the drug within its own borders. Between 1935

and 1939, a cannabis subcommittee, appointed by the Special Advisory Committee on Traffic in Opium and Other Dangerous Drugs of the League of

at ons, amasse a arge co ect on o ata on canna s. t oug t e s tuat on n n a was over oo e n t e researc e ort, t e ocuments pro uce y

t e su comm ttee s owe an awareness o t e cu tura erences n t e use o canna s an t e cu t es surroun ng contro o t e rug. ere was,however, little follow-up to this research with later decisions within the international system relying on information and reports of a less relevant nature. The

rst sess on o t e omm ss on on arcot c rugs o t e n not appo nt a su comm ttee on canna s, ut t e ega status o t e rug

soon ecame a concern or t ose ra t ng t e ng e onvent on; a process w c starte n . ter some e ate concern ng ts me ca use u ness an

harmfulness, and the selective use of the evidence base by those in favour of outlawing the drug, the definitive decision to adopt a prohibitionist position

on canna s n t e ng e onvent on was ta en y t e n . ga n t e was t e pr mary orce e n t s ec s on an as suc mo ze

t e appropr ate nternat ona organs w t n t e rug contro system. y t e t me o t e p en potent ary con erence or t e ng e onvent on t was a

foregone conclusion that cannabis would be placed under the strictest control regime (Bruun et al . 1975). Beyond negotiations for reservations concerning

transitional periods for phasing out the traditional use of the drug in countries like India, there was no discussion of the classification of cannabis alongside

ero n an coca ne w t n t e onvent on. esp te t e m te contemporary sc ent c ust cat on or t s state o a a rs, t ere rema ns a re uctance to

rev s t t e p ace o canna s w t n t e nternat ona rug contro system.



1

being tried by very large numbers of teenagers, regularly used by

a s gn cant m nor ty an , n some cases, av ng een use y a

ma or ty o t e a u t popu at on. n many respects t s now a so

cu tura y-em e e w t n yout cu ture. s w esprea an

embedded use implies that it will be less amenable to approaches that

primarily rely on enforcement through the criminal justice system.

e ev ence suggests t at as ong as canna s use rema ns ega ,

t e more severe cr m na pena ty sc emes are no more e y to eter

use t an are c v pena ty sc emes, ut cr m na reg mes resu t n

greater social costs to individuals and more criminal justice costs to

communities. Furthermore, criminalizing cannabis users also places

many c t zens outs e o t e aw an ra ses t e poss ty t at e t er

a) a arge ract on o t e popu at on are potent a y open to cr m na

c arges, w t t e correspon ng costs to n v ua s an soc ety

b) the law is largely unenforced, or enforced inequitably on certain

sectors of society e.g. ethnic minorities – potentially bringing the law

nto srepute. t present, t e status o canna s w t n t e ex st ng

convent ons means t at t s current y mposs e to eterm ne

w et er r ng ng canna s contro w t n a ega , regu ate rame-

work could further reduce cannabis-related harms, but this possibility

cannot be dismissed and, arguably, deserves cautious study.

egar ng e ect ve po c es, unsurpr s ng y, no s mp e so ut ons

ex st. owever, an ev ence- ase response to canna s-re ate

arms - nc u ng t ose to menta ea t - wou seem to requ re

a multi-faceted, developmental approach that resists populist

solutions. This briefing has identified a range of opportunities forurt er eve op ng ntervent ons w t n e ucat on, treatment an a

w er pu c ea t approac , eac o w c as prom se ut requ re

urt er eva uat on. owever, u t mate y, canna s-re ate arms are

only ever likely to be truly minimised in the longer term, if diverse,

underlying factors are also addressed. Consequently, any immediate

an ocuse response on ntervent ons s ou not e a owe

to o scure t e necess ty o a ress ng t e un er y ng structura

eterm nants o pro em canna s an ot er rug use.

Advisory Council on the Misuse of Drugs (2005) Further consideration of the

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Documents

Cannabis Report 08