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Drug and Alcohol Dependence 127 (2013) 72– 80

Contents lists available at SciVerse ScienceDirect

Drug and Alcohol Dependence

journa l h o me pag e: www.elsev ier .com/ locate /drugalcdep

he impact of the prohibition of benzylpiperazine (BZP) ‘legal highs’ on therevalence of BZP, new legal highs and other drug use in New Zealand

hris Wilkins ∗, Paul Sweetsurocial and Health Outcomes Research and Evaluation (SHORE), SHORE and Whariki Research Centre, School of Public Health, Massey University,New Zealand

r t i c l e i n f o

rticle history:eceived 18 December 2011eceived in revised form 7 May 2012ccepted 12 June 2012vailable online 20 July 2012

eywords:egal highsenzylpiperazine (BZP)rohibitioneneral populationrequent drug users

a b s t r a c t

Background: Benzylpiperazine (BZP) is the psychoactive ingredient in a range of ‘legal highs’ sold world-wide. BZP was prohibited in New Zealand in 2008.Aim: To investigate the impact of the prohibition of BZP legal highs on the prevalence of BZP, replacementlegal highs and other drugs.Methods: A population survey of BZP and other drugs was conducted in 2006 (while BZP was legal) andrepeated in 2009 (+12 months after BZP was prohibited). Respondents were asked to provide the reason(s)why they had stopped using BZP. Annual surveys of frequent drug users were conducted from 2006 to2010.Results: Last year prevalence of BZP among the general population fell from 15.3% in 2006 to 3.2% in 2009.The most common reasons for stopping BZP use in 2008 were ‘it’s illegal now’ (43%), ‘just experimenting’(26%), ‘don’t know where to get it now it’s illegal’ (24%) and ‘bad hangover effect’ (18%). Three per cent

of the general population had used any new legal high in 2009. Use of BZP declined among frequentmethamphetamine users from 32% in 2006 to 7% in 2010; among frequent ecstasy users from 65% in2006 to 11% in 2010; and among frequent injecting drug users from 30% in 2007 to 20% in 2010. The useof new legal highs in 2010 was lower than the former use of BZP in 2006.Conclusions: Unpleasant side-effects and the prohibition contributed to a decline in BZP use. The overalllevel of legal high use was lower following the prohibition of BZP.

. Introduction

There is concern in many countries around the world abouthe sale of a growing number of so called ‘legal highs’ containingreviously obscure psychoactive chemicals (European Monitoringentre for Drugs and Drug Addiction, 2011a, b; Griffiths et al., 2010;nited Nations Office on Drugs and Crime, 2011a, b; Winstock et al.,010). Benzylpiperazine (BZP) is one such substance used in a rangef legal high products known as ‘party pills’ (European Monitoringentre for Drugs and Drug Addiction, 2011a, b; Hillebrand et al.,010; Marre, 2008; Poon et al., 2010; Sheridan et al., 2007; Unitedations Office on Drugs and Crime, 2011a; Vince, 2006). BZP

s a central nervous system stimulant with approximately 10%he potency of dexamphetamine and subjective and physiolog-cal effects similar to other commonly known stimulants, such

s amphetamine and 3,4-methylenedioxymethamphetamineMDMA); (Baumann et al., 2004, 2005; Bye et al., 1973; Campbellt al., 1973; Lin et al., 2009; Antia et al., 2009). BZP has been

∗ Corresponding author at: SHORE and Whariki Research Centre, PO Box 6137,ellesley Street, Auckland, New Zealand. Tel.: +64 9 3666136; fax: +64 9 3665149.

E-mail address: c.wilkins@massey.ac.nz (C. Wilkins).

376-8716/$ – see front matter © 2012 Elsevier Ireland Ltd. All rights reserved.ttp://dx.doi.org/10.1016/j.drugalcdep.2012.06.014

© 2012 Elsevier Ireland Ltd. All rights reserved.

prohibited in many European countries, the United States,Australia, Japan, Sweden, South Africa and New Zealand (EuropeanMonitoring Centre for Drugs and Drug Addiction, 2007, 2008,2010; Hillebrand et al., 2010; Cohen and Butler, 2011). To date,there has been no published research evaluating the impact of theprohibition of BZP legal highs on the use of BZP and other drugs.Indeed, there are surprising few empirical studies of the impact ofprohibition on the prevalence of use of formerly widely used legalrecreational drugs (see MacCoun and Reuter, 2001; Musto, 1987).

The domestic BZP ‘legal high’ industry which developed in NewZealand during the early to mid-2000s was particularly sophisti-cated and mainstream by international standards, partly due toNew Zealand’s poor supply of ecstasy (Cohen and Butler, 2011;Sheridan et al., 2007; Wilkins et al., 2007). In 2005, a representativeof leading BZP manufacturers claimed that as many as 200,000 BZPpills (i.e., 50,000 four pill packs) were being sold each month in NewZealand generating retail sales of $24 million per year ($NZ; Cohenand Butler, 2011; Dawkins, 2008; Gee and Fountain, 2007; Sheridanet al., 2007; Social Tonics Association of New Zealand, 2005). New

Zealand manufacturers promoted BZP legal highs as legal and ‘safe’alternatives to ecstasy and methamphetamine (Cohen and Butler,2011; Sheridan et al., 2007). BZP was eventually prohibited in NewZealand in April 2008 following the findings of a number of studies

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hich found use of BZP legal highs to be associated with health riskssee Gee et al., 2005; Sheridan et al., 2007; Wilkins et al., 2008).

Theoretical expositions of the impact of prohibition have iden-ified mechanisms that can lead to both decreases and increasesn the use of a prohibited drug (MacCoun, 1993, 2010; MacCounnd Reuter, 2001). Prohibition can reduce the use of a drug byubjecting users to a risk of arrest and legal punishment (Moore,990), by making the drug more expensive and inconvenient tourchase (Kleiman, 1992; Moore, 1990; Reuter and Kleiman, 1986),nd more indirectly by supporting individual self-control and pro-oting informal social norms against use (MacCoun, 1993, 2010).lternatively, prohibition can lead to an increase in the use of arug by creating a ‘forbidden fruit effect,’ where use of the drug isssociated with rebellion, or by stigmatising users, and thus alien-ting them from conventional social norms against use (MacCoun,993, 2010; MacCoun and Reuter, 2001).

Empirical studies have found that while current users of ille-al drugs do not perceive legal penalties to be a major deterrent,egal penalties are often more relevant to those who have chosen toever use illegal drugs or who have experimented with illegal drugsut chosen not to continue use (Bewley-Taylor et al., 2009; Brownt al., 1971; Weatherburn et al., 2003). The latter two groups tendo live more conventional lifestyles with careers and responsibili-ies which are not consistent with breaking the law (Bewley-Taylort al., 2009; Kandel et al., 1997; MacCoun, 1993, 2010). Experi-nced drug users have been found to stop for a range of reasonsften unrelated to legal penalties including concerns about healthisks; pressure from a partner, family and friends; or due to agingr maturing out (Bachman et al., 1990; Brown et al., 1971; Hallt al., 2001; Kandel et al., 1997; Schelling, 1992; Weatherburn et al.,003). Individual decisions to use drug are also influenced by youthnd cultural trends; changes in availability and prices; changes inrescribing practices; stricter precursor controls; and targeted lawnforcement campaigns (Babor et al., 2010).

It is also increasingly recognised that the prohibition of onerug can affect the use of other substances, either positivelyr negatively. Legal high manufacturers in New Zealand arguedhe banning of BZP legal highs would result in an increase in

ethamphetamine use (Dawkins, 2008; TVNZ, 2007). Legal highanufacturers have also demonstrated a capacity to replace a

ewly banned substance with a new unrestricted one (Griffithst al., 2010; Vince, 2006; Winstock et al., 2010). In New Zealand,arty pill manufacturers primarily responded to the prohibition ofZP by introducing a new range of ‘non-BZP party pills’ contain-

ng 1-3 dimethylamylamine (DMAA), but other new legal highslso became available around this time including salvia divinorumnd synthetic cannabis (Cohen and Butler, 2011; New Zealand Lawommission, 2011; Sheridan et al., 2007).

The aim of this paper is therefore to compare the levels of usef BZP, new legal highs and other drugs both before and after therohibition of BZP, and to investigate the reasons BZP users had fortopping BZP use.

. Methods

The New Zealand Government formally announced its intention to prohibit BZPn June 2007, but parliamentary delays meant the legislation was not enacted untilpril 2008 (Dawkins, 2008; Expert Advisory Committee on Drugs, 2006). The moralnd health messages of the BZP prohibition can therefore be conceptualised as takingffect in 2007.

.1. General population survey

A national household survey of BZP and other drug use was conducted in New

ealand in early 2006 (during the time BZP party pills could be legally sold to those8 years or older) and was repeated in June 2009 (i.e., over 12 months after thenactment of the BZP ban in April 2008; see Wilkins et al., 2007, 2009; Wilkinsnd Sweetsur, 2008). Both surveys employed the same computer assisted telephonenterview (CATI) methodology and surveyed approximately 2000 people aged 13–45

ol Dependence 127 (2013) 72– 80 73

years from the general New Zealand population. The survey samples were weightedby eligible household size to adjust for the selection of only one person from eachhousehold. The 2006 and 2009 surveys achieved a 69% and 64% response rate respec-tively. Respondents were asked about the use of BZP and over 25 other drug typesin the previous 12 months, including new legal highs: ‘non-BZP party pills’; ‘salviadivinorum’; and ‘synthetic cannabis’. The survey interviewers were given extensivetraining in the identification of different ‘legal high’ products, and were providedwith resources identifying the names of BZP and non-BZP ‘legal high’ products. Thoserespondents who had ever tried BZP in 2009 were asked if they were using ‘more’,‘the same’, ‘less’ or had ‘stopped’, and were invited to provide up to five unpromptedreasons why they had changed their use. Those who had stopped using BZP wereasked what year they had stopped.

2.2. Survey of frequent drug users

A survey of frequent illegal drug users, known as the Illicit Drug MonitoringSystem or IDMS, has been conducted annually in New Zealand since 2006 (Wilkinset al., 2011a, b). The IDMS interviews three groups of frequent illegal drug users(i.e., frequent methamphetamine users, frequent injecting drug users and frequentecstasy users) from the three largest cities of New Zealand (i.e., Auckland, Welling-ton and Christchurch). Approximately 100 interviews of each of three frequent drugusing groups are completed each year (i.e., 300 in total). The number of interviewsconducted in each location is determined by set site targets and the final samplesare weighted by location and module to ensure consistent yearly comparisons. Thefrequent drug users are recruited using purposive sampling and ‘snowballing’ withthree separate community-level recruitment campaigns undertaken in each loca-tion. Respondents are screened for eligibility for the drug type they contact theinterviewer about and can only be interviewed for one of the groups (i.e., the groupsare mutually exclusive). Participants are required to be 16 years or older, have usedthe drug type of interest or injected a drug approximately monthly or more oftenin the past six months, and have resided in the site location for the past 12 months.Eligible participants are administered a structured face-to-face interview at a pub-lic venue of their choosing. Participants were asked about the use of BZP and over25 other drug types in the previous six months in each survey wave. In 2010, theywere asked about the use of the new legal highs: ‘non-BZP party pills’ (DMAA) and‘synthetic cannabis’.

3. Analysis

3.1. General population survey

Prevalence levels and corresponding confidence intervals werecalculated using logistic regression. Logistic regression was alsoused to test for differences in the proportion of respondents givingdifferent reasons for having stopped using BZP between 1999–2006and 2007–2009.

3.2. Frequent drug user survey

Spearman’s rank correlation coefficients were used to test fora trend in the proportion that used a drug from 2006 to 2010. Ap-value of less than 0.05 indicated a statistically significant trendacross the five years and the direction (positive or negative) of thecoefficient showed whether the trend was increasing or decreasing.We also tested for differences in drug prevalence between consec-utive years using logistic regression (e.g., 2008 vs. 2007).

All analysis was conducted in SAS, incorporating the effects ofweighting.

4. Results

4.1. Prevalence of BZP and other drug use in the generalpopulation

The population prevalence of BZP use in the previous 12 monthsfell from 15.3% in 2006 to 3.2% in 2009 (p < 0.0001) (Table 1). Therewas a small decrease in the last year prevalence of alcohol andtobacco use from 2006 to 2009. There were declines from 2006

to 2009 in the last year prevalence of nitrous oxide (3.2% vs. 0.7%,p < 0.0001) and amphetamine/methamphetamine (3.1% vs. 1.3%,p < 0.0001). There was no change from 2006 to 2009 in the last yearprevalence of ecstasy, LSD, cannabis, cocaine, tranquilliser, amyl

74 C. Wilkins, P. Sweetsur / Drug and Alcohol Dependence 127 (2013) 72– 80

Table 1Proportion of the general population aged 13–45 years old who had used different drug types in the past 12 months, 2006 and 2009.

2006 2009 2009 vs. 2006 % change 2009 vs. 2006

n = 2010 n = 2040

% 95% CI % 95% CI p-Value

Alcohol 82.7 80.7, 84.6 79.1 76.8, 81.1 0.0134 −4%Tobacco 34.2 31.9, 36.6 30.0 27.7, 32.3 0.0108 −12%Cannabis 17.0 15.3, 19.0 15.6 13.9,17.5 0.2694 n/aBZP 15.3 13.6, 17.1 3.2 2.4, 4.3 <0.0001 −79%Ecstasy (MDMA) 3.7 2.9, 4.7 3.0 2.3, 4.0 0.2926 n/aNitrous oxide 3.2 2.4, 4.3 0.7 0.4, 1.3 <0.0001 −78%Amphetamine/methamphetamine 3.1 2.4, 4.1 1.3 0.8, 1.9 0.0002 −58%LSD 1.7 1.2, 2.5 1.6 1.1, 2.4 0.8529 n/aCocaine 1.0 0.6, 1.7 0.6 0.4, 1.2 0.2351 n/aTranquillizers 0.6 0.3, 1.1 0.5 0.3, 1.1 0.8829 n/aAmyl nitrate 0.3 0.1, 0.8 0.9 0.5, 1.4 0.0656 n/aIce (crystal meth-amphetamine) 0.8 0.5–1.3 0.5 0.2–0.9 0.2439 n/aKetaminea 0.2 – – 0.3 – –Heroina 0.15 – 0.02 – – –Salvia divinorum – – 1.3 0.8, 2.1 – –Non-BZP legal part pills – – 1.2 0.8, 1.8 – –Synthetic cannabis – – 0.4 0.2, 0.9 – –Methylphenidate – – 0.3 0.1, 0.6 – –Any legal highb 15.3 13.6, 17.1 4.6 3.7, 5.8 <0.0001 −70%

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ource: BZP National Household Drug Survey, 2006 and 2009.a Low number of respondents prevents any reliable statistical comparisons.b Any legal high = BZP + salvia divinorum + non-BZP party pills + synthetic cannab

itrate and ice (crystal methamphetamine). A small proportion hadsed salvia divinorum (1.3%), non-BZP party pills (1.2%) or syn-hetic cannabis (0.4%) in the previous 12 months in 2009. A lowerroportion of the sample had used any new legal high (i.e., salviaivinorum, non-BZP party pills or synthetic cannabis) in 2009 com-ared to BZP in 2006 (2.5% vs. 15.3%, p < 0.0001). A lower proportionas also used any legal high (i.e., illegal BZP, salvia divinorum, non-ZP party pills or synthetic cannabis) in 2009 compared to BZP in006 (4.6% vs. 15.3%, p < 0.0001).

.2. Prevalence of BZP and other drug use among frequent drugsers (IDMS)

Among the frequent methamphetamine users, there was a con-istent decline from 2006 to 2010 in the use of ice (64% to 23%,

< 0.0001%), LSD (36% to 18%, p < 0.05%) and BZP (32% to 7%, < 0.05%) in the previous six months (Table 2 and Fig. 1). Thereere large declines in the use of BZP from 2007 to 2008 (i.e., the

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ig. 1. Proportion of frequent methamphetamine users who used BZP and selectedther drugs in the previous six months, 2006–2010.

year when BZP was prohibited; 44% vs. 14%, p < 0.0001); nitrousoxide from 2007 to 2008 (24% vs. 9% p = 0.003); LSD from 2008to 2009 (24% vs. 11%, p < 0.0001) and ice from 2009 to 2010 (53%vs. 23%, p = 0.0002). A lower proportion of the frequent metham-phetamine users had used any new legal high (i.e., ‘non-BZP partypills’, synthetic cannabis, salvia divinorum) in 2010 compared toBZP in 2006 (15% vs. 32%, p = 0.0023). A lower proportion of the fre-quent methamphetamine users had also used any legal high (i.e.,illegal BZP, ‘non-BZP party pills’, synthetic cannabis, salvia divino-rum) in 2010 compared to BZP in 2006 (19% vs. 32%, p = 0.0237).

Among the frequent ecstasy users, there were consistentdeclines from 2006 to 2010 in the use of methamphetamine (21% to8%, p < 0.05%), BZP (65% to 11%, p < 0.0001) and nitrous oxide (from47% to 24%, p < 0.05%, Table 2 and Fig. 2). There was a consistentincrease from 2006 to 2010 in the use of methylphenidate (13% to

32%, p < 0.05%). There were declines in the use of BZP from 2007 to2008 (46% vs. 25%, p = 0.02) and every year from 2007 to 2009; andnitrous oxide from 2006 to 2007 (47% vs. 32%, p = 0.015). The useof cocaine increased in 2008 and then declined in 2009. The use of

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Fig. 2. Proportion of frequent ecstasy users who used BZP and selected other drugsin the previous six months, 2006–2010.

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Table 2Six month prevalence of BZP and other drug use among frequent methamphetamine users, frequent ecstasy users and frequent injecting drug users, 2006–2010.

Frequent druguser group (%)

Year BZP Alcohol Cannabis Meth Ice Ecstasy LSD Methylphenidate(ritalin)

Nitrousoxide

Cocaine Heroin Ketamine Morphine Syntheticcannabis

Non-BZP legalparty pills

Salviadivinorum

Meth usersn = 114 2006 32 87 86 100 64 50 36 21 15 11 8 6 – – – –n = 110 2007 44 79 88 97 64 51 35 26 24 8 6 13 – – – –n = 137 2008 14*** 86 83 100 61 47 24 23 9** 11 6 8 16 – – –n = 105 2009 8 83 85 100 53 41 11*** 22 6 7 10 10 25 – – –n = 130 2010 7ˆ 82 87 99 23ˆˆˆ 43 18ˆ 25 9 8 8 5 22 10 7 0

% change 2008 vs. 2007 −68% n.s. n.s. n.s. n.s. n.s. n.s. n.s. −63% n.s. n.s. n.s. n.s n.s n.s n.s% change 2010 vs. 2006 −78% n.s. n.s. n.s. −64% n.s. −50% n.s. −40% n.s. n.s. n.s. n.s. n.s. n.s. n.s.

Ecstasy usersn = 111 2006 65 98 92 21 5 100 48 13 47 9 0 10 –n = 105 2007 46** 96 89 23 11 100 41 15 32* 5 0 11 – – –n = 135 2008 25** 95 91 13 6 100 45 19 28 18** 1 9 6 – – –n = 111 2009 15* 95 89 13 6 100 47 19 24 9* 3 20* 6 – – –n = 153 2010 11ˆˆˆ 99 89 8ˆ 2 100 32* 32ˆ 24ˆ 7 0a 7** 3 21 24 3

% change 2008 vs. 2007 −46% n.s. n.s. n.s. n.s. n.s. n.s. n.s. n.s. +260% n.s. n.s. n.s. n.s. n.s. n.s.% change 2010 vs. 2006 −83% n.s. n.s. −62% n.s. n.s. n.s. +146% −49% n.s. n.s. n.s. n.s. n.s. n.s. n.s.

IDUn = 93 2006 30 67 78 40 24 30 21 43 21 4 25 5 – – – –n = 109 2007 34 70 86 44 17 22 14 46 12 1 11* 6 – – – –n = 132 2008 18* 61 70** 47 30 18 13 37 6 8 21* 1 54 – – –n = 99 2009 16 60 72 50 27 13 10 40 6 1 19 7 62 – – –n = 128 2010 20 69 72 38 17 20 13 49 4ˆˆˆ 8a 19 5 55 9 7 0

% change 2008 vs. 2007 −47% n.s. −19% n.s. n.s. n.s. n.s. n.s. n.s. – +91% n.s. n.s. n.s. n.s. n.s.% change 2010 vs. 2006 n.s. n.s. n.s. n.s. n.s. n.s. n.s. n.s. −81% n.s. n.s. n.s. n.s. n.s. n.s. n.s.

Source: IDMS, 2006–2010.* Statistical test of prevalence of use of drug type in the past six months with prevalence of use in previous years (p < 0.05).

** Statistical test of prevalence of use of drug type in the past six months with prevalence of use in previous years (p < 0.01).*** Statistical test of prevalence of use of drug type in the past six months with prevalence of use in previous years (p < 0.0001).

ˆ Statistical test of correlation of prevalence of use from 2006 to 2010 (p < 0.05).ˆˆStatistical test of correlation of prevalence of use from 2006 to 2010 (p < 0.01).

ˆˆˆ Statistical test of correlation of prevalence of use from 2006 to 2010 (p < 0.0001).a Low number of respondents prevents any reliable statistical comparisons, n.s., not statistically significant.

76 C. Wilkins, P. Sweetsur / Drug and Alcoh

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ig. 3. Proportion of frequent injecting drug users who used BZP and selected otherrugs in the previous six months, 2006–2010.

etamine increased in 2009 and then declined in 2010. There wasn increase in amyl nitrate use from 2008 to 2009 (14% vs. 26%,

= 0.0290). A lower proportion of the frequent ecstasy users hadsed any new legal high in 2010 compared to BZP in 2006 (40% vs.5%, p = 0.0001). A lower proportion of the frequent ecstasy usersad also used any legal high in 2010 compared to BZP in 2006 (44%s. 65%, p = 0.0010).

Among the frequent injecting drug users, there was a consistentecline from 2006 to 2010 in the use of nitrous oxide (21% to 4%,

< 0.0001, Table 2 and Fig. 3). There were declines in the use of BZProm 2007 to 2008 (34% vs. 18%, p = 0.0138) and cannabis from 2007o 2008 (86% vs. 70%, p = 0.0084). There was a decrease in heroin userom 2006 to 2007 (25% vs. 11%, p = 0.0394), followed by an increasen heroin use from 2007 to 2008 (11% vs. 21%, p = 0.0442) to matchhe level found in 2006. A lower proportion of the frequent injectingrug users had used any new legal high in 2010 compared to BZP in006 (13% vs. 30%, p = 0.0039). There was no difference in the usef any legal high in 2010 compared to BZP in 2006 (26% vs. 30%,

= 0.5480).

.3. Change in the use of BZP in the general population

Eighty-nine per cent of the general population survey respon-ents who had tried BZP in 2009 said they had ‘stopped’ (n = 252),% said they were using ‘less’ (n = 12), 6% were using the ‘same’n = 13) and < 1% were using ‘more’ (n = 1). The proportion of those

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ig. 4. Proportion of those in the general population who had ever tried BZP whoeported stopping by the year they reported stopping (of those who could recall theear they stopped), 1999–2009.

ol Dependence 127 (2013) 72– 80

who had ever tried BZP who stopped increased steadily from 2005,peaked in 2007 (at 20%) before levelling out in subsequent years (at14% per year) (Fig. 4). Forty-two per cent of the respondents whohad ever tried BZP had stopped before the government announcedits intention to prohibit BZP (i.e., 1999–2006) and 47% had stoppedin the years following the announcement of the BZP prohibition(i.e., 2007–2009).

4.4. Reasons for having stopped BZP use among generalpopulation

In the years before the Government announced its intention toprohibit BZP (i.e., 1999–2006) most users reported they stoppedusing BZP because they ‘just didn’t like it/just experimenting’ (58%),due to the ‘bad hang-over effect’ (22%) and concern about ‘healthreasons’ (12%) (Table 3). Nine per cent of users stopped during theseyears because they were not old enough to purchase BZP followingthe imposition of the R18 restriction on purchase and supply in2005.

In the year that the prohibition of BZP was imposed (2008) themost common reasons given for stopping BZP use were becauseit was ‘illegal’ (43%), ‘just didn’t like it/just experimenting’ (26%),‘didn’t know where to get it now it’s illegal’ (24%), ‘bad hang-over effect’ (18%), ‘family reasons/responsibility/kids’ (11%) andfor ‘health reasons’ (8%). A higher proportion of BZP users hadstopped using BZP in 2007–2009 compared to 1999–2006 becauseBZP was ‘illegal’ (30% vs. 9%, p = 0.0009) and because they ‘did notknow where to get it now it was illegal’ (14% vs. 3%, p = 0.0314).Few BZP users reported stopping BZP use either before or afterthe prohibition because of ‘fear of addiction’ (<1% for all years),because BZP was ‘too expensive’ (2% both before and after prohibi-tion) or because of a preference for another drug type (<1% for allyears).

5. Discussion

We found steep declines in the use of BZP in New Zealand amongboth the general population and frequent drug users. The steepestdeclines in BZP use occurred among the frequent drug users follow-ing the prohibition of BZP in 2007, although the frequent ecstasyusers also reported a steep decline in BZP use in the year precedingthe ban. The frequent injecting drug users were the least respon-sive and the frequent ecstasy users were the most responsive to theimposition of the prohibition. The frequent ecstasy users tend tobe university students with little history of serious illegal drug useand this more mainstream background may make them more waryof changes in the law regarding recreational drugs. The frequentmethamphetamine users and frequent injecting drug users onlyreduced their use of BZP once the BZP prohibition was imposed in2008 while a substantial proportion of the general population sam-ple reported stopping in 2007 when the government had merelyannounced its intention to prohibit BZP. Again this may reflect thegreater conventionality of those in the general population samplecompared to these frequent drug users.

In the year that BZP was prohibited (2008), two-thirds of thosewho stopped using BZP reported stopping for reasons related tothe prohibition (i.e., because it was ‘illegal’ (43%) or they ‘didn’tknow where to get it now it was illegal’ (24%)). BZP users oftenreported one of the things they most liked about legal BZP partypills was that they were legal and hence somewhat legitimate touse (Green, 2008; Sheridan and Butler, 2009; Wilkins et al., 2006).The ‘bad hang-over effect’ and ‘concern about health risks’ were

important reasons for stopping BZP use both before and after theprohibition was imposed. A number of BZP studies have foundusers commonly reported a severe hang-over effect and unpleas-ant side effects from BZP use including insomnia, nausea, headaches

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Table 3Reasons provided by BZP users in the general population for having stopped using BZP by year stopped, 1999–2009.

Reason 1999–2004 2005 2006 2007 2008 2009 1999–2006 2007–2009 1999–2006 vs. 2007–2009 1999–2009(n = 37) (n = 30) (n = 38) (n = 53) (n = 37) (n = 32) (n = 105) (n = 122) (n = 242)a

% % % % % % % % p value %

Just do not like them/just experimenting 60 51 61 28 26 29 58 28 <0.0001 44Hangover/bad come down effects 11 32 25 18 18 7 22 15 0.1829 18Health related reasons 17 14 5 13 8 12 12 11 0.9776 12It is illegal/under 18 years old/fear of arrest 9 8 9 28 43 21 9 30 0.0009 21Too old

11 3 9 4 0 0 8 2 0.0266 4Family reasons/responsibility/kids 9 12 5 14 11 8 5 5 0.8378 8Not in social scene/do not party as much now 11 3 1 14 6 8 5 10 0.1484 7Saw bad effects on others 3 11 2 2 0 13 5 5 0.9626 4Past health problems with BZP 0 12 0 0 0 0 4 0 – 2Do not know where to get it now its illegal 5 3 0 6 24 16 3 14 0.0314 8Too expensive/did not earn enough 1 0 4 4 0 1 2 2 – 2Social pressure 0 0 5 0 0 0 2 0 – 1Job related reasons 0 0 2 0 0 7 1 2 – 1Against my religion/religious belief 1 0 0 0 0 0 1 0 – <1Prefer cannabis 0 2 0 0 1 0 <1 <1 – <1Parental pressure 0 3 0 0 0 0 1 0 – <1Prefer drinking alcohol 1 0 0 6 0 7 <1 4 – 2Pregnant 1 0 0 0 0 4 0 1 – 1No longer fun/got boring 0 0 0 0 0 4 0 1 – 1No time/too busy 0 0 0 3 4 0 0 2 – 1Fear of addiction 0 0 0 0 1 0 0 0 – <1Prefer other illegal drugs 0 0 0 2 0 0 0 1 – <1

Source: BZP National Household Drug Survey, 2009.a This number includes those respondents who could not recall the year they stopped using BZP.

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8 C. Wilkins, P. Sweetsur / Drug and

nd heart palpitations (Gee and Fountain, 2007; Nicholson, 2006;heridan and Butler, 2006, 2009; Theron et al., 2007; Vince, 2006;ilkins et al., 2008), while there have been a small number of

ases of life threatening toxicity (Balmelli et al., 2001; Gee andountain, 2007; Staack, 2007; Theron et al., 2007). The low depen-ency potential of BZP (see Wilkins et al., 2007) is likely to haveade it fairly easy for users to stop use once they experienced

dverse effects.To what extent did the prevalence of new replacement legal

ighs match the former levels of use of legal BZP party pills?mong the general population, the prevalence of any new legaligh in 2009 (i.e., over 12 months after the BZP ban) was lowerhan the prevalence of BZP in 2006. It may well be the case thatt takes longer than 12 months for a new legal high to gain popu-arity among the general public. Among the frequent illegal drugsers, the use of any new legal high in 2010 (over two years afterhe BZP ban) was also still lower than BZP use in 2006. However,9% of the frequent ecstasy users had used one of the new legalighs in 2010, demonstrating that considerable demand for legalighs remained. The overall prevalence of legal highs (including

llegal BZP) in 2010 was also lower than the former levels of BZParty pills for all the groups except for the frequent injecting drugsers.

To what extent could the decline in BZP use be attributedo some general trend in drug use in New Zealand? The preva-ence of amphetamine/methamphetamine use among the generalopulation also declined in 2009 compared to 2006 which raiseshe question whether the fall in BZP use was part of a broaderecline in stimulant or so called party drug use. This explanation

s not consistent with the stable prevalence of ecstasy use, and theteady increase in methylphenidate use (a pharmaceutical stimu-ant) among the frequent ecstasy users. We also found a substantialecline in the use of nitrous oxide use among both the general pop-lation and frequent drug users. Nitrous oxide had been widelyold as a ‘legal high’ from convenience stores in New Zealand upntil 2005 when the Ministry of Health announced that nitrousxide was a restricted drug under the Medicines Act. The Min-stry of Health wrote to vendors informing them of this decisionnd this led to a significant reduction of sales from conveniencetores.

To what extent did the prohibition of BZP led to the increasedse of other drugs. The question of drug substitution is one whichur cross-sectional survey design is least suited to answer, as its difficult to establish a clear causal link between changes in BZPse and the initiation of other drug use. The fact that we found

substantial decline in both BZP and methamphetamine use inhe years following the BZP ban does not appear, on the facef it, to be consistent with the substitution of BZP for metham-hetamine.

Finally, to what extent could the experience of the prohibition ofZP legal highs in New Zealand be replicated for other legal highs

n other countries? An important attraction of many legal highsppears to be that they are legal, convenient to purchase and some-hat legitimate to use (Hammersley, 2010; Measham et al., 2010;

heridan and Butler, 2009; Wilkins et al., 2006). It appears thatome people who use a legal high while it is legal will simply stopsing it once it becomes illegal as they are not comfortable with par-icipating in illegal activity, have family responsibilities, do not haveood social connections with illegal drug dealers, or are not inter-sting in continuing use once supply becomes more difficult. Theroduct characteristics of a legal high are also likely to be important

n regards to the effectiveness of prohibition. The unpleasant side-

ffects and low dependency potential of BZP meant relatively fewsers were determined to seek it out once it was banned. Other

egal highs, such as mephedrone, are reported to have compara-le or even superior pleasurable effects to cocaine and a similar

ol Dependence 127 (2013) 72– 80

dependency potential to cocaine (see McElrath and O’Neill, 2011;Winstock et al., 2010). Initial evaluations of the mephedrone banin the United Kingdom suggest some users have continued usingalthough it is not yet clear how widespread this is (McElrath andO’Neill, 2011; Winstock, 2010). The apparent success in limitingthe availability of nitrous oxide through the application of theMedicines Act in New Zealand also demonstrates that alternativeregulatory approaches to prohibition can be effective (see Winstockand Wilkins, 2011).

We acknowledge a number of limitations with this paper. Firstly,natural experiments of the impact of policy interventions are con-ducted under real world conditions which do not allow for thecontrol of all alternative explanatory factors and consequently theprecise causal influence of a policy intervention can remain a mat-ter of contention (Babor et al., 2010). We sought to more clearlyidentify the causal impact of the BZP prohibition by focusing onchanges in BZP and other drug use in the 12 months immediatelyfollowing the BZP ban in 2007; by examining trends in other druguse over the same years; and by examining the reasons providedby BZP users for stopping use. Secondly, BZP was illegal in 2009and as a consequence some in the general population may havebeen less willing to admit use in 2009 compared to 2006 whenBZP was legal. Respondents to general population drug surveyshave been found to under-report the use of illegal drugs, althoughdrugs which attract low legal penalties and social stigma, such ascannabis (and BZP), are much less affected (see Fendrich et al., 2004;Harrison et al., 2007). The magnitude of survey under-reportingfound for drug types such as cannabis would not be sufficient toexplain the large decline in BZP use found in our population sur-veys. The participants in the frequent drug user survey are unlikelyto be affected by under-reporting as they must admit serious illegaldrug use to be eligible to be interviewed for the study. Thirdly, thefrequent drug user sample is not representative of frequent druguse in New Zealand. The annual frequent drug user survey wasconducted using the same community level purposive methodol-ogy and the stable demographic profile of the three frequent druguser groups over the five years of the study indicates we broadlyinterviewed from the same community of drug users each year(see Wilkins et al., 2011a). Fourthly, the general population sur-vey was a landline telephone household survey and this samplingmethodology excludes some sections of the population such asthose living on the streets, hostels or imprisoned (see McAuliffeet al., 1998). We compared two identical landline telephone sur-veys conducted three years apart and so there is good reason toassume this type of under-coverage bias would be fairly consis-tent in each survey wave; meaning any changes found betweenthe surveys represented real changes. Our CATI system allows formultiple call-backs of a household at different days and times of theday, and for appointments to be made for when a selected partici-pant is home and the rigorous application of these procedures hasmeant our general population telephone samples have not under-represented young people compared to the population Census. Amore recent concern is the emergence of cell-phone only house-holds. Cell-phone only households currently only make up a verysmall proportion of total households in New Zealand (i.e., 5% atthe last New Zealand Census), and like non-telephone householdswhich also only make a very small proportion of total householdsin New Zealand, this reduces their influence on measures of alco-hol and drug use among the entire population (see Harding et al.,2011; Wilkins et al., 2003). It does not seem plausible that anyincrease in cell phone only households could have been respon-sible for a large decline in BZP use while leaving many other drugs

unaffected. The frequent drug users interviewed for the IDMS wererecruited at street level and so were not required to either live ina household or have access to a landline telephone to be inter-viewed.

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ole of funding source

Nothing declared.

ontributors

Chris Wilkins planned the paper and analysis, and wrote all text;aul Sweetsur conducted all the statistical analysis.

onflict of interest

No conflict declared.

cknowledgements

The funding for the 2006 and 2009 national household drugurveys was awarded from the New Zealand National Drug Pol-cy Discretionary Fund (NDPDF). The NDPF was jointly managedy the New Zealand Inter-Agency Committee on Drugs (IACD) andhe New Zealand Ministerial Committee on Drug Policy (MCDP).he Illicit Drug Monitoring System (IDMS) is conducted as part ofhe National Drug Policy. The views expressed in this article do notecessarily reflect the views of these funding agencies. The authorsave no connection with the tobacco, alcohol, pharmaceutical oraming industries or anyone substantially funded by one of theserganisations.

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