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Letters to the Editor
CANNABIS POTENCY: THE NEED FOR GLOBAL MONITORING In this issue of Addiction, Neisink et al. [1] report data from a systematic cannabis potency monitoring programme conducted in the Netherlands between 2005 and 2015. Following a dramatic rise between 2000 and 2004 [2], Δ9-tetrahydrocannabinol (Δ9-THC) decreased modestly (0.22% each year) from 2005 to 2015 [1]. Cannabidiol (CBD), a cannabinoid which may counteract some of the negative effects of Δ9-THC [3–6], was absent from most samples tested [1]. Some possible harms of chronic cannabis use (e.g. dependence, increased risk of psychosis) may be predicted by its cannabinoid profile [7,8]. Longitudinal cannabis monitoring programmes can assist investigations between Δ9-THC and CBD and population indicators of burden and morbidity. For example, Δ9-THC trends in the Netherlands [1,2] might predict treatment demand for cannabis dependence, which rose between 2000 and 2011 but is now stable or decreasing [9]. There are currently few data examining the links between cannabinoid profile and adverse outcomes, so enhanced monitoring programmes would assist in the assessment of this important issue. Rising and/or high Δ9-THC alongside a lack of CBD have been reported in a number of other countries [10–13]. However, not all have monitored potency regularly or at all, and some have found no reliable change [14]. Potency monitoring may be difficult and impractical in some countries for historical and legislative reasons. For example, in Australia, which has no legal imperative to test for potency, there are no longitudinal data monitoring programmes. The first major Australian study of potency [15] took a decade from design to completion due to difficulty in getting sufficient interest to fund it plus a number of legislative difficulties, yet it raises the same concerns as international data with its findings of very high Δ9-THC and low CBD levels in street-level seizures. It will be important to evaluate the impact of current and proposed regulatory changes, as some have been aimed specifically at cannabis potency. In 2011, calls were made to classify potent (≥ 15% Δ9-THC) cannabis as a ‘hard drug’ in the Netherlands, and Uruguay also proposed an upper limit [16]. When cannabis was re-classified as a more harmful drug (from Class C to B) in 2008, the UK Home Office stated: ‘The significant increase in both the market share of higher than average potency cannabis and its actual potency in the last few years in the UK are compelling factors’ [17]. Unfortunately, the effects of reclassification on potency are unclear, as the last comparable monitoring study was conducted in 2008 [10]. Initial results from the United States indicate that legal medical cannabis dispensaries were associated with a 1% rise of Δ9-THC in illicit seized samples [18]. The © 2015 Society for the Study of Addiction
effects of state legalization for pleasure are yet to emerge. However, these changes could facilitate monitoring at the retail level, offering methodological advantages [1,2] and evaluation of Δ9-THC and CBD trends in conditions of greater consumer choice. At a time when global cannabis policy is rapidly shifting, comprehensive monitoring will be a key step towards investigating the effects of these changes on cannabis products and cannabis users themselves. Declaration of interests Tom P. Freeman is funded by the Medical Research Council and declares no competing interests. The National Drug and Alcohol Research Centre at UNSW Australia is supported by funding from the Australian Government under the Substance Misuse Prevention and Service Improvements Grants Fund. Wendy Swift has no competing interests to declare. Keywords Cannabidiol, delta-9-tetrahydrocannabinol, dependence, drug policy, monitoring, potency, psychosis. 1
2
T. P. FREEMAN & W. SWIFT
Clinical Psychopharmacology Unit, 1
University College London, London, UK and National Drug and Alcohol Research Centre, 2
UNSWAustralia, Sydney, NSWAustralia
E-mail: [email protected]
References 1. Niesink R. J., Rigter S., Koeter M. W., Brunt T. M. Potency trends of Δ9-THC, cannabidiol and cannabinol in cannabis in the Netherlands: 2005–2015. Addiction 2015; doi:10.1111/add.13082. 2. Pijlman F., Rigter S., Hoek J., Goldschmidt H., Niesink R. Strong increase in total delta-THC in cannabis preparations sold in Dutch coffee shops. Addict Biol 2005; 10: 171–80. 3. Morgan C. J., Curran H. V. Effects of cannabidiol on schizophrenia-like symptoms in people who use cannabis. Br J Psychiatry 2008; 192: 306–7. 4. Morgan C. J., Schafer G., Freeman T. P., Curran H. V. Impact of cannabidiol on the acute memory and psychotomimetic effects of smoked cannabis: naturalistic study. Br J Psychiatry 2010; 197: 285–90. 5. Englund A., Morrison P. D., Nottage J., Hague D., Kane F., Bonaccorso S., et al. Cannabidiol inhibits THC-elicited paranoid symptoms and hippocampal-dependent memory impairment. J Psychopharmacol (Oxf) 2013; 27: 19–27. 6. Hindocha C., Freeman T. P., Schafer G., Gardener C., Das R. K., Morgan C. J., et al. Acute effects of delta-9-tetrahydrocannabinol, cannabidiol and their combination on facial emotion recognition: a randomised, double-blind, placebocontrolled study in cannabis users. Eur Neuropsychopharmacol 2015; 25: 325–34. 7. Freeman T. P., Winstock A. R. Examining the profile of high-potency cannabis and its association with severity of cannabis dependence. Psychol Med 2015; 45: 3181–9. Addiction, 111, 373–377
Letters to the Editor 8. Di Forti M., Marconi A., Carra E., Fraietta S., Trotta A., Bonomo M., et al. Proportion of patients in south London with first-episode psychosis attributable to use of high potency cannabis: a case–control study. Lancet Psychiatry 2015; 2: 233–8. 9. Wisselink D., Kuijpers W., Mol A. Key Figures in Addiction Care 2013. Houten: Stichting Informatie Voorziening Zorg; 2014. 10. Hardwick S., King L. A. Home Office Cannabis Potency Study 2008. St Albans, UK: Home Office Scientific Development Branch; 2008. 11. Licata M., Verri P., Beduschi G. Delta9 THC content in illicit cannabis products over the period 1997–2004 (first four months). Ann Ist Super Sanita 2005; 41: 483–5. 12. Mehmedic Z., Chandra S., Slade D., Denham H., Foster S., Patel A. S., et al. Potency trends of Δ9-THC and other cannabinoids in confiscated cannabis preparations from 1993 to 2008. J Forensic Sci 2010; 55: 1209–17.
© 2015 Society for the Study of Addiction
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13. Cascini F., Aiello C., Di Tanna G. Increasing delta-9tetrahydrocannabinol (Δ-9-THC) content in herbal cannabis over time: systematic review and meta-analysis. Curr Drug Abuse Rev 2012; 5: 32. 14. McLaren J., Swift W., Dillon P., Allsop S. Cannabis potency and contamination: a review of the literature. Addiction 2008; 103: 1100–9. 15. Swift W., Wong A., Li K. M., Arnold J. C., McGregor I. S. Analysis of cannabis seizures in NSW, Australia: cannabis potency and cannabinoid profile. PLOS ONE 2013; 8: e70052. 16. Coombes R. Cannabis regulation: high time for change? BMJ 2014; 348: g3382. 17. Home Office. Explanatory Note to the Misuse of Drugs Act 1971 (Amendment) Order 2008 (2008 No. 3130). London, UK: Home Office; 2008. 18. Sevigny E. L., Pacula R. L., Heaton P. The effects of medical marijuana laws on potency. Int J Drug Pol 2014; 25: 308–19.
Addiction, 111, 373–377
Letters to the Editor
CANNABIS POTENCY: THE NEED FOR GLOBAL MONITORING In this issue of Addiction, Neisink et al. [1] report data from a systematic cannabis potency monitoring programme conducted in the Netherlands between 2005 and 2015. Following a dramatic rise between 2000 and 2004 [2], Δ9-tetrahydrocannabinol (Δ9-THC) decreased modestly (0.22% each year) from 2005 to 2015 [1]. Cannabidiol (CBD), a cannabinoid which may counteract some of the negative effects of Δ9-THC [3–6], was absent from most samples tested [1]. Some possible harms of chronic cannabis use (e.g. dependence, increased risk of psychosis) may be predicted by its cannabinoid profile [7,8]. Longitudinal cannabis monitoring programmes can assist investigations between Δ9-THC and CBD and population indicators of burden and morbidity. For example, Δ9-THC trends in the Netherlands [1,2] might predict treatment demand for cannabis dependence, which rose between 2000 and 2011 but is now stable or decreasing [9]. There are currently few data examining the links between cannabinoid profile and adverse outcomes, so enhanced monitoring programmes would assist in the assessment of this important issue. Rising and/or high Δ9-THC alongside a lack of CBD have been reported in a number of other countries [10–13]. However, not all have monitored potency regularly or at all, and some have found no reliable change [14]. Potency monitoring may be difficult and impractical in some countries for historical and legislative reasons. For example, in Australia, which has no legal imperative to test for potency, there are no longitudinal data monitoring programmes. The first major Australian study of potency [15] took a decade from design to completion due to difficulty in getting sufficient interest to fund it plus a number of legislative difficulties, yet it raises the same concerns as international data with its findings of very high Δ9-THC and low CBD levels in street-level seizures. It will be important to evaluate the impact of current and proposed regulatory changes, as some have been aimed specifically at cannabis potency. In 2011, calls were made to classify potent (≥ 15% Δ9-THC) cannabis as a ‘hard drug’ in the Netherlands, and Uruguay also proposed an upper limit [16]. When cannabis was re-classified as a more harmful drug (from Class C to B) in 2008, the UK Home Office stated: ‘The significant increase in both the market share of higher than average potency cannabis and its actual potency in the last few years in the UK are compelling factors’ [17]. Unfortunately, the effects of reclassification on potency are unclear, as the last comparable monitoring study was conducted in 2008 [10]. Initial results from the United States indicate that legal medical cannabis dispensaries were associated with a 1% rise of Δ9-THC in illicit seized samples [18]. The © 2015 Society for the Study of Addiction
effects of state legalization for pleasure are yet to emerge. However, these changes could facilitate monitoring at the retail level, offering methodological advantages [1,2] and evaluation of Δ9-THC and CBD trends in conditions of greater consumer choice. At a time when global cannabis policy is rapidly shifting, comprehensive monitoring will be a key step towards investigating the effects of these changes on cannabis products and cannabis users themselves. Declaration of interests Tom P. Freeman is funded by the Medical Research Council and declares no competing interests. The National Drug and Alcohol Research Centre at UNSW Australia is supported by funding from the Australian Government under the Substance Misuse Prevention and Service Improvements Grants Fund. Wendy Swift has no competing interests to declare. Keywords Cannabidiol, delta-9-tetrahydrocannabinol, dependence, drug policy, monitoring, potency, psychosis. 1
2
T. P. FREEMAN & W. SWIFT
Clinical Psychopharmacology Unit, 1
University College London, London, UK and National Drug and Alcohol Research Centre, 2
UNSWAustralia, Sydney, NSWAustralia
E-mail: [email protected]
References 1. Niesink R. J., Rigter S., Koeter M. W., Brunt T. M. Potency trends of Δ9-THC, cannabidiol and cannabinol in cannabis in the Netherlands: 2005–2015. Addiction 2015; doi:10.1111/add.13082. 2. Pijlman F., Rigter S., Hoek J., Goldschmidt H., Niesink R. Strong increase in total delta-THC in cannabis preparations sold in Dutch coffee shops. Addict Biol 2005; 10: 171–80. 3. Morgan C. J., Curran H. V. Effects of cannabidiol on schizophrenia-like symptoms in people who use cannabis. Br J Psychiatry 2008; 192: 306–7. 4. Morgan C. J., Schafer G., Freeman T. P., Curran H. V. Impact of cannabidiol on the acute memory and psychotomimetic effects of smoked cannabis: naturalistic study. Br J Psychiatry 2010; 197: 285–90. 5. Englund A., Morrison P. D., Nottage J., Hague D., Kane F., Bonaccorso S., et al. Cannabidiol inhibits THC-elicited paranoid symptoms and hippocampal-dependent memory impairment. J Psychopharmacol (Oxf) 2013; 27: 19–27. 6. Hindocha C., Freeman T. P., Schafer G., Gardener C., Das R. K., Morgan C. J., et al. Acute effects of delta-9-tetrahydrocannabinol, cannabidiol and their combination on facial emotion recognition: a randomised, double-blind, placebocontrolled study in cannabis users. Eur Neuropsychopharmacol 2015; 25: 325–34. 7. Freeman T. P., Winstock A. R. Examining the profile of high-potency cannabis and its association with severity of cannabis dependence. Psychol Med 2015; 45: 3181–9. Addiction, 111, 373–377
Letters to the Editor 8. Di Forti M., Marconi A., Carra E., Fraietta S., Trotta A., Bonomo M., et al. Proportion of patients in south London with first-episode psychosis attributable to use of high potency cannabis: a case–control study. Lancet Psychiatry 2015; 2: 233–8. 9. Wisselink D., Kuijpers W., Mol A. Key Figures in Addiction Care 2013. Houten: Stichting Informatie Voorziening Zorg; 2014. 10. Hardwick S., King L. A. Home Office Cannabis Potency Study 2008. St Albans, UK: Home Office Scientific Development Branch; 2008. 11. Licata M., Verri P., Beduschi G. Delta9 THC content in illicit cannabis products over the period 1997–2004 (first four months). Ann Ist Super Sanita 2005; 41: 483–5. 12. Mehmedic Z., Chandra S., Slade D., Denham H., Foster S., Patel A. S., et al. Potency trends of Δ9-THC and other cannabinoids in confiscated cannabis preparations from 1993 to 2008. J Forensic Sci 2010; 55: 1209–17.
© 2015 Society for the Study of Addiction
377
13. Cascini F., Aiello C., Di Tanna G. Increasing delta-9tetrahydrocannabinol (Δ-9-THC) content in herbal cannabis over time: systematic review and meta-analysis. Curr Drug Abuse Rev 2012; 5: 32. 14. McLaren J., Swift W., Dillon P., Allsop S. Cannabis potency and contamination: a review of the literature. Addiction 2008; 103: 1100–9. 15. Swift W., Wong A., Li K. M., Arnold J. C., McGregor I. S. Analysis of cannabis seizures in NSW, Australia: cannabis potency and cannabinoid profile. PLOS ONE 2013; 8: e70052. 16. Coombes R. Cannabis regulation: high time for change? BMJ 2014; 348: g3382. 17. Home Office. Explanatory Note to the Misuse of Drugs Act 1971 (Amendment) Order 2008 (2008 No. 3130). London, UK: Home Office; 2008. 18. Sevigny E. L., Pacula R. L., Heaton P. The effects of medical marijuana laws on potency. Int J Drug Pol 2014; 25: 308–19.
Addiction, 111, 373–377
