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Comment & Response
September 2016

Effects of Cannabis Use on Human Behavior: A Call for Standardization of Cannabis Use Metrics

Author Affiliations
  • 1School of Psychology and Illawarra Health and Medical Research Institute, University of Wollongong, Wollongong, New South Wales, Australia
  • 2Brain & Mental Health Laboratory, Monash Institute of Cognitive and Clinical Neurosciences, School of Psychological Sciences, Monash University, Clayton, Victoria, Australia
JAMA Psychiatry. 2016;73(9):995-996. doi:10.1001/jamapsychiatry.2016.1329

To the Editor With rapidly shifting legislation worldwide in relation to recreational and medicinal cannabis use, the review by Volkow et al1 is timely. We highlight several additional noteworthy issues for consideration.

While further evidence has emerged that acute and long-term exposure to cannabis impairs cognition,2 there is still grossly insufficient evidence for recovery of function with abstinence. Neither the parameters of cannabis exposure nor the neural mechanisms subserving persistence or recovery have been elucidated. Well-controlled prospective studies monitoring restoration of brain function and structure from current use through prolonged abstinence are required to delineate the time course and moderators of potential recovery of cognitive function.

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    1 Comment for this article
    Standard Joint Unit and Public Health
    Hugo López-Pelayo, Cristina Casajuana, Mercè Balcells-Olivero, Jürgen Rehm , Antoni Gual. | Addiction Unit, Hospital Clínic de Barcelona; Fundació Clínic per la Recerca Biomèdica; Institut d'Investigacions Biomèdiques August Pi i Sunyer; Universitat de Barcelona
    The letter published on Cannabis and Behavior claiming for standardization of cannabis use metrics raises a very relevant topic. The exhaustive paper by Volkow et al (1) reviewing evidence on cannabis effects on human behavior makes us agree with Solowij and colleagues that time has come to tackle with standardization of cannabis use metrics and highlight this important knowledge gap.
    Previous preventive actions in the field have shown the importance of identifying hazardous users (regular users at-risk of worse consequences) (2). By now, specific subsets of cannabis users (e.g. adolescents and young adults, pregnant women, men with cardiovascular disease,
    personal or familiar history of psychosis) have been identified as at-risk population for cannabis exposure. Moreover, some authors have also identified risky cannabis use according to cannabis use patterns (frequency of consumption) (3). Nevertheless, definitions of at-risk population based on the amounts used, in order to differentiate risky cannabis users from regular users are still lacking (3).
    As stated in by Solowij et al (4), also from a public health perspective, standardization of cannabis use metrics is desired to facilitate early intervention in at-risk population among regular users. With alcohol in the nineties, Standard Drink Units (SDUs) were established in many countries (5,6), facilitating epidemiologic research and leading to further differentiation between low and high risky drinkers as he SDU was included in screening instruments (AUDIT or AUDIT-C (7)) . Bearing in mind the benefits of using a standardized unit, to establish an equivalent unit for cannabis seems an interesting and necessary option (8).
    Our group, using the experience gained through the Spanish SDU and AUDIT-C (6,7), began in 2013 a project aimed to establish a Spanish Standard Joint Unit (SJU). Participants were recruited in four different settings: university campuses, night clubs and other leisure places, cannabis association clubs (a form in Barcelona to use cannabis in a way tolerated by police) and out-patient mental health services. The project has faced some expected technical difficulties in its procedure, such as legal issues and the acquisition and management of cannabis samples. Additional difficulties arose from dealing with the highly variable consumption habits and patterns (e.g., smoked in cigarettes, vaporizers, eatable cannabis) as well as different form of used (e.g., marijuana, hashish, synthetic cannabis) .
    Our initial literature review targeted three key difficulties: a) how can we define cannabis hazardous and problematic use (9); b) which are the available validated instruments for early identification of at-risk populations (8), and c) what psychoactive cannabinoids need to be taken into account when defining the SJU (paper in revision). A pilot test was carried out to evaluate the study procedure and study instruments (manuscript accepted, publication ending). The field study consisted in collecting and analyzing donated joints of more than 300 users and interviewing almost 500 cannabis users of the province of Barcelona. The field study of the SJU has just finished and results will be presented in the following months. Comparisons to other countries and use cultures would be important and we hope to stimulate such research with this contribution.

    1. Volkow ND, Swanson JM, Evins AE, DeLisi LE, Meier MH, Gonzalez R, et al. Effects of Cannabis Use on Human Behavior, Including Cognition, Motivation, and Psychosis: A Review. JAMA Psychiatry [Internet]. American Medical Association; 2016 Mar 1 [cited 2016 Aug 26];73(3):292. Available from: http://archpsyc.jamanetwork.com/article.aspx?doi=10.1001/jamapsychiatry.2015.3278
    2. WHO | The ASSIST project - Alcohol, Smoking and Substance Involvement Screening Test. WHO. World Health Organization; 2015;
    3. Fischer B, Jeffries V, Hall W, Room R, Goldner E, Rehm J. Lower Risk Cannabis Use Guidelines for Canada ( LRCUG ): A Narrative Review of Evidence and Recommendations. Can Public Heal Assoc [Internet]. 2011;102(5):324–7. Available from: http://www.mendeley.com/catalog/lower-risk-cannabis-guidelines-canada-lrcug-narrative-review-evidence-recommendations/
    4. Solowij N, Lorenzetti V, Yücel M. Effects of Cannabis Use on Human Behavior: A Call for Standardization of Cannabis Use Metrics. JAMA psychiatry. 2016 Jul;
    5. Turner C. How much alcohol is in a “standard drink”? An analysis of 125 studies. Br J Addict. 1990;85(9):1171–5.
    6. Gual A, Martos AR, Lligoña A, Llopis JJ. Does the concept of a standard drink apply to viticultural societies? Alcohol Alcohol. Jan;34(2):153–60.
    7. Gual A, Segura L, Contel M, Heather N, Colom J. AUDIT-3 AND AUDIT-4: EFFECTIVENESS OF TWO SHORT FORMS OF THE ALCOHOL USE DISORDERS IDENTIFICATION TEST. Alcohol Alcohol. 2002 Nov;37(6):591–6.
    8. López-Pelayo H, Batalla A, Balcells MM, Colom J, Gual A. Assessment of cannabis use disorders: a systematic review of screening and diagnostic instruments. Psychol Med [Internet]. 2015 Apr 4 [cited 2015 Oct 26];45(06):1121–33. Available from: http://www.ncbi.nlm.nih.gov/pubmed/25366671
    9. Casajuana C, López-Pelayo H, Balcells MM, Miquel L, Colom J, Gual A. Definitions of Risky and Problematic Cannabis Use: A Systematic Review. Subst Use Misuse. 2016 Nov;51(13):1760–70.

    CONFLICT OF INTEREST: Hugo López-Pelayo has received honoraria from Lundbeck, Janssen and Teva, and travel grants from Lundbeck, Lilly, Janssen, Pfizer, Rovi, Esteve and Otsuka. María Mercedes Balcells has received honoraria from Lundbeck and travel grants from Janssen. Jürgen Rehm has received educational grants from Lundbeck unrelated to the work. He has also received travel support and honoraria from Lundbeck. Antoni Gual has received honoraria, research grants, and travel grants from Lundbeck, Janssen, Pfizer, Lilly, Abbvie D&A Pharma and Servier. All other authors declare no potential conflict of interest. Previous stated honoraria had no influence on this article.