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Working on a Standard Joint Unit: A Pilot Test/Estableciendo la unidad de porro estandar: estudio piloto.

Cannabis is the most abused illicit drug worldwide (United Nations Office on Drugs and Crime, 2015). In 2013, 30% of the Spanish population between 15-64 years declared to have consumed cannabis once in their lives (Delegacion del Gobierno para Plan Nacional sobre Drogas, 2015). Little is known on which consumption patterns increase the possibility of suffering cannabis-related consequences. Evaluating cannabis health outcomes faces several difficulties, as for example dealing with its variable composition or different quantities consumed. As a result, although doses have shown to be essential to evaluate drug-related outcomes, cannabis use is often only described by the frequency of use (Mariani, Brooks, Haney, & Levin, 2011; Norberg, Mackenzie, & Copeland, 2012; van der Pol et al., 2013; Walden & Earleywine, 2008). One example are characterizations of risky cannabis use, as for example daily use (Coffey, Lynskey, Wolfe, & Patton, 2000). However, specific information on the type of cannabis and its potency (concentration of 9-Tetrahydrocannabinol) is often missing, ignoring its importance when evaluating related health outcomes (Di Forti et al., 2009).

With alcohol, which is also characterized by a huge variability between types of beverages, similar difficulties were tackled establishing a standard unit (Miller, Heather, & Hall, 1991; Rodnguez-Martos Dauer, Gual Sole, & Llopis Llacer, 1999; Stockwell, Blaze-Temple, & Walker, 1991). Nowadays the "standard drink" is widely used in alcohol assessment and has contributed to the characterization of risky users, enabling public health recommendations.

Working on a homogenization of cannabis assessment could lead to equivalent benefits. A standard unit for cannabis would allow describing cannabis use patterns not only using frequency but also quantity. Few attempts to develop cannabis units have been published (Norberg et al., 2012; Zeisser et al., 2012). However, they show several weaknesses. For example, units base on grams of cannabis and do not consider that cannabis can have a high variability in its composition (EMCDDA, 2008). Meanwhile, quantity of cannabis' main psychoactive cannabinoid - 9-Tetrahydrocanna-binol (9-THC) (Mechoulam & Gaoni, 1964) - present in the proposed units remains unknown. As well as the "standard drink" accounts for grams of alcohol, a standardized unit for cannabis should consider the quantity of its main psychoactive constituent with implication on health (Hall & Degenhardt, 2009; Hall, 2015). In addition, standard units should be based on the most used administration form. For cannabis, smoking a rolled cigarette in form of a joint, is the most common administration form (U.S. Department of Health and Human Services, 2014).

The Spanish Ministry of Health, through its National Plan on Drugs, recently approved a project to establish a "Standard Joint Unit" (SJU). This unit will consider the quantity of 9-THC in donated joints. In order to check the likelihood of obtaining a SJU through a naturalistic study, a pilot test was conducted. The present paper reports its main results and analyzes preliminary data.

Material and methods


During September to December 2014 forty cannabis users were recruited by convenience in four different settings of Barcelona (Spain): universities, cannabis associations, one out-patient mental health service and nightclubs (N=10 in every setting). For the pilot study, the sample size was adjusted to 10% of the expected final study sample. Participant's eligibility criteria were (1) having consumed cannabis at least once in the last 60 days, (2) being able to decide to participate and 3) being adult.


Participants were informed about the study objective, anonymity and confidentiality of their data. Once accepted, they were administered a questionnaire. For the out-patient mental health service recruitment proceeded indirectly via informed psychiatrist who invited their patients to participate.


Questionnaires previously used in similar contexts were reviewed for suitable questions (Ministerio de Sanidad, Servicios Sociales e Igualdad, 2015; Ministerio de Sanidad, Servicios Sociales e Igualdad, 2013; Villalbi, Suelves, Salto, & Cabezas, 2011). Finally the pilot questionnaire included 15 questions, which can be divided into four groups: 1) So-cio-demographical variables (sex, age, marital status, highest educational level achieved and current employment status); 2) Patterns of cannabis use (type of cannabis derivate used, tobacco proportion used in joints, preparation of joints, frequency of cannabis consumption in the last 30 days, mean joints smoked on one typical occasion in the previous 30 days, joint sharing); 3) Preliminary data on the SJU (specified below) and predisposition to donate a joint for analysis; 4) Main reason for cannabis use and the Cannabis Abuse Screening Test (CAST) (Cuenca-Royo et al., 2012; Legleye, Karila, Beck, & Reynaud, 2007).

CAST screens for risk of problematic cannabis use, and consists of six questions, which can be answered with the options "never", "rarely", "from time to time", "fairly often" and "very often". Using the binary CAST option, final scores can be matched to either non problematic use (0-1), low risk of having cannabis-related problems (2-3) or high risk of having cannabis related problems (4-6). (Delegacion del Gobierno para el Plan Nacional sobre Drogas, 2009).

The construction of the SJU is based on the following data: type of derivate consumed, weekly expenditure on cannabis, weekly amount of grams consumed, weekly number of joints consumed and frequency of acquisition. During the pilot-test, no joints were collected for analysis.

For the final study joints will be analyzed using HPLC-UV, according to the recommended methods for the identification and analysis of cannabis and cannabis products by the United Nations Office on Drugs and Crime using HPLC-UV (United Nations Office on Drug and Crime, 2009).

Data Analysis

Descriptive statistical analyses were made using SPSS version 19. Percentages were used for categorical data and median, range and interquartile range for quantitative data.

Ethics statement

The study protocol was approved by the Committee on Ethics of the Hospital Clinic (HCB/2014/0770). No informed consent was necessary due to anonymous participation. Study procedures were planned according to the Declaration of Helsinki (World Medical Association Declaration of Helsinki, 2013).


Procedure and questionnaire

Recruitment proceeded without incidents and with a response rate of 95%. The designed questionnaire needed minimal changes like some additional response options. Only the question on the frequency of cannabis consumption in the last 12 months had to be reviewed due to incorrect formulation.

Sample description and preliminary data

a) Socio-demographical data

Participants (N=40) were mostly men (72.5%), young adults (median 24.5 years, range 18-47) and single (72.5%). At the moment of the survey, 40% had finished their secondary studies and 42.5% were working (Table 1).

b) Consumption patterns

Our sample consumed marihuana (85%), hashish (10%) and hashish oil (5%). Home-grown marihuana was the first supply in 34% of the marihuana users, who occasionally also acquired cannabis if their plants were not productive. The majority (70%) affirmed to smoke on more than 20 days in the last month, 55% declared to smoke 2 to 4 joints per smoking occasion and 68.5% usually do not share their joints. 85% stated to roll their joints similarly every time and 90% smoked cannabis with tobacco (Table 2).

c) Preliminary data on SJU and predisposition to donate a joint

Participants declared to roll 4 joints (median value) with 1 gram of cannabis (0.25 gr of cannabis/ joint). This proportion was similar for marihuana and hashish (Marihuana IQR=1.92; Hashish IQR=2.25). Preliminary data suggests that one joint costs on average less than 2 [euro] (data not shown in tables). Two out of three participants stated that they would donate a joint without receiving any retribution (67.5%). Thirteen individuals denied (6 at nightclubs, 4 at universities, 2 in out-mental health service and 1 in the cannabis association). Main reasons were not receiving retribution and wanting to smoke their joints.

d) Main reasons for consumption and CAST scores

Main reasons for cannabis consumption were seeking for positive feelings as for example pleasure (70%), avoid negative feelings as for example anxiety (20%) and neutral reasons as for example habit (10%). CAST scores were in 57.5% higher than 4 points (high-risk use).


Planned methodology to establish a SJU was tested. Participant's predisposition to donate a joint indicates that working on a SJU obtained through a naturalistic study approach is feasible. Additional data related to cannabis use could be retrieved with a questionnaire which needed minimal changes.

Study procedure and questionnaire

One out of three participants affirmed not to be predisposed to donate a joint, often due to no retribution. In order to incentivize joints donations, non-economical retribution options were studied. Finally for the donation the participant will receive a USB with preventive information on cannabis. Minimal changes were done to adapt the questionnaire. One example is the question on the type of derivate consumed, which was adapted to retrieve more than one option of consumption. This change was especially necessary for home-grown marihuana users, which occasionally also acquire cannabis. For the final study, these users will be asked to estimate the value (price) of their own cultivated cannabis.

Preliminary data on the Standard Joint Unit

To optimize our study resources, for the SJU only joints of the most prevalent types (marihuana and hashish) will be considered. Few donations of other joints are expected and might be discouraged due to higher prices.

The numbers of joints rolled with one gram of cannabis were comparable within marihuana and hashish (approximately 4 joints with 1gr of cannabis). This data is consistent with previous studies (van der Pol et al., 2013; van der Pol et al., 2014). Other comparable studies like the published by Norberg et al (2012) stated that a Standard Cannabis Unit accounted for 0.25gr of cannabis (Norberg et al., 2012), which is similar to our results. In our larger study, these data will be analyzed considering amounts of tobacco (%) and concentrations of the main cannabinoids (9-THC and CBD). The analytical procedure to quantify the cannabinoids was validated and will proceed following the recommendations of the UNODC (United Nations Office on Drug and Crime, 2009).

Most of our sample declared to roll their joints similarly every time (85%) and not sharing it (68.5%). Considering that most of our participants are nearly daily smokers of 2 to 4 joints per day, consuming up to 1gr of cannabis daily or nearly daily may not be uncommon among these cannabis users of Barcelona.

Information retrieved is believed to be consistent due to the high proportion of frequent users, who mostly roll their joints similarly every time and do not share them. These data include prices, grams acquired per occasion and number joints resulting from a specific cannabis amount. In consequence, proceeding to analyze the joints donated by the participants in the real study was decided.

Associations between quantity consumed and CAST results will be analyzed in the larger study. Preliminary data obtained through the pre-test indicate a significant prevalence of users having a high risk of suffering cannabis related problems. According to the definition of the European Monitoring Centre for Drugs and Drug Addiction, users consuming at least 20 days in the last month are high-risk users (EMCDDA, 2004). In our sample 70% declared to use cannabis on more than 20 days in the last month. With the CAST, 58% were categorized as high-risk users (CAST>4). The last edition of the Spanish National Survey on Drugs found that beyond cannabis users in the last year, prevalence of problematic cannabis use was 25% (Delegacion del Gobierno para Plan Nacional sobre Drogas, 2015). Associations with reasons for consumption will be explored and may reveal important data on personal risks as suggested in previous studies (Aleixandre, Rio, & Pol, 2004; Gonzalez, Saiz, Quiros, & Lopez, 2000).

Strengths and limitations

Reporting all phases of the study will contribute to the understanding of the SJU. Working on a SJU which considers quantity of 9-THC is innovative and to our knowledge no other feasibility reports have been published. With the pilot test we have been able to explore crucial aspects of the study, as for example the donation of joints. The pilot test has helped to improve our methodology and to avoid unnecessary costs.

The hetero-administered questionnaire may potentially have induced an information bias. Bivariate statistical analyses were not performed as variable categories were in some cases too infrequent. Nevertheless, pilot studies are meant to explore feasibility and adequacy of the study procedure.


The pilot test contributed to optimize our methodology, enhancing the likelihood of establishing a SJU. Standardized cannabis assessment which considers quantity is essential to explore which patterns of cannabis use increase the risk of suffering negative consequences. Due to cannabis high prevalence of use and its implications for public health, improving evidence-based knowledge on cannabis risks is highly needed.


Cristina Casajuana Kogel, Hugo Lopez-Pelayo, Maria Mercedes Balcells and Antoni Gual designed the study. Cristina Casajuana wrote the first draft of the manuscript. All other authors contributed to the editing and final review of the manuscript. All authors approved the final paper.


This study is founded by the Spanish grant of Plan National Sobre Drogas, Ministerio de Sanidad y Consumo (PNSD 20131082; Antoni Gual Sole). The conclusions of the article are only the responsibility of the authors and do not necessarily represent the official views of the institutions, who had no further role in study design, collection, analysis and interpretation of the data; in the writing of the paper; or in the decision to submit the paper for publication.

Conflict of interest

Hugo Lopez-Pelayo has received honoraria and travel grants from Lundbeck, Lilly, Janssen, Pfizer, Rovi, Esteve. Laia Miquel and Maria Mercedes Balcells have received honoraria from Lundbeck. Lidia Teixid6 has received honoraria from Pfizer. 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.


The authors thank Maria Estrada, Silvia Gomez, David Tinoco and Otger Amatller for their participation in the coordiantion and development of the field study. We also want to show our gratitude to the psychiatrists Dr. Blanch, Dr. Garcia-Rizo, Dr. Garrido and Dr. Goikolea and for the support given by Fundacio Clinic per la Recerca Biomedica, Institut d'Investigacions Biomediques August Pi i Sunyer, Agencia de Salut Publica de Catalunya- Generalitat de Catalunya, Energy Control and Fundacio Salut i Comunitat.


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(*) Institut d'Investigacions Biomediques August Pi i Sunyer (IDIBAPS). Barcelona (Spain); (**) Fundacio Clinic per la Recerca Biomedica. Barcelona (Spain); (***) Grup de Recerca en Adiccions Clinic (GRAC). Addictions Unit. Department of Psychiatry. Clinical Institute of Neuroscience, Hospital Clinic. Universitat de Barcelona. Red de Trastornos Adictivos (RTA); (****) Agencia de Salut Publica de Catalunya - Servei de Drogodependencies. Generalitat de Catalunya. Barcelona (Spain).

Send correspondence to:

Cristina Casajuana. c/ Villarroel 170, 08036 Barcelona (Spain). Telefono: +(34) 93 227 54 00 (ext. 4210) E-mail:

Received: October 2015; Accepted: January 2016.
Table 1. Socio-demographical characteristics of the sample recruited
for the pilot study (N=40).

Socio-demographical data                          Values

Men                                            29 (72.5)
Women                                          11 (27.5)

Median (IQR)                                    24 (8.75 years)
Range (years)                                 18 - 47 years

Marital status
Single                                         29 (72.5)
Married                                         4 (10.0)
Separated/ Divorced                              2 (2.0)
Widow/er                                         0 (0.0)
Others                                          5 (12.5)

Highest educational level achieved
Primary school (6 years of school completed)     1 (2.5)
4 years of secondary school completed           9 (22.5)
5 or more years of secondary school competed   14 (35.0)
University degree                              16 (40.0)

Working situation
Working                                        17 (42.5)
Unemployed                                     13 (32.5)
Currently absent from work                      5 (12.5)
Receiving a disability pension                   3 (7.5%)
Other situations without earning money           2 (5.0%)

Table 2. Description of consumption patterns and CAST scores of the
recruited sample (N=40).

Item asked                                                N (%)

Type of derivate consumed

Marihuana obtained in a cannabis association         18 (45.0%)
Home-gown marihuana                                  12 (30.0%)
Marihuana obtained in the illicit market               2 (5.0%)
Hashish                                               4 (10.5%)
Hashish oil                                            2 (5.0%)
Missing (several types of cannabis)                    2 (5.0%)
Tobacco use to roll the joint                        36 (90.0%)

Prepares the joints similarly                        34 (85.0%)

Frequency of consumption in the last 30 days

More than 20 days                                    28 (70.0%)
Between 10 and 19 days                                4 (10.0%)
Up to 9 days                                          8 (20.0%)

Number of joints consumed in one typical occasion

1 joint                                               8 (20.0%)
2-4 joints                                           22 (55.0%)
6-8 joints                                            5 (12.5%)
More than 9 joints                                     2 (5.0%)
Missing (consumed less than one joint per occasion)    3 (7.5%)

Shares the joint in most of the cases                13 (32.5%)

a CAST scores

0-1 (non-problematic use)                              2 (5.0%)
2-3 (low risk use)                                   15 (37.5%)
4 or more (high risk use)                            23 (57.5%)

Note. (a) CAST: Cannabis Abuse Screening Test
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Author:Casajuana, Cristina; Lopez-Pelayo, Hugo; Balcells, Maria Mercedes; Miquel, Laia; Teixido, Lidia; Col
Date:Dec 1, 2017
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