Cannabis and Young Users—A Brief Intervention to Reduce Their Consumption (CANABIC): A Cluster Randomized Controlled Trial in Primary Care

Catherine Laporte; Hélène Vaillant-Roussel; Bruno Pereira; Olivier Blanc; Bénédicte Eschalier; Shérazade Kinouani; Georges Brousse; Pierre-Michel Llorca; Philippe Vorilhon

doi:10.1370/afm.2003

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Author response: About IB efficacy in Primary Care
Catherine Laporte

Published on: 05 June 2017
About the relevance of brief interventions and screening on cannabis use conducted by general practionners
Francois Beck

Published on: 30 May 2017
Still no evidence that brief intervention in primary care affects drug use
Richard Saitz

Published on: 21 March 2017

Published on: (5 June 2017)
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Author response: About IB efficacy in Primary Care
Catherine Laporte, MD-PhD
Pr Saitz,
Thank you for your interest in our study and your highly relevant comments.
We strongly agree with the need of further studies to validate IB effectiveness and more specifically defining the descriptive criteria of target populations on which it will be most effective. Previous RCTs investigating cannabis-related IB showed its efficacy when applied to young (Martin, Walton, Walker, D'amico)...
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Pr Saitz,
Thank you for your interest in our study and your highly relevant comments.
We strongly agree with the need of further studies to validate IB effectiveness and more specifically defining the descriptive criteria of target populations on which it will be most effective. Previous RCTs investigating cannabis-related IB showed its efficacy when applied to young (Martin, Walton, Walker, D'amico) or moderate consumers (Martin, Walton, Bernstein), however other trials targeting similar populations did not show significant effect (Mc Cambridge, Palfai, Lee and your study published in JAMA in 2014). It is therefore crucial to further confirm these trends.
The goal of our study was to urge GPs to propose their 15 to 25-year-old patients to participate regardless of their consultation reason: thus we did not report any request for specific care related to cannabis use (this is stated in the 'study procedure' section: 'All general practitioners then had the 1 year in which to enroll the first 5 eligible patients in their practice, p132). Subjects committing to participate in a study could be more interested in the topic, or more ready to enter a care approach. Nevertheless, both study groups were potentially concerned by these issues, therefore having no impact on study outcomes. On the contrary, the Hawthorne effect in the control group might have decreased the difference in IB effect observed between the two groups (Braunholtz DA, Edwards SJ, Lilford RJ. Short term Evidence for a trial trial J Clin Epidemiol 2001: 54 (3): 217 24.).
The high number of lost to follow-up subjects might to follow-up subjects is common in intervention studies (D'Amico et al., Haller et al). As mentioned in the method section, we however applied different statistical approaches to ensure that this loss did not involve any attrition bias which could affect the final result. Finally, while the rate of loss to follow-up subjects was found to be higher than that expected (10% for GPs and 20% for subjects), the number of subjects was calculated based on relatively stringent criteria, notably in terms of statistical power (90%) and ICC (0.05 to 0.20). An a posteriori estimation of statistical power remains difficult in regards to the difference (p = 0.08) initially observed between randomization groups in terms of joints consumption. Finally, several studies have assessed the validity of self-reporting and shown that this did not prevent statement veracity (Copeland et al., 2001). Moreover, subjects and doctors behavior is known to change as soon as these participate to a study, but this applies to both groups (McCambridge et al., 2011; Smelt et al., 2010). Finally, in our study, we attempted to show the adequacy between an anonymous declaration through a self-administered questionnaire and a statement provided to the doctor during the interview. The Lin concordance was rather good (0.9) and in accordance with an honest declaration from young patients regarding their consumption.
Thank you again for your such critical comments, enriching the debate on the methodology of new healthcare systems evaluations (hereby training GPs to IB), specifically in primary care.
Competing interests: None declared
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Competing Interests: None declared.
Published on: (30 May 2017)
Page navigation anchor for About the relevance of brief interventions and screening on cannabis use conducted by general practionners
About the relevance of brief interventions and screening on cannabis use conducted by general practionners
Francois Beck, Director
Other Contributors:
Catherine Laporte and colleagues paper deals with a crucial issue for several reasons. In France, the health authorities have set up in 2006 a strategy for the widespread dissemination of the early detection and brief intervention on alcohol to general practitioners. This initiative was motivated by the existence of a World Health Organisation program to combat alcohol harmful use by the implementation of various regional...
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Catherine Laporte and colleagues paper deals with a crucial issue for several reasons. In France, the health authorities have set up in 2006 a strategy for the widespread dissemination of the early detection and brief intervention on alcohol to general practitioners. This initiative was motivated by the existence of a World Health Organisation program to combat alcohol harmful use by the implementation of various regional strategies aimed at promoting such brief interventions, but there has not been such a program for cannabis. As shown in a representative sample of 2,083 general practitioners surveyed in 2009 in France, only 8% reported discussing cannabis consumption at least once with each patient and 25% do not discuss it at all, or only if the patient explicitely asks for it [Beck et al., 2011]. According to Laporte and colleagues paper, general practitioners may not be completely well prepared to tackle with heavy cannabis users. The lower tobacco smoking prevalence in the intervention group (minus 12 points) is a limit that could have been more evoked in the discussion: it is for example possible that the intervention would have been less efficient with a more prevalent intervention group, as far as tobacco use can be a drag on cannabis cessation. However, the study concluded that general practitioners are undoubtely a very relevant first step to initiate a decrease in the use of the youngest and of moderate users. Recent results have shown that the age of onset for alcohol tobacco and cannabis was increasing, and the prevalence of those 3 products were declining between age 11 and 15, which is a very positive trend. Nevertheless, cannabis prevalence in France was still increasing between 2010 and 2014 at age 17, underlining a rapid evolution from experimentation to a regular use at this age. Considering that 90% of adolescents have seen a general practitioner at least once in the last twelve months (Spilka et al., 2015), efforts should be put on the 15-17 years old, and, for this target age group, brief intervention by the general practitioner is efficient and should be largely encouraged. Moreover, screening on cannabis use could at least be an appropriate first step to involve them in a process that could be connected to other devices such as the youth addiction outpatient clinics or the treatment and prevention centres for addiction. In this perspective, a recent French study underlined the need to empower the relations between school health providers (such as nurses and physicians) and the other addiction devices (Lecallier et al., 2012). As general practitioners are also required for other prevention and health promotion issues such as alcohol use, tobacco smoking, nutrition and physical activity, the task remains huge. It would be relevant to study the feasability of such an implemantation.
References: Beck F., Guignard R., Obradovic I., Gautier A., Karila L., 2011, Increasing trends in screening for addictives behaviors among general practitioners in France, Epidemiology and Public Health, 59, 285-294.
Lecallier D, Hadj-Slimane F, Landry M, Bristol-Gauzy P, Cordoliani C, Grelois M, Delva C, Michaud P, 2012, [Screening, referring and counseling of adolescents for substance abuse. A randomized controlled study on 2120 students]. La Presse Medicale 41: e411-e419. http://www.ncbi.nlm.nih.gov/pubmed/22445839
Spilka S., Le Nezet O., Ngantcha M., Beck F., Drug use in 17-year- olds: analysis of the ESCAPAD survey, Tendances, n? 100, OFDT, 1-8. http://en.ofdt.fr/BDD/publications/docs/eftassv5.pdf
Competing interests: None declared
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Competing Interests: None declared.
Published on: (21 March 2017)
Page navigation anchor for Still no evidence that brief intervention in primary care affects drug use
Still no evidence that brief intervention in primary care affects drug use
Richard Saitz, Professor and Chairman
The main message of this cluster RCT is that brief intervention is ineffective for cannabis use. The subgroup findings are intriguing and should serve not to conclude that the results "strongly support" efficacy for those under age 18 or nondaily use. Instead, since subgroup findings are so often not reproduced, they should serve to generate hypotheses and be tested in future studies. There are some concerns that limit any co...
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The main message of this cluster RCT is that brief intervention is ineffective for cannabis use. The subgroup findings are intriguing and should serve not to conclude that the results "strongly support" efficacy for those under age 18 or nondaily use. Instead, since subgroup findings are so often not reproduced, they should serve to generate hypotheses and be tested in future studies. There are some concerns that limit any conclusions that can be drawn from this study such as the substantial loss to follow-up (which could favor findings in the intervention group), and the use of self-report outcomes. Self-report can be valid but is suspect in brief intervention studies when participants in a BI are advised to use less, and then asked later if they are using less, making differential reporting (bias) in intervention and control groups very plausible. Another issue that the authors could help us with in the interpretation of the study is whether this study implemented universal screening to identify those with cannabis use or whether screening was selective or otherwise done. Whether or not brief intervention has efficacy may relate to whether patients are seeking help, are identified because their use is obvious to the clinician, or whether all are screened regardless of their characteristics. It is not clear what the case was in this study.
Competing interests: Payment for journal and text editing from BMJ, JAMA, UpToDate, American Society of Addiction Medicine for writings on related topics and for speaking at universities and nonprofits on related topics.
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Competing Interests: None declared.