Introduction

Cannabis is the most commonly used illegal drug in Europe; 14.6% of young adults (ages 15 to 34) have used cannabis within the past month (European Monitoring Centre for Drugs and Drug Addiction [1]. Cannabis use has been associated with different behavioral, cognitive and emotional deficits, including apathy, disinhibition and executive dysfunction [2, 3]. In addition, cannabis use is associated with significant negative social consequences, may act as a gateway to the use of other substances, and can trigger or worsen psychotic symptoms [4, 5]. Recent calls for research have highlighted that severe cannabis users are more likely to experience these symptoms, and hence more likely to request treatment for cannabis use disorders [6–8].

Psychological treatments for cannabis use disorders have been largely grounded on the Transtheoretical Model of Behavior Change. This framework fostered the application of motivational interventions, which capitalise on motivational factors that can stimulate cannabis users to quit the drug [9–11]. The model emphasises the relevance of motivational factors, such as Decisional Balance and Processes of Change, as the leverage to facilitate behavioural change [12–14].

Decisional Balance involves weighing up the perceived advantages (gains) and disadvantages (losses) of using cannabis versus quitting cannabis. Cognitive processes linked to disadvantages of smoking and gains of quitting have shown to shift the decisional balance in favour of quitting as indicated by research in nicotine dependence [15]. However, these cognitive processes are multidimensional, including both gains and losses in four different aspects: 1) Anticipated utilitarian effects for the self; 2) Anticipated utilitarian effects for significant others; 3) Self approval; 4) Anticipated effect on how one is regarded by significant others. Empirical evidence suggests that in individuals that are ready to change their behavior, the cognitive processes linked to the benefits exceed the ones of the costs [16]. Accordingly, decisional balance measures have been shown to predict clinical outcomes in nicotine use [17] and alcohol use disorders [12, 18].

The Processes of Change represent 10 different behavioural and experiential strategies for changing behaviour. They have been classified in cognitive-affective processes (defined as changes in the way people think and feel about their smoking) versus behavioural processes (defined as coping strategies that are utilized to change cannabis use behavior). Cognitive-affective processes include consciousness raising (CR), Dramatic Relief (DR), Environmental Re-evaluation (ER), Self-revaluation (SR), and Social Liberation (SO). Behavioural processes include Stimulus Control (SC), Counter Conditioning (CC), Reinforcement Management (RM), Self- Liberation (SL), and Helping Relationships (HR). Cognitive-affective processes are more often utilized during early stages of change, fostering awareness and control of thoughts, feelings and health-related goals [13, 14] and behavioural processes are more typical in later stages of change [19, 20].

Decisional Balance and Processes of Change facets are typically addressed in some of the most successful treatment interventions for cannabis dependence, such as motivational interventions. However, it would be relevant to determine which of these facets are actually endorsed by severe cannabis users, as the facets that better resonate with their own motivations will be likely to have stronger therapeutic effects. To address this unmet need, this study aims to compare Decisional Balance and Processes of Change in severe versus mild to moderate cannabis users in a community-based sample of young undergraduates. This comparison will identify the specific dimensions of Decisional Balance and Processes of Change that are endorsed by severe cannabis users, which are similar to treatment-seeking populations. Therefore, the results obtained in this community sample can be useful to inform the contents of motivational interventions in clinical samples. We hypothesised that severe cannabis users compared to mild users: 1) would endorse less gains and more losses related to using cannabis; 2) would endorse more behavioral and less cognitive processes of change.

Methods

Participants

The sample comprised community-dwelling young adults between 17 and 45 years of age, recruited from the student population of the University of Granada. Participants were recruited by university faculty during class breaks and were selected using a probabilistic sampling design. In particular, a cluster stratified sample design was adopted. Strata were based on the different university faculties. Cluster samples were extracted such that majors and years of study were represented in proportion to the total number of students in each faculty. Finally all students of the cluster sample were included in the final sample. There were 856 student participants recruited between September 2013 and June 2014. They were informed about the aims of the study and provided signed informed consent. Ethical approval was obtained from the Research Ethics Committee from the University of Granada.

All 856 participants completed the Severity of Dependence Scale (SDS) and 115 reported that they were cannabis users. We divided these 115 cannabis users in two groups. The first group comprised cannabis users of moderate severity (n = 84) and the second group comprised severe cannabis users (n = 31) as indicated by the SDS cut-off defined by Cuenca-Royo et al. [21]. In order to get similar sample sizes for group comparisons, we selected a random subsample of 31 moderate cannabis users by simple random sampling without replacement. The socio-demographic characteristics and variables related to cannabis smoking in the final sample can be seen in Table 1. We found sex differences in the severity of cannabis use: the moderate group consisted mostly of women and the severe group consisted mostly of men.

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Table 1. Baseline demographic and variables related to cannabis smoking of the participants classified in each of these categories (moderate versus severe).

https://doi.org/10.1371/journal.pone.0188476.t001

Results

We found a significant effect of Group on Decisional Balance (Wilks' Lambda = 0.051, F_11,50 = 83.900; p< 0.001; Eta = 0.949). Univariate tests of between-group effects revealed significant effects of Group on the total score of Gains (F_1,60 = 20.188; Mean Squared Error [Mce] = 2567.76; p< 0.001; Eta = 0.252) and in the specific dimensions of Utilitarian Gains for the Self (F_1,60 = 21.841; Mce = 276.79; p< 0.001; Eta = 0.267), Utilitarian Gains for Significant Others (F_1,60 = 9.622; Mce = 60.016; p< 0.003; Eta = 0.138) and Self-approval (F_1,60 = 12,281; Mce = 236.145; p< 0.001; Eta = 0.170). In all cases, the severe group had higher scores than the mild group. There were no significant differences in Losses. Mean, standard deviations and significance are presented in Table 2.

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Table 2. Mean and typical deviation to evaluate status cannabis abuse decisional balance and process of change.

https://doi.org/10.1371/journal.pone.0188476.t002

We also found a significant effect of Group on Process of Change (Wilks' Lambda = 0.357, F_10,51 = 9.175; p < 0.001; Eta = 0.643). Univariate tests of between-group effects revealed significant effects of Group on Self-Reevaluation (F_1,60 = 14.751; Mce = 133.565; p< 0.001; Eta = 0.197) and Counter-Conditioning (F_1,60 = 10.249; Mce = 108.452; p< 0.01; Eta = 0. 146). In all cases, the severe group had higher scores than the mild group. Mean, standard deviations and significance are presented in Table 2.

Covariates analyses including tobacco dependence and sex did not changed the above-reported findings.

Discussion

The aim of this study was to compare the different dimensions of Decisional Balance and Processes of Change in community-recruited participants with severe versus mild cannabis dependence, as indicated by the SDS. With regard to Decisional Balance we found that the severe group had higher scores in Utilitarian Gains for the Self, Utilitarian Gains for Significant Others, Self-approval and total Gains. Both severe and mild users perceived similar losses. With regard to processes of change we found that the severe group had higher scores in Self-revaluation and Counter-conditioning. These findings suggest that severe cannabis users are more aware of the potential gains of quitting the drug, and make more use of behavioral processes of change, compared to mild users. They also identify the specific processes that they use to foster self-change, which may be relevant to inform the contents of motivational interventions.

The Decisional Balance findings suggest that severe cannabis users can better perceive the importance of specific gains associated with cannabis use cessation. Utilitarian Gains for the Self (smoking cannabis does not help me to concentrate); Utilitarian Gains for Others (my cannabis use bothers other people) and Self approval (I am embarrassed to smoke cannabis) are specifically endorsed. These dimensions have shown to be associated with positive behavioral changes after treatment interventions in alcohol and tobacco dependent users [12, 17, 18]. Our results suggest that they could be effectively applied during motivational interventions for cannabis dependence.

The Processes of Change findings suggest that severe cannabis users are more likely to use particular behavioral Processes of Change (Self-revaluation and Counter-conditioning), whereas they did not differ from mild cannabis users with regards to cognitive Processes of Change. These behavioral Change Processes have been shown to be associated with reduction of problematic drug use in clinical samples [9– 14]. They are also associated with positive transitions within the stages of change [19, 20]. Therefore, these findings can also inform the design of motivational interventions for cannabis dependence. The implication of these findings is that severe cannabis users may be more sensitive to behavioral versus cognitive ingredients of these motivational interventions. Moreover, they imply that Self-Reevaluation and Counter-conditioning could be immediately applied in treatment-seeking cannabis users at the beginning of the treatment process.

In conclusion, our results are preliminary and need to be complemented by direct research on the treatment pathways of motivational interventions in cannabis dependence. Recent meta-analytical studies have examined these mechanisms, but have focused in the interventions format and design, but not specifically in the motivational ingredients [35, 36]. Our preliminary results can stimulate further research in this topic.

Supporting information

Acknowledgments

The data collection and the field work were performed by the FQM356 research group as part of the Andalusian Research Plan.