In the context where there is a need for effective interventions with long-term benefits for CUD in a population with SMD, this study aimed to evaluate the effects of a novel VR intervention to treat CUD for up to 1 year following the end of the intervention. Although avatar intervention for CUD links several preexisting concepts (eg, motivational approach, cognitive-behavioral approach, and relapse prevention), its particularity is that it allows patients to practice their strategies in a safe environment where cravings and emotions are elicited in a similar intensity to that of their daily life. This intervention’s relational and immersive aspects, which are entirely personalized, are hypothesized to enable the transposition of learning into everyday life [5758], leading to significant improvements. Indeed, results from this study show significant reductions in the total amount and frequency of cannabis use, which were maintained over time. Improvements were also noted in the severity of problematic cannabis use, negative consequences, motivation for change, psychotic symptoms, and quality of life.

Regarding the primary outcome, there was a significant decrease in the amount of cannabis use that was maintained until the 12-month follow-up visit and a significant decrease in the frequency at the 3-month follow-up. This result was also validated by a decrease in cannabis use as measured by quantitative urinary analyses. Moreover, cannabis consumption did not seem to have been replaced by other substances, as the total cost of drug acquisition remained lower at each time point when compared to the baseline. Although this is a pilot trial, these results are promising, as to the best of our knowledge, the existing interventions for CUD in a population with SMD generally show either no significant effects or, at best, small effects on cannabis use [39-4545undefinedundefinedundefinedundefinedundefinedundefined]. Indeed, there have been mixed results for cognitive behavioral–oriented interventions, motivational interviewing, the combination of both, and treatment as usual. In addition to practicing strategies in the VR environment, the relational approach is likely central to this intervention. Targeting interpersonal relationships, which are important factors influencing cannabis use, may be a key mechanism leading to potential benefits [82-84].

Regarding secondary outcomes, the severity of problematic cannabis use significantly decreased after the intervention, and these changes were maintained until the 12-month follow-up. Similarly, there was a significant reduction in the negative consequences associated with cannabis at the 6- and 12-month visits. Motivation for change initially improved but returned to baseline by the 6-month visit. Regarding strategies used to mitigate harms related to cannabis use, significant benefits were observed starting at 3 months and up to 12 months after the intervention. These results are in line with the literature on the subject. Indeed, when cannabis use is reduced, there is an improvement in the severity and the consequences associated with cannabis use [85]. Also, an increase in protective behavioral strategies was associated with fewer negative consequences associated with cannabis use [86]. Moreover, improving participants’ harm-reduction strategies associated with cannabis use is in line with the premise of the avatar intervention. As previously mentioned, using VR and a dialogical approach was hypothesized to allow a better transposition of the strategies into everyday life. A future study comparing a traditional face-to-face intervention to a VR intervention should evaluate whether the intensity of emotions contributes to the maintenance of acquired skills after the end of the intervention.

Interestingly, both quality of life and psychiatric symptoms, which had not significantly changed right after the intervention, showed significant improvements during the follow-up period. Considering that the postintervention assessment was administered within a week of the end of the intervention, it is likely that a delay between changes in consumption is necessary to achieve effects on quality of life and symptomatology. To the best of our knowledge, this is the first intervention for CUD to improve the quality of life and psychiatric symptoms in a population with SMD, and this was maintained up to 1 year after the end of the intervention. Although maintenance of medication during intervention was not an inclusion criterion in this pilot study, assessment of medication at baseline and postintervention showed little changes, which were not significant and thus not likely to influence the observed improvement in psychiatric symptoms. Nevertheless, significant changes were observed for 1 participant, which could have led to biased results. To overcome this potential limitation, an intention to maintain medication during intervention was added as an inclusion criterion in an ongoing randomized controlled trial. These results are partly in line with studies that have evaluated the evolution of psychiatric symptoms and quality of life in people with SMD over 1 year comparing three groups—(1) continued cannabis use, (2) discontinued use, and (3) no cannabis use [2987]. Regarding psychiatric symptoms, a meta-analysis observed that persistent cannabis use had a greater increase symptoms compared to those who had stopped. Also, individuals who had stopped using cannabis did not have a significantly different risk from nonusers. In particular, the severity of positive symptoms is affected in persistent cannabis users compared to those who have stopped. However, continued cannabis use did not increase negative symptoms [29]. Although the reduction in cannabis use likely contributed to the observed improvements in psychiatric symptoms, it is also possible that improved emotion management and greater interpersonal skills, which were both learned and practiced during the intervention, could also take part in these benefits [88]. Concerning the quality of life, there did not appear to be any significant difference between individuals who continued to use, those who stopped, and nonusers [87]. These results suggest that cannabis reduction alone may not fully explain the changes observed. Indeed, VR therapy for another psychiatric condition with a relational component showed significantly improved quality of life [89]. Changes in relationships with cannabis, others and oneself were at the core of each session; therefore, it is not surprising that benefits were observed in participants’ quality of life. Indeed, by promoting alternatives to consumption, participants may have developed new activities. Also, having acquired conflict resolution skills, it is possible that relationships with others may have improved. As the specific mechanisms of this new intervention have yet to be elucidated in comparison with a conventional face-to-face intervention, these will need to be more deeply investigated in future studies.

Participants’ engagement, as well as the acceptability and feasibility of the intervention were thoroughly evaluated in a prior study [63]. First, in response to an initially very high attrition rate, highly motivated participants were subsequently preferred, which resulted in a drastic reduction in dropouts. The overall attrition rate during the treatment was 40.6%, which is similar to those observed in a population with an SMD [9091]. Of the 19 participants who completed the postintervention evaluation, 4 additional participants dropped out before the last follow-up. Second, an analysis of baseline sociodemographic and clinical characteristics revealed that only amphetamine use disorder was associated with a reduced likelihood of completing the intervention and the follow-up. A meta-analysis likewise identified stimulant use disorder as an element influencing dropout rates in individuals with SMD [90]. To address potential selection bias, linear mixed models including the presence or absence of amphetamine use disorder as a covariable were calculated (data not shown), and the results remained grossly unchanged. Third, semistructured interviews were conducted until data saturation (n=11) to evaluate the participants’ satisfaction with each component of the intervention (eg content, frequency, number and sequence of sessions, appropriateness, and use of VR). Overall, the level of satisfaction was found to be high. Finally, adverse events were systematically recorded, showing that none of the participants discontinued [63]. Cannabis use can lead to increased hospitalization in our population, which is associated with substantial societal costs. Considering that, the costs associated with the acquisition of VR equipment and therapist training could be justified by a reduction in the use of health care services. Therefore, a cost-effectiveness analysis of VR use for CUD treatment in a population with SMD will be necessary prior to implementing this intervention in regular clinical practice [319293]. Additionally, technological advances in recent years have made VR equipment more affordable, which could eventually make it easily available and accessible in clinics, especially since therapists appear to be open to its use [9495]. Moving forward, it is foreseeable that most clinics and hospitals will make VR equipment available for therapists wishing to deliver various evidence-based interventions using this technology.

While the results suggest that the avatar intervention for CUD appears to be a promising avenue in individuals with SMD and CUD, the present trial has some important limitations to highlight. First, this study does not include a control group for comparison purposes. Considering studies have observed a regression toward the mean of psychiatric symptoms, naturally, in assessments with several time points as well as to control the nonspecific effects of psychotherapies, a control group intervention will be necessary in future clinical trials [9697]. Second, as there was no control group, the evaluators could not be blind to the intervention. Third, as this was a pilot trial, the sample size was small. To address these three major limitations, a single-blind randomized controlled trial with a projected enrollment of 150 participants comparing the avatar intervention for CUD with a conventional addiction intervention is underway. Fourth, the THC/CBD ratio was not considered, mainly because participants generally did not know exactly what they were consuming. A potential solution to this problem would be to analyze a sample of each participant’s cannabis; however, this raises ethical and legal issues that could be complex to resolve. Fifth, in this first clinical pilot, the interventions were offered by a single therapist. In the future, it is planned to integrate other service providers and to harmonize the intervention by means of training and an intervention manual. Finally, in the interests of desirability, patients may have underestimated their consumption. However, quantitative analyses of THC-COOH undertaken at baseline, postintervention, and the 3-month follow-up show a strong correlation with patients’ self-reported measures (as observed in other studies using similar quantification methods), indicating that they have a good assessment of their consumption [9899].