Psychiatric comorbidity in adolescents who abuse substances is the rule rather than the exception, with 61–88% having a dual diagnosis (1, 2). The coexistence of both disorders is associated with important disruptions in a range of functional domains, including academic attainment, social and family relationships (2, 3), and accidents (4). In addition, initiation of substance use at a younger age (5) and a faster relapse after treatment (6) are reported in youths with preexisting mental health problems. In turn, the natural course of psychiatric disorders may be affected by substance use, either due to negative psychosocial consequences associated with substance involvement (7) and/or to the direct effect of the substance on the central nervous system (8). In youths with mood or psychotic disorders, for example, daily use of cannabis is associated with a more severe clinical presentation, impaired cognitive and interpersonal abilities, and poorer responses to pharmacological treatments (9). The development of integrative treatment for substance use disorders (SUDs) and psychiatric disorders is therefore a priority (10, 11).

Among adolescents hospitalized for a psychiatric problem, 17–50% meet criteria for one or more SUDs (12–17). In a previous study of adolescents hospitalized in three psychiatric units in France, most subjects met criteria for a non-nicotine SUD: around 70% for cannabis, 60% for alcohol, and 20% for other substances (18). Unsurprisingly, those with dual disorders exhibited more severe clinical characteristics (e.g., more suicide attempts) and a higher level of functional impairment (e.g., more school absenteeism) than patients without SUDs. They also received more diagnoses of axis 2 comorbidities and were exposed to more severe psychological contexts (e.g., maltreatment or loss of a first relative) (18). Given the high prevalence of SUDs among adolescents who are hospitalized, and the poor clinical outcomes due to the negative interplay between both disorders, specific preventive interventions for addiction should be developed and evaluated in this population.

It is well established that treatments for SUDs and psychiatric disorders are less effective when provided separately (1, 6). Although the efficacy of integrated approaches for the management of dual disorders has been demonstrated in adolescents (10, 11), there is some concern that – in practice – the so-called “integrated approach” often consists of the addition of evidence-based treatments for both problems, with too few specific dual diagnostic or therapeutic tools. For example, in order to choose the optimal treatment, the sequence between substance use and other psychiatric symptoms in patients’ daily life should be explored, but we are not aware of any tool that would measure this pattern. Furthermore, treatment compliance is a key prognostic factor in addiction. For most teenagers, SUDs are commonly under-recognized as a health issue (19). The development of tools that promote better recognition of patients’ problems with substances, and enhance behavior change, would therefore be worthwhile. Digital approaches may be a promising avenue for health-related interventions among adolescents given their propensity to use digital technologies (20–24).

The uptake of smartphones in the general population has encouraged the development of apps used to facilitate real-time assessment of the patient in his/her natural environment [Ecological Momentary Assessment (EMA)] and allowed delivery of smartphone app interventions in this context.

Ecological momentary assessment consists of using computers or other devices to collect self-assessments repeatedly in real-time, in various situations of the participant’s daily life, either for research purposes or to provide participants with timely feedback and advice (25). Different terms have been used for this methodology since the 1980s, including “ambulatory assessment,” “experience sampling method,” or “real-time data capture.” Even though the terms differ, these approaches have the data collection in common (e.g., symptoms, behaviors, physiological processes, or daily life circumstances) while the participant undergoes normal activities. Therefore, this allows the interplay between contextual stressors, psychological distress, and maladaptive behaviors to be modeled (26). Compared to traditional measures using paper–pencil questionnaires, EMA is regarded as having many benefits for addiction research, including decreased recall bias, decreased contextual bias (25, 27), and increased validity to model the temporal sequence of events between risky situations, craving, and substance use (28, 29). Although such tools have been available for over 30 years, the emergence of smartphone applications as a platform for EMA greatly improved the acceptability and usability of this technology (30). In the last decade, EMA systems have been developed for adolescents with addictions (31) and applied to the assessment of psychiatric symptoms in outpatients with internalizing/externalizing disorders (32–36). In contrast with adults [e.g., Ref. (37)], EMA has not yet been assessed, to our knowledge, for studying the relationship between psychiatric symptoms and patterns of substance use in adolescents. In addition, the feasibility of using EMA in adolescents with severe psychiatric symptoms remains understudied.

The smartphone app Stop-Cannabis was developed in 2013 in Geneva, Switzerland with financial support from the local Health Department.¹ The app aims to help users reduce or stop their cannabis use and prevent relapse. Stop-Cannabis consists of several modules based on cognitive behavioral therapy strategies, motivational interviewing, and relapse prevention programs. Particular effort has been made to include the principles of self-determination (autonomy, competence, and relatedness) (38) into the app and promote its customization (39). As in other studies (40–42), participant interaction and rewards support the playful aspect of the intervention. Personalization of the users’ goals and the app main screen may further contribute to increase adoption by user (43). The contents of the application are summarized below [and described in detail in Ref. (39)]. Since February 2013, the Stop-Cannabis app [available on Google Play (Android) and (iOS) App Store] has been downloaded more than 13,000 times, and the app is currently used by 1,000 people every month. The app was reported to have a good level of acceptability among community users in an online satisfaction survey (39).

This study is part of a general collaborative research program between the child and adolescent psychiatric department team and the addiction unit. The purpose of this wider program is to inform the difference in the trajectories of inpatients adolescents with SUDs compared to other and to help developing a better clinical practice (i.e., early detection, clinical assessment, and therapeutics).

Participants will be adolescents (11–18 years old) who are hospitalized in the Department of Child and Adolescent Psychiatry at the Pitié-Salpêtrière University Hospital between September 2016 and September 2018. The participants will be assessed at baseline. According to the presence or absence of comorbid SUDs, they will be included in either the SUDs group or the control group. The SUDs group will receive the mobile apps, whereas the control group will not. Exclusive tobacco consumption is not considered to be a criterion for inclusion in the SUDs group. Inclusion to the non-SUD control group will be made according to a match with adolescents from the SUDs group (for age, gender, inpatient unit, and time of admission). Exclusion criteria include non-French speaking, those without a personal mobile phone, lack of informed consent from parents or from the adolescents, and any mental or physical problems that interfere with participation in the study (e.g., autism with very low communication abilities, severe to profound intellectual disability, severe motor disability).

A conservative approach was adopted for this feasibility study, which emphasizes descriptive and qualitative feedback. Consequently, based on the recommendations for pilot studies (44), we plan to include 80 participants (40 cases, 40 controls) over a 2-year inclusion period. As there are around 280 inpatient admissions per year in the Department of Child and Adolescent Psychiatry, i.e., n = 560 potential participants contacted at baseline during the 2 years, this will represent a 14% inclusion rate. We predict that the prevalence of SUDs will be similar to that previously reported (18). A good level of compliance with EMA and Stop-Cannabis is expected, consistent with previous studies that reported high levels of adherence (up to 80%) to similar tools in adolescents with comorbid psychiatric disorders (31, 45), and in adults with associated severe psychiatric disorders (32, 46). An acceptance rate of 80% is expected in the SUD group and 50% for the control group. A 50% retention rate at 1-year follow-up is anticipated based on previous longitudinal studies among adolescents (47). In case of a lower enrollment rate, we will either continue to enroll participants during an additional year (2019) in order to reach the intended sample size or use incentives (e.g., free participation in leisure and sport activities in groups) to encourage participant enrollment.

The EMA was designed as an app for mobile phones. This application allows several daily self-assessments (e.g., five times a day for 2 weeks at different times of the study/monthly). Data are collected in response to a signal from the EMA app that occurs at various times of the day. The app has been programed to send signals (i) a fixed number of times per day at predetermined times (e.g., at bedtime) and (ii) at random (with a balance between week, weekends, and holidays, with different time intervals in daytime). Participants are also asked to complete self-assessment immediately following substance use.

The same questions are presented regardless of assessment type. There are seven questions in total:

Information relating to substance use: ○

Daily use of each substance in list.

Participants will be trained on EMA use during the week prior to hospital discharge. They will be asked to respond to any signals within 1 h if possible. Consistent with other EMA protocols, participants will complete 2 days of practice data (not used for analyses), after which they will receive feedback on adequate use and compliance. Participants will then be invited to complete EMA assessments for 2 weeks, as this timeframe appears sufficient to monitor substance use (45). To limit attrition, participants will be paid 30€ for completing the baseline assessment and 10€ for each week of complete EMA data, up to a maximum possible payment of 60€ over 1 year.

Launched in 2013, Stop-Cannabis is available free on iOS and Android. It has been continuously updated and improved over the past 3 years, in response to users’ suggestions. When people use the app for the first time, they are asked to document their objectives and choose a quitting date. The app has several modules. First, it allows users to assess their cannabis usage profile (including motivations for use and severity of cannabis use) via different assessments (49). Users then receive an individually tailored feedback message that includes links to online psychoeducation and complementary resources. Second, motivational messages are regularly delivered using push-notification technology at different stages of the quitting process, on the basis of updated information regarding current substance use, the selected quitting date, and exposure to situations associated with a high risk of relapse documented by high levels of craving or irritability. Third, the app includes messages on how to cope with craving symptoms or emotional difficulties to enhance participants’ insight into contextual factors for substance use. Fourth, positive reinforcers, such as the number of days since quitting the substance and the amount of money saved, are displayed on the main screen and can be personalized (Figure 1). Fifth, a discussion forum called “The Tribe,” moderated by a psychologist, is available for all users to encourage discussion, mutual support, and information sharing. Sixth, the app includes direct access to a website² for additional information about substance use and online motivational interviewing training.

The app will automatically monitor the number of times each participant opens the app and records the number of times participants looked at or used each element. A Unique Device Identifier (UDI) is used to connect the participants’ device to the study database and will be replaced in the data set with a random ID for anonymity. After study completion, the UDIs will be automatically deleted from users’ devices. The app will be available for participants in the intervention group for 12 months. After this period, the app will automatically stop data collection. However, participants are free to use the app for as long as they want.

The study flowchart is shown in Figure 2. Each patient admitted to the Department of Child and Adolescent Psychiatry at the Pitié-Salpêtrière University Hospital during the study recruitment phase will be systematically screened for SUDs and eligibility at admission. The DEP-ADO questionnaire (50) will be used in the study to document substance use in the previous 12 months. The complete questionnaire is available free online³. The screening question will be “During the last twelve months, how often have you [has X] used one of the following substances: alcohol, cannabis, cocaine, inhalant/solvent, stimulant, hallucinogen, or heroin” (examples and trivial names are provided for each substance). For each substance, participants and their families will have the options of answering: “Never,” “Occasionally,” “Once per month,” “Once or twice per week,” “More than three times per week,” or “Daily.” The clinician version of the DEP-ADO will be completed by the clinician involved in usual care after an interview with the adolescent and his/her family. The self-report version will be completed by the adolescent, with assistance from a specially trained member of the paramedical staff. Assessments will be carried out within 3 days following admission and repeated after 1 week as an inpatient, and again if necessary (especially if the clinical condition is not compatible with self-assessment).

Urinary drug tests will be performed on all adolescents hospitalized in the Department of Child and Adolescent Psychiatry during the study recruitment phase. The tests screen for the presence of cannabis, cocaine, opiates, and amphetamines. In the interest of having as broad as possible a representation of the target population, we will include as “screen positive” those who answer at least “occasionally” to use of cocaine, inhalant/solvent, stimulant, hallucinogen, or heroin, and/or at least monthly use of cannabis or alcohol, and/or when their urine test indicates the presence of one of these substances.

All youths screened positively for substance use will be reported to the hospital’s liaison addiction unit (ECIMUD, a French acronym for coordination and medical care team for addictive disorders) for proper diagnosis and care. Systematic evaluation of the substance use and habits will be conducted via a semi-structured interview, which allows for scoring the RECAP index, the clinician version of the DEP-ADO, and the Cannabis Use Screening Test (CAST), a self-reported scale that focus on use of cannabis in the previous 6 months (51). Final diagnoses of SUDs will be made by one of the ECIMUD senior psychiatrists using DSM-5 criteria (52).

Participants (i.e., adolescents with SUDs and control subjects) will be approached by a researcher involved in the project (either a clinician specialized in child psychiatry or a master’s level psychologist) who will explain the study and obtain written informed consent from parents or guardian and assent from the adolescent. Participants will be assessed in the week prior to hospital discharge for sociodemographic data, psychosocial information, psychopathology, and substance use (see Variables and Instruments). All youths will be assessed in face-to-face interviews by a specially trained master’s level psychologist at 6-month and 1-year follow-up.

Table 1 lists the questionnaires and other assessments that will be used at baseline and at follow-up. The reading level of the questionnaires is grade 6. The questionnaires we plan to use to measure addiction are described below. A combination of self- and clinician-report measures with different time scales (i.e., DEP-ADO, 12 months; CAST, 6 months; RECAP, 1 month) will be used to examine whether EMA data are consistent with information collected in the traditional way. The second type of measures relate to psychopathology with the aim of examining the interplay between substance use and psychiatric disorders.

Information will be collected from both EMA data and from questionnaires administered during hospitalization and follow-up.

A degree of correlation higher than 0.70 is expected between EMA data and data collected using other methods (particularly frequency of use), in line with prior studies (46). EMA should lead to predictions regarding the course of SUDs over the 1-year follow-up (e.g., in term of persistence, severity, and functional impairment) at least as good as other methods; that would be of interest for the clinicians involved in usual care. A high level of compliance with EMA is expected, despite the relative severity of the study sample. Based on previous studies in adolescents (45, 67), participants are expected to complete a mean of more than 70% of random signals, 50% of end-of-day assessments, and 40% of both random and end-of-day assessments. Indeed, there is good evidence that EMA can be used by patients with severe psychiatric disorders (e.g., schizophrenia) or cognitive difficulties (32, 46).

This study will measure the prevalence and the characteristics associated with the presence of SUDs in a sample of adolescents hospitalized in a psychiatric setting. Findings are expected to be in a similar range as those previously reported by Daudin et al. (18). We will then examine the possible relationship between SUDs and specific psychosocial and clinical features of inpatient adolescents. We expect this study to confirm that both internalized and externalized disorders are significantly associated with SUDs and that the presence of SUDs is associated with a higher level of impulsivity, mood dysregulation/borderline traits, and sensation-seeking traits (68–70). We predict that a bidirectional positive relationship between the level of substance use and the severity of other psychiatric symptoms will be noted at a daily level, and – if confirmed – that this association would be strengthened in a context of interpersonal relationship (with family and with peers) compared to other situations. A significant negative association between the level of the Stop-Cannabis app use and the participant’s clinical outcome at follow-up is expected. Such additional exploratory analysis would provide preliminary information about the possible benefit of the app in naturalistic settings.