In France, addictive behaviors are a major public health problem. French adolescents are the most frequent users of cannabis in Europe, and the second most frequent users of other illicit substances [1]. The use of tobacco, alcohol and cannabis has serious physical, mental and social consequences [2,3]. It is during adolescence that addictive behaviors begin and become settled, with more early and considerable use in boys than in girls [4]. Primary prevention allows for acting with adolescents before the first experiments. Thus, preventing addictive behaviors at an early age can delay the entry into drug use and thus limit the risk of addiction in adulthood [5]. Nevertheless, the literature has shown that girls are more positive about school-based primary prevention programs than boys [6]. It is therefore important to implement this type of action while taking into account gender differences during its evaluation [7].

For a long time, primary prevention programs focused on imparting knowledge about illicit substances, but these have had no significant effect [8]. Today, prevention programs are centered around the acquisition of life skills. For the World Health Organization, life skills consist in the ability of a person to respond effectively to the demands and trials of daily life [9]. The development of these skills during adolescence can prevent substance use [10], which accounts for their integration into more modern prevention programs. The program named “Unplugged” is one of these new programs. Unplugged is an interactive European school-based curriculum against youth substance use, based on the comprehensive social influence approach [11] and life skills development [12]. It has been developed, implemented and tested in seven European Union countries [13]. Its effectiveness in preventing or reducing daily tobacco use, heavy alcohol use, recent cannabis use [14], as well as binge drinking and tobacco and alcohol use [15,16], has made Unplugged an effective program for dealing with substance use in adolescents.

Despite the effectiveness of these modern prevention programs, some studies have highlighted a gap between the acquisition of life skills and their application in context by the adolescents [17]. The acquisition of life skills is not always put into practice in the refusal to use illicit substances in the face of strong peer pressure. It is in response to this finding that we propose to modify the Unplugged program by adding a specific session: the “Intervention Program based on Self” project (IPSELF). Through this add-on session for the Unplugged program, it is proposed to bridge the gap with a 13th session for developing one’s self-concept. One’s self-concept refers to the extent to which one’s self-knowledge is defined, consistent and currently applicable to one’s attitudes and dispositions [18]. A positive self-concept favors increased effort, perseverance in the face of difficulties, the use of acquired abilities and strategies, and increased efficiency [19]. It also allows for better academic performance [20] by facilitating the acquisition of knowledge. Moreover, knowing oneself well can reduce the impact of social influence on substance use [21]. Thus, incorporating the development of positive self-knowledge through adaptive and protective identity development into substance abuse prevention interventions could have a lasting and protective impact [22,23]. The proposal of this study is therefore to develop self-concept abilities. Specifically, our session focuses on self-definition through positive character traits, personal values and the possible impact of one’s self-definition [24], in order to make the self-concept more positive. To do this, the session offers adolescents several activities. The first activity is a brainstorming session asking adolescents about what defines them. This discussion shows them that a multitude of things can define us. The goal is also to arrive at the concept of value. In the second activity, adolescents are asked to choose a person they admire (real or fictional) and to indicate the values that this person represents. The values proposed as examples are all positive. They then choose which of the values they would like to improve in themselves. This exercise allows adolescents to put into words what is important to them, that is, their values [25]. In the final activity, the adolescents pair up. Each must choose two values that define their partner and give an explanation for their choice. This exercise helps to show adolescents that others may see them differently than they see themselves [24]. From this session, small exercises on self-concept are to be completed at home by the adolescents for each of the following sessions.

The objective of this study was to implement and evaluate the effectiveness of the “Intervention Program based on Self” program, consisting of the Unplugged program sessions and a complementary session on self-concept development, by comparing it to the reference program Unplugged.

In order to examine the impact of self-concept on the effectiveness of the Unplugged program, the present study relies on the prototype willingness model. The prototype willingness model focuses on reactive decision making and deliberative decision making in order to predict behaviors [26,27]. It proposes that behavior is co-determined by behavioral intentions and behavioral willingness [28]. Behavioral intentions are deliberatively formed plans of action that are derived on the basis of individuals’ attitudes and subjective norms, whereas behavioral willingness is a general openness to behave that increases the likelihood of a behavior when an individual encounters “facilitating situations” [26]. In the theory of planned behavior, behavioral intention is determined by attitude, perceived norm and perceived control [29,30]. The attitude consists in all beliefs about the likely consequences of the behavior. The perceived norm refers to beliefs about the normative expectations of others. Perceived control corresponds to beliefs about the presence of factors that may facilitate or impede the performance of the behavior. The more favorable the attitude and subjective norm, and the greater the perceived control, and the stronger the person’s intention to perform the behavior should be. This theory has often been used in the prediction of substance use in adolescents [31,32,33], but it does not include the Self; the development of the self-concept should thus not act on this dimension of the model. The model also proposes that behavioral willingness is determined by prototype perceptions. Prototype perceptions are positive or negative valences that refer to the cognitive representations that someone holds for the typical members of social categories. Two types of prototype perceptions are typically studied in this model: the prototype favorability perceptions (the positive or negative evaluation of the prototype) and the prototype similarity perceptions (how similar individuals believe themselves to be to the prototype). They are recognized as influencing behavior through reactive decision making (behavioral willingness) rather than deliberative decision making (behavioral intention): the more favorably their image is assessed, the more willing they are to engage in the behavior. This finding has been observed for smoking and drinking in many studies [34,35,36,37,38,39,40]. In addition, studies have also shown that the more similar adolescents’ smoking or drinking images are to their self-images, the greater their willingness to smoke or drink [41,42]. Changing adolescents’ self-concept could therefore alter their similarity to the consumer prototype and their willingness to consume harmful substances.

This is why, in the test of the “Intervention Program based on Self”, we hypothesize a greater clarity of self-concept and greater gains in knowledge about themselves, with greater change in self-perception, for adolescents in the IPSELF program compared to those in the Unplugged program after participation. We believe that this development of self-concept will allow adolescents to feel less similar to prototype substance users and more similar to non-users, which should decrease their willingness to consume harmful substances, and thus reduce their consumption of them. We also believe that the knowledge gained about harmful substances in IPSELF will be more helpful in changing use behavior in adolescents than that gained in Unplugged. However, we expect no impact of self-concept on attitude, norm or control towards substance use, and thus no impact on the intention to use. We will consider the effect of gender in order to observe the effectiveness of each program for girls and boys, due to the differences in consumption and prevention sensitivity identified in the literature.