In this study, marihuana was the illicit drug of greater consumption among young adults who have transitioned from legal to illicit drug use. These data agree with official reports in Mexico for 2016 and 2017,(15) highlighting the prevalence of marihuana, which is quite above cocaine, inhalable substances, and hallucinogens. The aforementioned could be explained by the fact that it is the only substance with important growth in recent years, while the rest have had stable behavior. The literature(4-6) shows that marihuana is considered the entry way to the consumption of other illicit substances, denominated “hard drugs”, particularly cocaine and methamphetamines. Besides, an explanation on the high prevalence of marihuana use is that many young adults perceive it as a drug of little or no danger; likewise, in recent years, its legalization has been discussed in diverse public, political, academic, social, and legal settings.(16)

Regarding H1, which claims that personality traits influence on the transition from legal to illicit drug use, our results support said hypothesis, showing positive effects of the traits of neuroticism, extraversion, and openness to the experience; on the contrary, agreeableness and conscientiousness had negative effects on the drug use transition. As with the results from other studies,(17,18) when the personality traits of neuroticism, extraversion, and openness to the experience are present in an individual’s personality there is a higher probability for illicit drug use, while if the individual has higher personality traits of agreeableness and conscientiousness, the probability can be lower for the drug use transition to occur; this may be due to the harmful influence of lack of scrupulousness in substance abuse behaviors that reveal that lack of control of the behavior, increased impulsivity, and participation in risk behaviors found in the traits of neuroticism and extraversion, characterized by sociability, the need to have many friends, the taste for risk and a tendency to be aggressive, surely through social facilitation processes, and having a high number of friends engaged in behaviors outside the norm are associated with higher consumption during this evolutionary stage. Conversely, the trait of agreeableness is characterized by the capacity for altruism, compassion, and sensitivity with others; these characteristics are to a large measure why they do not show transition and agree with some authors.(19,20) In this sense, it is important for these personality traits to be indicators to bear in mind in the design of prevention programs that promote the development of these traits.

Hypothesis two proposes that the characteristics of the neighborhood environment and exposure to the opportunity of consumption increase the risk of the transition from legal drug use to illicit drug use. The findings permit supporting said hypothesis; according to the neighborhood characteristics, in this study a negative effect was shown, that is, a better perception of the quality in the neighborhood environment indicates lower probability of consumption. These data agree with the literature,(21,22) which indicate that unfavorable neighborhood conditions are a risk factor for the onset of drug use.

With respect to the number of opportunities to use drugs, the highest figures were reported by the young adults who have transitioned to illicit drug use, compared with those who have not transitioned. This is similar to another research(23) which found that exposure to the opportunity of consumption represents a higher risk with the use of drugs. In addition, said study indicates that exposure to the opportunity of consumption can be a cause on the initiation of illicit drug use due to the possibility that this represents of being in front of the substance and the ease of access to it without intentionally looking for it.

Hypothesis three proposes that social support and social stigma influence on the transition from legal to illicit drug use. Results permitted testing the study hypothesis, showing that social conditions, like social support and the perception of social stigma, are factors that inhibit the drug use transition. These results agree with other authors(24,25) that show that when the individual has higher perception of social support and greater perception of the stigma, which is understood as the stereotypes or negative physical, moral, or social prejudice that society implants in young adults who use drugs, there is lower probability to transition from illicit drug use. Social support from the family, peers, and from the environment can function as a protection factor due to the fact that by feeling as part of their environment, can serve to avoid the search for sensations through the drug use. Studies(24,26) have evidenced that inadequate social support in young adults has been related with maladaptive behaviors, including drug use, explaining that social support in function of the different sources of support predict the consumption of different substances. Thus, the results herein point to a protection relationship of social support mainly from the family. Thereby, the family becomes the core of the protection factors of social support against the transition of drug use. That is, the fact of feeling loved, esteemed, and protected by the family members is one of the principal resources the young person has to avoid getting involved or transitioning in the drug use.

Similarly, higher scores were reported of stigma in the young adults who had not transitioned to illicit drug use. This agrees with diverse studies, which indicate that stigmatization toward consumers of illicit drugs can be an isolation factor, besides they are subject to derogatory stereotypes or criminalization by society.(25,27) This can influence as a protection factor due to the public perception of the stigma in drug consumers, affect social and labor development, and - thus - avoid the rejection an illicit drug user may have. In spite of the results found, which reported that the perception of the stigma diminishes the transition to illicit drug use, studies(25,27) indicate that the stigmatization people who use drugs is marked with negative attributes that damage their social and mental development even when they have stopped consuming and are in rehabilitation, and this brings along a deficit in treatments or places for rehabilitation due to the lack of government support. In Mexico, programs have been developed to avoid discrimination in diverse vulnerable groups, like HIV patients, racial discrimination, among others; however, care for the group of drug users is scarce or null, and drug use is considered a public health problem, but more identified with security than with the individual consumers and their need for care. This may be because drug use is seen as an attitude related with a decision by each individual and not as a disease or ailment.

The prior results permit affirming that proposed in the Transitions Theory by Meleis, which indicates that transition conditions, like personal, community, and social factors or characteristics can facilitate or inhibit the experience of the transition from legal to illicit drug use. Meleis(8) indicates that transitions may be unhealthy and develop over a given time with responsibility to obtain a problematic result against the transition experienced, which will depend directly on the vulnerability presented by the person and on the facilitating or inhibiting conditions of the transition process, such as personal conditions, like beliefs, cultural attitudes, knowledge, and the community and social conditions in which the person is immersed. All of the aforementioned could harm or enhance the transition stage. According to Meleis,(8) these process patterns guide people to health or toward greater vulnerability, this permits nursing to evaluate patterns, like coping strategies to facilitate healthier results.

Nursing professionals are the principal caregivers of clients and families who undergo the transitions from legal to illicit drug use; in this sense, the role of nurses within primary care staff and specialized nurses can develop a leading role in actions regarding promotion of community health and in prevention to avoid the drug use transition in young populations from a multi-factor approach on addictions. Their contribution can be decisive in early detection, the initial approach, referral to specialized resources, and in the coordination and follow up from the different social and health teams, always from continuous communication with the user individual, bearing in mind individual needs and favoring the development of each patient. Nursing professionals, as professionals implied and called to lead these processes, must be capable of integrating the tools of the discipline to solve and avoid the transitions of the drug use.

It is important to recognize that this research has limitations. In the first place, by this being a case and control design, it is not possible to identify direct causality. This urges interpretation of the data with caution because the method was based on retrospective data; concerns are generated on the accuracy of the memory and it is important to consider using other types of designs for future research. Although the use of questionnaires is acceptable to collect information related with the use of substances, it is important to emphasize on the lack of biochemical or physiological indicators, so that the estimation of these variables is according to the answer provided by the participant.

The conclusion here is that the findings contribute to improving the understanding of some factors that intervene in the transition from legal to illicit drug use, such as personality traits, neighborhood characteristics, exposure to drug use, social support, and the social stigma of drug use, which could be useful to develop more effective interventions to prevent drug use. In future studies, it is important to consider a more detailed analysis of the quality and duration of the family relationships because they can be risk factors, as well as protection factors, necessitating their inclusion in future research and, thus, obtain a more complete picture of these relationships during adolescence and youth, to be taken into account in the design of interventions to prevent the transition from legal to illicit drug use. Additionally, we recommend replicating the study with longitudinal designs to broaden the data collection time and have more specific data. This is important because some of these factors are developed during early stages of life when information on these factors could be collected in more detail.