Submit to IJERPH Review for IJERPH Propose a Special Issue

Journal Menu

Journal Browser

Alcohol and Substance Use in Adolescents

Print Special Issue Flyer
Special Issue Editors
Special Issue Information
Keywords
Published Papers

A special issue of International Journal of Environmental Research and Public Health (ISSN 1660-4601). This special issue belongs to the section "Adolescents".

Deadline for manuscript submissions: closed (28 February 2023) | Viewed by 26549

Share This Special Issue

Special Issue Editors

Dr. Albert Espelt

E-Mail Website1 Website2
Guest Editor

1. Manresa Faculty of Health Sciences (UVic-UCC), 08242 Manresa, Spain
2. CIBER de Epidemiología y Salud Pública, Instituto de Salud Carlos III, 28029 Madrid, Spain
Interests: social epidemiology; alcohol use; adolescent health; social inequalities in health; drug addiction

Prof. Dr. Marina Bosque-Prous

E-Mail Website1 Website2
Guest Editor

Faculty of Health Sciences, Universitat Oberta de Catalunya, 08018 Barcelona, Spain
Interests: alcohol; substance use; public health; epidemiology; social determinants of health; planetary health
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Adolescence is a period of physical and psychological changes in which adolescents build their identity, peer groups are reinforced, and they start taking their own decisions. During this period of life, they start seeking new limits with risky health behaviors, such as experimenting with legal and illegal drugs. Factors that can explain adolescents’ risky health behaviors can be related to individual and contextual aspects. In this way, on the one hand, individual aspects such as the socio-economic position, the relationship with parents, nationality, age, gender, or parental marital status have been related to adolescents’ physical and mental health as well as their risk behaviors. On the other hand, contextual aspects such as the socioeconomic environment in which they live and relate to others have also been related with risky health behaviors at different levels (e.g., the school, neighborhood, or community level). Studying and being able to understand which are the factors that determine adolescents’ alcohol or substance use is crucial, as health-related habits that are acquired at early ages are kept until adult life. Social health determinants are one of the main factors influencing health and health behaviors, which generate social inequalities of health. This Special Issue of the International Journal of Environmental Research and Public Health (IJERPH) focuses on the current state of knowledge on the links between social determinats of health and alcohol and substance use in adolescents. Papers assessing preventive or polcy approaches to alcohol and substance use in adolescents are also invited for this Special Issue. New research papers, reviews, and case reports are welcome to this Issue. Papers dealing with new approaches to studying alcohol and substance use in adolescents are also welcome.

Dr. Albert Espelt
Prof. Dr. Marina Bosque-Prous
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. International Journal of Environmental Research and Public Health is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2500 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

alcohol use
substance use
adolescence
social determinants of health
social inequalities

Published Papers (12 papers)

Download All Papers

Research

Jump to: Review

12 pages, 324 KiB

Open AccessArticle

School Prejudice and Substance Use from Adolescence to Emerging Adulthood in the United States: Variation across Race and Ethnicity

by Xing Zhang and Daniel B. Lee

Int. J. Environ. Res. Public Health 2023, 20(5), 4171; https://0-doi-org.brum.beds.ac.uk/10.3390/ijerph20054171 - 25 Feb 2023

Viewed by 1366

Abstract

Background: Racial and ethnic disparities in health outcomes have been consistently documented in the health literature. Until recently, many studies have evidenced associations between prejudice and health behaviors using cross-sectional data. However, studies assessing the link between school prejudice and health behaviors from adolescence to adulthood are limited. Methods: To address this gap, we use data from Waves I, II, and III of the National Longitudinal Study of Adolescent to Adult Health (1994–2002) to examine how perceptions of school prejudice over time influence cigarette smoking, alcohol use, and marijuana use from adolescence to emerging adulthood. We also examine variation across race and ethnicity. Results: Results indicate that school prejudice in adolescence (Wave I) is associated with higher cigarette use, alcohol use, and marijuana use in later adolescence (Wave II). White and Asian adolescents who perceived school prejudice were more likely to use alcohol, while Hispanic adolescents were more likely to use marijuana. Conclusions: Efforts to reduce school prejudice among adolescents may have implications in reducing substance use. Full article

(This article belongs to the Special Issue Alcohol and Substance Use in Adolescents)

15 pages, 818 KiB

Open AccessArticle

Swedish High School Students’ Drug and Alcohol Use Habits throughout 2020

by Anis Sfendla, Kourosh Bador, Michela Paganelli and Nóra Kerekes

Int. J. Environ. Res. Public Health 2022, 19(24), 16928; https://0-doi-org.brum.beds.ac.uk/10.3390/ijerph192416928 - 16 Dec 2022

Cited by 2 | Viewed by 1864

Abstract

This study describes gender-specific patterns in alcohol and drug use among Swedish high school students throughout 2020 and questions the current cutoffs for identifying addiction in this population. From September 2020 to February 2021, 1590 Swedish upper secondary high school students (mean age 17.15 years, age range 15–19 years, 39.6% male, and 60.4% female) completed the anonymous, electronic survey of the Mental and Somatic Health without borders study. The respondents reported their substance use habits during the previous 12 months using the Drug Use Disorders Identification Test (DUDIT) and Alcohol Use Disorders Identification Test (AUDIT). They also answered questions about changes in their alcohol and illegal drug use habits after the COVID-19 outbreak. No gender differences were detected in the prevalence and degree of alcohol use. Compared to female adolescents, significantly more male adolescents used drugs (and to a significantly higher degree, although with a small effect size). Substance use problems peaked in females at age 17 and in males at age 18. The COVID-19 outbreak affected alcohol consumption and illegal drug use in male and female adolescents similarly. For both genders, of those who used illegal drugs, over 40% reported increased use after the outbreak. Our results reinforce previous suggestions of the narrowing of gender differences in Swedish adolescents’ risk behaviors and challenge the previously validated gender-specific cutoffs for the AUDIT and DUDIT. An improved understanding of the impacts of gender diversity and evolving gender roles and norms on behaviors and mental health is warranted. Full article

(This article belongs to the Special Issue Alcohol and Substance Use in Adolescents)

► Show Figures

Figure 1

14 pages, 719 KiB

Open AccessArticle

A Qualitative Study of Drug Treatment Conformity Behavior among Young Drug Users Who Are in Recovery in China

by Chen Li and Guandong Song

Int. J. Environ. Res. Public Health 2022, 19(22), 14832; https://0-doi-org.brum.beds.ac.uk/10.3390/ijerph192214832 - 11 Nov 2022

Viewed by 1958

Abstract

In response to social concerns about young drug users, this study aimed to qualitatively explore the types of drug treatment conformity behaviors and the processes of behavior formation among this population. Twenty-one young drug users were selected through purposive sampling, in-depth interviews were conducted using a semi-structured approach, and the data were then analyzed. The social conformity theory is used as the framework of the analysis, and the results indicate that drug treatment behaviors can be differentiated by the three types of motivation that produce conformity with drug treatment: the cognitive, affective, and utilitarian. These three types of motivations produce three types of conformity, respectively: drug treatment abidance, drug treatment compliance, and drug treatment obedience. They are affected by informational social influences, normative influences of significant others, and normative structural levels, respectively. We also propose a model of the information processing involved in drug treatment conformity. Based on an in-depth analysis of the characteristics and formation processes of the three different types of conformity, intervention strategies are proposed. This study has important guiding significance for helping young drug users maintain their drug rehabilitation ethics and successfully return to society. Full article

(This article belongs to the Special Issue Alcohol and Substance Use in Adolescents)

► Show Figures

Figure 1

13 pages, 827 KiB

Open AccessArticle

Compliance Checks Decrease Cigarette Sales Rates to Pseudo-Underaged Mystery Shoppers: A Quasi-Experimental Control Group Study

by Kristin Feltmann, Johanna Gripenberg and Tobias H. Elgán

Int. J. Environ. Res. Public Health 2022, 19(20), 13161; https://0-doi-org.brum.beds.ac.uk/10.3390/ijerph192013161 - 13 Oct 2022

Viewed by 1107

Abstract

To control adherence to age limits regarding sales of tobacco products, Swedish authorities can conduct compliance checks. Compliance checks involve prior information to all retailers, mystery shopping, and subsequent feedback to the retailers. This study investigated whether compliance checks can decrease the rates of cigarette sales to underaged adolescents. Test purchases of cigarettes were conducted using pseudo-underaged mystery shoppers, i.e., 18-year-old adolescents with a younger appearance not carrying ID, to measure the refusal rate and rate of ID checks. Test purchases were conducted at 257 retail outlets in 13 municipalities in Stockholm County at baseline 2017 and follow-up 2019, respectively. In between the measurements, six municipalities (intervention area) conducted compliance checks, and seven municipalities were used as a comparison. Comparing baseline and follow-up, rates of refusal (70.4 to 95.8%) and ID checks (80.3 to 95.8%) improved in the intervention area. In the comparison area, refusal rates increased (80.9 to 85.2%), and ID check rates remained stable (at 86.1%). Significant group × time interaction effects reveal that the rates of refusal and ID checks differently changed in the study areas over time. These results indicate that compliance checks are an effective method to decrease cigarette sales to underaged adolescents. Full article

(This article belongs to the Special Issue Alcohol and Substance Use in Adolescents)

► Show Figures

Figure 1

12 pages, 377 KiB

Open AccessArticle

Analysis of AUDIT Domains in Freshman Students in Spain: Three Cross-Sectional Surveys (2005, 2012 and 2016)

by Alicia Busto Miramontes, Lucía Moure-Rodríguez, Alba Regueira, Leonor Varela, Montserrat Corral, Adolfo Figueiras and Francisco Caamano-Isorna

Int. J. Environ. Res. Public Health 2022, 19(13), 7799; https://0-doi-org.brum.beds.ac.uk/10.3390/ijerph19137799 - 25 Jun 2022

Viewed by 1096

Abstract

Purpose: We aimed to evaluate changes in the frequency of drinking, alcohol dependence and alcohol-related harm in freshman college students from 2005, 2012 and 2016, and identify risk-associated factors. Method: A cross-sectional study involving 5009 freshman students was carried out in Spain in 2005, 2012 and 2016. The Dimensions of Alcohol Use Disorders Identification Test (frequency of drinking, symptoms of dependence and alcohol-related harm) was analysed. Adjusted relative risks (RRs) and their 95% confidence intervals were estimated using negative binomial regression. Results: Place of residence, positive expectancies and early onset of alcohol consumption continue to be crucial conditions for developing patterns of risky consumption, alcohol dependence and harm. Women and men were more vulnerable to alcohol harm and dependence when living away from home, having higher economic status and positive alcohol expectancies. Cohorts from 2012 and 2016 were at lower risk of risky alcohol consumption. Men belonging to the 2012 and 2016 cohorts were at lower risk of alcohol negative consequences compared with the 2005 cohort. However, women remained vulnerable over time to alcohol dependence and harm. Starting drinking after 16 protects them both from alcohol dependence and harm. Conclusions: Women are more vulnerable to alcohol dependence and harm in recent cohorts of freshmen. Limiting access to alcohol at a younger age and working on false positive expectancies could benefit freshmen by avoiding alcohol damage and alcohol dependence. Full article

(This article belongs to the Special Issue Alcohol and Substance Use in Adolescents)

14 pages, 350 KiB

Open AccessArticle

Violent Behaviours among Adolescents and Young Adults: Association with Psychoactive Substance Use and Parenting Styles

by Elisa Benedetti, Emanuela Colasante, Sonia Cerrai, Gilberto Gerra, Leonardo Tadonio, Pietro Pellegrini and Sabrina Molinaro

Int. J. Environ. Res. Public Health 2022, 19(7), 3756; https://doi.org/10.3390/ijerph19073756 - 22 Mar 2022

Cited by 4 | Viewed by 2189

Abstract

This study extends existing research on the relationship between psychoactive substance use among young people and violent behaviour, by evaluating the possible effect of the modification of parenting in a nationally representative sample of 14,685 Italian students drawn from the 2019 wave of the ESPAD Italia survey (51% male; mean age about 17 years). Parental dimensions considered in the study were rule-setting, monitoring, and emotional support, as well as the possible absence of a parent. Relative risk ratios and binary logistic regressions were used to estimate the associations separately for adolescents (15–17) and young adults (18–19). Overall, parental rule-setting, perceived parental monitoring, and emotional support were protective factors for substance use, and the strength of this relationship increased with the frequency of use. Among adolescents, the absence of a parent represented a risk factor. In both age groups, the odds of engaging in violent behaviour was increased among those reporting alcohol intoxication and substance use and the greater the frequency of use, the greater the increase in the odds. As parental monitoring and emotional support decreased, the odds of engaging in violent behaviour increased (except in the case of lower parental support among young adults), while the opposite applies to parental rule-setting. The odds of engaging in violent behaviour were increased among those reporting the absence of a parent only in the adolescent age group. Parental rule-setting was found to have an effect only among adolescents, increasing the odds of violent behaviour among frequent drinkers. Our results might be helpful to signal adolescents who would be more prone to adopt violent behaviour in order to target prevention policies. Full article

(This article belongs to the Special Issue Alcohol and Substance Use in Adolescents)

14 pages, 2021 KiB

Open AccessArticle

Parenting Styles as a Moderator of the Association between Pubertal Timing and Chinese Adolescents’ Drinking Behavior

by Hui Ling, Yaqin Yan, Hong Feng, Amin Zhu, Jianren Zhang and Siyang Yuan

Int. J. Environ. Res. Public Health 2022, 19(6), 3340; https://0-doi-org.brum.beds.ac.uk/10.3390/ijerph19063340 - 11 Mar 2022

Cited by 2 | Viewed by 2161

Abstract

Background: Previous work has indicated that pubertal timing and parenting styles are associated with adolescents’ drinking behavior, but studies on the relationship between the above three variables are lacking. Methods: Participants were 1408 Chinese adolescents aged 11–16 years old (46.52% girls). The data emphasized pubertal timing, parenting styles, drinking behavior, and socioeconomic and demographic characteristics of the adolescent and his or her family. Results: Early pubertal timing was related to drinking behavior; however, parenting styles played a moderating role. For male adolescents, father emotional warmth, mother rejection, and mother emotional warmth moderated the relationship between early pubertal timing and drinking behavior. For female adolescents, mother rejection, mother emotional warmth, and mother over-protection moderated the relationship between pubertal timing and drinking behavior. Conclusions: Parenting styles that include emotional warmth, rejection, and over-protection appear to influence the negative outcomes associated with early pubertal timing, and may be useful in reducing adolescents’ drinking behavior. Full article

(This article belongs to the Special Issue Alcohol and Substance Use in Adolescents)

► Show Figures

Figure 1

11 pages, 510 KiB

Open AccessArticle

Prevalence of and Factors Associated with Club Drug Use among Secondary Vocational Students in China

by Jincong Yu, Qingfeng Wu, Yuqin Wu, Jiang Li, Qinxuan Wu, Huiping Cao and Zengzhen Wang

Int. J. Environ. Res. Public Health 2021, 18(19), 10408; https://0-doi-org.brum.beds.ac.uk/10.3390/ijerph181910408 - 03 Oct 2021

Viewed by 2143

Abstract

To understand the prevalence of and factors associated with club drug use among Chinese secondary vocational students, a nationally representative survey was conducted. The multistage cluster sampling strategy was employed to select participants. A total of 9469 students from eleven secondary vocational schools in five cities completed self-reported questionnaires, which included information on club drug use, sociodemographic variables, individual factors, as well as peer and family related factors. The data were separately analyzed with Poisson regression models for female and male students. The overall lifetime prevalence of club drug use was 2.7% (258/9469), and male students had higher prevalence than female students (3.5% vs. 1.9%, p < 0.001). Female and male students shared four risk factors (i.e., having ever smoked, perceiving social benefit expectancies, peer drug using and perceiving peer’s approval of drug use) and one protective factor (i.e., having medium or high levels of refusal skills) for club drug use. Moreover, family drug using and having a part-time job were two additionally independent risk factors for club drug use among male students. These findings indicate that the problem of club drug use among Chinese secondary vocational students is worthy of attention. The prevention of club drug use should address multiple risks and protective factors on individual, peer and family levels. Full article

(This article belongs to the Special Issue Alcohol and Substance Use in Adolescents)

► Show Figures

Figure 1

14 pages, 379 KiB

Open AccessArticle

Contextual Determinants in Alcohol, Tobacco and Cannabis Consumption, Mood and Bullying during Adolescence

by Ainara Díaz-Geada, Núria Obradors-Rial, Antoni Baena, Ester Teixidó-Compañó, Ester Colillas-Malet, Narmeen Mallah, Lucía Moure-Rodríguez, Francisco Caamaño-Isorna and Tivy Barón-Garcia

Int. J. Environ. Res. Public Health 2021, 18(16), 8480; https://0-doi-org.brum.beds.ac.uk/10.3390/ijerph18168480 - 11 Aug 2021

Cited by 3 | Viewed by 1781

Abstract

The present study aimed to explore the differences in the consumption of alcohol, tobacco and cannabis, mood and bullying between adolescents. A cross-sectional study was carried out in five regions of Northern Spain (one in Galiza and four in central Catalonia) that share similar socioeconomic characteristics and encompass around 10,000 inhabitants each. Students living in Burela, Galiza (N = 71) were compared to those of Central Catalonia (N = 193). The independent variable was the municipality of residence. The dependent variables encompassed: weekly available pocket money, Family Affluence Scale, self-classified academic qualification, place of origin, alcohol consumption, tobacco and cannabis smoking, negative mood and bullying. The mean age and their 95% confidence intervals (95% CI) of participants were similar between the regions (Burela: 15.90 years (15.68–16.13) and Central Catalonia: 15.36 years (15.28–15.44)). More than half of the participants were females (Burela, Galiza (53.5%) and Catalonia (54.9%)). Prevalence ratios (PR) and their 95% CI were estimated using Poisson regression models. In comparison with adolescents from Burela (Galiza), those living in Central Catalonia had higher prevalence of diverse academic levels (adjusted PR = 3.92 (1.78–8.66)), tobacco consumption (adjusted PR = 2.41 (1.47–3.97)) and negative mood (adjusted PR = 5.97 (3.05–11.70)). Even when dealing with regions with similar socioeconomic characteristics and number of inhabitants, differences exist in terms of the socioeconomic level, tobacco consumption, mood and bullying, as reported by adolescents. Full article

(This article belongs to the Special Issue Alcohol and Substance Use in Adolescents)

14 pages, 625 KiB

Open AccessArticle

Consumption of Alcohol, Cannabis, and Tobacco in a Cohort of Adolescents before and during COVID-19 Confinement

by Judit Rogés, Marina Bosque-Prous, Joan Colom, Cinta Folch, Tivy Barón-Garcia, Helena González-Casals, Esteve Fernández and Albert Espelt

Int. J. Environ. Res. Public Health 2021, 18(15), 7849; https://0-doi-org.brum.beds.ac.uk/10.3390/ijerph18157849 - 24 Jul 2021

Cited by 30 | Viewed by 4849

Abstract

The aim of this study was to identify changes in the hazardous consumption of alcohol, tobacco, and cannabis, due to the COVID-19 lockdown in 2020 in a cohort of schooled adolescents from Central Catalonia. We also analyzed the effect of the individual and social factors on risky consumption during confinement. This longitudinal study involved a subsample of 303 adolescents aged 14–18 years, who were attending 4th year of compulsory secondary education (ESO), 2nd year of college preparation (baccalaureate), or Vocational and Educational Training (VET). We collected data before COVID-19 lockdown (October 2019–February 2020) and 2 months after the lockdown ended. We estimated the prevalence of risky substance use in the sample at baseline for each independent variable. We used Poisson regression models with robust variance to compute the Cumulative Incidence (CI) and Relative Risk (RR), with their respective 95% confidence interval. We found that VET students had a significantly (p < 0.05) higher risk of substance use: binge drinking (RR = 3.21 (95%CI: 1.00–10.34)); hazardous drinking of alcohol (RR = 3.75 (95%CI: 1.12–12.54)), hazardous consumption of cannabis (RR = 3.75 (95%CI: 0.65–21.59)) and daily smoking of tobacco (RR = 4.82 (95%CI: 1.74–13.39)). The results showed a general trend of reduction of consumption during COVID-19 confinement period. This study suggests that VET students were more likely to engage in hazardous drinking of alcohol and daily smoking of tobacco. No statistically significant differences were found for the other age groups and variables. Full article

(This article belongs to the Special Issue Alcohol and Substance Use in Adolescents)

► Show Figures

Figure 1

15 pages, 351 KiB

Open AccessArticle

Personal Variables of Protection against Cannabis Use in Adolescence: The Roles of Emotional Intelligence, Coping Styles, and Assertiveness as Associated Factors

by Sara González-Yubero, Susana Lázaro-Visa and Raquel Palomera

Int. J. Environ. Res. Public Health 2021, 18(11), 5576; https://0-doi-org.brum.beds.ac.uk/10.3390/ijerph18115576 - 23 May 2021

Cited by 5 | Viewed by 2512

Abstract

(1) Background: Many public bodies have warned of the increased consumption of cannabis, particularly among adolescents. From the Positive Youth Development approach, the promotion of personal protective factors takes on special importance against some risks, such as the consumption of addictive substances. (2) Methods: This research is one of the first to study the role of trait and ability emotional intelligence in relation to cannabis use and with respect to other personal variables of protection, such as coping styles and assertiveness. For this purpose, a final sample of 799 schoolchildren was obtained. (3) Results: After controlling for age and gender, the results of the regression analyses revealed that emotional perception, emotional facilitation, emotional clarity, emotional repair, active coping style, and assertiveness were inversely and significantly associated with cannabis use behaviors. On the other hand, the emotional attention and avoidant coping style factors were positively and significantly associated with these behaviors. (4) Conclusions: These findings provide new evidence that could be useful in terms of guiding health-promoting clinical and educational interventions at an early age. Full article

(This article belongs to the Special Issue Alcohol and Substance Use in Adolescents)

Review

Jump to: Research

22 pages, 1380 KiB

Open AccessReview

Psychological Interventions for Cannabis Use among Adolescents and Young Adults: A Systematic Review

by Yara Bou Nassif, Hassan Rahioui and Isabelle Varescon

Int. J. Environ. Res. Public Health 2023, 20(14), 6346; https://0-doi-org.brum.beds.ac.uk/10.3390/ijerph20146346 - 12 Jul 2023

Cited by 1 | Viewed by 2254

Abstract

Regular cannabis use during adolescence can lead to cognitive, psychological, and social consequences, causing significant distress. Although psychological interventions are the mainstay type of treatment for cannabis use disorder, the results remain mixed among youths. The objective of this review is twofold: to identify the existing psychological interventions for cannabis use among youths, and to assess the evidence regarding the effectiveness of those interventions. Randomized controlled trials focused exclusively on cannabis use among adolescents and young adults were included. Three databases—Embase, PsycInfo, and PubMed—were searched to identify relevant peer-reviewed manuscripts published before February 2022 in English and French. The risk of bias was assessed using the Cochrane Collaboration’s tool. Twenty-five randomized controlled trials were included. Fourteen studies reported a significant outcome related to cannabis use. These were mainly non-intensive, online interventions that aimed to improve the patients’ relationships and emotion regulation. This review highlights the need to conduct additional randomized control trials that target cannabis use disorder specifically among adolescents. These randomized control trials should also aim to reduce the risk of bias related to psychiatric comorbidities as well as detection and attrition problems. Full article

(This article belongs to the Special Issue Alcohol and Substance Use in Adolescents)

► Show Figures

Figure 1

Journal Menu

Journal Browser

Alcohol and Substance Use in Adolescents

Share This Special Issue

Special Issue Editors

Special Issue Information

Keywords

Published Papers (12 papers)

Research

Review

Further Information

Guidelines

MDPI Initiatives

Follow MDPI