2.1. Ethics
The study was approved by the Clinical Research Ethics Committee of the International University of La Rioja (reference PI: 018/2020) and was conducted in accordance with the latest version of the Declaration of Helsinki. A permit from the management boards of the schools that agreed to participate in the study was obtained. Information about the study was provided to adult students and to the parents or legal guardians of underage students. Participation was voluntary and non-remunerated. All participants provided consent to being included in the study, and parents provided authorization in the case of minors. Participants were able to withdraw from the study at any time. The school board was informed about students who did not wish to participate.
2.2. Participants and procedures
The study included Spanish-speaking adolescents who were enrolled in any course of junior high school or high school in Spain. Individuals with mental disorders or cognitive difficulties that could affect their understanding of the assessment battery were excluded. Of 3304 schools contacted online, three schools agreed to participate, representing different socio-economic profiles and geographical areas in Spain.
The assessment was conducted online through Google Forms due to the COVID-19 pandemic, with teachers supervising the process after receiving training. A total of 674 adolescents initially agreed to participate, and after removing incomplete questionnaires, the final sample consisted of 650 adolescents, evenly distributed between boys and girls with a mean age of 16.0 years (SD = 1.1).
2.3. Instruments
2.3.1. Pornography use and problematic pornography use
2.3.1.1. Frequency and type of pornography use
The frequency of pornography use was measured with a self-designed item with the question: How often do you watch pornography? with 12 response possibilities from "Never" to "Five or more times a day.". Three dichotomous items (yes/no) were used to explore the exposure of adolescents sexually explicit material on the internet: accidental exposure (In the last year, when you were doing an online search or surfing the web, did you ever find yourself on a website that showed pictures of naked people or people having sex when you didn't want to be on that type of website?), intentional exposure (“Have you ever accessed a porn website on purpose or downloaded sexual images on purpose?), or sexual content received by others (“In the last year, have you ever opened a message or a link in a message that showed you real pictures of naked people or people having sex that you didn't want to see?).
2.3.1.2. Problematic Pornography Consumption Scale (PPCS-18) [27]
The PPCS-18 measures PPU with 18 Likert-type items with seven options of responses (1 = Never; 7 = All the Time). The scale has 6 sub-factors: salience, emotional modification, conflict, tolerance, relapse, and abstinence. The total score ranges from 18 to 126, with an established cut-off score ≥ 76 indicating high-risk of PPU. Good psychometric properties were observed in the original validation (∝ = 0.93) [27]. In the study sample, internal consistency was α = 0.93 for the total score; α = 0.77 for salience; α = 0.84 for tolerance; α = 0.73 for mood modification; α = 0.82 for relapses; α = 0.80 for withdrawal; and α = 0.77 for conflicts.
2.3.1.3. Pornography Consumption Inventory (PCI) [28]
The PCI assesses pornography-use motivations. The scale contains four factors (i.e., sexual pleasure, emotional avoidance, arousal seeking and sexual curiosity). The scale includes 13 Likert-type items, with response options going from 1 = Never to 5 = Many times. The scores range from 15–75. There is no established cut-off, with higher scores indicating higher tendencies to use pornography for specific reasons. The Spanish validation was used in the present study. This version demonstrated excellent reliability > 0.90 for all factors and an internal consistency of 0.93 [29]. In the study sample, internal consistency ranged between very good to excellent for the different factor scales (α = 0.88 for emotional avoidance, α = 0.93 for sexual curiosity, α = 0.95 for excitement-pleasure), and α = 0.94 for the total score.
2.3.2. Sexual Double Standard
2.3.2.1. An abridged Spanish version of the Sexual Double Standard Scale (SDSS) [30]
The SDSS is a scale that determines the extent to which people exhibit sexual double standards (SDSs). SDSs involve different criteria and values assessing sexuality of men and women, typically giving more sexual freedom to men and rewarding them for engaging in sexual activity [31]–[33]. The SDSS includes 26 items that range from Disagree Strongly (0) to Agree Strongly (3) and requires 5 minutes to complete. Scores range from − 30 (indicating acceptance of greater sexual freedom for women) to 0 (reflecting identical standards for men and women) to 48 (indicating more acceptance of the traditional double standard, suggesting acceptance of greater sexual freedom for men). The authors of the SDSS indicate it has a reliability of 0.73 in women and 0.76 in men [31].
In this study, the Spanish abridged version of the scale was used, with a reliability of 0.84 for the subscale Acceptance for sexual freedom and 0.87 for the subscale Acceptance for sexual shyness [30]. Test-retest reliabilities were good for both subscales, obtaining correlation coefficients over 0.70. In our study sample, internal consistency was α = 0.78.
2.3.3. Online Sexual Abuse
2.3.3.1. Escala Breve de Abuso Sexual Online (Brief Scale of Online Sexual Abuse; EBASO) [34]
The EBASO consists of 14 items that correspond to the online sexual victimization factor of the Juvenile Online Victimization Questionnaire (JOV-Q; [35]). This brief version of the questionnaire assesses the frequency of online sexual victimization in the last 12 months. It has four options of responses ranging from 0 (never) to 3 (always). The total score is a sum of each item’s answers. A higher score indicates greater frequency of experiencing sexual abuse online during the prior year. This version of the scale presents a reliability of 0.93 and an adequate internal consistency (α = 0.87) [34]. In our study sample, internal consistency was α = 0.93.
2.3.4. Loneliness
2.3.4.1. The University of California Los Angeles Loneliness Scale – Version 3 (UCLA-LS version 3) [36]
The UCLA-LS version 3 assesses the severity of loneliness with 20 items. Scores range from 20 to 80, and higher scores reflect greater loneliness. In the present study, the version previously adapted and validated in a Spanish sample was used with a Cronbach's alpha of 0.91 [37]. In our study sample, internal consistency was α = 0.7 for the total score.
2.3.5. Permissiveness
Permissiveness was assessed with a scale adapted and modified from previous research [38] that assessed instrumental and commitment attitudes towards sexual relations in relation to pornography use. It includes a dichotomous scale (Yes and No) with 13 items in relation to these variables. Some examples are "Sex is mainly physical," "Sex is just a game," or "It is important to accumulate experience with multiple sexual partners." Higher scores indicate greater levels of permissiveness.
2.3.6. Sociodemographic variables
Sociodemographic variables included age (12, 13, 14, 15, 16, 17 and 18 years old or more), sex (female, male, or other with specification), educational level (12 to 18 years of education, adapted to the school system in Spain), and family relationship (from very bad to excellent). Each item included the possibility of answer abstention.
2.4 Statistical analysis
We applied a network-based analysis (a promising analysis that reveals inter-relationships among elements and analyzes the structures of identified links [39], [40]. This study modeled networks with Gephi 9.2 for Windows [41], a software platform specifically developed for the analysis and visualization of networks within datasets with diverse structures (the system is available at http://gephi.org). This software provides a powerful spatialization process and the computation of multiple parameters of centrality, density, and modularity-clustering.
Separate networks were obtained for boys and girls. The nodes analyzed in the study were the PPCS, PCI, SDSS, EBASO and UCLA scores, reasons for pornography use, presence of risky sexual behaviors, permissiveness, and perceived family relationships. The magnitudes and signs of edges were calculated from the partial correlation matrix between nodes to obtain adjusted connectors and avoid the presence of biased relationships due to confounding effects. The initial data structure for the networks resulted in 22 nodes and 231 potential edges, most of which had very low weights (partial correlations around 0). To simplify this initial complex structure, only edges with significant results (p < 0.10) were included, resulting in a final structure with 60 edges for the girls’ network (26.0% of all potential connections) and 93 edges for the boys’ network (40.3% of all the potential connections).
The prominence and linkage capacity of nodes within a network can be measured through different indexes, with the most frequently used being the centrality and closeness of a node [42]. In this study, node-level relevance within the network was measured with centrality parameters, specifically eigenvector centrality indexes (calculated from the weighted sum of centrality measures of all nodes connected to a node). High centrality indexes evidence that the information contained in a concrete node is highly relevant for the whole graph. The node-level linkage was measured through the closeness indexes (which measure how close the node is to all the other nodes in the graph). High closeness indexes indicate a short average distance between one node and all the other nodes. Therefore, nodes with high closeness values have a high capacity to promote relevant changes in other parts of the network. Conversely, they are also highly vulnerable to modifications by any part of the structure.
Empirical clusters of nodes (called communities or modules in network theory) were automatically identified [43]. The existence of clusters indicates the possibility of grouping variables that highly interconnected to each other and poorly connected with nodes outside the cluster.
Other graph distance measures used in the study were: (a) the (average) path length, calculated as the mean of the shortest paths between all pairs of nodes (this value represents a measure of the efficiency of information transport in the network); and, (b) the diameter, calculated as the greatest distance between the two furthest nodes (representing the maximum eccentricity of any vertex in the graph) [44]. The density of the graph was also estimated as the number of connections divided by the number of possible connections, which provides a measure of how close the network is to being complete. A complete graph includes all possible edges and achieves a density measure equal to 1.