1. Introduction
Adolescence is a period when individuals achieve sexual and psychological maturity, and the development of teenage sexuality is deeply intertwined with other aspects of development, such as the formation of morality, values, and identity. This process is shaped by the complex interplay between individuals and their socio-ecological environment [
1]. The onset of sexual activity during adolescence is a normative developmental milestone. By the age of 19, nearly 70% of both males and females reported that they had ever had sexual intercourse [
2]. Therefore, in this context, the definition of sexual health remains crucial. Sexual health is fundamental to the overall health and well-being of individuals, couples, and families, as well as to the social and economic development of communities and countries. When viewed affirmatively, sexual health requires a positive and respectful approach to sexuality and sexual relationships, as well as the possibility of having pleasurable and safe sexual experiences, free from coercion, discrimination, and violence [
3].
Sexual curiosity during adolescence often leads to engagement in sexual activities or the consumption of sexual content. At this stage, many critical biological and psychological changes occur, for which many teenagers are not sufficiently prepared, often exposing them to stress [
4]. Furthermore, this period, representing the transition between childhood and adulthood, carries health and social implications and requires special attention [
5]. The theory of the “maturity gap”, which highlights the disparity between accelerated biological development and the lagging psychological and social development of youth, must be considered. This phenomenon becomes particularly evident in the context of ongoing cultural and societal changes in countries such as Poland [
6].
Before the age of 20, the vast majority of teenagers in Poland have experienced various sexual behaviours, ranging from intimate kissing, masturbation, touching, and caressing to sexual intercourse. However, there are significant individual differences in the timing of sexual initiation in European societies [
7]. Although sexual development, including sexual initiation, is a natural part of adolescence, teenage sexuality is often studied from a health risk perspective [
8,
9]. It is often assumed that teenage sexuality and related behaviours are inherently problematic, while in reality, they should be recognised as part of a normative developmental process.
From a life-course perspective, the process of sexual development begins in the foetal stage [
10] and includes a range of diverse behaviours and stages, with adolescence representing a critical transition in this context [
11]. However, since cultural norms regarding sexuality change over time, research should focus on individuals’ perceptions of the appropriateness of the timing of their sexual debut, rather than the specific age at which it occurs [
12].
Currently, sexual initiation during adolescence and later, both within and outside of marriage, is discussed in various cultural contexts. The emergence of modern contraceptive methods and the availability of abortion procedures have further separated the sexual sphere from the reproductive sphere [
13]. It is worth noting, however, that the scientific literature emphasises that sexual initiation can have adverse consequences when sexual behaviours occur at too early an age, not as a conscious decision, in accidental circumstances, or without proper awareness of the associated risks [
14,
15]. Moreover, different risky health behaviours can co-occur among teenagers, suggesting that there may be a possible temporal and causal sequence between them [
16].
Sexual behaviours during adolescence are also largely influenced by contextual factors, especially within the family and school environment [
17]. During adolescence, teenagers receive information about sexuality from both formal sources, such as school sex education programs, and informal sources, such as parents and the media [
18]. It remains an important fact that in European societies—in Poland, for instance—girls receive more information about sexuality than boys, and the range of topics discussed, both in school and within the family, is limited. Moreover, boys perceive the content as primarily focused on girls’ experiences. As a result, they turn to other sources (such as peers, media, and the internet) to educate themselves about sexual issues. Therefore, comprehensive and evidence-based sex education is crucial for supporting the psychosexual development of young people [
19,
20].
Focusing solely on the negative aspects of sexuality while ignoring its potential beneficial aspects impoverishes the scientific understanding of the process of sexual development during adolescence. Additionally, this may hinder efforts to minimise risks and promote a positive approach to mental and physical health among youth [
13]. Furthermore, research findings highlight the urgent need to consider contextual aspects in sexual education strategies offered by health and educational institutions [
17]. Providing young people with positive experiences can facilitate interventions, including modifying their behaviours and promoting health-enhancing activities, such as avoiding tobacco use, drug abuse, and excessive alcohol consumption [
21].
The Health Behaviour in School-aged Children (HBSC) study provides a unique source of information on the sexual behaviours of adolescents aged 15–16, and the range of collected information is continually expanding [
22]. In the HBSC 2017/18 study, Poland recorded one of the lowest percentages of 15-year-olds after sexual initiation among the 33 countries involved. Long-term observations show an increase in this percentage from 2010 to 2014, followed by a decline from 2014 to 2018 [
23]. Attempts to identify factors determining early sexual initiation have been made in many countries and cultural circles, including recently in Bulgaria [
24], Canada [
25], Italy [
26], and Ireland [
27], often in the context of clusters of risky behaviours. However, these studies focused only on 15-year-olds, and the factors considered mainly included family and school influences. The protocols of subsequent rounds of HBSC studies differ in the set of recommended optional questions, and each country can also choose and include additional national items.
A substantial amount of attention has been dedicated to the examination of the factors that influence the early initiation of sexual activity, a phenomenon that has been defined in various ways across the cited literature. It should be noted that the HBSC study revealed that the age of first sexual contact for adolescents is often around 16 years old. It is therefore recommended that older adolescents be included in the analysis, with a view to observing the frequency and determinants of sexual initiation up to the age of majority, which in Poland is 15 years of age. As is the case in the majority of countries worldwide, the age of sexual initiation has been on a gradual decline, reaching a current range of 15 to 18 years [
28]. In countries, such as Poland, that include older age groups in HBSC surveys, the initiation of sexual activity up to the age of 17 has been studied [
29].
Our study aims to identify the principal factors influencing the onset of sexual activity among adolescents and to explore the gender-specific determinants of sexual development. This allows for the identification of the elements of daily life and the environment that exert the greatest influence on adolescents’ sexual decisions and behaviour. It is of the utmost importance to gain an understanding of these processes in order to safeguard the mental and emotional well-being of adolescents [
30]. The lack of comprehensive sex education has been identified as a significant contributing factor to the emotional difficulties experienced by adolescents, including feelings of confusion, embarrassment, and anxiety. Furthermore, adolescents face psychological costs, including the unconscious perpetuation of harmful stereotypes and beliefs about their own and other sex and gender roles. Additionally, they incur behavioural costs that limit their capacity to make responsible decisions, anticipate consequences, and plan for the future [
31].
The aim of the present study, therefore, is to present the determinants of the age of sexual initiation among Polish youth aged 15–17, in the light of selected factors characterising their lifestyle and functioning within the family. A range of family factors and risky behaviours, whose significance has been demonstrated in other studies, are considered. An original element is the inclusion of how free time is spent, functioning in social relationships with peers, and the characteristics of the place of residence, as well as adjusting the analyses for self-assessment and academic achievement.
2. Materials and Methods
2.1. Sample
The cross-sectional study involved 3296 (out of 3478) school students aged 15–17 who participated in the Polish edition of the international HBSC survey during the 2017/2018 school year (respondents for whom data were missing for key variables had been excluded). The sample consisted of 46.4% boys and 53.6% girls. The survey was conducted at 138 schools across all of Poland’s provinces using traditional paper questionnaires. Participants were from 118 ninth-grade classes (N = 1815) and 84 eleventh-grade classes (N = 1581). The older cohort was included in the Polish study beyond the international HBSC protocol. The survey procedure was detailed in the national report [
32].
2.2. Research Tool
The dependent variable was taken to be the age of first sexual intercourse. In the section of the questionnaire concerning youth sexual behaviours, the question was asked: “Have you ever had sexual intercourse (sometimes this is called ‘making love’, ‘having sex’, or ‘going all the way’)?”. If the response was affirmative, the next question was: “How old were you when you had sexual intercourse for the first time?”—with seven possible answers ranging from 11 years or younger to 17 years or older.
As independent variables, in addition to gender (male or female), 15 factors potentially influencing the age of sexual initiation were considered. These included factors related to lifestyle, family characteristics, environment, self-assessment of health and appearance, and selected personal resources. Twelve of these factors were derived from the international protocol, three were national questions, and a total of seven were occasionally analysed in 2018 but were not included in the Polish questionnaire for the newer round of HBSC 2022.
2.3. Lifestyle Questions
Lifetime substance use was considered. For example, the question was: “On how many days (if any) have you drunk alcohol?” Similar questions were asked about smoking cigarettes, e-cigarettes, and marijuana. Although these questions are sourced from the ESPAD survey protocol [
33], the response categories differ (never, 1–2 days, 3–5 days, 6–9 days, 10–19 days, 20–29 days, 30 days or more). A standardised scale (mean 0, SD = 1) was created using Principal Component Analysis (PCA) from four questions about four substances, divided into three intervals. Excessive substance use was defined as a z-score > 1, with 50% of the sample in the middle group. Additionally, there was a question about lifetime episodes of alcohol intoxication: “Have you ever had so much alcohol that you were really drunk?” with five response categories: never; yes, once; yes, 2–3 times; yes, 4–10 times; yes, more than 10 times. These were recoded into three categories: never, rarely (1–3 times), and often (4+).
The factor of whether participants attained the recommended level of physical activity was considered a health-promoting behaviour. The respective MVPA index (moderate to vigorous physical activity), based on the Prochaska test [
34], indicates the number of days per week the respondent exercised for at least 60 min. Participants were classified as inactive, low-active, moderately active, or meeting the MVPA criterion of 7 days.
Using an optional block of questions from the HBSC protocol, non-constructive ways of spending free time with peers were examined. Two items from the full block were included in the study after the initial selection process, with those that did not correlate with the age of initiation being excluded in the univariate analysis. The question was: “In your leisure time, how often do you engage in the following activities?”. One possible activity was “shopping for fun in shopping malls”, with the following responses: daily, several times a week, several times a month, a few times a year at most, or never. These were recoded into never, rarely, and often. Another question concerned organised group activities in free time: “In your leisure time, do you do any of these organized activities?” explaining that: “Organized activities refer to those activities that are done in a sport or another club or organization”. Based on six co-occurring responses (team sports, organised individual sports, attending art school/club, youth organisations like Scouts, leisure centres or after-school clubs, church meeting or singing), participants were categorised as having none, one, or two or more activities.
Social engagement was also measured using the social self-efficacy scale devised by Muris [
35], containing eight statements with five response categories from “not at all” to “very well”. The total scale ranges from 0 to 32 points, divided into three intervals with cut-off points at 16/17 and 25/26. The scale is unidimensional, with a Cronbach’s alpha of 0.844 in this sample.
2.4. Questions on Family and Neighbourhood
Four family characteristics were analysed: structure, affluence, social position, and perceived support. Family structure referred to the individuals the adolescent lived with, categorised as follows: intact (both biological parents), step-parent (a mother or father together with a step-parent or partner), single parent, or other. Social position of the family was measured using a visual scale adapted nationally from an international prototype [
36] with a ladder ranging from 0 to 10 points, divided into three intervals: 0–5; 6–8; 9–10. Family support was measured using the multidimensional scale of perceived social support (MSPSS) by Zimet et al. [
37], focusing on the family dimension. The MSPSS has seven response categories from “very strongly disagree” to “very strongly agree”, labelled only at the extremes. The total scale ranges from 0 to 24 points, divided into three intervals: 0–11; 12–22; 23–24. Cronbach’s alpha was 0.942.
2.5. Questions on Other Factors
The analyses were also adjusted for academic achievement and self-assessment of health and appearance. Academic achievement was analysed using a visual scale, similar in source and graphic form to the family social position scale, but with a different categorisation: 0–4, 5–7, and 8–10 points. The mandatory question about self-assessed health in the HBSC protocol is “Would you say your health is…?”, with response categories: excellent, good, fair, and poor, recoded into three intervals by combining fair and poor. The optional question about self-assessed appearance is: “Do you think you are…?” with response categories: very good looking, quite good looking, about average, not very good looking, not at all good looking, recoded from worst to best assessment.
Below the sample is profiled in terms of the above independent variables, in tables showing the analysis results.
2.6. Statistical Analysis
In the statistical analysis, methods for censored data were utilised. This approach allowed for combining data from youth aged 15 and 17 into one group, enabling more extensive use of the collected information. For respondents who declared sexual initiation, the reported age was used. For those who had not yet experienced initiation, the exact age at the time of the survey was used, treating the observation as censored at that point. Factors influencing sexual initiation were examined using survival analysis methods, also known as time failure models. Potential influencing factors were categorised into three groups as described earlier. In the univariate analysis, the Kaplan–Meier method was used to estimate the age of initiation (with standard errors), calculate the number of censored observations, and compare groups using the Mantel–Cox log-rank test. In the multivariate analysis, the Cox proportional hazards model was applied, presenting adjusted hazard ratios (HR) with 95% confidence intervals (CIs). This approach is widely used in studies on the age of sexual initiation [
38]. In Dutch studies, the assumptions required for the Cox model were verified, demonstrating its applicability to the determinants of first sexual intercourse [
39].
4. Discussion
Adolescence represents a pivotal phase in human development characterised by profound physical, hormonal, and psychological changes. This transitional period fosters cognitive growth, including the emergence of formal operational thinking and abstract reasoning abilities. Concurrently, adolescents begin to anticipate the consequences of their actions, forge their identities, navigate social interactions, and explore their sexuality [
40]. While prevailing research often focuses on early sexual initiation, it frequently overlooks other critical behaviours that may influence sexual activity.
Our analysis, drawing on HBSC data, focuses on the age of sexual initiation among Polish adolescents, revealing that compared to peers in other countries, Polish youth generally commence sexual activity later, with notable disparities between genders. Higher rates of sexual initiation among boys at both 15 and 17 years old align with data from other global studies [
41,
42]. Additionally, in countries with less progressive gender role attitudes and greater gender inequalities, fewer girls report early sexual initiation, contributing to larger gender differences in these countries [
23,
43].
In discussing the obtained results, we primarily focused on factors that proved to be significant in the multivariate model of initiation age determinants. Differences in models estimated for both genders were discussed in more detail, while factors that were found to be insignificant were briefly mentioned.
Our findings indicate that adolescents who engage more frequently in psychoactive substance use tend to initiate sexual activity earlier, a trend similarly observed among those with more frequent episodes of excessive alcohol consumption. Notably, we found that excessive alcohol intake disproportionately impacts sexual initiation among girls. Adolescent sexual activity often occurs in settings where psychoactive substances are available [
44], with some reports indicating substance use during recent sexual encounters [
45]. Those initiating sexual activity early are more likely to engage in substance use during adolescence compared to their peers who initiate later or abstain [
46]. Additionally, early sexual debut correlates with a history of drug use [
47], underscoring the broad and nonspecific associations between normative sexual behaviours and substance use during adolescence and emerging adulthood [
48].
Other studies have also suggested that risky behaviours in young people are often linked to risky sexual behaviours, and the negative consequences of these behaviours seem to be more pronounced in young women [
49]. Given that alcohol consumption is prohibited for minors, young women engaging in such behaviour tend to participate in riskier social contexts, such as unsupervised gatherings where older, unfamiliar men may be present [
45,
50]. In these environments, the belief that alcohol reduces sexual inhibitions and increases the likelihood of casual sexual encounters is pervasive, fostering expectations of engaging in such behaviours [
51]. Young women in these settings may feel pressured both internally and externally to engage in sexual activity, irrespective of their actual readiness [
52].
Multivariate analyses using the Cox proportional hazards model confirm that adolescents reporting low family support tend to initiate sexual intercourse at a younger age, with a stronger protective effect observed among girls. Parental and familial influences play pivotal roles in sexual development, with sexual socialisation commencing in late childhood and continuing through adolescence, involving parents, siblings, peers, and other significant adults. Notably, the frequency of discussions about sexuality correlates with the quality of parent-child relationships during adolescence, with a notable decrease in the percentage of boys engaging in such discussions when relationships are strained [
19]. Adolescents benefiting from comprehensive sex education and robust parental support are more likely to delay sexual initiation, use contraception during their initial sexual experiences, and exhibit social competence in sexual interactions and satisfaction [
7,
53,
54,
55]. Comprehensive sex education should address not only the biological but also the psychological and emotional dimensions of sexuality, equipping young people to engage in safe and fulfilling sexual experiences [
56].
Regarding other family-related variables, our study found only a high family social position was found to correlate with earlier sexual debut, particularly among boys. However, reviews in the literature highlight that individuals who begin sexual activity at an early age are more vulnerable to risk factors stemming from family dysfunctions (e.g., conflicts, low parental supervision, and absence of parents) [
57,
58,
59].
Adolescents engaging in physical activity every day of the week demonstrated earlier sexual debut—a trend more pronounced among boys and those reporting very good health status. This finding aligns well with previous research highlighting physical activity as a significant predictor of early sexual initiation, with adolescents involved in physical activity being more likely to engage in early sex [
60,
61]. Sports clubs may not only provide an environment conducive to youth physical activity but also serve as spaces where interactions with potential sexual partners occur, thereby facilitating early sexual encounters [
60].
Regarding external and environmental factors, adolescents who spent more time with friends or peers had a lower average age of first sexual intercourse. Additionally, those attending organised extracurricular activities, as well as those who spent time with peers in less constructive ways, initiated sexual activity earlier. According to the classical ecological model, many environmental factors, such as leisure time activities, can significantly impact adolescent sexual development, including early sexual initiation [
62]. Prospective studies in the United States have shown that adolescents spending more unsupervised time with peers were more likely to engage in sexual intercourse [
61,
63]. Furthermore, studies have demonstrated the existence of peer effects related to early sexual debut, casual sex, and unprotected sex, confirming that peer characteristics influence sexual activity [
64]. Peers impact adolescent sexuality and sexual behaviours by projecting conventional or deviant lifestyle models, sexual attitudes, and behaviours, and serving as sources of information and social approval or disapproval for certain attitudes and behaviours [
65].
School achievements were also found to correlate with the timing of sexual debut. Adolescents with low school achievements initiated sexual activity earlier, with this factor remaining significant only for girls in the model. However, other studies have indicated that abstaining from sex until age 19 and a higher age of first sexual intercourse were stronger predictors of successful development for boys, although still significant also for girls [
66]. The negative impact of sexual debut on school attachment and academic performance has also been noted [
67].
One particularly interesting finding of our study is that self-rated appearance, when high, was associated with earlier sexual initiation. However, in our model, this was found to be significant only for girls. Body image is a sensitive issue for many individuals, as contemporary Western culture places a strong emphasis on physical appearance. Therefore, both men and women may feel pressured to “look right.” Studies indicate that satisfaction with appearance is associated with reporting fewer sexual problems, particularly less likelihood of experiencing issues related to lack of pleasure, arousal, and orgasm [
68], which may explain why a more attractive appearance is linked to a greater willingness to engage in sexual activity. The strong association between girls’ first sexual intercourse and their appearance may be related to objectification, which occurs in social and cultural contexts and through potential romantic and sexual partners. Sexual images of women and girls are prevalent in mainstream media and are linked to sexual behaviour outcomes [
40].
Strengths and Limitations
Our analysis has utilised a distinctive approach to understanding the factors influencing the age of sexual initiation among Polish adolescents, employing a large sample and time failure models. A key advantage of this approach is its focus on the determinants of the age of initiation rather than just the occurrence of initiation or early initiation, distinguishing Cox models from traditional logistic regression.
In determining the validity of this method, we drew upon the findings of other studies [
39]. Nevertheless, some authors [
69] put forth more sophisticated accelerated failure-time models. The data available and the method used for the time-to-failure model permitted the exact age of the respondents to be taken into account, which is important given the age range of the qualified students. It was possible to accurately determine the age of the adolescent at the time of the incident, although another limitation is the approximate age at which it occurred. As previously stated in the introduction, the advantage of our study using methods typical of censored data is the observation of adolescents at a time when they often choose to engage in sexual contact. However, this is not a complete observation, and the relatively low percentage after initiation made median estimation impossible.
Another significant limitation is the reliance on self-reported data and the cross-sectional nature of the study, which limits causal inference. Efforts were made to minimise bias, such as asking about experience with substance use over the respondents’ lifetime, rather than just over the past 30 days.
Possible reverse causality is also a consideration that must be kept in mind for many factors. Satisfying romantic relationships and positive first sexual experiences might improve self-esteem, promote healthy behaviours, and enhance peer group functioning. There may be concerns about the set of factors influencing the age of sexual initiation, but estimating the combined impact of 17 factors distinguishes this study from others. One important additional factor to consider including in future analyses is the pubertal timing.
Our use of data from 2018 may also be seen as a limitation. Although the data are relatively older, the use of these data for the present study nevertheless have some justifications: later HBSC studies (2022 in Poland) were conducted during the COVID-19 pandemic, which disrupted social relationships. Additionally, the Polish questionnaire changed significantly, making it impossible to repeat identical analyses with newer data. Adolescents may also feel discomfort about their first sexual experience, especially if it was influenced by partner or social pressure or sexual arousal.
Our study is limited in that it does not consider respondents’ subjective perception of the timing of their first sexual intercourse. Given that feeling that one’s sexual initiation occurred too early or too late can have psychological consequences [
70], future research should take this into consideration, as in studies like Rouche et al. [
71].
Lastly, there has been a significant shift in the way media are used, which has, in turn, altered the methods for measuring media engagement. Future research should incorporate media usage within models, taking into account the fact that young people internalise views on sexuality as a result of their media consumption [
72].
5. Conclusions
Recognising sexual debut as a natural aspect of adolescent development is crucial for understanding this stage as a part of normal maturation. However, it is imperative to acknowledge the diverse factors influencing the age of sexual initiation, including social, emotional, educational, and familial influences. Analysing these factors is essential for developing effective interventions and educational strategies aimed at promoting healthy sexual development and reducing potential negative consequences associated with early sexual debut. Moreover, in the comprehensive model, when the entire population was examined, gender was not a significant factor. However, the most notable outcome is that the predictors vary between boys and girls. The factors influencing performance in boys differ from those affecting performance in girls. These findings remain pivotal because they indicate that distinct strategies may be necessary to support boys and girls in tailored sex education.
Our study highlights that frequent use of psychoactive substances strongly predicts earlier sexual initiation, with even moderate use exerting an impact. While gender did not directly influence the age of initiation, our findings indicate that boys are more likely to initiate earlier if they are highly physically active and spend considerable time with peers. Conversely, for girls, a positive self-assessment of their appearance tends to correlate with earlier initiation, whereas good academic performance and strong family support tend to delay their decision to engage in sexual activity.
Educational efforts should prioritise ensuring that adolescents have positive, enjoyable, and respectful first sexual experiences, alongside a thorough understanding of consent. Encouraging self-esteem, fostering emotional connections, and promoting open communication with both parents and partners are essential components of effective sexual education programs [
73]. These programs should be inclusive and tailored to the diverse experiences and identities of young people, aiming to empower them to make informed and responsible decisions about their sexual health and relationships.
