Adolescence is characterized by rapid physical, mental and social development and it is the time when adolescents become autonomous and independent from their parents. As their sexual identity develops, adolescents naturally get to explore sex. These sexual curiosities of adolescents lead to tolerance for exposure to pornography and sexual behavior, and they may result in sexual intercourse and the development of diseases such as sexually transmitted disease (STD) and human immunodeficiency virus (HIV) infections. In the United States, a half of 20 million new STD infections occurring each year are reported to occur among youth aged 15 to 24 [2]. Having multiple sex partners, having sex with a stranger, and unprotected sexual intercourse without using protective devices such as condoms may result in HIV infections, STD infections and unwanted pregnancies, inflicting deleterious effects on the health of youth [3].

The use of Short Message Service (SMS) and social media such as the Social Network Service (SNS) (services that enable communication or interaction with others online [4]) affects thoughts and behavior of youth and plays an important role in the formation of social relations [5]. Social media usage can be defined as the use of a kind of web service that collects most contents from users or other web sites [4]. Today, for most young people, the use of social media which enables social interaction through Internet access on a smart phone becomes an indispensable part of their daily activities [6].

Cambodia has shown considerable growth in digital technology in the last few years. As a result, in 2016, the number of Internet users increased to 2.1 million, and social media users and mobile phone users were estimated to be 4.9 million and 4.4 million, respectively. In addition, among youth aged 18 to 24, 44% are Facebook users and 56% are Instagram users, showing the active use of social media among Cambodian youth [7]. Among Cambodians aged 15 to 24, the accessibility level of mobile phones is 98% in urban areas and 96% in rural areas [8]. These data show that the use of social media via the Internet is becoming general among all youth in Cambodia regardless of their residence areas.

The various forms of the use of SMS and social media give many advantages to young people, but these means of communication also have some drawbacks [9]. For example, SMS is an inexpensive and easy way to communicate and coordinate events with friends and is also used as a way to maintain friendship [10]. However, at the same time, it involves the risk that it may affect sexual intercourse since it enables youth to exchange sexually explicit pictures or messages with each other (sexting) [11]. In addition, youth can use social media to write about their favorite movies and events, hobbies and experiences in text or images, receive feedback from their peers, and expand relationships through communication and interaction with their peers [5]. Social media play an important role in sexual socialization by enabling youth to establish their sexual identity and produce sexual expression [12]. In addition, adolescents acquire important and sensitive sexual health information through social media rather than traditional health information services such as books [13]. However, sex-related information shared on social media has low reliability because the accuracy of contents is uncertain, and the use of SMS and social media involves potential risks, such as the behavior of sending sexually explicit SMS messages or pictures on a mobile phone, exposure to inappropriate contents, and cyberbullying [9]. Previous studies have shown that the uses of SMS and social media are linked to sexual intercourse in young people. In a study of Latino teenagers in 12 public high schools in Maryland, USA, the score for sexual intercourse was 2.0 times higher in teenagers using SMS 100 or more times than those using SMS less than 100 times, and teenagers accessing social media at least once per day had a 2.1 times higher score for sexual intercourse than those accessing social media less often [14]. In addition, in a study of Nigerian adolescents, the score for sexual intercourse experience was found to be higher in adolescents using social media frequently (58.8%) compared to those not using them frequently (47.5%) [15]. This can be attributed to the fact that the social media platform provides more ways and opportunities for youth to interact with others and SMS and social media increase the dynamics of such relationships.

Cambodia is one of the countries with the highest percentage of the youth population in Southeast Asia and the population aged 10~24 accounts for 28.4% of the total population of Cambodia [16]. In 2010, among Cambodian youth aged 10 to 24, 4% of men and 14% of women reported having sexual intercourse experience before the age of 18, and the percentages increased to 5% for men and 18% for women in 2014 [1617]. Especially, the rate of sexual intercourse experience for teenagers aged 18 to 19, which are the ages of third-year high school students in Cambodia, has been increasing from 19.3% in 2010 to 29.8 % in 2014 for boys and from 8.1% in 2010 to 10.6% in 2014 for girls [18]. Social media usage among teenagers in Cambodia is increasing actively [7], and since Cambodia has a culture in which talking about sex in public is taboo [20], young people share inaccurate information about sex through SMS or social media in an indiscreet manner, which may jeopardize the sexual health of adolescents, so there is a need to pay attention to and conduct research about the impact of social media use on sexual behavior in terms of health aspects. According to a United Nations (UN) report in 2018, out of a total of 67,000 people infected with HIV in Cambodia, 3,400 persons are 10~19 years old and 4,100 persons are 15~24 years old, with the population aged 10~24 accounting for 11.2% of the total HIV-infected people [21], so it is important to identify factors affecting sexual health in Cambodian youth and to find solutions.

The majority of adolescents begin to have sexual intercourse when they are in high school and the rate of sexual intercourse experience increases with the school year [19]. Although youth in Cambodia are exposed to open sexual culture through the increased use of the Internet and social media, it is difficult to share information on healthy sex due to the culture forbidding open discussions about sex in public, and especially, for youth in rural areas, a conversation about sex is a more sensitive issue [20]. In addition, in Cambodia, the fertility rate of teenagers attending high school is twice higher in rural areas than in urban areas (26 persons in urban areas and 52 persons in rural areas per 10 million people), and the average age when girls experience sexual intercourse for the first time is lower in rural areas (21.0 years in urban areas and 23.8 years in rural areas) [1718]. In this context, considering the negative effects of sharing inaccurate and inappropriate information about sex and exposure to pornography in relation to the recent active use of SMS and social media among Cambodian youth, research is required to investigate the relationship between the degree of the use of SMS and social media and sexual intercourse in Cambodian adolescents in order to develop and apply programs for sexual health of adolescents. However, there have been few studies on the influencing factors for sexual intercourse of youth in rural areas of Cambodia. Especially, there is no study on the effects of the use of SMS and social media on sexual intercourse. Therefore, this study aimed to investigate the relationship between SMS and social media and sexual intercourse in high school students in rural areas of Cambodia and to examine the effects of the use of SMS and social media on sexual relationships to provide basic data necessary for future program development and education for HIV prevention and sexual health promotion for Cambodian youth.

The purpose of this study is to examine the effect of the use of SMS and social media on sexual intercourse in high school students in rural areas of Cambodia and the specific objectives of this study are as follows:

This study is a descriptive research to investigate the effects of the use of SMS and social media on sexual intercourse in third-year high school students in rural areas in Cambodia.

The participants of this study were third-year high school students in three rural regions of Cambodia, Kampong Cham, Kampong Chhnang, and Koh Kong. The specific inclusion and exclusion criteria for selection of participants were as follows:

The minimum sample size for this study was calculated using the statistical method for multiple regression analysis of G*Power 3.1 Program by assuming the significance level α=.05, medium effect size of .15, power of .95, and the number of factors of 20. As a result, the minimum sample size was determined to be 222 persons, and 483 copies of the final questionnaires were used in the analysis, so the minimum sample size was satisfied.

Three rural areas, Kampong Cham, Kampong Chhnang, and Koh Kong, were randomly selected. Kampong Cham is located 124 km to the north east of the capital, Phnom Penh, and the region has the largest population of 1.75 million and has 41 high schools. Kampong Chhnang is located 91km to the north of Phnom Penh and has 523,000 residents and 16 high schools. Lastly, Koh Kong is located in the southwestern part of the country, 271 km away from Phnom Penh, and has 122,000 residents and 21 high schools in the region [22]. For this study, one high school was randomly selected in each region. 97 out of 102 persons (agreement rate: 95.1%) in Kampong Cham, 300 out of 307 persons (agreement rate: 97.7%) in Kampong Chhnang and 103 out of 105 persons in Koh Kong (agreement rate: 98.1%) agreed to participate in the study. A total of 500 copies of the questionnaire were collected, but 483 people were included in the final analysis excluding 17 copies with missing data.

Before collecting the data, the research purpose and intent and participation methods were explained to the principal of each school and approval for the recruitment of participants among students was obtained. According to the formal procedures, a document with the descriptions of the school name, the school principal's contact information, and the research schedule was submitted to the Ministry of Education, and after explaining the research purpose and method through a meeting with officials of the Ministry of Education, the final approval was obtained from the minister of the Ministry of Education. Then, after arriving at each school, we met with the school principal and staff in charge to explain about the research in detail and discussed the schedule and methods not to disturb classes before conducting data collection.

The data collected in this study were analyzed using the SPSS/WIN 23 program and specific procedures are as follows.

Two trained Cambodian research assistants, one person with a master's degree in nursing and a doctoral student in nursing, entered the classroom and provided sufficient explanations about the study to students. After obtaining informed consent from the students who agreed to participate in the questionnaire survey, the participants were asked to complete a self-administered questionnaire. Before conducting the questionnaire survey, participants were informed about confidentiality of their responses of the questionnaire and that if they wanted to withdraw from the survey while completing the questionnaire, they could do anytime without any disadvantages. Considering private and sensitive contents of survey questions such as sex intercourse experience, the homeroom teacher was asked not to be in the classroom and students were seated apart from each other with the maximum space between tables to secure confidentiality of individuals. After the questionnaire survey was completed, prepared gifts were given to the participants to express appreciation. The data collection was carried out after obtaining the approval from the IRB of the university which the researcher belongs to (2017-06-013-001).

The general characteristics of the participants are shown in Table 1. Male students were 42.2% of the total participants, and female students were 57.8%, and the average age was 18.24±1.06 years (male: 18.53±1.15 years; female: 18.03±0.94 years). 99.2% had religion and 11.8% drank alcohol. As for parents' occupation and education level, 93.0% had a father with a job and 69.8% had a mother with a job. Regarding the education level of parents, the highest proportion of parents had no formal education and 40.8% of fathers and 42.9% of mothers had no formal education. 67.1% of the participants lived with their parents, and 20.5% lived with a single parent. In addition, with respect to the frequency of having dinner with the family per week, the percentage for 5~7 times a week was highest (53.8%).

Table 2 shows the degrees of the use of SMS and social media. 97.9% of the students used mobile phones and 2.1% did not. 86.3% used the Internet and 8.3% used SMS more than 100 times a day. As for the mean frequency of SMS use, the participants used SMS 2.39±10.47 times a day with parents, 20.63±128.81 times a day with friends, and 15.72±146.34 times a day with opposite gender friends. 94.4% had a social networking account but 5.6% had no social networking account, and 73.5% had two or more accounts. Among them, 86.7% had a Facebook account.

Table 3 shows the results of cross-tabulation analysis of the relationships of the general characteristics of participants and sexual intercourse according to the use of SMS and social media. The score for sexual intercourse was higher in male students than female students (χ²=11.17, p=.001), in students who drink alcohol than non-drinkers (χ²=38.16, p<.001), and in students taking photos with a mobile phone than those who do not (χ²=6.35, p=.013). Among youth using SMS, the score for sex intercourse was statistically significantly higher in the group exchanging SMS messages with opposite gender friends than in the group exchanging SMS messages with same gender friends (χ²=7.49, p=.006). However, in the case of the use of SMS, e-mail, watching videos, surfing the Internet or playing games, the use of SMS 100 or more times a day, and the use of social media through Facebook, Twitter, YouTube or Instagram on a mobile phone, exchanging SMS with parents and exchanging SMS with friends, the comparison between participants doing each type of activity and those not doing it showed that there was no statistically significant difference in sexual intercourse.

Table 4 shows the effects of the use of SMS and social media on sexual intercourse among participants after controlling for gender and drinking status of the participants.

To examine the impacts of SMS and social media use on sexual intercourse among participants, logistic regression analysis was performed and the results showed that the regression model was significant (χ²=47.28, p<.001).

Students using SMS on a mobile phone was 5.83 times (p=.020) more likely to have sexual intercourse experience and students taking pictures with a mobile phone was 0.04 times (p=.045) more likely to have sexual intercourse experience, compared to students who do not do such activities using a mobile phone. In addition, students drinking alcohol were 15.19 times more likely to have sexual intercourse experience compared to non-drinkers (p=.001). However, the use of SMS more than 100 times a day or the use of social media such as Facebookwith was found to have no significant relationship with sexual intercourse.