In this study, 14.1% (95% CI: 13.3, 15.0) of all students in the participating schools had ever had sex before. A study of sexual behavior among vocational students in northern Thailand found that 46.5% had ever had sex, and males were more sexually active than their female counterparts . This difference with the Bangkok study may be due to varying socio-demographic and cultural context between the two study areas. A study in South Korea , found that only 5% of high school students were sexually active, which is in stark contrast to a study in the Poland where more than 78% of students attending universities had ever had sex . It is not clear whether these wide differences in sexual activity are attributed to different definitions of sex, time period, or other differences among sample populations and data collection methods.
4.1 The prevalence of risky sex behavior (RSB)
Most studies have defined RSB as (1) Not using condoms for every episode of sex; and (2) Having two or more sexual partners. In adolescents, RSB includes sexual debut at a very young age, a factor which is also associated with reproductive health risk, such as unprotected sex. Use of mood-altering drugs before or during sex also contributes to RSB . Some studies define RSB differently as, for example: (1) Number of sexual partners during the lifetime; (2) Inconsistent use of condoms; and (3) Unwanted or unplanned pre-marital pregnancy [26, 27]. Others also refer to exchanging sex for cash or in-kind compensation as RSB . RSB can produce negative consequences beyond the individual, such as family conflict, damage to relationships, legal disputes, and/or financial problems . Unprotected sex is often the focus as a root cause of these problems because of its association with STIs and unwanted pregnancy. Worldwide, unprotected sex for both male and female adolescents rank second in the health risk category . Over the past 15 years, a large proportion of adolescents in Central and Eastern Europe reported having RSB, which is associated with an increase in STIs other than HIV. The same is true for teen pregnancy and abortion rates . These public health issues have prompted research into the factors influencing adolescent RSB . In addition, definitions of RSB are becoming more standardized, and they now include coercion at sexual debut and forced sex in the past year as criteria. These factors have clinical utility and can be integrated into RSB prevention education programs.
The prevalence of RSB among college and university students in Ethiopia ranged from 23.3–60.9%. The estimated prevalence of RSB among college and university students was 40.6% and 42.4%, respectively. The estimated overall prevalence of RSB was 41.6% . Those results reflect a higher level of RSB than found in other studies conducted in Africa, North America, and Europe. Differences may be due to sample size, age of the sample, calculation of the rates, and definition of RSB .
4.2 Factors associated with RSB
Adolescent RSB represents a serious public health concern that is detrimental to health and well-being. RSB (e.g., multiple sex partners, not using condoms) negatively affect health by directly contributing to risk for STIs and unintended pregnancy . There is significant evidence suggesting that having a history of child sexual abuse contributes to RSB in adolescents . Adolescents who were sexually abused at a young age are at higher risk of premature sex, having sex with multiple partners, having sex under the influence of drugs, having sex with an uncommitted partner, and having unprotected sex . Consistent with this study, adolescents exposed to sexual abuse had 1.67 times more chance of experiencing RSB than adolescents without a history of sexual abuse.
Results reveal a high prevalence of adolescent contraceptive use in Bangkok. More than two-thirds of sexually-active teens in this study have used birth control. Condoms are the most common method of birth control for this adolescence. This is consistent with previous evidence highlighting condoms as the most prevalent method of contraception among adolescents [7,34,]. followed by emergency contraception, and withdrawal . This study did not examine factors which might influence a teen’s decision to use contraception. However, the findings of some suggest that the preference for condoms stems from adolescent concern about perceived side effects of other methods . Adolescent girls report using contraception more than their male counterparts. This is different from previous studies in Africa and Asia that found that adolescent males were more likely to use contraception with their female partners . The differences may be attributable to the phrasing of questions about using contraception, cultural differences across countries, and knowledge acquisition through online sources.
The relationship between adolescent sex and substance use has been analyzed. There is evidence from studies that adolescent substance use is predictive of later RSB. Sexually-active teenagers may begin to spend more time with other sexually-active friends, and find themselves in social environments that facilitate substance abuse [11, 38]. Adolescent RSB is more common when use of mood-altering substances is involved . A study found that use of addictive drugs before last sex was prevalent among adolescents . This study provides some evidence that is consistent with a possible explanation for the relationship between RSB and adolescent substance use. Substance use disorders are often associated with RSB. For example, studies have shown that, after excessive consumption of alcohol, a person may be more prone to RSB such as promiscuity, neglecting to use a condom, and general reduction of inhibitions which might deter unsafe behavior. Studies have found that RSB often coincides with other deviant behaviors.
The present study analyzed the relationship between alcohol use and RSB among students who had ever had sex. Students who consumed alcohol had more RSB than those who did not consume alcohol. Our findings are consistent with recent studies reporting that alcohol use before sex is more likely to lead to unprotected sex [12–15]. The association between alcohol use and RSB is empirically supported in a variety of studies. However, most of those studies are cross-sectional and, thus, causality cannot be inferred. Some studies have found a significant association between alcohol use and having multiple, concurrent sex partners [13, 39]. However, there are also inconsistent results from studies of the relationship between alcohol consumption and promiscuity  and consistent condom use . Studies have shown that alcohol consumption may lead to RSB by biological mechanisms (i.e., the alcohol myopia theory) in that alcohol inhibits condom use behavior through the pharmacological effect of alcohol on cognitive ability. While alcohol is a well-known behavioral stimulant for sex, mechanisms to inhibit RSB (such as prevention of STIs and pregnancy) are inadequate to meet the challenge. The relationship between alcohol use and RSB is complex and may be influenced by a combination of social, physiological, and individualistic personality traits . The relationship between alcohol consumption related to sexual activity and promiscuity may be explained by the alcohol expectancy theory . This theory explains that people who drink alcohol tend to be less nervous, are able to have more sex, and experience a perceived increase in sexual prowess. Teenagers are more likely to consume alcohol before sex when in certain social situations, such as when on group dates, at parties, or at bars .
Adolescent cannabis use is a growing public health problem. In this study, the overall prevalence of cannabis use in the past year was approximately 6.9%, and adolescents who used cannabis had 3.7 times more chance of experiencing RSB than adolescents who did not use cannabis. These findings are consistent with previous research which found an association between marijuana use and an increased risk of sex among a sample of adolescents. . Marijuana use is prevalent in high-income countries. For example, in the United States, approximately 0.7% of 13–14-year-olds and 3.4% of 15–16-year-olds use marijuana daily, and 22.2% of teens report using marijuana in the past month . The use of marijuana may affect RSB. For example, studies have found that marijuana users are more likely to have their first sex at an earlier age than non-users. Plus, marijuana has been linked to RSB, such as having multiple sex partners. It has been speculated that cannabis use may increase the risk of RSB through negative effects on neurodevelopmental or decision-making abilities . Other factors include personality traits, self-perception, social status, and attractiveness. The main risks from marijuana use include premature sex (e.g., having sex before age 15), promiscuity, and the accompanying risk of STIs, HIV, and unplanned pregnancy [19, 44].
The results of this study were not significantly different from previous studies in that 20.8% of sexually-experienced adolescents used e-cigarettes in the last 30 days, and male adolescents engaged in smoking tobacco and e-cigarettes more than their female counterparts. Similarly, research indicates that adolescence e-cigarette use is linked to developmental, physiological, and psychosocial effects, including nicotine addiction, which can cause cardiovascular problems, loss of perception/attention/mood, impulsivity, increased anxiety, and poor academic performance . Additionally, adolescents who used e-cigarettes were more likely to report having four or more sexual partners in their life than non-vapers. The prevalence of condom use at last sex among e-cigarette users was lower than non-e-cigarette users . In the current study, adolescents who smoked e-cigarettes had 1.59 times more chance of having RSB compared to adolescents who did not smoke e-cigarettes. These findings confirm that adolescent substance use is associated with higher rates of involvement in sexual behavior and RSB among adolescents [46Another study found that high school student users of e-cigarettes were more promiscuous than non-users . However, the reason for these relationships is unknown. Studies suggest that perceptions of general behavioral risk are low. High impulsivity and normative perceptions of peer involvement in risky behaviors may lead to multiple substance abuse, RSB, and other health risks . Therefore, these findings highlight the need to further study of the association of e-cigarette use and RSB. A previous study identified intrinsic factors of individuals and normative perceptions of peer engagement when trying to develop and implement RSB prevention and health interventions among adolescents.
This study found that one out of three sexually-experienced adolescents had considerable loss of property from gambling. Adolescents who gamble had 1.73 times more chance of RSB compared to adolescents who did not gamble. Male adolescents had more gambling behavior than their female counterparts. This contrasts with some previous studies which found variable prevalence of gambling among adolescents, with 77–88% of adolescents and young adults generally engaging in one form of gambling or another . That prevalence rate is relatively high compared to the older population, with a prevalence of gambling between 39% and 50% . Adolescence are more likely to start social gambling with friends and family, and gambling has the potential to negatively affect an individual's well-being, which may include issues related to relationships, family, finances, social status, and career pursuits . According to a study in Uganda, 62% of youth gambled, and gamblers were more male than female. The findings from the current study also found that male adolescents gamble more than female adolescents. [50A systematic review of national studies published in 2014 reported that the prevalence of problem gambling in North America was in the range of 2.1–2.6%, and in Oceania from 0.2–4.4%. By contrast, in Europe, the prevalence of problem gambling ranged between 0.2% and 12.3%. These results are hard to verify and may differ across countries and settings due to response bias and survey methodology. Additionally, studies may differ significantly based on inclusion criteria and target populations. These methodological concerns have led to outcomes that vary greatly from country to country or between different studies in the same country . The vast majority of adolescence who gamble consider themselves prone to problem behaviors, and they may not see a link between gambling and health risk, particularly RSB. Gambling is associated with emotional, physical and mental problems, and many adolescences who gamble excessively experience stress, anxiety, and depression. Gambling addicts often experience mood swings that reflect their winnings and losses. However, this uncertainty makes gambling addicts prone to anger and irrational outbursts. These mood disorders also make gamblers more vulnerable to unprotected sex and sex with multiple sex partners, or even exchanging sex for cash or in-kind compensation if gambling debt becomes too onerous .
Although the study reflects some acceptable quality assurance outcomes, the RSB data in this study were self-reported and, thus, subjects may under- or over-report their own RSB. Also, the survey focused on RSB in the past year, and targeted adolescents in high school Years 2 and 5, and vocational Year 2 students. Thus, the sample is probably not representative of all adolescents, either in Bangkok or Thailand generally. Researchers need to consider studies using community-based qualitative research methods to determine strong predictors of RSB among adolescents. Inquiries about sexual harassment may have inappropriate metrics such as excluding the severity, duration, and frequency of the harassing behavior, and how that affects RSB.