Early sexual initiation and risk factors in Serbian adolescents: data from the National Health Survey.

The European Journal of Contraception and Reproductive Health Care, 2014; 19: 211–219

Eur J Contracept Reprod Health Care Downloaded from informahealthcare.com by Fudan University on 05/10/15 For personal use only.

Early sexual initiation and risk factors in Serbian adolescents: Data from the National Health Survey Vida Jeremic´∗, Bojana Matejic´†, Ivan Soldatovic´‡ and Sandra Radenovic´∗ ∗Department of Humanities, †Institute of Social Medicine, and ‡Institute for Biostatistics and Health Research, School of Medicine, University of Belgrade, Belgrade, Serbia ............................................................................................................................................................................................................

ABSTRACT

Objectives To identify factors associated with sexual initiation before the age of 17 among Serbian adolescents and to assess whether the latter is associated with other risky behaviours, such as tobacco, alcohol and illicit drug use, and fighting. Methods The study was an analysis of data gathered by the 2006 Serbian National Population Health Survey in which information concerning adolescents was obtained by means of questionnaires. Data were analysed using descriptive statistics and a logistic regression model. Results A total of 474 adolescents aged 15 and 16 completed the survey. Multivariate logistic regression analysis showed that male respondents reporting sexual initiation were significantly more likely to smoke daily and to have experienced two or more episodes of drunkenness in the past. Female respondents reporting sexual initiation were significantly more likely to live with both parents, to feel insecure in school, to smoke daily and to drink more than once a week. Conclusions A strong association was found between adolescent sexual initiation and substance abuse. Although a causal relationship is evidently not established, one might contemplate including measures lowering the frequency and intensity of substance abuse in health prevention programmes and interventions aiming at reducing the risks associated with sexual initiation.

K E Y WO R D S

Adolescents; Sexual initiation; Risk factors; Serbia

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I N T RO D U C T I O N

Reproductive health issues affecting youths are a matter of concern in all transitional countries. Transition in Serbia has led to an impoverishment of the population, deprivation in educational and employment opportunities for youngsters, and deficiencies in the provision of sexual and reproductive health (SRH) care to that age group. In addition,

sexual education in Serbian schools has been neglected in the past decades, with the exception of sporadic initiatives mostly set up and sponsored by nongovernmental organisations1,2. Most published accounts indicate that countries undergoing socio-economic transition are confronted with an increase in risky behaviours among adolescents. Among others, consumption of tobacco

Correspondence: Vida Jeremic´, Department of Humanities, Dr Subotica 8, 11000 Belgrade, Serbia. Tel: ⫹ 381606361076. E-mail: vida.jeremic@ med.bg.ac.rs, [email protected] © 2014 The European Society of Contraception and Reproductive Health DOI: 10.3109/13625187.2014.897320

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Early sexual initiation in Serbian adolescents

(particularly by girls), alcohol, and illicit drugs may directly or indirectly jeopardise their reproductive health. Moreover, evidence on record shows an increase in the pregnancy rate, the abortion rate and the incidence of sexually transmitted infections (STIs) among teenagers3,4. Statistical data support the aforementioned conclusions: the fertility rate for women aged 15 to 19 was 22 per 1000 in Serbia during the 2005–2010 period, which is significantly higher than that in developed European countries5. Unfortunately valid data on incidence and prevalence of STIs in developing and transitional countries are scarce, because STI surveillance has been neglected and poorly funded. Since 2002 new cases of HIV infections have been more commonly diagnosed among Serbs aged 15 to 29 (47% in 2008 vs. 22% in 2002)6. Early sexual initiation (‘sexarche’) is one of the factors most closely associated with adverse effects on reproductive health, like STIs and unwanted pregnancies7–9. The age at sexarche has dropped worldwide, with Serbia and other former Yugoslav countries being no exceptions10. Delaying sexual initiation is considered an important HIV prevention strategy for adolescents in both developing and developed countries11. The objectives of this study were to identify factors associated with sexarche before the age of 17 among Serbian adolescents, and to assess whether it was linked with other risky behaviours, such as tobacco, alcohol and illicit drugs use, and involvement in brawls. METHODS

Design and study population This paper is based on a secondary data analysis of the 2006 National Population Health Survey, a large crosssectional study conducted by the Ministry of Health of the Republic of Serbia, with the support of the World Bank, the World Health Organization Regional Office for Europe, and the Institute of Public Health of Serbia12. A stratified two-stage representative sample of the population of Serbia was taken into consideration, which included all households registered in the 2002 Serbia Population Census. For this paper, the database concerning 15 and 16 years old respondents was analysed. Our study protocol was approved by the ethics committee of the Serbian Ministry of Health. 212

Information on adolescent health was obtained by means of a face-to-face- and a self-administered questionnaire, both of which were derived from the standard questionnaires employed in similar surveys (WHO Health Survey 2002, SF-36)13,14. Two weeks prior to the start of the survey, all questionnaires were pre-tested in ten cities in Serbia, and then validated15. Questionnaires were administered by trained interviewers. Each interview team consisted of two interviewers and one healthcare professional16. To ensure confidentiality and honesty, the questionnaires were anonymous, and were filled out by the respondents in privacy, not in the presence of other members of the household. Information was gathered on demographic characteristics and socioeconomic status, hygiene habits, diet, physical activity, behaviour in traffic, injuries, lifestyle, reproductive health, knowledge about health, health selfassessment and life satisfaction, relations with others, mental health characteristics, use of health services and satisfaction with health care. Variables For the purpose of this survey 13 variables were analysed. The main dependent variable, sexual initiation, was identified by means of a ‘yes’ answer to the question ‘Have you ever had sexual intercourse?’ As all respondents were either 15 or 16 years old, an affirmative answer indicated sexual initiation before the age of 17. Unfortunately, in the National Health Survey no distinction was made in accordance with the respondent’s sexual orientation so that the term ‘intercourse’ could mean either a heterosexual or a homosexual sexual act. The independent variables were grouped into two clusters. The first cluster of variables consisted of socio-economic determinants. To determine objectively socio-economic status, the adolescents were classified according to the Demographic and Health Survey Wealth Index into five socio-economic groups or quintiles: poorest, poorer, middle class, richer and richest17. Subjective socio-economic status was assessed through the question: ‘How would you rate your family’s socio-economic status?’ Answers were on an ordinary scale: lower ⫽ 1, lower-middle ⫽ 2, middle ⫽ 3, upper-middle ⫽ 4, and upper class ⫽ 5. The type of settlement was categorised as urban or rural. In addition, family structure was analysed, whereby two main

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categories were considered: living with both natural parents, and other living arrangements. As a form of educational indicator, the answer to the question ‘What was your grade point average in the preceding school year?’ was employed. A six-point scale was used, and answers were categorised as follows: excellent ⫽ 1, very good ⫽ 2, good ⫽ 3, enough ⫽ 4, repeating a year (grade) ⫽ 5, did not go to school ⫽ 6. Furthermore, attachment to school was based on a group of questions querying feelings about, and perceptions of, the school environment. Finally, social support was defined as having anyone to help the respondent in any situation, which was assessed through questions ‘Is there anyone you can count on in any situation?’ and ‘Is it easy for you to talk about problems with your parents?’ The second group of variables was related to risky behaviour. Four risky substance use variables were included: current frequency of tobacco use, drinking of any sort of alcohol every week, having been drunk twice or more in the past, and any marijuana consumption in the past. Moreover, respondents were asked if they had ever been involved in a physical fight. All these variables were dichotomous, with YES/ NO answers. Statistical analysis Use was made of the SPSS 15.0 statistical software package (SPSS Inc., Chicago, IL, USA). First the data were analysed by means of descriptive statistics: the variables were categorical and ordinal, and are presented as frequencies and percentages. The logistic regression model was applied to examine the possible effects of socio-economic characteristics and other risky behaviours of the respondents on the risk of sexual initiation before the age of 17, dividing the participants by gender into two subpopulations. Univariate logistic regression analyses of the 13 variables were computed to identify those that were significantly associated with the likelihood of reported sexual initiation. Exact logistic regression analysis was done for variables that had had no observations in one of the categories. Significant variables were included in multiple logistic regression models using the backward conditional selection procedure. The results are presented as adjusted odds ratios (ORs) with 95% confidence intervals (CIs). All p-values lower than 0.05 were considered significant.

R E S U LT S

A total of 474 adolescents aged 15 and 16 completed the survey, of whom 228 (48 %) were girls and 246 (52%), boys. Experience of sexual initiation was reported by 49 (10%) of the respondents, 14 (6%) of the girls, and 35 (14%) of the boys. Median age at sexual initiation was 15. The distributions of all explanatory variables are given in Table 1. There were fewer than 10% missing cases for all variables. Estimates of the adjusted odds ratio with confidence intervals and statistical significance for each variable included in the univariate model are presented in Tables 2 and 3 for male and female respondents, respectively. Results of the multivariate logistic regression are presented in Tables 4 and 5. Univariate logistic regression revealed that male respondents reporting sexual initiation were significantly more likely to have a poorer grade point average in the preceding school year, and to indulge in various other risky behaviours such as smoking and drinking (Table 2). Multivariate logistic regression analysis confirmed that sexarche before the age of 17 was associated with tobacco and alcohol use (Table 4). Female respondents with sexarche before the age of 17 were significantly more likely to live with both parents, to have a poorer grade point average in the preceding school year, to feel insecure in school, and to be involved in other risky activities such as tobacco, alcohol and marijuana use (Table 3). Multivariate logistic regression analysis confirmed association of sexual initiation with living with both parents, feeling insecure in school, smoking and drinking (Table 5).

DISCUSSION

Findings and interpretation Of all the 15- and 16-year-old adolescents participating in this study, 10% reported having had sex. The proportion of boys was significantly greater (14% vs. 6%), as expected. This difference may be due to the false accommodation to normative gender roles, which is not uncommon18. Two main findings emerged from this study. First, regarding the socio-economic factors, only the association of living in an intact family and sexual


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Table 1 Characteristics of the study population.


Socio-economic determinants Living with both parents Objective SES (Wealth index) Poorest Poorer Middle class Richer Richest Subjective SES Lower Lower-middle Middle Upper-middle Upper Type of settlement Urban Rural Grade point average in the preceding school year Excellent Very good Good Enough School attachment I only had bad experience Feel bored Feel insecure Feel under pressure School is a nice place to stay My school friends accept me Social support (having someone to count on in every situation) Feel able to talk about private matters with parents Risk behaviours Smoking daily Drinking weekly Marijuana consumption in the past Drunkenness twice or more in the past Was involved in fights

Boys (n ⫽ 246)

Girls (n ⫽ 228)

213 (87%)

194 (85%)

42 54 45 65 40

(17%) (22%) (18%) (26%) (16%)

40 56 44 46 42

(17%) (25%) (19%) (20%) (18%)

27 58 120 36 4

(11%) (24%) (49%) (15%) (2%)

28 71 98 26 5

(12.3%) (31%) (43%) (11%) (2%)

142 (58%) 104 (42%)

124 (54%) 104 (46%)

45 86 88 11

(18%) (35%) (36%) (4%)

77 76 57 5

(34%) (33%) (25%) (2%)

15 58 16 91 151 216 224 229

(6%) (24%) (6%) (37%) (61%) (88%) (91%) (93%)

8 41 19 83 153 205 213 206

(3%) (18%) (8%) (36%) (67%) (90%) (93%) (90%)

11 20 5 36 24

(4%) (8%) (2%) (15%) (10%)

5 (2%) 5 (2%) 2 (1%) 15 (7%) 28(12%)

SES, socio-economic status.

initiation was observed; this finding was unexpected. Also a negative association of school attachment and sexual initiation was statistically significant for the girls. Second, other risky behaviours (like daily smoking and having been drunk twice or more in their lifetime for boys, and daily smoking and weekly drinking for girls) significantly increased the odds of also having had sexual initiation.

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Strengths and limitations of the study Strengths of the study were that all variables selected for analysis had previously been shown to be associated with early sexual initiation, validated instruments were used, and the objective socio-economic status was measured through the Demographic and Health Survey Wealth Index.


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Table 2 Boys: Factors significantly associated with reported sexual intercourse in univariate logistic regression.


Socio-economic determinants Living with both parents Objective SES (Wealth index) Poorest Poorer Middle class Richer Richest Subjective SES Lower Lower-middle Middle Upper-middle Upper Rural type of settlement Grade point average in the preceding school year Excellent Very good Good Enough School attachment I only had bad experience Feel bored Feel insecure Feel under pressure School is a nice place to stay My school friends accept me Social support (having someone to count on in every situation) Feel able to talk about private matters with parents Risk behaviours Smoking daily Drinking weekly Marijuana consumption in the past Drunkenness twice or more in the past Was involved in fights

Ever had sex (n ⫽ 35) 30 (86%)

Never had sex (n ⫽ 211) 183 (87%)

OR (95% CI)

p-value

1.089 (0.390–3.042)

0.870

38 47 38 55 33

(18%) (227%) (18%) (26%) (16%)

1.415 1.750 1.727 2.015

1 (0.385–5.196) (0.473–6.474) (0.504–5.916) (0.542–7.499)

0.862 0.601 0.402 0.384 0.296

3 (9%) 8 (23%) 22 (63%) 2 (6%) 0 14 (40%)

24 50 98 34 4 90

(11%) (24%) (47%) (16%) (2%) (43%)

1 1.280 (0.311–5.260) 1.796 (0.496–6.500) 0.471 (0.073–3.035) 0 0.896 (0.432–1.858)

0.450 0.732 0.372 0.428 0.999 0.769

3 12 12 5

(9%) (37%) (37%) (16%)

42 74 76 6

(21%) (37%) (38%) (3%)

1 2.270 (0.606–8.504) 2.21 (0.590–8.276) 11.667 (2.202–61.819)

0.029 0.224 0.239 0.004

4 11 1 15 20 32 33

(12%) (34%) (3%) (47%) (62%) (100%) (94%)

11 47 15 76 131 184 191

(6%) (24%) (8%) (39%) (66%) (93%) (94%)

4 7 7 10 7

(117%) (20%) (20%) (29%) (20%)

33 (94%)

7 9 2 16 2

196 (93%)

(20%) (26%) (6%) (46%) (6%)

4 11 3 20 22

(2%) (5%) (2%) (9%) (10%)

2.416 1.672 0.39 1.405 0.840 8.489 1.123

(0.719–8.112) (0.751–3.719) (0.050–3.070) (0.663–2.978) (0.387–1.822) (0.934–105.36) (0.242–5.206)

1.263 (0.276–5.778)

12.937 6.294 3.838 8.042 0.819

(3.560–47.014) (2.383–16.620) (0.618–23.856) (3.581–18.060) (0.379–1.770)

0.154 0.208 0.372 0.375 0.658 0.058 0.882 0.764

0.000 0.000 0.149 0.000 0.612

OR, odds ratio; CI, confidence interval; SES, socio-economic status.

The study also had some limitations. The data were taken from the National Health Survey which had a large sample and a high response rate from a large population, but the eventual number of adolescents with sexual initiation was rather small (14 girls and 35 boys), which limits the generalisation of the results. Further, the data were based on self-reported behaviour and are

thus susceptible to biases associated with recall and veracity. In addition, in view of the cross-sectional nature of the study, only associations between factors and reported behaviour were brought to light; a causal link between these was not proven. Finally, because this survey represents a secondary analysis of data, only a limited number of variables were available for exploration.


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Table 3 Girls: Factors significantly associated with reported sexual intercourse in univariate logistic regression.


Socio-economic determinants Living with both parents Objective SES (Wealth index) Poorest Poorer Middle class Richer Richest Subjective SES Lower Lower-middle Middle Upper-middle Upper Rural type of settlement Grade point average in the preceding school year Excellent Very good Good Enough School attachment I only had bad experience Feel bored Feel insecure Feel under pressure School is a nice place to stay My school friends accept me Social support (having someone to count on in every situation) Feel able to talk about private matters with parents Risk behaviours Smoking daily Drinking weekly Marijuana consumption in the past Drunkenness twice or more in the past Was involved in fights

Ever had sex (n ⫽ 14)

Never had sex (n ⫽ 214)

OR (95%CI)

p-value

7 (50%)

187 (88%)

7.192 (2.335–22.156)

0.001

(29%) (14%) (29%) (14%) (14%)

36 54 40 44 40

(17%) (25%) (19%) (21%) (19%)

0.333 0.900 0.409 0.450

1 (0.058–1.916) (0.210–3.865) (0.071–2.363) (0.078–2.605)

0.630 0.218 0.887 0.318 0.373

2 (14%) 4 (29%) 8 (52%) 0 0 6 (43%)

26 67 90 26 5 98

(12%) (31%) (42%) (12%) (2.3%) (46%)

0.778 1.154 0.434 2.316 0.888

1 (0.104–9.091) (0.211–11.814) (0–5.707) (0–32.028) (0.298–2.646)

1.000 1.000 1.000 0.528 1.000 0.831

0 5 (50%) 5 (50%) 0

77 71 52 5

(38%) (35%) (25%) (2%)

1 7.142 (0.953– ⫹ Inf) 9.691 (1.288– ⫹ Inf) 1 (0– ⫹ Inf)

0.056 0.025 –

8 37 16 79 147 195 200

(4%) (18%) (8%) (39%) (72%) (97%) (95%)

0.730 2.973 4.982 1.038 0.571

4 2 4 2 2

4 3 4 6 10 13

0 (40%) (30%) (40%) (60%) (100%) (93%)

12 (86%)

2 3 1 2 3

(14%) (21%) (7%) (14%) (21%)

194 (91%)

3 2 1 13 25

(1%) (1%) (0%) (16%) (12%)

(0.104– ⫹ Inf) (0.799–11.067) (1.174–21.148) (0.284–3.795) (0.155–2.101)

1.000 0.104 0.029 0.955 0.400

0.650 (0.077–5.474)

0.692

0.619 (0.129–2.962)

0.548

11.722 28.909 15.231 2.577 2.266

(1.786–76.927) (4.371–191.181) (0.901–257.587) (0.521–12.745) (0.677–7.578)

0.010 0.000 0.059 0.246 0.184

OR, odds ratio; CI, confidence interval; SES, socio-economic status; ⫹ Inf, the upper limit of the confidence interval tends towards infinity.

Differences in results in relation to other studies The link between socio-economic factors and health behaviour in adolescents is not well understood: European and US studies have led to divergent conclusions in this regard19,20. Some authors recommended extension of the study population beyond the adolescent period into young adulthood and entry into 216

the labour market21,22. Other contextual and cultural factors (e.g., media portrayal of sexuality) that may play important roles in the determination of the decision on sexual initiation in Serbian teenagers should be explored. Furthermore, the observation that living in an intact family and having good communication with parents increased the likelihood of having had one’s


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Table 4 Boys: Multivariate logistic regression model of factors associated with reported sexual intercourse. Variable Grade point average in the preceding school year Smoking daily Drinking weekly Drunkenness twice or more in the past

OR (95%CI)

p-value

1.671 (0.976–2.863) 6.241 (1.334–29.199) 2.286 (0.630–8.299) 4.278 (1.690–10.824)

0.061 0.020 0.209 0.002


OR, odds ratio; CI, confidence interval.

sexarche is opposed to findings of several western studies23–25. Ours – as just mentioned – are not in line with those of many other investigators; possibly good family relations in our study sample may have increased the self-confidence of adolescents, leading to their perception of being mature enough to initiate sexual relationships. Regardless of the integrity of the family, it could be assumed that all adolescents in Serbia experience a lack of parental control due to competing demands of life in a country in transition, which goes along with low income, the need to combine several jobs, anxiety and depression affecting the parents, and leaving the teenagers more often unsupervised. This problem should be the subject of further in-depth analyses. Attachment to school was well-documented in many previous studies as being associated with a lesser risk for a wide range of health risk behaviours in both developing and developed countries24,26–28, as it was in ours. Teenagers’ attachment to school may be an indicator of attachment to adult society and conventional institutions rather than to youth culture. Tobacco, alcohol and drug misuse was found to be an important predictor of early sexual initiation in

many studies. It was shown that – as they have similar psychological and social roots – health risk behaviours tend to cluster during adolescence. Madkour et al. observed a significant positive association between substance abuse and sexual initiation among boys and girls across five nations (Finland, France, Poland, Scotland, and the USA), although the associations were significantly stronger in European nations than in the USA, which was explained by differences in the cultural acceptability of adolescent alcohol and tobacco use, and by a variability in public health approaches to adolescent substance abuse between European nations26. Results from another Balkan transitional country, Croatia, were in line with our own: daily smoking and weekly drinking significantly raised the odds of having had an early sexual initiation for boys, while marijuana use and daily smoking were the strongest factors for girls29. Relevance of the findings: Implications for stakeholders Our results shed light on factors associated with sexual initiation, which is needed to identify adolescents at risk. First, the findings imply that some of the

Table 5 Girls: Multivariate logistic regression model of factors associated with reported sexual intercourse. Variable Living with both parents Grade point average in the preceding school year Feel insecure in school Smoking daily Drinking weekly Marijuana consumption ever

OR (95% CI) 11.847 1.609 13.187 24.249 8.971 7.495

(1.928–72.800) (0.611–4.240) (1.980–87.815) (1.659–354.329) (1.084–74.214) (0.028–2020.491)

p-value 0.008 0.336 0.008 0.020 0.042 0.481

OR, odds ratio; CI, confidence interval.


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conventional socio-economic indicators of reproductive health, such as socio-economic status and family structure may not be suitable for assessing adolescents in Serbia. However, the importance of school environment in the promotion of adolescent reproductive health was confirmed, implying that adolescent SRH promotion interventions should definitely include sex education in schools, and implementation by the latter of all measures required to optimally meet the needs of their teenage students. Secondly, the strong association of tobacco, alcohol and drug misuse with sexarche before the age of 17 indicates that adolescent preventive and promotional programmes and policies should have a broader and more comprehensive approach, addressing individual- as well as societal determinants of risk behaviour. Unanswered questions and future research Further in-depth qualitative research of individual and specific contextual predictors of risky behaviour of adolescents is needed to complete the complex picture of developing lifestyle patterns in Serbian adolescents. Measurement of the reproductive health status in the study sample would be useful to identify predictors of unfavourable reproductive health outcomes. Furthermore, marginalised groups of youths (e.g., street children, children in residential care, Roma children, homosexual adolescents) should be included in the research, because of their specific needs and increased vulnerability to coercion and violence.

CONCLUSION

Our findings have important implications for public healthcare provision. A strong association was found between sexual initiation and substance abuse among teenagers, indicating that health prevention and promotion programmes and interventions should comprehensively address the reductions of both substance abuse and early sexual initiation. Such an approach involving community, school, family and peers would contribute to the prevention of complex risk behaviours among Serbian adolescents. AC K N OW L E D G E M E N T S

The 2006 National Population Health Survey for the population of Serbia was carried out by the Ministry of Health of the Republic of Serbia with financial and professional support of the World Bank, the World Health Organization Regional Office for Europe (Country Office Serbia) and the Institute of Public Health of Serbia ‘Dr Milan Jovanovic Batut’. The authors would like to thank Lynne Katsikas for the linguistic editing of the manuscript. Source of funding: The Ministry of Education, Science and Technology of the Republic of Serbia (grant no.175087). Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and the writing of the paper.

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"Sexting" and its relation to sexual activity and sexual risk behavior in a national survey of adolescents.

Children and adolescents presenting to chiropractors in Norway: National Health Insurance data and a detailed survey.

Sexual abuse in a national survey of adult men and women: prevalence, characteristics, and risk factors.

Correlations between Poor Micronutrition in Family Members and Potential Risk Factors for Poor Diet in Children and Adolescents Using Korean National Health and Nutrition Examination Survey Data.

Associations between motor vehicle crashes and mental health problems: data from the National Survey of Adolescents-Replication.

Opioid abuse and depression in adolescents: Results from the National Survey on Drug Use and Health.

Active Commuting to School in Mexican Adolescents: Evidence From the Mexican National Nutrition and Health Survey.

Asthma outcomes in children and adolescents with multiple morbidities: Findings from the National Health Interview Survey.

Analysis of Epidemiology and Risk Factors of Atopic Dermatitis in Korean Children and Adolescents from the 2010 Korean National Health and Nutrition Examination Survey.

Risk factors and their relation to initiation of alcohol use among early adolescents.

Prevalence and associated factors of tinnitus: data from the Korean National Health and Nutrition Examination Survey 2009-2011.

Self-Assessed Health and Socioeconomic Inequalities in Serbia: Data from 2013 National Health Survey.

Addressing Stroke Risk Factors in Black and White Americans: Findings from the National Health and Nutrition Examination Survey, 2009-2010.

Food intake patterns and cardiovascular risk factors in Japanese adults: analyses from the 2012 National Health and nutrition survey, Japan.

Estimating the association between metabolic risk factors and marijuana use in U.S. adults using data from the continuous National Health and Nutrition Examination Survey.

Services for adolescents with psychiatric disorders: 12-month data from the National Comorbidity Survey-Adolescent.

Sexual risk behavior in young adulthood: broadening the scope beyond early sexual initiation.

Factors Associated with Early Smoking Initiation among Korean Adolescents.

Violence and illegal drug use among adolescents: evidence from the U.S. National Adolescent Student Health Survey.