Design
The current study used data from the Tracking Opportunities and Problems in Childhood and Adolescence (TOPP) study, a community-based longitudinal study of Norwegian children (22, 23). In 1993, Norwegian mothers were recruited to participate when bringing the index child to a routine 18-month vaccination at a municipal child health center. In the first stage, 913 of 1,081 invited families participated (response rate 84%). The 19 health care areas included in the TOPP study were representative of the overall diversity of communities in Norway; 28% of the families lived in large cities, 55% in small towns, and 17% in rural areas) (23).
The study was approved by The Data Inspectorate and the Regional Committee for Medical Research Ethics (#S-04167). Study participants did not give written or oral informed consent, as that was not a requirement at the time of data collection. This is a requirement today, and the Regional Committee for Medical Research Ethnics in Norway have approved the study without informed consent (#S-04167/#2013/2052), due to respondents being given written information before and after each data collection about 1) Current and future research findings and topics; 2) The confidentiality of the participants; 3) The possibility to skip questions, and 4) The right to withdraw from the study at any point. All analyses for the current paper used anonymous cross-sectional data from the final wave (T8) in late adolescence/young adulthood (ages 18-20).
The sample
The current study included young women aged 18-20 (n = 295) participating in 2011, when the TOPP questionnaires involved sexual history and sexual risk behaviors. Of the participants, 216 of the 295 (73.2%) reported to have had heterosexual vaginal intercourse. Two cases were removed from the sample due to inconsistent or missing responses, leading to a sample of 214 young women.
Attrition
Data from the health clinics showed that non-responding mothers did not differ from responding mothers in maternal age, education, employment status, or marital status when joining the study (23). Multiple logistic analyses of adolescent participation showed that female gender and high maternal education predicted young adult participation in 2011 (24). Variables such as maternal age, living with the father, maternal work status, and the family’s financial situation did not predict young adult participation at 2011. The associations between variables at baseline compared to the last waves of the study did not differ among drop-out versus remaining families, suggesting that estimated associations between variables are generalizable (25).
Measurement
Experience and frequency of emergency contraception use was measured with the question “Have you ever used emergency contraception?” with the response alternatives “Have not used” (0) and “Have used” (1), and the follow-up question: “If so, how many times?” The response was used either as a continuous variable or categorized as: “Never used” (0), “Used once” (1), and “Used two or more times” (2) (19) .
Use of regular contraception in the past year was measured by one question: “During the past 12 months, which type(s) of contraception have you/your partner used?” with the possibility to tick one or several response alternatives: “No contraception,” “Condom,” “Oral contraceptives/contraceptive injection,” “Other types,” and “I don’t know.” Responses of “Other types” and “I don’t know” were excluded from further analysis. A new categorical variable was constructed: “Consistency of regular contraceptive use the past year,” with three possible responses: “No use” (0), “Inconsistent use” (1) (ticked both No contraception and one or more of the methods of regular contraception), and “Consistent use” (2) (ticked of any kind of contraceptive method and did not tick No contraception).
Use of contraception during last intercourse was measured by the question: “At last intercourse, which type(s) of contraception did you/your partner use?” with the same response alternatives as the question about the past year. A categorical variable of contraceptive use at last intercourse was computed as “Non-use” (0) or “Use” (1).
Participants were also asked if they had ever had unprotected intercourse/sex without condoms or any other contraceptives while drunk (“Never” (0) “Once” (1), or “Two or more times” (2)).
Sexual history included self-reports about intercourse debut age, total number of sexual partners, number of sexual partners the past year, abortion, and sexually transmitted infections (STIs). The question of STIs was formulated as follows: “Have you ever received treatment for a sexually transmitted infection (venereal disease) such as chlamydia, herpes, genital warts or similar?”
Risk behaviors.
Externalizing behavior was measured with the TOPP Scale on Antisocial Behavior (TSAB; 24). The TSAB consists of 13 items mapping domains of externalizing behavior, partly based on the model by Loeber et al. (26), and items from other Scandinavian scales (27-29). Items covered actions one had done or participated in during the past year (e.g., shirked school or work, been in a fight, taken money from someone in one’s family without permission, stolen, or tried marihuana). Responses were rated on a 5-point Likert scale from “Not done it” (0) to “Done it more than 10 times” (4). Cronbach’s alpha for TSAB in this study was 0.68. A high mean score indicated more externalizing (antisocial) behavior the past year.
Alcohol use was measured by the Alcohol Use Disorder Identification Test (AUDIT; 30), in order to identify excessive drinking and risky consumption (31). The use of AUDIT in the adolescent population aged 14 to 18 is supported by research (32). Items were rated on Likert scales in which higher response categories equaled drinking in higher frequencies and more units. In the current study, only the total sum of scores was calculated, and a high mean score indicated more or less hazardous alcohol use. The internal consistency in this study was a =.79.
Sociodemographic factors.
Educational attainment was measured by asking if participants attended or had finished any education program, such as “General studies at high school,” “Vocational high school,” “One to two years of higher education,” “Three years at college or university,” or “Four or more years at university college or university.”
Nine possible living arrangements were re-categorized into three possible responses: “Live with mother and father” (1), “Live with one parent/move between parents” (2), and “Live alone or with other than parents” (3).
Maternal education (maternal reports) was categorized as “High school or less” (0) and “Higher education” (1).
Family economy (maternal reports). The four response alternatives were “We manage very poorly,” “We manage poorly,” “We manage,” “We are well off.” These were re- categorized as “Poor or OK” (0) and “Good” (1).
Statistical analysis
Descriptive statistics using cross-tabulation with chi-square test, and correlations (Pearson's r) between study variables were obtained. Effect size criteria used for correlations were as follows: between 0.10 and 0.30, small; 0.30-0.50, medium; >0.50, large (33). A series of two-way between-groups analyses of variance (ANOVA) were carried out to examine the difference between groups within regular contraception users and emergency contraception users.