Transitions to Sexual Intercourse and Substance Use Among South African High School Students

1
Transitions to Sexual Intercourse and Substance
Use Among South African High School
Students Lori-Ann Palen, Edward A. Smith Linda
L. Caldwell The Pennsylvania State
University Funded by NIH R01 DA01749, NIH T32
DA017629-01A1
DISCUSSION
RESULTS
METHOD

• Of sexual intercourse and substance use,
  substance use was typically the first risk
  behavior to be initiated.
• Youth were more likely to initiate new risk
  behaviors during the school year than during the
  summer months.
• There were no significant treatment group
  differences in engagement in, or transitions to,
  risk behavior.
• Details of Model-fitting
• The best-fitting models fit reasonably well
  G2boys(2031) 740, G2girls(2031) 497.
• The final measurement parameters showed that
  participants had a high probability of being
  classified into the correct treatment group
• (?boys .89, ?girls .89) and risk behavior
  condition (Pboys .91, Pgirls .96).
• The best-fitting models were the ones in which
• the proportion of participants in each risk
  behavior condition and probabilities of
  transition between these conditions were equal
  across treatment groups.
• the probabilities of transition were different by
  timing (over school year vs. over summer) but
  otherwise equal (T1?T2 T3?T4, T2?T3 T4?T5).

• These results suggest that researchers and
  practitioners should give greater attention to
  potential mechanisms driving the association
  between substances and the initiation of sexual
  behavior.
• We should also attempt to understand the social
  and environmental factors underlying
  school/summer differences in transitions to risk
  behavior in this population.
• While this study provided no evidence of
  treatment effects on risk behavior transitions,
  we believe recently-implemented program
  modifications may result in effects for future
  cohorts.

• PARTICIPANTS
• 2,416 students from Mitchells Plain, South
  Africa
• Participating in a research trial of a
  classroom-based leisure, life skill, and
  sexuality education program (42 program, 58
  control)
• Five assessments beginning and end of Grades 8
  and 9, beginning of Grade 10
• Baseline demographics mean age 14.0 years, 51
  female, 86 Coloured (derived from Asian,
  European and African ancestry)

• MEASURES
• Composite dichotomous substance use variable,
  indicating whether participants had used alcohol
  and/or marijuana in their lifetime
• Dichotomous variable indicating whether
  participants had engaged in vaginal sexual
  intercourse in their lifetime

Figure 1 Proportion of participants in each risk
behavior condition at Time 1.

• ANALYSIS
• Latent transition analysis (LTA Lanza, Flaherty,
  Collins, 2002) using WinLTA 3.1 software
  (Collins, Lanza, Schafer, Flaherty, 2002)
• Parameters estimated
• Measurement precision
• Proportion of participants in each risk behavior
  condition (no risk behavior, substance use only,
  sexual intercourse only, both risk behaviors)
• Probability of transition between conditions
• Probabilities of impossible transitions (e.g.,
  substance use ? no risk behavior) were fixed at
  zero.
• Chi-square difference tests were used to compare
  competing models of risk behavior.
• Preliminary analyses showed that the measurement
  parameters varied significantly by gender.
  Consequently, separate models were fit for boys
  and girls.

Figure 3 Proportion of participants in each risk
behavior condition at Time 5.
Figure 2 Probability of remaining in previous
risk behavior condition.