Table 4.
Probabilities of transitioning between substance use profiles at ages 13–17 by race
| Black girls | No use: Age 14 | Alc use: Age 14 | Polydrug use: Age 14 | Forward Transitions | Backward Transitions |
|---|---|---|---|---|---|
| No Use: Age 13 | .82 | .16 | .02 | .18 | |
| Alc Use: Age 13 | .12 | .63 | .25 | .25 | .12 |
| Polydrug: Age 13 | .00 | .22 | .78 | .22 | |
| Age 15 | Age 15 | Age 15 | |||
| No Use: Age 14 | .79 | .19 | .02 | .21 | |
| Alc Use: Age 14 | .05 | .76 | .19 | .19 | .05 |
| Polydrug: Age 14 | .00 | .23 | .76 | .23 | |
| Age 16 | Age 16 | Age 16 | |||
| No Use: Age 15 | .90 | .10 | .00 | .10 | |
| Alc Use: Age 15 | .00 | .83 | .16 | .16 | .00 |
| Polydrug: Age 15 | .01 | .00 | .99 | .01 | |
| Age 17 | Age 17 | Age 17 | |||
| No Use: Age 16 | .82 | .18 | .00 | .18 | |
| Alc Use: Age 16 | .01 | .88 | .11 | .11 | .01 |
| Polydrug: Age 16 | .05 | .14 | .81 | .19 |
| White girls | No use: Age 14 | Alc use: Age 14 | Polydrug use: Age 14 | Forward Transitions | Backward Transitions |
|---|---|---|---|---|---|
| No Use: Age 13 | .79 | .13 | .08 | .21 | |
| Alc Use: Age 13 | .04 | .82 | .14 | .14 | .04 |
| Polydrug: Age 13 | .00 | .00 | 1.00 | .00 | |
| Age 15 | Age 15 | Age 15 | |||
| No Use: Age 14 | .86 | .09 | .04 | .13 | |
| Alc Use: Age 14 | .13 | .65 | .21 | .21 | .13 |
| Polydrug: Age 14 | .00 | .00 | 1.00 | .00 | |
| Age 16 | Age 16 | Age 16 | |||
| No Use: Age 15 | .80 | .14 | .06 | .20 | |
| Alc Use: Age 15 | .02 | .88 | .11 | .11 | .02 |
| Polydrug: Age 15 | .03 | .04 | .93 | .07 | |
| Age 17 | Age 17 | Age 17 | |||
| No Use: Age 16 | .75 | .19 | .06 | .25 | |
| Alc Use: Age 16 | .12 | .85 | .03 | .03 | .12 |
| Polydrug: Age 16 | .01 | .00 | .99 | .01 |
Notes: Black (n=611) and White (n=465) groups were analyzed separately. Invariance of item response probabilities across time was specified in the LTA model for each race.
Alc=alcohol. The “Poludrug use” class generally represents some combination (i.e., 2 or more) of alcohol, cigarettes, and marijuana use in the past year.
Bold font indicates membership in the same substance use profile at consecutive ages (e.g., ages 13 and 14); values representing stability (i.e., probability of staying in the same profile at consecutive ages) are on the diagonal. For example, among Black girls, the probability of staying in the “No use” profile at ages 13 and 14 is .82, and at ages 14 and 15 is .79; the probability of staying in the “Alcohol Use” profile at ages 13 and 14 is .63, and at ages 14 and 15 is .76.
“Forward transitions” refer to moving from a profile representing less substance involvement to a profile representing more substance involvement (e.g., transition from “no use” to “alcohol use”). Cells in the “Forward transitions” column represent the sum of the forward transition probabilities for a given row. As an example, for transitions between ages 13 and 14, forward transitions include moving from “no use” at age 13 to “alcohol use” at age 14 (transition probability=.16) and “polydrug use” classes (transition probability=.02) for a sum of .18 forward transitions for the “no use” class at age 13. In addition, the forward transition from “alcohol use” at age 13 to the “polydrug use” class at age 14 was estimated to be .25.
“Backward transitions” refer to moving from a profile representing greater substance involvement to a profile representing less substance involvement (e.g., transition from “alcohol use” to “no use”). Cells in the “Backward transitions” column represent the sum of the backward transition probabilities for a given row. As an example, for transitions between ages 13 and 14, backward transitions include moving from “alc use” at age 13 to “no use” at age 14 (transition probability=.12). In addition, the backward transition from “polydrug use” at age 13 to “alcohol use” class at age 14 was estimated to be .22 (the estimate for backward transition from age 13 “polydrug use” to “no use” at age 14 was 0).