Study 1
D’Amico and colleagues (2018) conducted a randomized controlled trial of the motivational interviewing (MI) intervention, CHAT, at four primary care (PC) clinics from April 2013 to November 2015. Three of the clinics were in Pittsburgh, Pa., and one was in Los Angeles, Calif. Adolescents between ages 12 and 18 who entered any one of the four clinics for an appointment during the 2.5-year study period were asked to participate in the study by a member of the research team. Although survey materials were provided in English and Spanish and facilitators were bilingual, adolescents were required to speak English to be eligible for the study. Parental consent was required for participants under the age of 18. Eligible adolescents were then screened using the National Institute of Alcohol Abuse and Alcoholism Screening Guide (NIAAA-SG). Those who screened in as at-risk were randomized to either CHAT or enhanced usual care. Each adolescent was invited to complete four web surveys: at baseline, and at 3-, 6-, and 12-months post-baseline. The final follow-up was completed in January 2017. Adolescents who were randomized into CHAT met with a facilitator following completion of the baseline survey and participated in the 15- to 20-minute intervention in a private room without a parent present. Adolescents who were assigned to the enhanced care control group received an alcohol and other drugs (AOD) informational brochure developed by the research team.
The sample included 294 youths. The CHAT group (n = 153) was 59.6 percent female, with an average age of 16. In terms of race/ethnicity, 64.7 percent were Hispanic, 20.3 percent were Black, 12.4 percent were white, and 2.6 percent were multiethnic or other race/ethnicity. Of the adolescents in CHAT, 91.5 percent reported having ever used alcohol in their lifetime, and 82.4 percent reported marijuana use. The comparison or enhanced usual care (UC) group (n = 141) was 55.4 percent female, with an average age of 15.9. In terms of race/ethnicity, 68.1 percent were Hispanic, 12.8 percent were Black,10.6 percent were white, and 8.5 percent were multiethnic or other race/ethnicity. Of the adolescents in UC, 93.6 percent reported having ever used alcohol in their lifetime, and 82.3 percent reported marijuana use. Approximately 19.8 percent of the CHAT group met criteria for an alcohol use disorder, compared with 17.3 percent of the UC group. Additionally, 38.6 percent of the CHAT group met criteria for a cannabis use disorder, compared with 40.7 percent of the UC group. There were no statistically significant differences between the two groups at baseline.
Outcomes were defined as drinking, heavy drinking, marijuana use, negative alcohol consequences, negative marijuana consequences, perceived peer use (of alcohol and marijuana), time spent around peers who use (alcohol and marijuana), and resistance self-efficacy (alcohol and marijuana). Alcohol use, heavy alcohol use, and marijuana use were assessed by asking “During the past [time frame], how many times did you try or use [at least one full drink of alcohol] [drink more than 5 drinks] [marijuana]?” Negative consequences were measured by asking participants to rate how often they experienced a particular negative consequence in the past year or past 3 months on a scale of 0 (never) to 7 (20 or more times). There were six consequences for alcohol, including “doing something they regretted because of drinking” and four consequences for marijuana, including “had trouble concentrating because of marijuana use”. Peer influence was assessed by two items asking about perceived peer use (e.g., “How many in a group of 100 students drink alcohol/smoke marijuana?”) and two items that asked about the amount of time the participant spent around peers who use alcohol or marijuana, rated on a scale from 0 (never) to 3 (often). Resistance self-efficacy (RSE) for alcohol and marijuana was defined as the average of four items from 1 (I would definitely use) to 4 (I would definitely not use) based on different situations (e.g., “if my friend was using” or “if you were bored at a party”). RSE ranged from 1 to 4, with higher scores indicating greater RSE.
Intervention effects were measured using linear regression models with the outcome value at the follow-up periods as the dependent variable. The CHAT indicator was included as the primary independent variable while the outcome value was controlled for at the baseline. Standard covariates such as age, gender, mother’s education, and race/ethnicity were also controlled.
