Participants

We recruited young adults ages 21–25 to an alcohol technology study using social media, other web ads and flyer postings. Inclusion criteria were self-report of 4 or more heavy drinking days (4 or more drinks for women, 5 or more for men), 1 or more days with an eBAC of 0.10% or higher, and 10 or more days with 1 or more alcoholic drinks in the past 30 days. Exclusion criteria were treatment-seeking or past-12-month substance misuse treatment; urine positive for illegal drugs except THC; current DSM-IV substance dependence except alcohol; history of medically-assisted detoxification or current withdrawal; 2 breath alcohol (BrAC) readings >0.00% at the outset of appointments; a medical issue contraindicating alcohol use; body mass index <18.5 or >35; pregnancy, lactation or birth control refusal in women; a recent prescription for or current psychotropic drug use; psychosis/severe psychiatric conditions; disliking beer; or past-12-month moderate drinking app use. The study was approved by the institutional review board. Data collection occurred between February 2017-April 2020.

The sample was divided about evenly between men and women. Regarding race and ethnicity, the sample was 63.6% white, non-Hispanic/Latino/a, 20.2% Hispanic/Latino/a, 8.1% Asian, 3% Black/African-American, 2% other or mixed race and 3% did not report. A slight majority (51.5%) were not currently students. On average, participants drank on more than half of the days in the month, reported heavy drinking about 1 out of every 3 days, nearly 6 drinks per drinking day, a mean eBAC almost twice the legal limit and peak eBAC almost 4 times the legal limit. There were no differences in demographics or baseline drinking across study technology conditions (Table 2).

Sample Characteristics by Study Technology Condition and Overall

Notes. A-A= African-American, eBAC = estimated blood alcohol concentration, heavy drinking day = 5 or more for men, 4 or more for women. There were no statistically significant differences across study technology condition for any of these variables.