Group-based Intervention for Alcohol, Drugs and Aggression Among Club Patrons
Phase: NA
Conditions: Drink Too Much, Drinking, Binge, Drunk, Drug Use, Aggression, Aggression Sexual, Peer Group, Safety Issues, Harm Reduction
Sponsor: Pacific Institute for Research and Evaluation

AA022331—NCT3652688 
 
 Updated 1-9-25  
 
 Study Protocol and Statistical Analyses for  
Group-based Intervention for Alcohol, Drugs and Aggression Among Club Patrons 
AA022331 
 
Principal Investigator:  
Brenda A. Miller, Ph.D.,Prevention Research Center, PIRE, Berkeley, CA  
Co-Investigators:  
Hilary Byrnes, Ph.D., Prevention Research Center, PIRE, Berkeley, CA  
Beth Bourdeau, Ph.D., Prevention Research Center, PIRE, Berkeley, CA  
Joel Grube, Ph.D., Prevention Research Center, PIRE, Berkeley, CA  
David Buller, Ph. D., Klein Buendel, Golden, CO.  
Project Coordinator:  
Veronica Rogers, B.S., Prevention Research Center, PIRE, Berkeley, CA  
 
 
I 
Background information  
Our prior research indicated that most (91.6%) of club patrons arrive in groups (Miller, et 
al., 2015). Considerable evidence indicates that peers can influence drinking and drug use 
(Dumas et al., 2014; O’Grady et al., 2011; Phua, 2011). The peer group can engage in 
preventive or protective behaviors for group members ( Boekeloo &Griffin, 2009; Boekeloo 
et al., 2009) and prior research indicates a willingness for club patrons to look out for each 
other when in the club environment (Byrnes et al., 2016).  
I 
II. Purpose of Study  
 

Our primary purpose was to engage groups of young adults who are planning an evening of 
partying at nightclubs and to determine whether the social group that arrived together 
would protect each other from harms related to drinking and drug use and partying. The 
intervention was designed to provide skills to identify early signs of alcohol/drug related 
problems as well as threats to personal safety from aggression. The intervention provided 
skills for individuals to intervene with each other to avoid unwanted outcomes like overuse 
of alcohol/drugs, experiences of aggression (physical/sexual). The primary outcome was to 
increase these protective actions within the group. Secondary outcomes included 
decreasing actual alcohol/drug use and experiences of aggression.  
III. Study Design  
a. Description of intervention  
Nightlife Safety Plans (NSP) was designed to be a brief, group-based intervention, delivered 
to nightclub patrons as they entered the club. NSP was designed to encourage group 
members to look out for each while partying at the club. The underlying premise was to use 
social influences in positive, nonjudgmental ways to encourage more protective behaviors 
within the group. Four major objectives were addressed in this brief intervention: 1) to 
assess the level and type of risks related to over use of alcohol/drugs, aggression (physical 
or sexual) and safety within the group; 2) to develop an ability to recognize early indicators 
of problems that were likely to escalate; 3) to deliver practical, simple actions within the 
group that would lower the likelihood of negative outcomes when group members detected 
risks; 4) to encourage a group consensus to initiate safety actions within the group. A risk 
algorithm based upon survey questions at entrance and calculated in real time, predicted 
group risk levels for overuse of alcohol/drugs, aggression (physical or sexual), and unsafe 
exit (driving impaired). Computer tablets were programmed to show the specific level of 
risk that their group was in danger of experiencing that night based upon the algorithms. 
Examples of early indicators of risk behaviors likely to lead to unwanted outcomes were 
provided to aid early detection of problems. Finally, actions that could be taken to de-
escalate the situation were demonstrated.  
The intervention was conveyed in visual pictures drawn by a graphic artist to convey the 
message with minimal reading required. Finally, each group was asked to discuss and form 
a consensus to the types of strategies that they were willing to implement if an early 
indicator was observed that might lead to an unwanted outcome for the group. There was 
total of 15 pages of interactive content programmed on the tablet and on average groups 
spent 5.5 minutes reviewing the content (SD=1 minute, 4 seconds).  
 

b. Description of the Control Condition  
The control condition consisted of information about fire safety at nightclubs. Examples of 
fires that had occurred in nightclubs were provided. Patrons were encouraged to identify 
exit locations in the club and to agree, a priori, meeting locations outside the club should 
they become separated in an emergency. A discussion after reviewing the fire safety 
materials was part of the control condition to mirror the group discussion of the 
experimental condition.  
 
c. Selection and Exclusion of Subjects & Randomization procedures 
There are two levels of randomization in this study. First, participants were randomly 
approached on the sidewalk. Social groups arriving at the club together were randomly 
approached using the portal recruitment methodology (Johnson et al., 2012; Miller et al., 
2009, 2013b). The first person to cross an imaginary line on the sidewalk in front of the club 
was approached to recruit this person and their social group. Nightclubs with at least 200 
patrons on a typical weekend night were contacted to seek permission to establish a data 
collection site outside the club. Clubs held different types of events on different nights, 
attracting different patrons, depending upon the event being featured. A total of 41 events 
across 7 nightclubs in the San Francisco area were selected for the data collection from 
June 2016 through October 2017. These events occurred on Friday and Saturday evenings 
when the attendance was the greatest. Patrons who were attending the club that evening 
and were arriving with at least one other person who agreed to participate were considered 
eligible. Anyone working that evening at the club was not eligible. A total of 352 groups, 
representing 959 patrons were included in the study. The study was able to recruit 25% of 
the groups that were stopped and given a description of the study and data collection 
procedures which included breath tests for estimates of blood alcohol levels and oral fluid 
samples for detecting drug use and surveys at entrance and exit. Retention for the sample 
was 88% at exit. Recruitment and data collection occurred outdoors with a data collection 
site adjacent to the entrance to the club. Participants provided informed consent, and all 
study procedures were approved by the Pacific Institute for Research Evaluation’s 
Institutional Review Board.  
 
d. Survey  and Randomization Procedures  
 

Once patrons agreed to participate in the study, each participant was given a unique 
number on a wrist band that allowed matching of individuals within a group and 
entrance/exit data. No names were collected to provide anonymity.  
Computer tablets were handed to each participant to complete the entrance survey. Oral 
fluid samples for drug analyses and breath tests for determining blood alcohol level were 
collected during this time by trained research staff. Groups were randomly assigned to 
either experimental or control after the data for the entire group was collected at baseline. 
At this point, the research assistant was made aware of the random assignment to either 
experimental or control condition for the group. Randomization was determined by a 
randoms number table that determine whether the first group was experimental or control. 
Given that multiple groups were recruited simultaneously, the supervisor was tracking the 
assignments of condition and alerting the research assistants as to this assignment. The 
experimental condition consisted of the Nightlife Safety Plans (NSP) intervention described 
above. The control condition was given the Fire safety information described above. Given 
that both the experimental and control group conditions focused on safety in the club, we 
did not disclose to the participants which safety intervention was under investigation in this 
study. Once the group finished, they were given an incentive ($15) and reminded that we 
would complete a survey when they exited the club with an additional incentive ($25) 
offered. As patrons exited the club, they were surveyed again, using the same procedures 
established at entrance.  
e.  Measures 
Primary Outcomes:  
Number of Protective actions to keep the Group Safe: For each individual, five types of 
actions were assessed related to identifying a potential problem (observing overuse, 
physical, or sexual aggression) for a friend: There were 5 possible actions to keep their 
group members safe that were assessed at exit from club (checked in with friends to 
assess safety during evening, monitored group members alcohol consumption, 
encouraged pacing drinking, discouraged drug use, encouraged steps to sober up).  
Protective action reported for physical aggression incident: Among those who experienced 
physical aggression, the prevalence of a group member taking action(s) to intervene was 
reported.  
Protective action reported for sexual aggression incident: Among those who experienced 
sexual aggression, the prevalence of a group member taking action(s) to intervene was 
reported.  
Secondary outcomes  

Legally intoxicated: Breathalyzer readings were recorded and all participants who were at a 
reading of .08 % alcohol or higher, were considered to be legally intoxicated. 
Prevalence of recreational drug use: Oral fluid samples were sent to an outside laboratory 
for analyses.  Substances were assayed into the following seven categories (1) 
tetrahydrocannabinol (THC); (2) cocaine-including benzoylecgonine, cocaethylene, 
norcocaine; (3) amphetamine/3,4-methylenedioxy-methamphetamine(MDMA), including 
methamphetamine, methylenedioxyamphetamine (MDA), and 
methylenedioxyethylamphetamine(MDEA); (4) opiates/analgesics, including morphine, 
codeine, oxymorphone,6 a.m., hydrocodone, hydromorphone, and oxycodone; (5). 
methadone; (6). phencyclidine (PCP); and (7). ketamine. Any drug use was considered 
positive for drug use. 
Leaving club with Friends arrived with: At exit, participants were asked if they were leaving 
the club with the same group of friends with whom they arrived. 
Other Pre-Specified outcomes 
Experienced sexual aggression: While at the club, the respondent was asked if someone 
touching them sexually in a way that they did not want to be touched or did something else 
sexual to the respondent that they did not want them to do 
Experienced physical aggression:  While at the club, respondent was asked if someone 
intentionally pushed, shoved, or punched 
Experienced sexual harassment: While at the club, respondent was asked if sexually came 
on to them after indicating no interest 
f. Sample characteristics  
The average age of participants was 28 years and 43% were female. A fifth of the sample 
identified as Hispanic or Latino and racial characteristics were as follows:  44% white, 21% 
Asian, 18% unknown or not reported, 8% Black, 7% more than one race, 2% Native 
Hawaiian or other Pacific Islander, 1% American Indian or Alaska Native.   
g. Analyses  
Number of Protective actions to keep the Group Safe: These items were summed to create 
an index of protective actions for each individual. Then an average score was created within 
the group based upon the scores of each group member divided by the number of 
individuals in the group. This provided an overall indicator of how safe the group was 
because of the collective action of the members.  

Protective action reported for physical aggression incident: Among those who experienced 
physical aggression, the percent who reported some protective action by a member of their 
group was reported.    
Protective action reported for sexual aggression incident:  Among those who experienced 
sexual aggression, the percent who reported some protective action by a member of their 
group was reported. 
Legally intoxicated: Percent who were legally intoxicated (BAC.08% or higher). Breath 
samples provided an estimate of the blood alcohol concentration (BAC) and the MarkV 
Alcovisor (PAS Systems International, Fredericksburg VA) was used to obtain the breath 
samples. The estimate of the BAC is presented as measured by this device. Given the short 
window of time (average of 1 hour 54 minutes, SD=1 hour, 3 minutes) that persons were in 
the club, only exit BAC is used to reflect drinking and this represents a cumulative total for 
the evening. Level of intoxication reported which reflects the legal standard of BAC= 0.08% 
or higher.  
Prevalence of recreational drug use: Any use of recreational drugs present in oral fluid tests 
based upon lab results. Laboratory analyses were conducted using the Quantisal 
collection device (Immunalysis Corporation, Pomona, CA) to assess the following drug 
categories: (a)Tetrahydrocannabinol (THC); (b) cocaine, including benzoylecogonine, 
coaethylene, and norcocaine; (c) amphetamine/e, 4 methylenedioxy-methamphetamine 
(MDMA), methamphetamine, methylenedioxy-amphetiamen (MDA), and 
methylenedioxyethylamphetamine (MDEA); (d) opiates/analgesics, including morphine, 
codeine, oxymorphone, 6-acetylmorphine, hydrocodone, hydropmophone, and 
oxycodone; (3) methadone; (f) phycyclidine (PCP), and (g) ketamine. Self-report of GHB 
was also assessed (no lab tests were available for this drug). The prevalence of any drug 
use at exit from the club was created.  
Physical Aggression experienced: Participants were asked at the exit survey whether 
anyone had intentionally pushed, shoved, or punched you while at the club during the 
evening.  
Sexual aggression experienced: Participants were asked at the exit survey whether anyone 
had touched you in a sexual way that you did not want or do something else sexual to you 
that you didn’t want them to do.  
Leaving club with friends arrived with: The prevalence of the safety action to leave the club 
with the same friends with whom they arrived.  
Females comprised 45.3% of the sample. Ethnicity/race was as follows: 44.2% White, 
21.5% Asian, 7.9% African American, 1.7% Pacific Islander, 1.3% Native American, 7.1% 

multiracial, 6.8% other, and 9.5% unknown. Slightly more than a fifth (21.1%) were 
Hispanic. The average age was 27.99 years (SD=6.35). The average group size was 3.38 
persons (SD1.43).  
Descriptive analyses were conducted for the overall group and for the experimental and 
control groups. To account for the clustering within event and group, mixed-model 
regressions in SPSS were used to test simple effects of the intervention on continuous 
background variables. Parallel models were conducted for categorical background 
variables using Mplus Version 7 (Muthen & Muthen, 1998-2015).For key outcomes, 
multilevel models via mixed-model regressions in SPSS 21 were conducted to account for 
nesting by event and group. Analyses used an intent-to-treat approach to examine 
assignment to the intervention as a predictor, controlling for background variables, history 
of drinking/other drug use and risk level. Listwise deletion was used for missing cases.  
I 
IV. Assessment of Efficacy-Overview  
 
Exposure to the intervention, NSP, significantly increased the number of safety actions 
taken within the group to protect others in their group from the unintended consequences 
from behaviors and experiences in the club that evening related to alcohol use and drug 
use (Byrnes, Miller, et al., 2019a). The study found that group cohesion related to fewer 
safety strategies being used and that group cohesion was unrelated to AOD use (Byrnes, 
Miller, et al., 2019b). This suggests that more risk taking behavior may occur when groups 
are familiar and comfortable with each other, possibly lowering their sense of risks. The 
relatively low rates of experiencing physical and sexual aggression impacted the power of 
the intervention to assess protective actions related to physical or sexual incidents that 
occurred in the evening. Although the main focus of the intervention was on taking actions 
to reduce harms, there was also an impact on a secondary outcome related to alcohol use. 
For participants exposed to NSP, there was a significantly lower BAC at exit. Prevalence of 
recreational drug use was not impacted by the intervention but prior research (Miller et al., 
2013b) indicates that few club patrons (<6%) convert from no drug use at entry to drug use 
at exit, indicating that recreational drug use has already been initiated prior to coming to 
the club. The intervention did not significantly alter the rates of physical or sexual 
aggression while at the club. However, aggression experiences are less under the control of 
the participants as persons outside the group can be the offender in these incidents. Thus, 
the group can respond and de-escalate the impact of the aggression but may not be 
effective at keeping aggressive incidents from happening. Finally, participants exposed to 
the intervention were significantly more likely to leave as a group and “stick together.” Given 
that the intervention was focused on promoting looking after each other for the evening, 

this was an important safety impact. There are anecdotal reports of individuals leaving the 
club with someone they just met or being assaulted while traveling home by themselves. 
However, data on the prevalence of this type of experience is not available from prior 
studies or this study. 
Interpretation of the findings need to take into consideration that NSP was designed to 
impact the participants for the single evening at a club. It is unknown whether providing this 
type of brief intervention in real world settings could facilitate a more widespread adoption 
of these basic strategies as part of club safety behaviors adopted by patrons. It is unknown 
how the single exposure to the intervention might impact subsequent trips to a nightclub. It 
is unknown whether a single individual exposed to the intervention might practice any of 
the skills in other social groups in future evenings at a nightclub. The study has limitations 
introduced by only being conducted in one geographic location but the results are made 
more robust by the diversity of race/ethnicities, genders, gender identities, and ages 
represented in this sample.  
I 
V. Assessment of Safety (Adverse events, ethics)  
 
There were no serious adverse events or adverse events connected to the intervention.  
I 
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