research paper-College student substance abuse

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Addictive Behaviors

journal homepage: www.elsevier.com/locate/addictbeh

Personality, marijuana norms, and marijuana outcomes among college students

Matthew R. Pearsona,⁎, John T.P. Hustadb, Clayton Neighborsc, Bradley T. Connerd, Adrian J. Bravoa, Marijuana Outcomes Study Team1

a Center on Alcoholism, Substance Abuse, and Addictions, University of New Mexico, United States b College of Medicine, Pennsylvania State University, United States c University of Houston, United States d Colorado State University, United States

H I G H L I G H T S

• We examined impulsivity, sensation seeking, hopelessness, and anxiety sensitivity. • We examined marijuana descriptive norms, injunctive norms, and internalized norms. • Marijuana norms fully/partially mediated personality-marijuana outcome associations. • Internalized norms mediated the effects of impulsivity and sensation seeking. • Normative beliefs could be targeted as part of personality-tailored interventions.

A R T I C L E I N F O

Keywords: Personality Descriptive norms Injunctive norms Internalization of college marijuana use culture Marijuana use Marijuana consequences Impulsivity Sensation seeking

A B S T R A C T

Based on the high prevalence of marijuana use among college students, we examined distal and proximal antecedents to marijuana-related outcomes in this population. Specifically, we examined three marijuana-related perceptions (descriptive norms, injunctive norms, and internalization of college marijuana use culture) as po- tential mediators of the associations between four personality traits (impulsivity, sensation seeking, hope- lessness, and anxiety sensitivity) and marijuana-related outcomes (marijuana use, negative marijuana-related consequences). In a large sample of college student marijuana users (n = 2129), our path analysis revealed marijuana-related perceptions to significantly mediate the associations between personality and marijuana-re- lated outcomes. Specifically, internalization of college marijuana use culture mediated the effects of both im- pulsivity and sensation seeking on marijuana-related outcomes. Not only do our findings suggest the importance of distinct types of marijuana-related norms in predicting marijuana involvement, but also the possibility that such normative beliefs could be targeted as part of personality-tailored interventions.

1. Introduction

Marijuana use and risk for cannabis use disorder peaks around the college years (Center for Behavioral Health Statistics and Quality, 2015). In fact, approximately 30% of college students report past year use of cannabis (Johnston, O'Malley, Miech, Bachman, & Schulenberg,

2015), which is a much higher frequency than the general population (10%, Hasin et al., 2015). College students are also at a significantly higher risk for cannabis use initiation compared to same-aged in- dividuals not enrolled in college (Miech, Patrick, O'Malley, & Johnston, 2017). Consequently, it is important to identify risk factors that are associated with negative marijuana-related consequences in the college

http://dx.doi.org/10.1016/j.addbeh.2017.08.012 Received 14 April 2017; Received in revised form 21 July 2017; Accepted 16 August 2017

⁎ Corresponding author at: Center on Alcoholism, Substance Abuse, & Addictions, University of New Mexico, 2650 Yale Blvd SE MSC 11-6280, Albuquerque, NM 87106, United States.

1 This project was completed by the Marijuana Outcomes Study Team (MOST), which includes the following investigators (in alphabetical order): Amber M. Anthenien, University of Houston; Adrian J. Bravo, University of New Mexico; Bradley T. Conner, Colorado State University; Christopher J. Correia, Auburn University; Robert D. Dvorak, University of Central Florida; Gregory A. Egerton, University at Buffalo; John T. P. Hustad, Pennsylvania State University College of Medicine; Tatyana Kholodkov, University of Wyoming; Kevin M. King, University of Washington; Bruce S. Liese, University of Kansas; Bryan G. Messina, Auburn University; James G. Murphy, The University of Memphis; Clayton Neighbors, University of Houston; Xuan-Thanh Nguyen, University of California, Los Angeles; Jamie E. Parnes, Colorado State University; Matthew R. Pearson, University of New Mexico; Eric R. Pedersen, RAND; Mark A. Prince, Colorado State University; Sharon A. Radomski, University at Buffalo; Lara A. Ray, University of California, Los Angeles; Jennifer P. Read, University at Buffalo.

E-mail address: [email protected] (M.R. Pearson).

Addictive Behaviors 76 (2018) 291–297

Available online 31 August 2017 0306-4603/ © 2017 Elsevier Ltd. All rights reserved.

MARK

student population, including personality variables, marijuana-related perceptions, and marijuana use.

1.1. Personality traits

Personality traits are often theorized as distal antecedents to beha- vior (e.g., marijuana use and marijuana-related negative consequences) according to the Acquired Preparedness Model (Smith & Anderson, 2001), Theory of Planned Behavior (Ajzen, 2011), and the Health Belief Model (Rosenstock, 1974) because they can influence individual beliefs or perceptions. A wide range of personality traits have been examined as putative antecedents to substance use outcomes including the Big Five personality traits (Terracciano, Löckenhoff, Crum, Bienvenu, & Costa, 2008) and specific facets of impulsivity (Cyders & Smith, 2008; Whiteside & Lynam, 2001). More specifically, marijuana use has been associated with impulsivity, sensation-seeking/ high openness to experience, depression, and anxiety sensitivity, among others (Bonn-Miller, Zvolensky, & Bernstein, 2007; Feldstein Ewing, Filbey, Loughran, Chassin, & Piquero, 2015; Flory, Lynam, Milich, Leukefeld, & Clayton, 2002; Fu et al., 2002). In the present study, we focus on four traits: a) impulsivity (reacting to internal/external influ- ences without considering possible negative outcomes), b) sensation seeking (pursuing exciting/pleasurable activities), c) hopelessness (de- pressed affect), and d) anxiety sensitivity (fearing bodily sensations associated with arousal). Not only has each of these traits been shown to be associated with increased risk for substance use and/or associated problems (Hustad, Pearson, Neighbors, & Borsari, 2014; Pearson & Hustad, 2014; Woicik, Stewart, Pihl, & Conrod, 2009), but also they form the basis of multiple successful personality-targeted substance use interventions (e.g., Conrod, Castellanos-Ryan, & Mackie, 2011). To further inform the development of successful personality- targeted interventions, it is important to determine the factors that mediate the effects of personality traits on substance use outcomes. These mediators provide potential treatment targets specific to in- dividuals who endorse one or more traits associated with marijuana use.

1.2. Marijuana-related norms

Marijuana-related perceptions can be viewed as proximal ante- cedents (i.e., putative mediators of the associations between personality and marijuana-related outcomes) by extending Cox and Klinger's (1988) motivational model of alcohol to marijuana use. As predicted by the Theory of Planned Behavior (Ajzen, 2011) and the Health Belief Model (Rosenstock, 1974), distal personality variables are expected to influence actual behavior through proximal antecedents like descriptive and injunctive norms. Descriptive norms reflect the perceived pre- valence, quantity, and/or frequency of substance use by others whereas injunctive norms reflect the extent to which one believes that others approve/disapprove of one's substance use (Cialdini, Kallgren, & Reno, 1991). Descriptive and injunctive norms both predict substance use more broadly (Borsari & Carey, 2003; Neighbors, Lee, Lewis, Fossos, & Larimer, 2007) and marijuana use specifically (Neighbors, Geisner, & Lee, 2008).

There is growing evidence suggesting that norms-based interven- tions are missing a key type of normative beliefs: internalization of college marijuana use culture. Osberg et al. (2010) introduced a con- struct of alcohol perceptions about the role of drinking in the college experience, or internalization of college drinking culture, as assessed by the College Life Alcohol Salience Scale (CLASS). These perceptions re- garding the relative importance of drinking in college appear to be correlated with personal alcohol use and negative consequences cross- sectionally (Osberg et al., 2010; Osberg, Insana, Eggert, & Billingsley, 2011) and prospectively (Moser, Pearson, Hustad, & Borsari, 2014; Osberg, Billingsley, Eggert, & Insana, 2012). Collectively, these findings suggest that this construct holds promise as a potential intervention

target in alcohol use research. Recently, a measure of internalization of college marijuana use culture was developed that demonstrated con- vergent validity with its associations with multiple marijuana-related outcomes (Pearson, Kholodkov, Gray, & Marijuana Outcomes Study Team, 2017).

1.3. Norms as mediators

Two studies most relevant to the present study examined alcohol- related perceptions (alcohol descriptive norms, alcohol injunctive norms, and internalization of college drinking culture) as possible mediators of the effects of personality on alcohol-related outcomes. Specifically, Hustad et al. (2014) found that internalization of college drinking culture was the most robust predictor of alcohol-related out- comes and the most robust mediator of the effects of personality (i.e., impulsivity, sensation seeking, anxiety sensitivity, and hopelessness) on alcohol use outcomes in a sample of incoming freshmen. Pearson and Hustad (2014) largely replicated these findings in a sample of mandated college students. Taken together, it appears that substance perceptions may in part explain how personality traits exert an effect on substance use outcomes.

1.4. Purpose of present study

The present study aimed to evaluate whether marijuana-related norms mediate the influence of personality traits on marijuana use and negative marijuana-related consequences. Specifically, we examined how four personality traits (impulsivity, sensation seeking, anxiety sensitivity, and hopelessness) related to three marijuana-related norms variables (descriptive norms, injunctive norms, and internalization of college marijuana use culture) and in turn marijuana-related outcomes (typical frequency of marijuana use and negative consequences from marijuana use) in a manner consistent with previous studies (Hustad et al., 2014; Pearson & Hustad, 2014). Consistent with these previous studies on internalization of college drinking culture, we hypothesized that a measure of internalization of college marijuana use culture will mediate the effects of sensation seeking and impulsivity on marijuana use outcomes. In addition, we hypothesized that internalization of college marijuana use culture will have a direct relationship on mar- ijuana use frequency and marijuana-related negative outcomes after controlling for other variables (e.g., descriptive norms and injunctive norms).

2. Method

2.1. Participants and procedures

We recruited 8141 college students from Psychology Department Participant Pools at 11 different participating universities in 11 dif- ferent states in the United States between fall 2015 and spring 2016 (for additional information, see Pearson, Liese, Dvorak, & Marijuana Outcomes Study Team, 2017). Participants provided informed consent prior to completing the survey online, and were provided with research participation credit as an incentive. Our analytic sample included 2129 college students who reported using marijuana in the past 30 days. The majority of the analytic sample was White, non-Hispanic (60.4%) or of Hispanic/Latino ethnicity (18.3%) were women (59.2%), and reported a mean age of 19.95 (SD = 3.66) years. This study was approved by the IRB at each participating institution.

2.2. Measures

2.2.1. Marijuana consequences Marijuana consequences in the past month were assessed using the

50-item Marijuana Consequences Questionnaire (MACQ; Simons, Dvorak, Merrill, & Read, 2012). All items (0 = no, 1 = yes) were

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summed to create a total score.

2.2.2. Marijuana use Among past month marijuana users, marijuana use frequency was

determined using a modified measure based on the Daily Drinking Questionnaire (DDQ; Collins, Parks, & Marlatt, 1985). Specifically, each day of the week was broken down into 6 4-hour blocks of time (12a-4a, 4a-8a, 8a-12p, etc.), and participants were asked to report at which times they used marijuana during a “typical week” in the past 30 days. We created a typical marijuana use frequency estimate by summing the total number of time blocks for which they reported using during the typical use week (range: 0–42).

2.2.3. Marijuana descriptive norms Marijuana descriptive norms were assessed using the same mar-

ijuana use frequency measure to assess one's own marijuana use (see above); however, each participant reported his/her perception of the typical marijuana use for the “typical college student” for each day of the week and block of time (12a-4a, 4a-8a, 8a-12p, etc.). We used the descriptive norms during a typical use week by summing the appro- priate time blocks (range: 0–42).

2.2.4. Marijuana injunctive norms Marijuana injunctive norms were operationalized by averaging 3

items probing perceived approval (ranging from “strong disapproval” to “strong approval”) of one's “best friends” for three behaviors (“using marijuana,” “using marijuana daily,” and “using marijuana to get high”).

2.2.5. Internalization of college marijuana use culture The Perceived Importance of Marijuana to the College Experience

(PIMCES; Pearson, Kholodkov, et al., 2017) is an 8-item measure de- veloped to assess the degree to which marijuana is perceived to be an integral part of the college experience. Based on the 15-item CLASS measure (Osberg et al., 2010), 13 of the original items were relevant to marijuana use (e.g., “Parties or social gatherings with marijuana are an integral part of college life” and “To get high on marijuana is a college rite of passage”). Factor analyses were used to settle on a final subset of 8 items using a 5-point response scale (1 = strongly disagree, 5 = strongly agree).

2.2.6. Personality The Substance Use Risk Profile Scale (SURPS; Woicik et al., 2009) is

a 23-item measure with a 4-point response scale (1 = strongly disagree, 4 = strongly agree) that assesses four personality traits that are asso- ciated with substance use: hopelessness, impulsivity, anxiety sensi- tivity, and sensation seeking.

2.3. Data analysis plan

Path analysis using Mplus 7.1 (Muthén & Muthén, 1998–2016) was

conducted to examine the proposed model such that personality traits predicted marijuana-related perceptions, which in turn predicted mar- ijuana use frequency and marijuana consequences. We examined the total, direct, and indirect effects of each predictor variable on outcomes using the bias-corrected bootstrap based on 1000 bootstrapped samples (Efron & Tibshirani, 1993). Bootstrapping creates empirically-derived sampling distributions from which statistical tests are based. Im- portantly, bootstrapping does not rely on the assumption that indirect effects are normally distributed and provides a powerful test of med- iation (Fritz & MacKinnon, 2007). Bootstrapping is also a method of estimating statistical significance that is robust to small departures from normality (Erceg-Hurn & Mirosevich, 2008).

3. Results

3.1. Preliminary analyses

Descriptive statistics and bivariate correlations are shown in Table 1. The personality traits were modestly correlated with each other with the weakest association between hopelessness and anxiety sensitivity (r = 0.10) and the strongest association between hope- lessness and impulsivity (r = 0.26). The marijuana-related perceptions were also modestly correlated with each other with the weakest asso- ciation between descriptive norms and internalization of college mar- ijuana use culture (r = 0.12) and strongest association between in- junctive norms and internalization of college marijuana use culture (r = 0.22). These modest associations assured that our model would not have issues with multicollinearity.

3.2. Path analysis

3.2.1. Direct effects Direct effects in the full model are depicted in Fig. 1. Impulsivity

(β = 0.23) and sensation seeking (β = 0.08) had unique positive direct effects on internalization of college marijuana use culture. Sensation seeking had a unique positive direct effect on injunctive norms (β = 0.11), and hopelessness had a unique negative direct effect on injunctive norms (β = −0.10). None of the personality traits sig- nificantly predicted descriptive norms. Hopelessness (β = 0.07), an- xiety sensitivity (β = −0.09), and each of the marijuana perception variables (internalized norms: β = 0.18; injunctive norms: β = 0.23; descriptive norms: β = 0.26) had unique positive direct effects on marijuana use frequency. Hopelessness (β = −0.06), impulsivity (β = 0.13), and internalization of college marijuana use culture (β = 0.13) had unique positive direct effects on marijuana con- sequences; and descriptive norms (β = −0.06) and injunctive norms (β = −0.06) had unique negative direct effects on marijuana con- sequences.

3.2.2. Indirect effects on marijuana use frequency The decomposition of total, direct, and indirect effects is shown in

Table 1 Correlations, means, standard deviations, and Cronbach's alphas for study variables.

1 2 3 4 5 6 7 8 M SD

1. Hopelessness (0.87) 1.88 0.49 2. Sensation seeking −0.21 (0.76) 2.86 0.53 3. Anxiety sensitivity 0.10 −0.13 (0.71) 2.52 0.47 4. Impulsivity 0.26 0.22 0.16 (0.79) 2.15 0.50 5. Internalization of college marijuana use culture 0.09 0.12 0.03 0.25 (0.93) 2.44 0.74 6. Injunctive norms −0.14 0.13 −0.03 −0.04 0.22 (0.89) 5.31 1.28 7. Descriptive norms −0.00 −0.01 0.01 0.01 0.12 0.14 – 9.06 7.99 8. Marijuana use frequency 0.04 0.06 −0.09 0.03 0.26 0.30 0.31 – 5.76 6.92 9. Marijuana consequences 0.16 0.05 0.04 0.20 0.24 0.05 0.06 0.35 8.10 7.83

Note. Significant correlations (p < 0.05) are in bold typeface for emphasis. Cronbach's alphas are in parentheses and shown on the diagonals.

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Table 2. Hopelessness had a weak positive total effect on marijuana use frequency, which was decomposed into a slightly larger positive direct effect on marijuana use frequency and a smaller negative indirect effect through injunctive norms. Sensation seeking had a weak positive total effect on marijuana use frequency, which was explained by positive indirect effects through injunctive norms (accounted for 47.95% of the total effect) and internalization of college marijuana use culture (ac- counted for 24.66% of the total effect). Anxiety sensitivity had a ne- gative total effect on marijuana use frequency, which contained a very similarly sized negative direct effect and no significant indirect effects. Impulsivity had a non-significant positive total effect on marijuana use frequency, which was decomposed into a non-significant negative di- rect effect on marijuana use frequency, and significant positive indirect effects via descriptive norms and internalization of college marijuana use culture.

3.2.3. Indirect effects on marijuana consequences All four personality traits had significant indirect effects on mar-

ijuana consequences (see Table 2). Hopelessness, sensation seeking, and impulsivity had positive indirect effects on marijuana consequences via internalization of college marijuana use culture (accounting for 4.55%, 20.31%, and 16.60% of their total effects, respectively). Hopelessness and impulsivity had positive indirect effects on marijuana consequences via injunctive norms (accounting for 4.55% and 1.60% of their total effects, respectively), whereas sensation seeking had a negative indirect effect via injunctive norms. Hopelessness had a positive indirect effect on marijuana consequences via marijuana use frequency (accounting for 20.71% of the total effect); whereas anxiety sensitivity had a ne- gative indirect effect on marijuana consequences via marijuana use frequency. Sensation seeking and impulsivity had significant positive double-mediated effects (i.e., sequential mediation) on marijuana

Fig. 1. Path model of associations (standardized effects) among personality traits, marijuana-related perceptions, marijuana use, and marijuana consequences. Only sig- nificant effects (p < 0.05) are shown. Although the cor- relations among personality variables as well as the corre- lations among marijuana perception variables were estimated, they are not shown for reasons of parsimony.

Table 2 Total, direct, and indirect effects of personality on marijuana outcomes via descriptive norms (DN), injunctive norms (INJ), and the internalized norms (INT).

Independent variable: Hopelessness Sensation seeking Anxiety sensitivity Impulsivity

B LL UL B LL UL B LL UL B LL UL

Dependent variable: marijuana use Total indirect −0.26 −0.57 0.02 0.48 0.19 0.76 0.04 −0.27 0.34 0.49 0.17 0.84 Specific indirect effects DN −0.04 −0.22 0.15 −0.05 −0.22 0.12 0.03 −0.14 0.20 0.06 −0.10 0.27 INJ −0.34 −0.51 −0.18 0.35 0.20 0.51 0.00 −0.17 0.16 −0.14 −0.30 0.02 INT 0.12 −0.00 0.25 0.18 0.07 0.32 0.01 −0.12 0.13 0.57 0.39 0.78

Direct effect 1.04 0.45 1.68 0.26 −0.27 0.77 −1.38 −2.01 −0.84 −0.26 −0.87 0.35 Total effect 0.79 0.08 1.47 0.73 0.15 1.38 −1.35 −2.03 −0.77 0.23 −0.45 0.92 Dependent variable: consequences Total indirect 0.50 0.20 0.80 0.34 0.08 0.63 −0.53 −0.84 −0.26 0.53 0.19 0.90 Specific indirect effects DN 0.01 −0.04 0.06 0.01 −0.03 0.07 −0.01 −0.06 0.03 −0.01 −0.08 0.02 INJ 0.09 0.01 0.23 −0.09 −0.22 −0.01 0.00 −0.05 0.05 0.04 0.00 0.13 INT 0.09 0.00 0.20 0.13 0.05 0.25 0.01 −0.09 0.11 0.42 0.24 0.63 Marijuana use 0.41 0.17 0.70 0.10 −0.10 0.33 −0.55 −0.83 −0.33 −0.10 −0.37 0.14 DN ➔ marijuana use −0.02 −0.08 0.06 −0.02 −0.09 0.05 0.01 −0.06 0.08 0.02 −0.04 0.11 INJ ➔ marijuana use −0.13 −0.21 −0.07 0.14 0.08 0.22 0.00 −0.07 0.06 −0.06 −0.12 0.00 INT ➔ marijuana use 0.05 −0.00 0.10 0.07 0.03 0.13 0.00 −0.05 0.05 0.23 0.15 0.32

Direct effect 0.70 1.49 2.34 0.31 −0.34 0.94 0.60 −0.18 1.32 2.00 1.29 2.70 Total effect 1.98 1.14 2.93 0.64 −0.08 1.38 0.06 −0.77 0.85 2.53 1.78 3.34

Note. All parameter estimates and significance test are based on 1000 bootstrapped samples. Significant effects (p < 0.05) are in bold typeface for emphasis.

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consequences via internalization of college marijuana use culture and marijuana use frequency (personality ➔ internalization of college marijuana use culture ➔ marijuana use frequency ➔ marijuana con- sequences), accounting for 10.94% and 9.09% of their total effects, respectively. Sensation seeking had a positive double-mediated effect on marijuana consequences via injunctive norms and marijuana use frequency (accounting for 21.88% of the total effect); whereas hope- lessness had a negative double-mediated effect on marijuana con- sequences via injunctive norms and marijuana use frequency.

4. Discussion

The purpose of this study was to investigate the direct and indirect effects of personality on marijuana outcomes via marijuana norms using a large sample of college students from 11 US universities. Findings indicated that internalization of college marijuana use culture mediated the effect of sensation seeking and impulsivity and this construct had a direct effect on both marijuana use frequency and negative con- sequences consistent with the research hypotheses. Descriptive norms, injunctive norms, and internalization of college marijuana use culture partially or fully mediated the effects of four personality variables that are commonly associated with substance use. While injunctive, de- scriptive, and internalization of college marijuana use culture had a direct effect on marijuana use frequency, it is notable that the new construct representing the internalization of marijuana norms as as- sessed by the PIMCES (Pearson, Kholodkov, et al., 2017; Pearson, Liese, et al., 2017) was the only perception variable with a positive direct effect on negative consequences after controlling for other variables. Collectively, these findings add to a growing body of research in- dicating that these personality and marijuana-related perception vari- ables have unique contributions on marijuana outcomes.

The present study extends several findings regarding alcohol use reported in Hustad et al. (2014) and Pearson and Hustad (2014) to marijuana use. First, in all three studies, sensation seeking and im- pulsivity predicted internalization of college substance use culture, which in turn mediated effects on use, and double-mediated effects on consequences via internalization of college substance use culture and use. Second, all three perception variables predicted use in the multi- variate path model; however, the two alcohol studies found injunctive norms to predict less alcohol use quantity, whereas our injunctive norms measure predicted increased marijuana use frequency. Third, both hopelessness and impulsivity still had modest direct effects on consequences even when controlling for all other variables in the model, suggesting that we need to identify other constructs that may explain these associations (e.g., marijauna use expectancies; Hayaki et al., 2011; Vangsness, Bry, & LaBouvie, 2005).

In addition, our results are generally consistent with Neighbors et al. (2008) that found injunctive and descriptive norms to be significantly positively associated with marijuana outcomes. In contrast, Buckner (2013) found that descriptive marijuana use norms for the “average student” using a similar measure to the present study were not sig- nificantly related to marijuana outcomes in a sample of college students (N = 223). Instead, Buckner found descriptive norms for a “close friend” were significantly related to marijuana use, supporting other research suggesting more proximal reference groups have more of an influence (LaBrie, Hummer, & Lac, 2011). Recent changes in marijuana policies and differences between the geographic representations in the current study and previous studies may account for these differences (Wu, Swartz, Brady, Hoyle, & Workgroup, 2015).

In terms of the power of prediction, our model accounted for 20.9% of the variance in marijuana use frequency and 18.7% of the variance in marijuana consequences, which is somewhat lower than the mandated student alcohol sample (27.3%, 25.0%) and substantially lower than the incoming freshmen alcohol sample (41.5%, 40.9%). One notable difference between our study and the two alcohol studies is that we assessed marijuana use frequency instead of quantity; both alcohol

studies assessed alcohol use quantity. In the alcohol literature, alcohol quantity is more strongly associated with consequences than frequency and our discrepant findings might be related to marijuana use mea- sures. For example, alcohol is sold with known potency in exact amounts (12 oz of beer with 5.5% alcohol), allowing the assessment of “standard drinks. However, participants may have difficulty converting their marijuana use into a standard quantity given differences in mar- ijuana potency and methods of administration.

4.1. Clinical implications

On average, participants reported experiencing approximately eight negative marijuana-related consequences during the past month pro- viding support for the need for evidence-based primary and indicated interventions for marijuana misuse. Multi-component and theory-based interventions that are designed to reduce internalization of college marijuana use culture, injunctive norms, and descriptive norms are expected to reduce the number of marijuana-related harms given the indirect and direct relation for these variables on marijuana outcomes. It is notable that the correlation between injunctive norms and mar- ijuana use frequency in the current study was larger (r = 0.30) than the correlation between injunctive norms and weekly alcohol use in the previous studies (rs = 0.00 to −0.08; Hustad et al., 2014, Pearson & Hustad, 2014). Given the stronger observed relation between injunctive norms and marijuana use, it is possible that interventions that target injunctive norms will be more effective at reducing mar- ijuana use than alcohol use in college-aged samples, especially when framed around one's close friends rather ‘typical’ college students. De- scriptive and injunctive marijuana norms can be addressed in a Moti- vational Interview (e.g., Lee et al., 2013) or Personalized Feedback Interventions (e.g., Stephens, Roffman, Fearer, Williams & Burke, 2007).

Given these findings and previous results indicating that inter- nalization of college drinking culture are negatively associated with motivation to change alcohol use in a sample of mandated college students (Qi, Pearson, & Hustad, 2014), it appears that interventions that reduce internalization of college marijuana use culture will also decrease marijuana use and associated harms. However, it currently is not clear how to address internalization of college marijuana use cul- ture. Concerted efforts to change the campus environment and mar- ijuana culture (e.g., reduction of businesses near campus that sell marijuana paraphernalia and increased enforcement and fines for marijuana use, when applicable) and motivate college students to participate in marijuana-free activities (Murphy et al., 2012; Yarnal, Qian, Hustad, & Sims, 2013) may have the strongest impact to reduce marijuana misuse through internalization of college marijuana use culture.

As summarized in Hustad et al. (2014) and Pearson and Hustad (2014), a personality-targeted intervention (see Conrod et al., 2011) may be another promising approach to reduce substance misuse. In these interventions, individuals who have elevated personality vari- ables (e.g., impulsivity) can learn new and empirically-based techni- ques (e.g., behavioral skills training, coping skills training, or relaxation training) and/or receive psychopharmacological treatment to help them improve their ability to self-regulate the effects of their person- ality on their behavior. Given our results, increased self-regulation would be expected to have a direct effect on marijuana use outcomes for individuals who score high in impulsivity, hopelessness, and anxiety sensitivity, along with an indirect effect on marijuana outcomes through perception variables for these same personality traits and sensation seeking.

4.2. Limitations and recommendations for future research

Although the large sample size from 11 host sites gives us con- fidence in these findings, it is worthwhile to mention that these data are

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based on self-report. Future studies should consider including biological markers and collateral reports. In addition, we were unable to infer causality due to the cross-sectional, non-experimental nature of this study. Longitudinal/experimental studies are needed to better under- stand the relations among these variables. Previous research indicates that alcohol descriptive norms are drastically elevated before college (e.g., Hustad et al., 2014) and internalization of college drinking culture before college are positively related to drinking in college (Moser et al., 2014). Thus, future prospective studies are needed to investigate the relation between marijuana use norms and internalization of college marijuana use culture prior to college and their effects on marijuana use during college.

4.3. Conclusion

These results provide additional support for the unique direct and indirect effect of personality traits (impulsivity, sensation seeking, hopelessness, anxiety sensitivity) and perceptions (internalization of college marijuana use culture, injunctive norms, and descriptive norms) on substance use and associated negative consequences. These findings are consistent with similar studies using samples of college student drinkers (Hustad et al., 2014; Pearson & Hustad, 2014), suggesting that these personality traits and normative beliefs may influence multiple health behaviors. Furthermore, the construct related to internalization of college marijuana use culture needs additional attention, especially in intervention development and outcome research, as well as across states with different legal marijuana policies (i.e., states with and without legal access to cannabis).

Role of funding sources

MRP is supported by a career development award (K01AA023233) from the National Institute on Alcohol Abuse and Alcoholism (NIAAA). AJB is supported by a training grant (T32AA018108) from the NIAAA. NIAAA had no role in the study design, collection, analysis or inter- pretation of the data, writing the manuscript, or the decision to submit the paper for publication.

Contributors

MRP coordinated the efforts of the Marijuana Outcomes Study Team to collect all data, conducted analyses, and drafted the manuscript. All other authors edited the manuscript, contributed to sections of the manuscript, and have approved of the final manuscript.

Conflict of interest

All authors declare that they have no conflicts of interest.

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