ReviewMarijuana use and physical dating violence among adolescents and emerging adults: A systematic review and meta-analysis
Introduction
In the U.S., marijuana policy is changing rapidly at the state level. Statutes that effectively end sanctions for marijuana use by adults (>21 years) have been passed in Washington D.C., Washington, Oregon, Colorado, and Alaska. Additionally, Washington D.C. and 20 states have removed criminal penalties for use and possession (i.e., decriminalization), and 35 states have passed laws allowing for medical use (National Conference on State Legislatures (NCSL, 2016a, NCSL, 2016b. Policy changes may have notable implications for adolescents and emerging adults because they have the highest rates of marijuana use (Johnston et al., 2014, Johnston et al., 2015; Table 1), and are at developmentally sensitive time periods. Nationally-representative data from 2013 show that 23% of high school students and 20% of 18–25 year olds report past 30-day marijuana use (Substance Abuse and Mental Health Services Administration (SAMHSA, 2014, Kann et al., 2014). As restrictions on marijuana are loosened, there is concern of a coming increase in marijuana use among adolescents and emerging adults, which could be coupled with commensurate increases in behavioral problems associated with use (Testa and Brown, 2015).
We have limited knowledge about the associations between marijuana use and behavioral problems, but are in a period in time when such information is very much needed. It is necessary to develop a comprehensive understanding of the associations between marijuana use and specific public health problems in general, and among adolescents and emerging adults in particular, given their high levels of use and developmental stage (American Academy of Pediatrics, 2015, Ghosh et al., 2016). This knowledge can inform policy decisions, and can enable the public health sector to anticipate how changes in marijuana policy and use might impact other behavioral problems, so as to mitigate adverse consequences.
Dating violence is an example of a behavioral problem that could be influenced by marijuana use, though there is not yet a scientific consensus as to the association between the two (Testa and Brown, 2015). The fact that there is strong support for an association between alcohol and partner violence among youth (Rothman et al., 2012, Shorey et al., 2011) highlights the importance of considering substance use as a risk factor for partner violence. To fill this knowledge gap, we review and summarize the existing literature describing what is known about the association between marijuana use and physical dating violence (PDV) among adolescents and emerging adults in the U.S.
Approximately 10% of U.S. high school students report having experienced PDV victimization in the past year (Rothman and Xuan, 2013, Kann et al., 2014). Estimates of the prevalence of PDV perpetration among the same population range from 12%–31% (Rothman et al., 2010, Taylor and Mumford, 2016, Haynie et al., 2013, Coker et al., 2014). Although population-based estimates of PDV among emerging adults are harder to obtain, results from nationally-representative surveys and studies of college students suggest that the prevalence is also high (Berger et al., 2012, Smith et al., 2003, Black et al., 2010). Approximately 10%–40% of 18–21 year olds report PDV in a relationship (Johnson et al., 2015b, Johnson et al., 2015c, Halpern et al., 2009).
The consequences of PDV can be serious. Those who are victimized are at increased risk for multiple negative outcomes including physical health problems, depressive symptomatology, unhealthy eating behavior, academic difficulties, and physical injury (Fletcher, 2010, Bonomi et al., 2013, Ackard et al., 2007, Coker et al., 2000, Exner-Cortens et al., 2013). Youth who perpetrate PDV also have significant psychosocial problems, and are at an increased risk for perpetrating partner violence in adulthood (Gidycz et al., 2007, Smith et al., 2003).
Two recent reviews highlight relevant information about the association between marijuana use and dating violence (Testa and Brown, 2015, Vagi et al., 2013). First, Vagi et al. reviewed longitudinal studies (published from 2000 to 2010) to identify risk and protective factors for dating violence perpetration among 10–24 year olds. Of the 20 studies included in that review, just one examined marijuana use as a risk factor, and results were not statistically significant (Foshee et al., 2010). An important lesson from Vagi et al.’s (2013) work is that marijuana has been infrequently examined in etiological research on dating violence, particularly in comparison to alcohol.
Second, Testa and Brown (2015) conducted a narrative review of 30 studies (published since 2008) that addressed marijuana use and dating violence perpetration among youth and adults. They concluded that there is likely a modest positive association between marijuana use and partner aggression globally, i.e., an association between the two over a given time period, or at two or more different time points. However, they further note that the two behaviors have not been shown to be linked in studies that examine “event-level” associations, i.e., marijuana use occurring on the same day as dating violence. The limited information from event-level studies raises the possibility that global associations could simply reflect two co-occurring, but not mechanistically related, behaviors.
Both reviews suggest important next steps for research on marijuana use and PDV, which we address in this study. First, neither summarizes marijuana use in association with PDV victimization, which is a notable gap. Second, at this stage in the science, a systematic review and meta-analysis on the topic are warranted. Results would provide a quantitative, summative estimate of the association between marijuana use and PDV to provide additional context to the existing reviews. Third, results of existing studies should be viewed in terms of both their study design as well as the theorized mechanisms, so as to better understand how marijuana use might be associated with PDV globally, and at the event level (Testa and Brown, 2015). There are several theoretical explanations for how marijuana use could increase risk for partner violence, and we review them below.
One class of potential mechanisms linking marijuana use to partner violence relates to how the substance impacts users’ physiological and psychological state. First, use impairs cognition and creates perceptual distortions (Pope and Yurgelun-Todd, 1996, Goldstein, 1985). Consequently, people who have used marijuana may interpret others’ actions as aggressive even if they are not, and respond combatively. Second, marijuana may impair the ability to tamp down aggressive impulses, and thereby increase the risk for aggressive behavior in conflict situations (Moore and Stuart, 2005, Yanowitch and Coccaro, 2011, Temple et al., 2013, Friedman, 1998). Third, marijuana can make some users feel paranoid, anxious, or panicky, which could elevate risk for conflict (Moore and Stuart, 2005). Relatedly, marijuana use increases heart rate, and the physiological arousal associated with an increased heart rate may increase the likelihood of aggressive behavior (Moore and Stuart, 2005). A fourth explanation relates to symptoms of withdrawal; which may contribute to irritability and, therefore, increase the risk for conflict and aggression (Moore and Stuart, 2005, Smith et al., 2013, Smith, 2002, Testa and Brown, 2015).
Further explanations relate to the interaction between people and their social environments. Specifically, an association between marijuana use and PDV perpetration could be situational – purchasing and using marijuana may bring one into settings and social contexts where violence is more likely (Bean, 2001). Friedman (1998) identifies a “systematic dimension” model, which suggests that those who use marijuana may become involved in violence because it is intrinsic to the selling of illicit substances. Among youth, this may be reflected in friendship with peers who use or sell illicit drugs and/or who engage in high levels of violence.
A final explanation relates to “problem behavior theory.” The premise of problem behavior theory is that adolescents have psychosocial motivations to engage in a variety of risk behaviors – such as dating violence and substance use (Jessor, 1987). This theory would suggest that there are antecedent variables that increase risk for both marijuana use and PDV, and that their co-occurrence reflects those antecedent motivations rather than one behavior “causing” the other.
Because adolescents and emerging adults who use marijuana often have partners who use it as well, the theoretical explanations linking marijuana use to PDV perpetration described above may also increase risk for victimization (Shorey et al., 2008). Additionally, marijuana use may contribute to impaired relationship decision-making (Grant et al., 2012), which could: (1) increase susceptibility to entering into unhealthy or violent dating relationships, (2) reduce capacity to end such relationships, and (3) decrease the ability to pick up on cues that a partner may be dangerous (Shorey et al., 2008). A final explanation for an association between marijuana use and PDV is that adolescents and emerging adults may use marijuana to cope with the emotional distress and anxiety associated with being in a violent relationship (Weiss et al., 2014, Shorey et al., 2016).
Given the changing marijuana policy landscape, there is concern that youth marijuana use will increase, which could lead to commensurate increases in associated risk behaviors, including dating violence (Testa and Brown, 2015). To summarize what is known about the association between marijuana use and PDV victimization and perpetration among adolescents and emerging adults, we conducted a theory-based systematic review and meta-analysis of the relevant literature. We focused on adolescents and emerging adults aged 11–21 because they have high levels of marijuana use, and because relationships among this population are distinct from relationships among those in older age groups. Specifically, younger couples are less likely to cohabitate, be married, and have children together, and their relationships tend to be shorter in duration and have lower levels of commitment and trust (Shorey et al., 2008, Shorey et al., 2011, Johnson et al., 2015b, Johnson et al., 2015c).
Section snippets
Methods
PRISMA is an evidence-based minimum set of items for reporting the procedures involved in systematic reviews and meta-analyses (Moher et al., 2009). Using guidelines outlined in the PRISMA Statement, we reviewed articles examining the association between marijuana use and PDV that had been published in peer-reviewed academic journals. We reviewed articles that included: (1) an assessment of marijuana use; (2) an assessment of PDV victimization, perpetration, or both; and (3) a quantitative
Overview
Five studies examined marijuana use in association with PDV victimization, and the results vary by the age group of respondents. Although the studies do not provide evidence for an association between the two variables among emerging adults, they do offer support for an association among adolescents. Below we describe results by age group of study participants.
Narrative synthesis – adolescents
In crude (i.e., unadjusted) models, each of the three studies with adolescent samples demonstrated a statistically significant
Discussion
We conducted a systematic review and meta-analysis to summarize the evidence supporting an association between marijuana use and physical dating violence (PDV) victimization and perpetration among adolescents and emerging adults. Findings suggest an association between the two, and also demonstrate that the magnitude of the association is strongest among adolescent girls. Results are consistent with a prior meta-analysis that reported an association between marijuana use and partner violence
Conclusion
Our rationale for conducting this research was to provide needed information about a prevalent risk behavior, dating violence, and its association with marijuana use. This work responds to calls to prioritize research assessing the public health effects of marijuana use given the evolving policy landscape (Azofeifa et al., 2016). Our findings show that dating violence is associated with marijuana use among youth, although the reasons why remain unclear and there is no indication that marijuana
Contributors
Renee M. Johnson and Kristin E. Schneider coordinated the literature search; Michael LaValley conducted the analysis; and all authors assisted with writing and data interpretation.
Financial disclosure
No financial disclosures were reported by the authors of this paper.
Role of funding source
Funding for this study was provided by grants from NIH: K01DA031738 (PI: Johnson), K01AA017630 (PI: Rothman), and T32DA007292 (PI: Johnson; Schneider). The study sponsor had no role in determining study design; data collection, analysis, or interpretation; writing the report; or the decision to submit the report for publication.
Conflicts of interest
None.
Acknowledgements
We appreciate the assistance of multiple graduate students who worked on this review, including: Dr. Anna Flynn, Courtney Kaczmarsky, Taylor Parnham, and Erin Anderson Goodell.
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