Several studies show that the several facets of the UPPS-P model of impulsivity are highly intercorrelated. Including all five traits in a single model can create statistical suppression and make it difficult to interpret each unique effect. In order to address this issue, we first examined the correlations between each trait to guide decisions for which traits to examine for mediation. Specifically, we examined Negative Urgency [NU], Positive Urgency [PU], and Lack of Perseverance [PS] because, as reported below, they were significantly associated with both MDD and marijuana outcomes in this sample. A total of eight mediational models were tested. First, we tested separate models for each of the marijuana outcomes , for each of the mediators , which resulted in a total of six models. Then, we tested two models with all mediators entered simultaneously in order to examine whether any significant associations remained. Finally, given the cross-sectional nature of the data, followup mediation analyses with reverse directionality were tested, where marijuana use and problems were specified as the predictor, or independent variable; MDD was specified as the outcome, with impulsivity measures remaining as mediators of interest. The primary data analyses were a structural equation model with maximum likelihood estimation to using AMOS 24.0 . All models regressed the dependent variable onto covariates . Covariates were allowed to correlate with each other in single and multiple mediator models. In order to estimate mediation effects, bootstrapped and bias-corrected 95% confidence intervals were estimated for the indirect effects. Mediation is tested by examining the direct, indirect, and total effects. Significant mediation effects are apparent when indirect effects are significant and total effects are reduced in the presence of the mediator. To assess the degree to which the structural models fit the sample variance-covariance data,vertical grow rack system two criteria of model fit were relied upon: the Comparative Fit Index , and the root-mean- square error of residual approximation .
Although guidelines for good fit vary, values above for CFI and below .05 for RMSEA are considered acceptable.The goal of the present study was to better understand mechanisms associated with high rates of co-occurring MDD and problematic marijuana use by examining the role of specific facets of the UPPS-P model of impulsive personality in this comorbidity. To our knowledge, the current study is the first to systematically examine the role of these personality traits between MDD and marijuana use and problems. As hypothesized, we found that NU partially accounted for the relationship between MDD and marijuana problems, but this was not true of the other impulsivity traits. Consistent with previous research, we found that MDD was associated with marijuana use and problems. Although this is not the first study to examine the relationship between MDD and marijuana use and problems, it is the first to examine how individual dispositions to impulsive/rash action may help explain the association between these two clinical problems. We were also able to replicate previous research suggesting an association between MDD and NU. The current study expands this literature by suggesting that individuals with MDD and high levels of NU are in turn more likely to have greater number of marijuana problems. Importantly, our results also suggest that NU is the only trait in the UPPS model that accounted for the association between MDD and marijuana problems. This is consistent with theory suggesting the increased negative affect experienced by those with mood disorder, such as MDD, may lead to increased substance-related problems. This high rate of negative affect may be particularly problematic for individuals also high in NU, who may in turn be more likely to act impulsively when experiencing negative mood states, and thus be more likely to experience problems related to substance use.
Although results in support of this mediational pathway are compelling, remaining variance in our models suggest alternative pathways may exist to explain this comorbidity. For example, marijuana coping motives have also been shown to mediate the relationship between MDD or other affective vulnerabilities, such as anxiety and distress tolerance, and marijuana use and problems in general and veteran populations. Contrary to our hypothesis, this mediational pathway was not present for marijuana use, indicating that NU is specifically implicated in the experience of problematic marijuana use. This is consistent with work suggesting that NU is a robust predictor of both marijuana problems and alcohol problems, although the relationship between NU and marijuana problems has received far less attention. Previous studies have used similar methods to explain the relationship between MDD and alcohol use and problems. In one study of young adult drinkers, NU significantly mediated the relationship between depressive symptoms and alcohol problems when controlling for alcohol use. Similarly, King and colleagues examined which of the UPPS-P model traits might moderate the relationship between depressive symptoms and alcohol problems among college student drinkers. They found that although NU was the strongest predictor of alcohol problems, lack of premeditation was the only moderator of depressive symptoms and alcohol problems. Although this study examined impulsivity traits as moderators, it is important to mention as they found unique associations between NU and depressive symptoms when examining alcohol problems, which is consistent with our findings with marijuana problems. The present study expands this knowledge by not only showing that the relationship between MDD and marijuana problems may be partially explained by NU, but also in a population of military veterans. Veterans often have higher rates of MDD and substance use disorders including CUD compared to the general population, and thus an important target population for intervention. The present research has important treatment and prevention implications for individuals with MDD and marijuana problems.
Given the emerging evidence of an association between NU and marijuana problems in a number of different populations,vertical grow system it may be important for clinicians to assess for NU to be aware of the additional risk for those with MDD and high levels of NU. Although we focused on the directional pathway of MDD predicting marijuana-related behvaiors, it is also important to acknowledge that longitudinal evidence also exists to suggest that marijuana use is prospectively associated with depressive symptoms and other mood disorders [see review: 16]. Therefore, individuals at risk for depression and those with MDD should consider avoiding using marijuana, as it could in turn exacerbate the severity of depressive symptoms.Alcohol, tobacco, and marijuana are the three most commonly used drugs of abuse in the US , and cross-sectional, epidemiological findings suggest that it is common for individuals to report concurrently using these substances . The prevalence of, problems arising from, and motives underlying the co-use of alcohol and tobacco have been well documented . Approximately 20% of regular tobacco smokers are also heavy-drinkers , and those who use both substances tend to regularly do so simultaneously . The chronic, simultaneous use of cigarettes and alcohol yields adverse consequences. First, heavy-drinking tobacco smokers experience more frequent and severe negative health consequences as compared to those who use either drug alone . Second, this simultaneous co-use creates substantial impediments to smoking cessation among this sub group. Alcohol use is associated with substantially poorer smoking cessation rates and, at a more fine-grained level of analysis, a smoking lapse is four times more likely to occur in the context of a drinking episode as compared to a non-drinking episode . The understanding of the daily, event-level patterns of simultaneous cigarette and alcohol co-use, for example how use of one drug can acutely increase craving for and drive use of the other , contributed to line of research focused on developing pharmacological and behavioral treatments that are specifically tailored for individuals who are dependent on both substances . Thus, characterizing patterns of drug co-use at the individual rather than population level may be beneficial in identifying the behavioral mechanisms that drive problematic, simultaneous substance use in order to leverage that knowledge into targeted treatments for co-abusing populations. While marijuana is the most commonly used illicit drug in the world and is becoming increasingly legal in the USA, relatively little is known about event-level patterns of marijuana co-use with alcohol and/or tobacco. In the US, past year marijuana use more than doubled between 2001– 2002 and 2012–2013 with a near parallel magnitude of increase in the prevalence of cannabis use disorder . While there is still some debate on this topic , the national rise in the prevalence of marijuana use, particularly in adults, appears to be related to the increasing number of states that fully legalized or legalized medicinal use over this same time . As more states legalize or decriminalize marijuana use and its use becomes more tacitly accepted across the country, it is expected that prevalence of marijuana use and CUD will continue to rise .
Although marijuana is considered less harmful to self and others compared with alcohol and tobacco , acute and chronic marijuana use is indeed associated with a wide variety of health risks , and treatment outcomes for CUD are generally poor across various intervention types . These adverse consequences from marijuana use and poor treatment outcomes are thought to be exacerbated by the commonality of marijuana being used concurrently with other substances . Given the rising prevalence of marijuana use, CUD, and their related health and treatment problems, it is critical to characterize situations and patterns in which marijuana is concurrently and simultaneously used with other drugs of abuse. At the population level, concurrent alcohol and marijuana use is quite common, with over 75% of marijuana users reporting alcohol use . Large scale, longitudinal survey data suggest that most who report concurrently using alcohol and marijuana also use both drugs simultaneously, and simultaneous use is associated with heightened heavy-drinking behavior, drunk driving, adverse social consequences, and harm to self and others . As alcohol consumption across youth to adulthood is substantially higher in marijuana users than non-users , it is not surprising that marijuana use and CUD are each associated with the development and maintenance of AUD . Simultaneous marijuana and alcohol use is increasing in younger populations, and in states that have recently legalized marijuana use, there have been early indications of increases in impaired driving stemming from simultaneous co-use . Lastly, concurrent alcohol and marijuana use has consequences for treatment as well: using marijuana during alcohol treatment is associated with poorer alcohol treatment outcomes , and when attempting to reduce their marijuana use, drinkers with and without AUD have reported increased alcohol craving and consumption . As observed with the co-use of alcohol and tobacco, alcohol and marijuana appear to regularly be coad ministered in a pattern that escalates severity of use of each drug and creates impediments in reduction of drug use. Similar to findings with alcohol, epidemiological studies suggest concurrent marijuana and cigarette use is highly prevalent and problematic. Recent findings indicate that more than two-thirds of current marijuana users concurrently use tobacco , and up to 53% of current tobacco users also use marijuana . The co-use of these substances is increasing, particularly in individuals who were initially tobacco only users and/or live in states where marijuana use is legal . Relatedly, there is bidirectional evidence that tobacco or marijuana use precedes and increases the likelihood of future use of the other substance . Concurrent marijuana and tobacco use, vs. use of either substance alone, is associated with increased risk of CUD, more psychosocial and mental health problems, more severe nicotine dependence, heavier alcohol consumption, and poorer treatment outcomes for both substances . As with alcohol co-use, simultaneous use of marijuana and tobacco is common among youths and adults and associated with more severe drug use and worse health outcomes than concurrent use . For example, individuals who simultaneously use marijuana and tobacco are at heightened risk for escalating consumption to hazardous levels, development of dependence, and poor cessation outcomes for each substance . In summary, epidemiological studies indicate that marijuana and tobacco or alcohol are commonly co-used in a concurrent and simultaneous fashion, and the co-use of these substances, particularly when used simultaneously, is related to greater quantity and frequency of use, development of dependence, and health problems above and beyond the use of each substance alone.