Moreover, small sample sizes of students in different academic disciplines precluded meaningful analyses to understand whether or not the observed results held true for students pursuing different types of careers. Future research that replicates the results of this study are needed, particularly in light of the small, yet significant, effect sizes observed. While the associations between graduate degree completion and both alcohol use frequency before enrollment  and marijuana use frequency after enrollment  were statistically significant, the magnitude of these effects calls into question the practical significance of these findings. As discussed, prior research among other student samples supports these findings. However, this study alone should not be used as sole evidence of the presence of an association between substance use and graduate degree completion, and results should be interpreted with caution. This study contributes to the literature on the relationship between marijuana use and academic achievement.For graduate students who appear to be struggling academically, a comprehensive assessment that includes marijuana use might be warranted in order to understand possible risk factors for dropout. University communities have a unique structure and set of resources,and graduate school is an opportune time to intervene while these supports are in place. A multitude of factors influence graduate degree obtainment other than alcohol and marijuana use, and future research is needed to provide a fuller understanding of the barriers and facilitators of success during graduate school. Of particular value would be multi-campus studies that capture graduate student populations from a wide range of degree types and academic disciplines.

Recent data from the 2018 Monitoring the Future Study suggests there has been a resurgence of marijuana  use in young adults over the last three and a half decades.Specifically, vertical grow system past 12-month and past 30-day MJ use in 19–22 year old college students are at the highest levels reported since 1983. Furthermore, 43% of 19–22 year old college students report past year MJ use, 25% report past month MJ use, while about 5.8% report frequent MJ use.In an ongoing study examining the behaviors, attitudes and values of substance users, MJ was considered the least risky among illicit substances in 18–30 year olds.In addition, the study indicates that over the past 11 years, there has been a continuous decline in perceived risk of regular MJ use. Changing attitudes have likely contributed to the legalization of recreational MJ use in eleven states and Washington D.C. MJ use has also increased in states where recreational use has been legalized making it a critical time to better understand whether young adult MJ use affects neurocognitive functioning.Adolescence and young adulthood are periods of active biopsychosocial development and brain maturation. Given the protracted development of the prefrontal cortex, young adulthood is a critical period for the maturation of executive functions. Therefore, the establishment and maturation of structural and functional connections between the prefrontal cortex and other brain regions important in higher-order cognitive functions  during the third decade of life may be especially sensitive to the neurotoxic effects of substance use.The primary psychoactive constituent of MJ, delta-9-tetrahydocannabinol,directly targets endocannabinoid receptors located in the prefrontal cortex. Acute THC binding to cannabinoid receptor 1 has been shown to increase dopamine release and neural activity.THC exposure may disrupt cortical gamma oscillatory activity due to GABAergic reduction and neuronal hyperactivation in the prefrontal cortex  leading to disruptions in dopamine regulation which may contribute to cognitive impairments in executive functioning associated with MJ use.Previous studies have reported cognitive functioning impairments in adolescent and young adult MJ users.

Frequent MJ use has been shown to impair attention and concentration  as well as verbal fluency.On executive functioning tasks, MJ users were slower on Go trials on the Go/NoGo Task,made more commission and omission errors on the Stroop Color Word Test,and made more perseverative errors  and had lower executive function standard scores on the Wisconsin Card Sorting Test,compared to healthy controls. In addition, daily MJ use has been linked to executive functioning impairments in cognitive flexibility and inhibition,both of which play important roles in decision-making.Adaptive decision-making is necessary for selecting healthy choices without significant personal risk, but poor decision-making can lead to risky choice, such as the maintenance of heavy or frequent substance use. Previous research on decision-making in MJ users has been mixed. Many studies have indicated that frequent MJ use is associated with deficits in decision-making performance,while some studies have found no clear group differences between chronic MJ users and healthy controls.These mixed findings may be attributed to the heterogeneity of decision making tasks, variability in MJ use history and the neuro developmental stage at first MJ use. In addition, the ages of participants in these studies ranged from adolescents to middle-aged adults and the criteria for frequent MJ use varied from >1 occasion of MJ use/week in the past year  to 25 out of 30 days of MJ use for at least five years,highlighting differences in inclusionary criteria for MJ users.One of the most widely used neurocognitive measures of risky decision-making is the Iowa Gambling Task,which simulates real life decision-making, the cognitive ability to select the most adaptive course of action among a set of possibilities. Evidence of deliberate risk taking and impulsivity have been measured using IGT performance.Many studies examining the effects of chronic MJ use on cognitive functioning have utilized the IGT to measure decision-making performance. A study examining group differences on net IGT scores between healthy controls and MJ users who smoked MJ for at least two years and who currently smoked at least four times/week, showed that greater frequency of MJ use was related to poorer IGT performance.

This study found that cannabis users had significant impairments in decision-making and risk-taking compared to healthy controls,suggesting chronic MJ users have difficulty in changing their decision-making strategy towards advantageous card choices. In a subsequent study, frequent MJ users showed a preference for selecting decks having greater wins and infrequent, but greater punishments,further indicating that MJ users may have a more difficult time in anticipating and strategizing monetary gain and loss. Frequent MJ use has also been shown to influence brain activity in regions associated with decision-making while participants performed the IGT during functional magnetic resonance imaging  and positron emission tomography. A previous study indicated that chronic MJ users exhibited significantly less activity in the anterior cingulate cortex and medial frontal cortex, brain regions that are believed to play roles in impulse control and decision-making, during strategy development for the IGT.This reduction of brain activity during monetary loss suggests MJ users may be less sensitive to negative feedback. Furthermore, chronic MJ users showed increased regional cerebral blood flow in the ventromedial prefrontal cortex compared to healthy controls during monetary decision-making and reward processing which may indicate that MJ users have greater sensitivity to rewards.These studies provide support for the important role of the prefrontal cortex in decision making skills and highlight the vulnerability of this region to the effects of frequent MJ use during young adulthood.Despite growing research on the effects of frequent MJ use on cognitive deficits in memory, attention and psychomotor function,there has been less attention on the influence of frequent MJ use on executive functioning, especially in young adults.Specifically, the effects of frequent MJ use on decision-making performance is mixed and not well understood. While some studies indicate cannabis users have significantly impaired decision-making capacities and greater risk taking tendencies,other studies suggest no clear differences between frequent MJ users and healthy controls.To our knowledge, only one study  examined the effects of MJ use on risky decision-making within a narrow age range of 18–20 year old young adult college students and found MJ users showed a preference for selecting cards in decks A and B, leading to greater wins with infrequent but greater punishments.The current study aims to replicate and extend these findings by investigating the effects of frequent MJ use on risky decision-making in young adult college students, 18–22 years old.

We chose to specifically examine the effects of frequent MJ use on decision-making in this population as  MJ use is most prevalent during emerging adulthood,  the prefrontal cortex continues to mature during this time, and  MJ use has been associated with poorer academic outcomes in college students,suggesting a window of vulnerability to the effects of frequent MJ use on adaptive decision-making in this population. Furthermore, given that the prefrontal cortex undergoes sex-specific maturation during adolescence,examining the role of sex on decision-making may highlight important differences in risk-taking between MJ users and healthy controls. Specifically, research suggests female participants are more sensitive to losses in advantageous decks on the IGT compared to male participants and, as a consequence, need additional trials before they achieve a similar level of performance.These behavioral differences could be related to underlying neurobiological differences in the activation of the prefrontal cortex. Male participants may be better at suppressing reward-driven behaviors as right dorsolateral prefrontal cortex activity has been reported in males but not females during the IGT.Decision-making differences could also be associated with sex differences in the rate of white matter maturation, as male youth show steeper increases in white matter development relative to female youth.A previous study examined sex differences in decision-making on the IGT in young adult MJ users and found that heavier MJ use was associated with poorer decision-making performance in males but not females.However,mobile grow systems to our knowledge, no studies have examined group-by-sex interactions on risky decision-making in young adult MJ users and healthy controls.The aims of the proposed study were to examine the influence of frequent MJ use on risky decision-making in college students using the IGT. A secondary aim was to conduct an exploratory analysis examining group-by-sex interactions on risky decision-making in young adult college students. Since we were interested in examining decision making within active MJ users who were not yet undergoing cannabis withdrawal, we asked participants to remain abstinent from all substance use for 12 h prior to the study visit to attempt to avoid any withdrawal symptoms that may contribute to impairments in decision making. We hypothesized that  frequent MJ users would have poorer performance than healthy controls, indicated by lower net IGT scores;  frequent MJ users would show faster reaction times in card selection compared with healthy controls, which would reflect greater impulsive tendencies during decision-making; and  younger age at first MJ use, greater cumulative MJ use and greater recent MJ use would be related to lower net IGT scores in MJ users.

Participants were recruited through flyers posted around the community and at MJ dispensaries as well as through social media advertising. Written consent was obtained from participants who contacted the laboratory to complete an interview to determine eligibility for the study. Following an eligibility interview, eligible participants were invited to take part in a study visit that included measures of substance use and psychosocial functioning as well as neurocognitive tasks of executive functioning. All participants were asked to abstain from substance use for at least 12 h prior to the study visit to limit effects of acute intoxication on neurocognitive measures. No participants appeared intoxicated at the time of the study visit. After providing consent for participating in the study visit, participants provided a urine sample for a 12-panel urine toxicology test and completed a breathalyzer test to confirm absence of alcohol intoxication. All MJ+ had a positive urine toxicology screen for THC, while all HC had a negative urine toxicology screen for THC. Further, all participants had a blood alcohol concentration of 0.00 at the time of the study visit. A nicotine metabolite test for cotinine was not conducted for this study; thus, recent nicotine use was assessed through self-report. At the end of the study visit, participants were compensated with an Amazon e-gift card. All study procedures were approved by the Oregon State University Institutional Review Board  and were in accordance with ethical guidelines of research with human participants.The IGT was administered to participants on a computer. Four card decks  were displayed to participants on the computer screen. Participants were read a standardized task script and told that the objective of the game was to win as much money as possible.