However, in marijuana users, the inverse effect has been observed. For instance, in a study by Terracciano et al.,marijuana users exhibited greater “excitement-seeking” and “activity”compared to non-users. The authors postulated that these facets of extraversion may contribute to marijuana use. Reports of marijuana use may also be more highly associated with extraversion due to the more communicative personality traits  implicated in admission of illegal activity. However, in line with the studies mentioned above, the more robust effect is likely the similarly of the extraversion “excitement-seeking” facet, and sensation-seeking, which is a well established risk factor for drug use.Together with our findings of greater openness in marijuana users, we speculate potential specificity of personality traits in different substance using population. This underlines the need to characterize substance-using populations relative to each other.Additionally, given the widely accepted association between novelty-seeking and sensation seeking in marijuana users,it may be through extraversion that these risk factors lead to substance use disorders.Thus, greater sensation seeking in drug abusers would suggest that extraversion could be a risk factor  as others may suggest in other SUDs. In addition to openness, other factors that discriminated marijuana users from nicotine users in our study have been linked to neurological systems responsible for appetitive-approach behaviors.Recent imaging work has shown specific brain mechanisms associated with similar traits including motivation, optimism, and enthusiasm. For example, DeYoung et al. showed that extraversion scores covaried with medial orbitofrontal cortex volume, which has also been shown to be altered in long-term marijuana users.Agreeableness was positively associated with retrosplenial PCC,mobile vertical rack which is implicated in altered sensory awareness in addiction.

Similarly, genetic mechanisms have also been associated with personality traits. For instance, COMT Val158Met allele has been posited to modulate extra version.Together, these results suggest potential mechanisms for the association between these personality traits and marijuana use. The current findings of greater openness in marijuana users also fit within the framework put forth in studies of marijuana use motives. Specifically, out of five putative motives for marijuana use,highest endorsements have been reported for those that require openness, such as the enhancement motive,followed by social  then expansion  motives.Future studies are needed to directly examine this relationship.However, altogether, these findings suggest that the openness personality factor is a risk marker for engagement in marijuana use  as a means to expand on one’s life experience .Delta-9-tetrahydrocannabinol,the main psychoactive component of marijuana, binds to CB1 cannabinoid receptors in the brain. Endogenous cannabinoids are involved in the regulation of emotional responses, including mood, anxiety, and aggression,and laboratory studies support an acute impact of THC on mood and emotion.CB1 receptor expression is highest during adolescence, dropping thereafter into adulthood with the most pronounced decreases observed in limbic regions critically involved in emotion regulation.Thus, adolescent exposure to THC may have lasting consequences on the developing brain that specifically impact the regulation of emotion. Some support for this comes from structural imaging studies showing volumetric differences in adolescent marijuana users compared with controls in limbic regions,including the amygdala, hippocampus, and insula.For example, larger amygdala volumes were observed in female marijuana users compared with controls, which was further associated with depression and anxiety symptoms.Other work has observed that marijuana users have differences in cerebral blood flow and resting connectivity compared with controls in brain regions involved in emotion, including the insula and temporal cortex.Together, the evidence supports an association between marijuana use during adolescence and an alteration of the neural systems supporting emotion regulation. However, to date only one study has investigated the effects of marijuana use on brain functioning during an emotion task. This study of adult heavy marijuana smokers found decreases in anterior cingulate and amygdala activation during the viewing of masked affective faces, suggesting a difference in the way marijuana users process emotional information.

To date, no studies have investigated how the use of marijuana specifically during adolescence impacts these processes; thus, one goal of the current study was to address this gap by investigating brain functioning during emotion arousal in 17–22 year-old heavy marijuana smokers who began their use earlier in adolescence. Furthermore, although there is evidence for a prospective relationship between early marijuana smoking and later negative emotionality,the literature regarding the intermediary brain processes in this relationship has been less clear. The work reviewed above has been crosssectional, and consequently, inferences cannot be made regarding causal relationships among history of marijuana use, brain functioning, and negative affect. Therefore,this study uses a prospective design to better address the nature of the relationship and to investigate whether emotion-related brain function in late adolescence/emerging adulthood mediates a relationship between prior marijuana use and later emotional functioning. We investigate two facets of emotional functioning, which are grounded in the temperament and personality literature—negative emotionality and resiliency.Negative emotionality is the propensity to experience depressed mood, anxiety, and irritable anger. Resiliency is the ability to flexibly adapt one’s level of control—in either direction—in response to the demands of the environment. It involves thoughtful, deliberate control of behavior in challenging or stressful circumstances and freer expression in circumstances where it is appropriate.This type of self-regulation is a critical aspect of emotional regulation.Note that the construct of resiliency is not directly related to the idea of resilience to adversity. Rather, resiliency has its conceptual roots in the temperament-based work of the Blocks,who identified the related construct of ego resiliency. Using a prospective, longitudinal design, we investigate negative emotionality and resiliency measured at three time points:  at the approximate age when the heavy marijuana smokers initiated use ;  within one year prior to participation in the functional magnetic resonance imaging  study of emotion arousal ; and  approximately three years after participation in the fMRI study.Information on occasions of marijuana use was collected prospectively on an annual basis from age 11 up to the time of participation in the fMRI study.

This design allows us to investigate the impact of marijuana use during adolescence on the development of negative emotionality and resiliency and on emotion-related brain function, and to investigate whether emotion-related brain function mediates a relationship between prior marijuana use and later emotional functioning.Forty participants were selected from an ongoing fMRI study of adolescents and young adults recruited from the Michigan Longitudinal Study.The MLS is an ongoing, prospective community-recruited study of families with parental alcohol use disorder  along with a contrast sample of families without AUD drawn from the same neighborhoods.All parent diagnoses were ascertained by a clinical psychologist based on Diagnostic Interview Schedule – Version 4  and established at time of recruitment and via multiple face-to-face diagnostic assessments ofthe parents over the course of the youth’s life. Families in which the target offspring exhibited signs of fetal alcohol syndrome  were excluded from the original ascertainment. Exclusionary FAS characteristics included prenatal or postnatal growth retardation or both, central nervous system involvement, and characteristic facial dysmorphology.From the time of enrollment, all family members are assessed at 3-year intervals with an extensive psychosocial battery of measures assessing temperament, behavioral symptomatology, IQ, school performance, social interaction, etc. During the 11–26 year-old period, all offspring are also assessed annually on substance use and problems. Full details on the prospective assessment and data collection protocol in the MLS can be found elsewhere.One hundred and thirty 17–22 year old offspring from the MLS have completed an emotion arousal task during fMRI.Exclusionary criteria for the fMRI study included neurological, acute, uncorrected, or chronic medical illness, current or recent  treatment with centrally active medications, or history of psychosis in first-degree relatives. The presence of most active primary Axis I disorders was also exclusionary; this did not include unmedicated mood and anxiety disorders, antisocial personality disorder, or substance use disorder. The goal of this work was to investigate the impact of heavy marijuana use during adolescence on later emotional functioning, as well as potential brain function mediators of this effect.

Using a prospective design, we investigated two outcomes related to emotional functioning: negative emotionality and resiliency. We found that heavy marijuana users did not differ from controls in emotional functioning early in adolescence when marijuana use was initiated, whereas in late adolescence/early adulthood, heavy users had more negative emotionality and less resiliency than controls. To investigate the impact of adolescent marijuana use on emotion-related brain functioning, we compared neural responses to emotional words in heavy marijuana users and controls. Compared with controls, heavy users had less activation in emotion processing and integration regions,vertical grow rack including the right insula, prefrontal cortex, and occipital cortex during the viewing of negative words, and in a region involved in attentional control  during the viewing of positive words. Amygdala activation was lower to both negative and positive words in heavy users compared with controls. Further, we found heightened activation to positive words in the dorsolateral prefrontal cortex among heavy users. Activation in prefrontal cortex during the viewing of negative stimuli mediated an association between marijuana use and both negative emotionality and resiliency at follow-up. Activation in visual association regions of the occipital cortex mediated an association between marijuana use and later resiliency, but not negative emotionality.Heavy marijuana users scored higher on negative emotionality than controls at the approximate ages of 20 and 23, whereas groups did not differ at approximately age 13, when heavy users initiated use. Furthermore, exploratory analyses revealed that negative emotionality decreased from early adolescence to young adulthood in controls—consistent with normative changes —but not in heavy users. Importantly, we observed an association between greater lifetime marijuana use occasions and higher negative emotionality at age 20, after controlling for early levels  of negative emotionality. These findings are in line with other longitudinal work showing that adolescent marijuana users had increased depression, anxiety, and suicidality in young adulthood, but marijuana use was not associated with premorbid differences in negative affect.Thus,the current results add to previous work supporting an association between early marijuana use and later negative affectivity.

We also investigated the impact of marijuana use on resiliency, as self-regulation plays a critical role in emotional functioning .We found no difference between groups inresiliency at the age of marijuana initiation, whereas differences emerged in late adolescence/early adulthood, with lower resiliency in the heavy use group. Although conceptualized as a temperament/personality trait, evidence indicates that resiliency improves throughout adolescence and into adulthood in healthy individuals.Here we found that resiliency increased over time in controls but notin heavy users. Furthermore, lifetime occasions of marijuana use was negatively correlated with resiliency, even after taking into account early level of resiliency. Resiliency is inversely related to depression and internalizing problems in children  and emerging adults,and positively related to effective social interaction  and social status.A reciprocal longitudinal relationship has been demonstrated between resiliency and positive emotionality from adolescence to early adulthood, as well as with the effective management of negative emotions.It is possible, therefore, that adolescent marijuana use may impact emotional functioning partially through an influence on resiliency; however further work in a larger sample is required to determine these longitudinal relationships. A central goal of this study was to characterize the neural mechanisms through which adolescent marijuana use exerts its effects on later emotional functioning. We found that activation in the right prefrontal cortex to negative words mediated the association between heavy marijuana use and both negative emotionality and resiliency at follow-up. Specifically, activation in the right middle frontal gyrus and dorsolateral superior frontal gyrus was lower in heavy users than controls, an effect that was associated with decreased resiliency and increased negative emotionality at follow-up. This area of the prefrontal cortex has been referred to as the caudal dorsolateral prefrontal region  and is closely connected with motor and supplementary motor regions.Prior work has found activation ofthe caudal dlPFC and associated regions during the reading of high-arousal emotional words.The supplementary motor and premotor regions are important for emotion processing and empathy  and may regulate approach-withdrawal tendencies to emotional stimuli by integrating limbic and motor responses.A recent meta-analysis found that activation in these regions decreased to negative stimuli in alexithymia, a trait characterized by difficulties with experiencing and processing emotions.The current findings suggest that heavy marijuana use during adolescence may impact caudal dlPFC functioning, impairing the processing and integration of emotional stimuli and lead to increased negative emotionality.