Effects Of Chronic Marijuana Use Research Articles

Chronic Marijuana Use, Inhibitory Control, and Processing Speed in Young Adult College Students

Marijuana is the most widely used illicit substance in the United States, and its use is especially prevalent among young adults. Over the past two decades, there has been an overall decline in perceived harmfulness of marijuana use in young adults ages 18-30, despite growing evidence that chronic marijuana use may be associated with cognitive impairment. There have been mixed results regarding the effects of chronic marijuana use on inhibitory control. Furthermore, previous literature has shown inconsistent results regarding processing speed in marijuana users. The current study examined inhibitory control and processing speed in chronic marijuana-using young adult college students and healthy controls ages 18-22. 33 healthy controls (mean age: 19.18 ± 1.13; 18 male) and 28 chronic marijuana users (mean age: 20.25 ± 1.17; 19 male) were included in the study. Chronic marijuana users had to have used marijuana ≥5 times/week over the past year to be eligible. Participants were instructed to remain abstinent from marijuana use for 12 hours prior to the study visit. The 30-day Timeline Followback (TLFB) was used to assess recent marijuana use and participants were asked to estimate age at first marijuana use and lifetime days of marijuana use. Participants completed the Stroop Color Word Task (SCWT), and the interference t-score was used as a measure of inhibitory control. Furthermore, we examined marijuana use characteristics (i.e. age at first use, lifetime marijuana use, and past 30-day marijuana use) in relation to performance on the SCWT. Additionally, exploratory analyses investigated differences in the color and word conditions of the SCWT between the two groups and as a function of marijuana use characteristics. Results indicated no significant group differences on the interference, word, and color conditions of the SCWT. Furthermore, there were no significant correlations between age at first use, lifetime marijuana use, and past 30-day marijuana use with any conditions of the SCWT, but, there was a trend for greater past 30-day marijuana use to be associated with poorer performance on the color condition (r(26) = -0.26, p = 0.09). These findings indicate that chronic, heavy marijuana use may not be associated with impairments in inhibitory control or processing speed, which is consistent with other studies examining current use, heavy use, and chronic use in adolescents, young adults, and adults. Further research is needed to determine whether chronic, heavy marijuana use during young adulthood affects higher-order cognitive functioning skills needed for success in college, starting a career, and transitioning into adulthood.

Effects of chronic marijuana use on driving performance

Objectives: The effects of marijuana on driving pose a significant public health concern. More studies on chronic marijuana use in driving are needed. The study objectives were to (1) assess differences in the Standardized Field Sobriety Test (SFST) and driving performance outcomes between chronic medical marijuana users and nonusers and (2) identify a cutoff tetrahydrocannabinol (THC) concentration above which chronic medical marijuana users demonstrate driving impairment.Methods: This prospective cross-sectional study assessed 31 chronic marijuana users and 41 nonusers. Rapid Detect Saliva Drug Screen 10-panel was administered to all participants. Participants were given a simple visual reaction time test (SVRT) and SFST consisting of the horizontal gaze nystagmus (HGN), the one leg stand (OLS), and the walk and turn (WAT) tests. The STISIM Drive M100 driving simulator assessed driving performance. Driving parameters included standard deviation of speed (SDS), deviation of mean lane position, off-road accidents, collisions, pedestrians hit, and car-following modulus, delay, and coherence. Cannabinoid blood plasma was obtained from marijuana users.Results: Marijuana users and nonusers did not differ in age (40.06 ± 13.92 vs. 41.53 ± 15.49, P = .6782). Marijuana users were more likely to fail the SFST (P = .005) and the WAT (P = .012) and HGN (P = .001) components. Marijuana users had slower SVRT (P = .031), less SDS (P = .039), and lower modulus (P = .003). Participants with THC >2 ng/mL (P = .017) and TCH >5 ng/mL (P = .008) had lower SDS. Participants with THC >2 ng/mL (P = .021) and THC >5 ng/mL (P = .044) had decreased modulus.Conclusion: Chronic marijuana users had slower reaction times, deviated less in speed, and had difficulty matching a lead vehicle’s speed compared to nonusers. The effects on SDS and modulus were present at cutoffs of 2 and 5 ng/mL.

The effects of chronic marijuana use on circadian entrainment

Animal literature suggests a connection between marijuana use and altered circadian rhythms. However, the effect has not yet been demonstrated in humans. The present study examined the effect of chronic marijuana use on human circadian function. Participants consisted of current users who reported smoking marijuana daily for at least a year and non-marijuana user controls. Participants took a neurocognitive assessment, wore actigraphs and maintained sleep diaries for three weeks. While no significant cognitive changes were found between groups, data revealed that chronic marijuana use may act as an additional zeitgeber and lead to increased entrainment in human users.

Long-term effects of marijuana use on the brain.

Questions surrounding the effects of chronic marijuana use on brain structure continue to increase. To date, however, findings remain inconclusive. In this comprehensive study that aimed to characterize brain alterations associated with chronic marijuana use, we measured gray matter (GM) volume via structural MRI across the whole brain by using voxel-based morphology, synchrony among abnormal GM regions during resting state via functional connectivity MRI, and white matter integrity (i.e., structural connectivity) between the abnormal GM regions via diffusion tensor imaging in 48 marijuana users and 62 age- and sex-matched nonusing controls. The results showed that compared with controls, marijuana users had significantly less bilateral orbitofrontal gyri volume, higher functional connectivity in the orbitofrontal cortex (OFC) network, and higher structural connectivity in tracts that innervate the OFC (forceps minor) as measured by fractional anisotropy (FA). Increased OFC functional connectivity in marijuana users was associated with earlier age of onset. Lastly, a quadratic trend was observed suggesting that the FA of the forceps minor tract initially increased following regular marijuana use but decreased with protracted regular use. This pattern may indicate differential effects of initial and chronic marijuana use that may reflect complex neuroadaptive processes in response to marijuana use. Despite the observed age of onset effects, longitudinal studies are needed to determine causality of these effects.

Marijuana, feijoada and the debate on drug legalization

Feijoada is one of the most typical dishes of Brazilian cuisine, commonly made from a mixture of black beans and several cuts of pork and beef. It is served with rice, farofa (toasted, seasoned manioc flour), sauteed collard greens, and sliced oranges, among other side orders. In the most sophisticated recipes it can take more than 30 ingredients, including spices and side dishes. One does not have to be a cook, chef, or expert to distinguish beans—the main ingredient of the dish—from complete feijoada. Marijuana, the popular name of Cannabis sativa, has more than 400 compounds, many of which are named “cannabinoids” (substances that affect receptors carrying the same name) (Pate, 2002). In an analogy with feijoada, Δ9-tetrahydrocannabinol (Δ9-THC), responsible for the psychoactive effects of the drug (Zuardi, 2008), could be the beans. In the early twentieth century, when the active principles of the drug had not yet been isolated, marijuana extracts were marketed by large pharmaceutical companies for a number of indications (Fankhauser, 2002). However, the therapeutic use declined within a few years due to the difficulty in obtaining reproducible effects and to the introduction of other drugs for the same indications of marijuana at that moment. Marijuana extracts have a wide variability in their composition, stability, and potency. Thus, consonant with the principles of the evolution of pharmacotherapy, effort has been put into the development of purer cannabinoid compounds that can be accurately measured, thus reducing the risk of significant undesirable side effects. In the first half of the 1960s the chemical structures of the major cannabinoids were determined by Professor Raphael Mechoulam from Israel, including Δ9-THC. Around 80 cannabinoids have been described to date, with different effects and many with therapeutic potential. Cannabidiol (CBD), for example, which makes up to 40% of marijuana extracts, has several effects opposite to those of Δ9-THC, including anxiolytic and antipsychotic properties (Crippa et al., 2010). Differently from Δ9-THC, the use of CBD alone does not cause the typical effects of marijuana, and Brazilian, American, British, and Israeli groups are in the leading edge of research on the therapeutic potential of this compound (Carlini, 2010). Today, CBD is being tested in Brazil in Parkinson's disease, schizophrenia, social phobia, post-traumatic stress disorder, smoking, epilepsy, depression, and other conditions (Crippa et al., 2010; Schier et al., 2012). It can be said, therefore, that cannabinoids are components of marijuana, but that the two are not synonyms. That is, cannabinoids are not marijuana. Marijuana is the most commonly used illicit drug in many countries, despite evidence showing that it may cause transient psychiatric symptoms and cognitive alterations depending on the dose. Moreover, chronic marijuana use may also cause long-lasting cognitive alterations and trigger the onset of psychiatric disorders in vulnerable individuals, depending on the dose, frequency, and earliness of use (Solowij et al., 2002; Manrique-Garcia et al., 2012), although these findings are still under debate. The marijuana withdrawal syndrome has gained increased recognition and it is known that some individuals may develop dependence (Hasin et al., 2008). Currently available therapeutic interventions—both pharmacological and non-pharmacological—have shown less than optimal efficacy. Modern neuroimaging studies show alterations in brain function with chronic, repeated use of marijuana (Bhattacharyya et al., 2012). Furthermore, clinical complications such as cancer and breathing and immunological problems have also been associated with the use of the drug. However, as cannabis is often smoked in conjunction with tobacco and/or other drugs, the relationship between chronic use and these problems is so far inconclusive (Lader, 2009). Therefore, the effects of chronic marijuana use on health need careful evaluation. The existing evidence about these effects is also confounded and misleading, as it considers marijuana and cannabinoids to be equivalent. All scientific debate concerning the legalization of marijuana should necessarily be informed by empirical data from clinical trials and epidemiological studies. Any debate occurring on a background of political positions, ideological biases and, even worse, personal beliefs will only increase confusion, and postpone concrete decisions. Cannabinoids and drugs that act in the endocannabinoid system have been shown to have a fantastic therapeutic potential and there is reason to believe that they could benefit millions of people worldwide. A better understanding of the mechanisms of action of these compounds, with the ensuing legalization of cannabinoids, would be an outstanding scientific breakthrough, leading to a significant decrease in burden, and improved quality of life for people with many diseases and disorders. Conversely, the debate on the legalization of marijuana for recreational purposes should only take place after society and the scientific community is clearly informed about the potential complications of the drug or its possible low-risk profile. In order to do this, however, it is crucial to separate the wheat from the chaff, beans from feijoada or—in this case—cannabinoids from marijuana.

Sex Hormones Levels as Influenced by Cannabis sativa in Rats and Men

2 Abstract: This study targeted the possible effects of chronic marijuana use on reproductive hormones. To pursue this effect, the levels of the testosterone, the Luteinizing Hormone (LH) and the Follicle Stimulating Hormone (FSH) were assayed in men users in Sudan and in Cannabis sativa extract treated rats. Results were compared to non using groups as controls. Luteinizing Hormone (LH), Stimulating Hormone (FSH) and testosterone levels showed significant changes after 10 days in rat groups. In all addicted men groups, only slight non significant changes were observed compared to non users. These findings supported previous studies and concluded that C. sativa can significantly influence the levels of sex hormones in rats.

Effects of Chronic Marijuana Use on Brain Activity During Monetary Decision-Making

Marijuana (MJ) acutely acts on cannabinoid receptors that are found in numerous brain regions, including those involved in reward processing and decision-making. However, it remains unclear how long-term, chronic MJ use alters reward-based decision-making. In the present study, using [(15)O]water PET imaging, we measured brain activity in chronic MJ users, who underwent monitored abstinence from MJ for approximately 24 h before imaging, and control participants, while they took part in the Iowa Gambling Task (IGT), a monetary decision making task that strongly relies on the ventromedial prefrontal cortex (vmPFC). During PET imaging, participants took part in the standard and a variant version of the IGT as well as a control task. Chronic MJ users performed equally well on the standard IGT, but significantly worse than controls on the variant IGT. Chronic MJ users and control subjects showed increased regional cerebral blood flow (rCBF) in the vmPFC on both versions of the IGT compared to the control task. In the two-group comparison, chronic MJ users showed significantly greater rCBF than controls in the vmPFC on the standard IGT and greater activity in the cerebellum on both versions of the IGT. Furthermore, duration of use, but not age of first use, was associated with greater activity in the vmPFC. Thus, chronic MJ users tend to strongly recruit neural circuitry involved in decision-making and reward processing (vmPFC), and probabilistic learning (cerebellum) when performing the IGT.

Combined and independent effects of chronic marijuana use and HIV on brain metabolites.

The effects of chronic marijuana (MJ) use on brain function remain controversial. Because MJ is often used by human immunodeficiency virus (HIV) patients, the aim of this study was to evaluate whether chronic MJ use and HIV infection are associated with interactive or additive effects on brain chemistry and cognitive function. We evaluated 96 subjects (30 seronegative nondrug users, 24 MJ users, 21 HIV without MJ use, 21 HIV + MJ) using proton magnetic resonance spectroscopy and a battery of neuropsychological tests. The two primarily abstinent MJ user groups showed no significant differences on calculated estimates of lifetime grams of delta9-tetrahydrocannabinol exposure, despite some differences in usage pattern. The two HIV groups also had similar HIV disease severity (CD4 cell count, plasma viral load, HIV dementia staging, Karnofsky score). On two-way analyses of covariance, HIV infection (independent of MJ) was associated with trends for reduced N-acetyl aspartate (NA) in the parietal white matter and increased choline compounds (CHO) in the basal ganglia. In contrast, MJ (independent of HIV) was associated with decreased basal ganglia NA (-5.5%, p = 0.05), CHO (-10.6%, p = 0.04), and glutamate (-9.5%, p = 0.05), with increased thalamic creatine (+6.1%, p = 0.05). HIV + MJ was associated with normalization of the reduced glutamate in frontal white matter (interaction p = 0.01). After correction for age, education, or mood differences, MJ users had no significant abnormalities on neuropsychological test performance, and HIV subjects only had slower reaction times. These findings suggest chronic MJ use may lead to decreased neuronal and glial metabolites, but may normalize the decreased glutamate in HIV patients.

Cardiovascular consequences of marijuana use.

This review describes what is known about effects of marijuana and cannabinoids in relation to human physiological and disease outcomes. The acute physiological effects of marijuana include a substantial dose-dependent increase in heart rate, generally associated with a mild increase in blood pressure. Orthostatic hypotension may occur acutely as a result of decreased vascular resistance. Smoking marijuana decreases exercise test duration in maximal exercise tests, increases the heart rate at submaximal levels of exercise. Tolerance develops to the acute effects of marijuana smoking and delta9-tetrahydrocannibol (THC) over several days to a few weeks. The cardiovascular responses that occur in response to THC are mediated by the autonomic nervous system, with recent findings also demonstrating that the human cannabinoid receptor system plays a role in regulating the cardiovascular response. Although several mechanisms exist by which marijuana use might contribute to the development of chronic cardiovascular conditions or acutely trigger cardiovascular events, there are few data regarding marijuana/THC use and cardiovascular disease outcomes. A large cohort study showed no association of marijuana use with cardiovascular disease hospitalization or mortality. However, acute effects of marijuana use include a decrease of the time until the onset of chest pain in patients with angina pectoris; one study has shown that marijuana may trigger the onset of myocardial infarction. Patients who have coronary heart disease or are at high risk for the development of CHD should be cautioned about the potential hazards of marijuana use as a precipitant for clinical events. Research directions might include more studies of cardiovascular disease outcomes and relationships of marijuana with cardiovascular risk factors, studies of metabolic and physiologic effects of chronic marijuana use that may affect cardiovascular disease risk, increased understanding of the role of the cannabinoid receptor system in cardiovascular regulation, and studies to determine if there is a therapeutic role for cannabinoids in blood pressure control or for neuroprotection after stroke.

Platelet dense granule secretion and aggregation in adolescents with conduct disorder: effects of marijuana use

Background: We had previously reported a decrease in agonist-induced platelet dense granule secretion in blood samples from male adolescents with and without Conduct Disorder (CD). In an augmented sample, we have now employed multivariate modeling to examine the simultaneous effects of CD and regular monthly alcohol and marijuana use on both the dense granule secretion and aggregation phases of agonist-induced platelet responses. Methods: Blood samples were obtained from adolescents with and without a CD diagnosis. Platelet dense granule secretion and aggregation responses to a variety of agonists were examined in the laboratory. Results: Significant multivariate interactions of CD status with regular marijuana use were found for responses to collagen, ADP alone, and ADP plus 0.2 μg. of serotonin. Responses in platelets from youth with CD, but without regular marijuana use differed from other subjects. Multivariate main effects of marijuana use alone on platelet responses to arachidonic acid and ADP plus 1.0 μg. of serotonin were found. No effects of alcohol use were found. Conclusions: The results demonstrate an interaction between CD and the effects of chronic marijuana use for several agonists in this platelet model system, and further support the possibility of a variation in signal transduction mechanisms in CD.

Effects of chronic marijuana use on human cognition

Impairments of human cognition and learning following chronic marijuana use are of serious concern, but have not been clearly demonstrated. To determine whether such impairments occurred, this study compared performance of adult marijuana users and non-users (N = 144 and N = 72, respectively) matched on intellectual functioning before the onset of drug use, i.e., on scores from standardized tests administered during the fourth grade of grammar school (Iowa Tests of Basic Skills). Subjects were given the twelfth grade versions of these tests (Iowa Tests of Educational Development) and other, computerized cognitive tests in successive test sessions. "Heavy" marijuana use (defined by use seven or more times weekly) was associated with deficits in mathematical skills and verbal expression in the Iowa Tests of Educational Development and selective impairments in memory retrieval processes in Buschke's Test. The retrieval impairments were restricted to words that were easy to visualize. Impairments depended on the frequency of chronic marijuana use, i.e., "light" and "intermediate" marijuana use (defined by use one to four and five to six times weekly, respectively) were not associated with deficits. Intermediate use was associated with superior performance in one condition ("fuzzy" concepts) of a Concept Formation test.

Effects of chronic marijuana use on testosterone, luteinizing hormone, follicle stimulating hormone, prolactin and cortisol in men and women

To investigate possible effects of chronic marijuana use on reproductive and stress hormones, we assayed testosterone, luteinizing hormone, follicle stimulating hormone, prolactin, and cortisol in 93 men and 56 women with a mean (± S.E.) age of 23.5 ± 0.4 years. Hormone values were compared among groups of subjects stratified according to frequency of marijuana use (frequent, moderate and infrequent; N = 27, 18, and 30, respectively) and non-using controls ( N = 74). Chronic marijuana use showed no significant effect on hormone concentrations in either men or women.

The effects of chronic marijuana use.

Summary There has been much controversy in the literature as to whether marijuana is detrimental to the psychological functioning of the user. In light of this issue, 14 male and female users, nonusers, and quitters of high school and college age were studied in a pre-posttest design to determine if chronic use affects the variables of aggression, frustration, alienation, and social- and self-adjustment. The quitters group discontinued use for two months after a two-week baseline period. Statistical analysis showed no significant differences among groups on any of the measures. Relating these findings to the literature suggests that differences which have been previously indicated may be due to the use of naive vs. experienced marijuana users as Ss.