Although we report complete data for all analyses, meta analyses of cross-sectional studies examining cough, sputum production, and wheezing were limited by heterogeneity. Heterogeneity was likely related to the lack of uniform assessment of marijuana use and outcome ascertainment . Our current understanding of the long-term health effects of marijuana could be improved by standardized assessment tools for marijuana use and studies with larger samples of marijuana-only users and longer follow-up times. Low-strength evidence indicates that smoking marijuana is associated with cough, sputum production, and wheezing. Current understanding of marijuana’s effect on pulmonary function tests and development of obstructive lung disease is insufficient and is limited by low exposure and young study populations. Given rapidly expanding use, we need large scale longitudinal studies examining the long-term pulmonary effects of daily marijuana use.Marijuana is one of the most widely used illicit substances world-wide. Although it has been reported that marijuana use rate has stabilized or even decreased in recent years in most high-income countries, the continuing high prevalence of use among adolescents and young adults is a cause for concern. Such emerging trends have heightened interest in the link between mental health problems and adolescent marijuana use to inform policy and prevention efforts. Understanding the comorbidity between psychopathology and marijuana use is complicated. Marijuana use is associated with numerous different psychiatric disorders, cannabis drying racks commercial each of which tend to co-occur with one another. Additionally complicating matters is the potential bidirectional nature of this association, with evidence that marijuana use may both predict and result from poor zmental health.
A parsimonious explanation of this comorbidity may be that a small set of transdiagnostic psychopathological vulnerabilities that give rise to numerous mental health conditions may also contribute to and result from marijuana use. Such transdiagnostic vulnerabilities may account for the pervasive patterns of psychiatric comorbidity with use of marijuana and other substances. One such transdiagnostic vulnerability is anhedonia— diminished capacity to experience pleasure in response to rewards. As a subjective manifestation of deficient reward processing capabilities, anhedonia is believed to result from hypoactive brain reward circuitry. While anhedonia is a core feature in a DSM-defined major depressive episode, it has also been linked to other psychopathologies comorbid with drug use, including psychosis, borderline personality disorder , social anxiety, attention deficit hyperactivity disorder and post-traumatic stress disorder and has therefore been proposed to be a transdiagnostic process. Departing from its consideration as a ‘symptom’ of a disease state as in DSM-defined major depression, anhedonia has also been conceptualized as a continuous dimension, upon which there are substantial inter individual differences. Individuals at the lower end of the anhedonic spectrum experience high levels of pleasure and experience robust affective responses to pleasurable events, whereas those at the upper end of this spectrum exhibit more prominent deficits in their pleasure experience.Anhedonia operates as a ‘trait like’ dimension that is stable yet malleable, which is empirically and conceptually distinct from other emotional constructs, such as reward sensitivity , alexithymia and emotional numbing , sadness and negative affect. Recent literature documents a consistent association between anhedonia and substance use in adults.
To the best of our knowledge, there has been only prior study of the association between anhedonia and marijuana use in youth, which found higher anhedonia levels among treatment-seeking marijuana users than healthy controls in a cross-sectional analysis of 62 French adolescents and young adults. Given the absence of longitudinal data, it is unclear whether anhedonia is a risk factor for or consequence of adolescent marijuana use. Because youth with higher anhedonia levels experience little pleasure from routine rewards they may seek out drugs of abuse, such as marijuana, which stimulate neural circuitry that underlie pleasure pharmacologically. Alternatively, repeated tetrahydrocannabinol exposure during adolescence produces enduring deficits in brain reward system function and anhedonia-like behavior in rodent models. In observational studies of adults, heavy or problematic marijuana use is associated with subsequent anhedonia and diminished brain reward region activity during reward anticipation. Consequently, it is plausible that anhedonia may both increase risk of marijuana use and result from marijuana use. Because early adolescence is a period in which risk of marijuana use uptake is high and the developing brain may be vulnerable to cannabinoid-induced neuroadaptations, this study estimated the strength of bidirectional longitudinal associations between anhedonia and marijuana use among adolescents during the first 2 years of high school. The primary aim was to test the following hypotheses: greater baseline anhedonia would be associated with a faster rate of escalation in marijuana use across follow-up periods; and more frequent use of marijuana at baseline would be associated with increases in anhedonia across follow-ups. A secondary aim was to test whether these putative risk pathways were amplified or suppressed among pertinent sub-populations and contexts.
Associations of affective disturbance and other risk factors with adolescent substance use escalation have been reported to be amplified among girls, early- onset substance users and those with substance-using peers.We therefore tested whether associations between anhedonia and marijuana use were moderated by gender, history of marijuana use prior to the study surveillance period at baseline and peer marijuana use at baseline.To characterize trajectories of anhedonia and marijuana use across time, latent growth curve modeling was applied to estimate a baseline level and linear slope for both anhedonia and marijuana use. Univariate latent growth curve models were first fitted for marijuana use and anhedonia separately to determine the shape and variance of trajectories. A two-process parallel latent growth curve model was then fitted, which simultaneously included growth factors for anhedonia and marijuana use after adjusting for covariates listed above and including within-construct level-to-slope associations. The parallel process model was constructed to test: bidirectional longitudinal associations by including directional paths from baseline anhedonia level to marijuana use slope as well as baseline marijuana use level to anhedonia slope; and non-directional correlations between baseline levels of anhedonia and marijuana use and between anhedonia slope and marijuana use slope. Significant directional longitudinal paths between anhedonia and marijuana use in the overall sample were tested subsequently in moderation analyses of differences in the strength of paths across subsamples stratified by moderator status using a multi-group analysis. Analyses were performed using Mplus with the complex analysis function to adjust parameter standard errors due to clustering of the data by school. To address item- and wave-level missing data, full information maximum likelihood estimation with robust standard errors was applied. Continuous and categorical ordinal scaled outcomes were applied for anhedonia and marijuana use, vertical grow racks cost respectively. The Akaike information criterion and the Bayesian information criterion were used to gauge model fit in which lower values represent better-fitting models. For moderator analyses, χ2 differences were calculated using log-likelihood values and the number of free parameters contrasting the model fit with equality constraints on the anhedonia–marijuana use path of interest across groups stratified by the moderator variable. Standardized parameter estimates and 95% confidence intervals are reported. Significance was set at α = 0.05 .Youth with higher levels of anhedonia at baseline were at increased risk of marijuana use escalation during early adolescence in this study. In addition, levels of anhedonia and marijuana use reported at the beginning of high school were associated cross-sectionally with each other.
To the best of our knowledge, the only prior study on this topic found higher levels of anhedonia in 32 treatment-seeking marijuana users than 30 healthy controls in a cross-sectional analysis of French 14–20-year-olds who did not adjust for confounders. The current data provide new evidence elucidating the nature and direction of this association in a large community-based sample, which advances a literature that has addressed the role of anhedonia predominately in adult samples. The association of baseline anhedonia with marijuana use escalation was observed after adjustment of numerous possible confounders, including demographic variables, symptom levels of three psychiatric syndromes linked previously with anhedonia and alcohol and tobacco use. Consequently, it is unlikely that anhedonia is merely a marker of these other psychopathological sources of marijuana use risk or a non-specific proclivity to any type of substance use. The temporal ordering of anhedonia relative to marijuana was addressed by the overarching bidirectional modeling strategy, which showed evidence of one direction of association and not the other direction . Ordering was confirmed further in moderator tests showing that the association of anhedonia with subsequent marijuana use did not differ by baseline history of marijuana use. Thus, differences in risk of marijuana use between adolescents with higher anhedonia may be observed in cases when anhedonia precedes the onset of marijuana use. Why might anhedonia be associated uniquely with subsequent risk of marijuana use escalation in early adolescence? Anhedonic individuals require a higher threshold of reward stimulation to generate an affective response and therefore may be particularly motivated to seek out pharmacological rewards to satisfy the basic drive to experience pleasure, as evidenced by prior work linking anhedonia to subsequent tobacco smoking escalation. Among the three most commonly used drugs of abuse in youth , marijuana may possess the most robust mood-altering psychoactive effects in young adolescents. Consequently, marijuana may have unique appeal for anhedonic youth driven to experience pleasure that they may otherwise be unable to derive easily via typical non-drug rewards. The study results may open new opportunities for marijuana use prevention. Brief measures of anhedonia that have been validated in youth, such as the SHAPS scale used here, may be useful for identifying teens at risk who may benefit from interventions. If anhedonia is ultimately deemed a causal risk factor, targeting anhedonia may prove useful in marijuana use prevention. Interventions promoting youth engagement in healthy alternative rewarding behaviors without resorting to drug use have shown promise in prevention, and could be useful for offsetting anhedonia-related risk of marijuana use update. Moderator results raise several potential scientific and practical implications. The association was stronger among adolescents with friends who used marijuana, suggesting that expression of a proclivity to marijuana use may be amplified among teens in environments in which marijuana is easily accessible and socially normative. The association of anhedonia with marijuana use escalation did not differ by gender or baseline history of marijuana use. Thus, preventive interventions that address anhedonia may: benefit both boys and girls , aid in disrupting risk of onset as well as progression of marijuana use following initiation and be particularly valuable for teens in high-risk social environments. While anhedonia increased linearly over the first 2 years of high school on average, the rate of change in anhedonia was not associated with baseline marijuana use or changes in marijuana use across time. Given that anhedonia is a manifestation of deficient reward activity, this finding is discordant with pre-clinical evidence of THCinduced dampening of brain reward activity and prior adult observational data, showing that heavy or problematic marijuana use is associated with subsequent anhedonia and diminished brain reward region activity during reward anticipation. Perhaps the typical level and chronicity of exposure to marijuana use in this general sample of high school students was insufficient for detecting cannabinoid-induced manifestations of reward deficiency. Longer periods of follow-up may be needed to determine the extent of marijuana exposure at which cannabinoid-induced reward functioning impairment and resultant psychopathological sequelae may arise. Strengths of this study include the large and demographically diverse sample, repeated-measures follow-up over a key developmental period, modeling of multi-directional associations, rigorous adjustment of potential confounders, high participation and retention rates and moderator tests to elucidate generalizability of the associations. Future work in which inclusion of biomarkers and objective measures is feasible may prove useful. Prevalence of heavy marijuana use was low in this sample, which precluded examination of clinical outcomes, such as marijuana use disorder. Students who did complete the final follow-up had lower baseline marijuana use and anhedonia, which might impact representativeness. Further evaluation of the impact of family history of mental health or substance use problems as well as use of other illicit substances, which was not addressed here, is warranted.Medical marijuana has moderate-to-high-quality evidence to treat conditions including chronic pain, neuropathic pain, spasticity due to multiple sclerosis, and chemotherapy associated nausea and vomiting .