The reality is that cannabis cannot be pigeonholed as strictly helpful or harmful. Instead, meaningful discussion about its potential benefits and harms requires careful and nuanced consideration of the scientific literature, coupled with a humble attitude. As delineated in a recent and thorough review paper in the International Review of Psychiatry , the relationship between cannabis and mental health is especially complicated.
For example, with respect to depression, the science is clear that the endocannabinoid system plays a role in mood regulation. Some people might sense this intuitively: they will tell you that cannabis can help with their depressive symptoms. But there have been no randomized controlled trials to date that support the use of the cannabis plant or particular cannabinoids in the treatment of depressive disorders.
Further, and perhaps counterintuitively to some people, the scientific data that do exist are mixed and actually tilt towards the idea that ingested cannabis plant material likely leads to the development and worsening of depressive symptoms.
These findings are not satisfying. They are not straightforward. They suggest the possibility of the development of cannabis-based medicines for depression while simultaneously cautioning against the self-medicated use of cannabis for depression.
A similarly confusing picture has been painted by the scientific literature for other psychiatric conditions. For example, two of the best-known cannabinoids found in the cannabis plant are deltatetrahydrocannabinold THC and cannabidiol CBD. In general, THC has been shown to produce anxiety and psychotic features , especially at higher doses, whereas CBD has been shown to produce anxiolytic and antipsychotic effects.
Mirroring this complexity, the current state of the scientific data for the use of cannabis in treating post-traumatic stress disorder symptoms are also mixed , whereby cannabis has demonstrated both helpful and harmful effects depending on many factors. The story about cannabis and addiction is no less confused.
This means that while a mere one in 10 people who ever try cannabis at least once might develop an addiction, this still represents a very large number of people. The topic of cannabis and addiction has been turned on its head in recent years as cannabis has entered the discussion as a treatment for addictions to other substances—most notably opioids.
Share via Email Smoking potent forms of cannabis greatly increases the risk of mental illness, a major study has found. Experts have previously flagged a link between cannabis use and psychosis, particularly among vulnerable people with heavy use of the drug. Now research suggests the potency of the cannabis is also important, with patterns in cannabis use linked to how often new cases of psychotic disorders arise in different cities.
The team says that equates to about 60 fewer cases per year in south London. Does marijuana use really cause psychotic disorders? Moreover, using a longitudinal analysis over 24 months, the researchers found that changes in cannabis dose did not predict changes in positive symptoms severity, even when patients became abstinent.
Notable strengths of this study are its dose—response analysis and its detailed quantification of cannabis use, with mean use in the sample being 4 days per week and an average of 2. However, the results were not adjusted for confounders, including other drug use. Another study, Dubertret et al. A cross-sectional analysis by Tosato et al.
Similarly, in a prospective, longitudinal cross-sectional study by Barrowclough et al. After adjustment for confounders, abstinence from cannabis 90 days preceding the assessment was found to be related to improved global functioning adjusted coefficient, 4. After controlling for confounders, van Dijk et al. Negative Symptoms Dubertret et al. Barrowclough et al. The longitudinal analysis of data from this cohort up to 24 months revealed no association between cannabis dose and negative symptom severity adjusted coefficient, 0.
Similarly, a prospective longitudinal study by Barrowclough et al. Cognition Power et al. Sanchez-Torres et al. Cannabis-using patients with the a priori vulnerability i. Discussion of Findings With regard to the effects of cannabis use on positive symptoms, the data are considered mixed.
Studies report both worsening and no effect of cannabis use on positive symptoms in schizophrenia. The limitations observed in the reviewed studies included variable adjustment for other drug use and baseline symptom severity; issues with study design observational ; a reliance on self-reports; and variable analyses of cannabis use i.
However, these studies, combined with human experimental studies demonstrating that cannabis can worsen positive symptoms in patients with schizophrenia, were also considered when determining the strength of evidence.
With regard to negative symptoms, the data reviewed were generally more homogenous, with most studies reporting either an absence of association between cannabis use and negative symptoms or else reduced negative symptoms in cannabis users. Variable adjustments for other drug use and baseline symptom severity were noted as limitations in some studies. Overall, the data provide support for the conclusion that cannabis use does not worsen negative symptoms in patients with psychotic disorders.
With regard to cognition in patients with psychotic disorders, the data reviewed in the systematic reviews suggest better cognitive performance in some cognitive domains in patients with psychotic disorders and cannabis use disorders, and in patients with a history of cannabis use, as compared to patients with psychotic disorders and no cannabis use disorder diagnosis. The limitations of two of the systematic reviews— Yucel et al.
This study found better cognitive performance only in subjects with a lifetime history of cannabis use, but not recent cannabis use. The systematic review by Donoghue and Doody focused on longitudinal studies in schizophrenic subjects with and without comorbid cannabis use and found that cannabis users performed better on some measures of cognition, including verbal learning and memory, attention and psychomotor speed, and global cognitive factor tests, than non-cannabis users.
The three reviewed studies showed similar effects; however, the largest study was more precise and had narrower confidence intervals. Estimates for the size of the effect are small to moderate. The primary articles reviewed indicate more mixed results than the systematic reviews. Overall, the totality of data favor the conclusion that a history of, but not recent, cannabis use is associated with statistically significant performance improvement on measures of cognitive function in patients with psychotic disorders.
It is not clear how the difference in scores might translate with respect to overall improved outcomes in functioning beyond the test setting. Furthermore, other data do not support the notion that acute cannabis exposure improves cognitive performance in patients with psychotic disorders, as acute intoxication is associated with impaired cognitive performance in cognitive domains of memory, learning, and attention see Chapter Among the multiple potential explanations of the data indicating better performance on certain measures of cognition in patients using cannabis are that these patients represent a higher-functioning subgroup of psychotic patients or that cannabis users who achieve abstinence have better premorbid cognitive status.
Additionally, it has been proposed that a history of cannabis use may have exerted neuroprotective effects in patients with psychotic disorders. Finally, we find insufficient data from which to draw conclusions regarding the effects of cannabis on risk for suicide in patients with psychotic disorders. The risk factors for developing bipolar disorder are not clear; however, research suggests that brain structure, genetics, and family history may contribute to its onset NIMH, Given that cannabis is reportedly the most commonly used illicit drug by individuals with bipolar disorders Zorrilla et al.
Systematic Reviews The committee identified one systematic review, Gibbs et al. The authors searched multiple databases for English language studies published through and included studies that were experimental, prospective, cohort, or longitudinal. The overall search strategy yielded six studies with a total of 14, participants who met the inclusion criteria.
The meta-analysis showed an association between cannabis use and new onset of manic symptoms in individuals without preexisting bipolar disorder OR, 2. However, the researchers did not report information about the patient characteristics, the total number of subjects, age, gender, cannabis form, the ascertainment of mania symptoms, or other features of the two studies. Furthermore, due to the low number of studies that contributed to their research findings, the authors describe their conclusions as prelimnary and tentative.
However, after adjusting for sociodemographic and clinical variables, the association was attenuated and no longer statistically significant aOR, 1. Using the same NESARC dataset as Feingold, Cougle and colleagues 10 found that the risk of a past-year bipolar disorder diagnosis was elevated in regular e. Cougle and collaborators reminded readers about the correlational nature of the study design and noted that causality could not be inferred from their conclusions.
They also cautioned that the increased risk in bipolar disorders might be due to augmenting the psychotic features in frequent cannabis users i. Also, Cougle and collaborators warned that in adjusting for other psychiatric comorbidities they only adjusted for those that fulfilled diagnostic thresholds, not other psychiatric symptoms that could explain the relationships of interest. Discussion of Findings Overall there is some evidence to support the association between cannabis use and the increased incidence of bipolar disorders.
Although there is support for this association, more information is needed on the potential mediators that could explain the relationship as well as whether the risk is likely to occur only in conjunction with the use of other substances such as alcohol or nicotine. For example, panel studies that have evaluated the relationship found the magnitude of the relationship to be similar, but once alcohol or other substances were adjusted for in the statistical models, the associations diminished or became insignificant.
This suggests that the constellation of behaviors that includes the use of cannabis, alcohol, and other substances might all play roles in the risk for bipolar disorders, with those different roles being difficult to disentangle. See Box for additional discussion on the complex relationship between substance use and mental health disorders.
Systematic Reviews The committee identified Gibbs et al. Gibbs et al. The three studies were published in , , and The studies used clinical samples of 50 new-onset bipolar patients ages 16 to 54, first-episode DSM-IV bipolar I patients ages 18 to 72, and 3, bipolar inpatients and outpatients age not reported. No other information gender, country, etc.
Using Cox regression models, Zorrilla and colleagues found that cannabis use versus no use was associated with time to recovery HR, 0. However, when alcohol and other substance use variables were included in the model as confounders, only the time to recurrence remained significantly associated with cannabis use HR, 1. Discussion of Findings The evidence on the association between cannabis use and the course and symptoms in patients with bipolar disorder is modest, but it is suggestive that cannabis use moderates the course of bipolar disorder by increasing the time to recovery, relapse, and recurrence of manic phases.
As discussed in the section above, when adjustments for alcohol and other substance use variables are included in the model as confounders, only the time to recurrence remains as significantly associated to cannabis use. The authors suggest that part of the problem of being able to find a conclusive relationship between the frequency of cannabis use and mania or hypomania symptoms might be due to the resemblance of mania and hypomania symptoms to psychotic symptoms, making it difficult to discriminate between these types of symptoms.
It should also be noted that in some of the studies reviewed above, the analyzed patient populations were undergoing treatment for bipolar disorder, adding an additional layer of limitations to the research findings. In reviewing the literature on the relationship between cannabis use and bipolar disorder, the committee identified various limitations in the studies discussed above, including a lack of biogenetic covariates that could relate to both cannabis use and bipolar disorders, as well as other psychological symptoms that are not adjusted in these studies.
Many of these studies do not take into account the variance among the subtypes of cannabis or in the potency or route of administration, all of which could lead to difference in results.
Also, the lack of precision in measuring the frequency of cannabis use at baseline and in measuring follow-up data remains a problem. Across the many depressive disorders that exist e. The endocannabinoid system is known to play a role in mood regulation NIDA, ; therefore, the committee decided to explore the association between cannabis use and depressive disorders or symptoms. Systematic Reviews The committee identified two systematic reviews that assessed the association between cannabis use and the risk of developing depressive disorders or symptoms: Lev-Ran et al.
The most recent systematic review is discussed. Lev-Ran et al. When the authors identified multiple studies reporting on the same population cohort at different time points, only one study the most recent reporting on the respective cohort was included.
The authors identified 14 studies published between and Sample sizes ranged from to 45,, with 10 of the samples having 1, or more participants. The ages of patients at cannabis assessment included high school age, subjects ages 12 to 17 or 12 to 16, and older groups ages 18 to A wide range of measures were used to assess cannabis use: namely, any cannabis use in the previous 30 days; any previous cannabis use; cannabis use disorder; cannabis use one or more times per month; any cannabis use in the previous year or heavy use at least once per week in the previous month ; at least five previous occasions of cannabis use or heavy use at least weekly ; any use in the previous 6 months; or more than 4 occasions of use per month in a 5-year period.
Thus, the comparison group lower level of exposure to cannabis in the latter studies included nonusers, as well as individuals using cannabis less than weekly, or individuals not having a cannabis use disorder. Studies varied in their approaches to adjust for confounding factors, ranging from none to adjustment for more than 20 variables. The analysis showed that cannabis use was associated with a small increase in risk for depressive outcome pOR, 1. The analysis further revealed a dose—response relationship, with a slightly higher OR observed in seven studies comparing heavy cannabis use to non-cannabis users pOR, 1.
Primary Literature Although several primary research studies found a positive association, the confounding factors of polydrug use or unspecified cannabis use made it difficult for the committee to make conclusions on the overall findings Brook et al.
Additional studies reviewed provided mixed findings on the association between cannabis use and depression or depressive symptoms Crane et al. A consideration of the confounding factors led to several of these mixed findings. For example, Sillins et al. The investigators sought to determine the association between the maximum frequency of cannabis use before age 17 and seven developmental outcomes, including depression. Because this was an integrated study, the outcomes of depression were assessed by different measures i.
The investigators of this study created a dichotomous measure of moderate or severe depression in the past week to the past month between ages 17 and 25 years. Using combined data adjusted for study-specific effects, the investigators found a significant asssociation between adolescent cannabis use and the study's measure of depression less than monthly use, OR, 1.
However, after adjusting for relevant covariates in the analysis, this association became insignificant and negligible in size less than monthly use, aOR, 1. The authors noted that the confounding factors spanning the individual's background and functioning as well as parental and peer factors likely affected the change in the research findings.
Discussion of Findings The evidence reported suggests that cannabis use, and particularly heavy cannabis use, is associated with a small increase in the risk of developing depressive disorders. This evidence is supported by a good-quality recent systematic review that included 10 longitudinal studies with sample sizes between and 45, Although the supplemental studies from the primary literature reported mixed findings, the committee concludes that there is a strong enough evidence base to support the conclusion that there is an association between cannabis use and a small increased risk pOR of 1.
The possible relationship between heavy cannabis use and the development of depressive disorders or symptoms needs to be further explored.
Given that these relationships are associational and not necessarily causal, it is important to note possible alternative explanations for the mixed findings. For example, within the literature, a reverse association between cannabis use and depressive disorders has been documented, and the relationship may be bidirectional Horwood et al. This complex scenario is consistent both with the known protective roles of the endocannabinoid system in the control of mood and affect and with the propensity of cannabinoid receptors to undergo desensitization following prolonged activation.
See Box for an additional discussion on this topic. To review the research on the potential therapeutic effects of cannabis or cannabinoids on major depression disorder, please refer to Chapter 4 Therapeutic Effects of Cannabis and Cannabinoids. Systematic Reviews The committee did not identify a good- or fair-quality systematic review that reported on the association between cannabis use and the course, symptoms, or other endpoints in individuals with a depressive disorder.
Primary Literature The committee did not identify any good-quality primary literature that reported on the association between cannabis use and the course, symptoms, or other endpoints in individuals with a depressive disorder and that were published subsequent to the data collection period of the most recently published good- or fair-quality systematic review addressing the research question. It is the 10th most common cause of death in the United States, with an estimated 13 suicidal deaths per , individuals; it is often related to mental illness, substance abuse, or a major stressful event CDC, ; MedlinePlus, Cannabis is widely used for both medical and recreational purposes Azofeifa et al.Duration of use did not differ between patients and controls, nor did other drug use. The possible relationship between heavy cannabis use and the of cannabis on behavior, to understand how cannabis interacts with alcohol and other drugs to influence behavior, and. The causes of addiction are multifaceted and fukuyama historiens afslutning essay help solutions will continue to be multipronged.
The strongest evidence to date concerns links between marijuana use and substance use disorders and between marijuana use and psychiatric disorders in those with a preexisting genetic or other vulnerability. It is important to note that the present review does not include findings from controlled laboratory studies. Thus, the comparison group lower level of exposure to cannabis in the latter studies included nonusers, as well as individuals using cannabis less than weekly, or individuals not having a cannabis use disorder. For the occasional user, cannabis is relatively safe. They also found a significant relationship between cannabis use disorder at baseline and incident social anxiety disorder among young adults aOR, 2.
The causes of addiction are multifaceted and the solutions will continue to be multipronged. Cannabis-using patients with the a priori vulnerability i.
In addition, this group of studies collectively adjusted for approximately 60 different potential confounders, including other substance use, personality traits, sociodemographic markers, intellectual ability, and other mental health problems. Using the same NESARC dataset as Feingold, Cougle and colleagues 10 found that the risk of a past-year bipolar disorder diagnosis was elevated in regular e. Systematic Reviews The committee did not identify a good- or fair-quality systematic review that reported on the association between cannabis use and the risk of developing PTSD. Those with only the Met variant were unaffected by cannabis use. Primary Literature Although several primary research studies found a positive association, the confounding factors of polydrug use or unspecified cannabis use made it difficult for the committee to make conclusions on the overall findings Brook et al.