If you use marijuana regularly, you might be wondering if it’s neurotoxic. Some studies have shown that long-term marijuana use may negatively affect your memory, concentration, and IQ. And, if you have anxiety or depression, you may be even more susceptible to its effects.
Cannabinoids cause neurotoxic effects
The role of cannabinoids in neurodegenerative diseases is controversial. However, numerous in vitro and animal studies have reported the protective effects of cannabinoid agonists on neurons in cultures. They may also offer treatment for the refractory effects of chemotherapy-induced nausea and vomiting. Although the mechanism by which cannabinoids act is unclear, it appears to involve interactions with the hepatic cytochrome P450 enzyme system.
A recent Cochrane meta-analysis of randomized controlled trials of cannabinoids assessed their effect on various outcomes. Specifically, the authors assessed the effectiveness of cannabis-derived drugs in the treatment of refractory chemotherapy-induced N/V.
In addition to demonstrating a number of interesting properties, these drugs had few side effects and did not cause significant impairments in gastrointestinal function. Furthermore, their low dosage requirements and high excretion rate did not impede drug clearance. On the whole, the cannabinoid effects of cannabis-based medications seem to be well worth the bother.
For instance, it has been reported that a dose of medicinal Cannabis taken as a herbal tea for 15 consecutive days had no negative effect on drug clearance in humans. There are, however, several caveats to such an observation. Most importantly, a sudden cessation of cannabinoid intake is not associated with a rapid decline in plasma concentrations. And, while marijuana has been shown to induce the expression of endocannabinoids, the pharmacological proof is somewhat tenuous. Nevertheless, the endocannabinoid system plays an important role in the stress and stress-related disorders of the human psyche.
The most notable effect of a cannabinoid on the brain is its ability to mitigate the effects of oxygen-glucose deprivation (OGD) on hippocampal function. One such study found that a single dose of 10 mM THC, the psychoactive component of marijuana, induced a 50 percent drop in hippocampal neuronal death within two hours. This effect was further attenuated by the presence of CBD. It is likely that many other cannabinoid compounds have similar therapeutic benefits.
Another example of a cannabinoid with neuroprotective benefits is Bay 38-7271, a synthetic cannabinoid that has shown promising neuroprotective properties in both focal ischemic rat models and traumatic brain injury (TBI) models. Interestingly, the aforementioned THC-induced decrease in hippocampal cell loss has been accompanied by an increase in dendritic length in the CA3 pyramid cell layer.
Lastly, a dose of D9-THC, a more potent form of the compound, has been shown to induce apoptosis in hippocampal neurons. Similarly, a dose of CP-55, a cannabinoid agonist, has been found to protect cortical neurons from glutamatergic excitotoxicity.
Long-term marijuana use may affect memory, concentration, and IQ
Several studies have been conducted on the long-term effects of marijuana use on cognitive abilities. Long-term marijuana users experience a larger IQ decline than short-term users. However, more research is needed to better understand how frequent and long-term cannabis use affects intelligence.
Researchers in New Zealand investigated how long-term marijuana use affects memory, attention, and IQ. The study examined 1,000 New Zealanders born in the early 1970s. They were monitored for 25 years. After this time, they were given MRIs of their brains. Results showed that those who used cannabis regularly had changes in the nucleus accumbens, which plays a role in processing information, memory, emotion, and motivation. Those who did not use marijuana had a higher IQ.
In midlife, regular cannabis users showed cognitive deficits similar to those seen in non-users who later develop dementia. This may be due to structural changes in the brain that occur shortly after functional brain changes. There are other factors that can explain cognitive decline, such as environmental and genetic factors.
Although the study did not rule out other factors that could account for the decline in IQ, it did not find a significant relationship between marijuana use and IQ. The researchers also did not control for the differences in education levels of study members.
These results are inconsistent with other studies on the impact of marijuana on the brain. Studies that focused on adolescent cannabis users report different outcomes. For example, one study found that heavy marijuana use in adolescence is associated with mental health disorders, such as schizophrenia. Another study found that young users reported problems with attention and memory.
Rocio Martin-Santos and colleagues at the University of Barcelona performed a review of 43 studies on chronic marijuana use. Most of the studies focused on adolescents and did not include older adults. Despite the limitations, the study provides new evidence that the effects of marijuana are less clear in adults.
The adolescent-onset cannabis group exhibited a large IQ decline. They lost more than five points between the ages of thirteen and eighteen. Those who stopped using the drug as adults did not regain the lost IQ. Those who were persistent in their use had an overall IQ decline of six to eight points. Those who started smoking marijuana before age sixteen showed white matter changes, which are part of the brain’s structure and function. Higher impulsivity was associated with these changes.
Some of these results may be explained by behavioral traits that are known to predict substance use. People who are less conscientious and have lower IQs are more likely to use drugs. Other studies show that heavy use in adolescence is linked to higher dropout rates, more unemployment, and increased welfare dependence.
A prospective longitudinal study will allow scientists to explore how marijuana use affects neuropsychological functioning over the long term. Until more research is done, it is unlikely that anyone can tell exactly how much marijuana users will experience an IQ decline.
Anxiety and depression increase susceptibility to cannabis
Adolescents who use cannabis often or in high doses experience an increased risk of depression and anxiety disorders. This is not a new finding, but it is not well-studied in longitudinal samples. In the past, studies have only looked at correlations between anxiety and depression and cannabis use. However, the results of these studies have varied. For example, one study found no association between heavy marijuana use and anxiety, while another found an association between cannabis use and depression.
Another study examined the relationship between social anxiety disorder and cannabis use. The authors found that the co-occurrence of both disorders leads to greater impairment and distress. Cannabis use was found to be a significant contributing factor in a small subset of SAD patients.
A prospective birth cohort-linked national register study found a modest association between cannabis use and depression. Researchers used a kh2-test to test for the relationship between cannabis and depression. The result was a statistically significant association between cannabis and depression for individuals who smoked five or more times during adolescence. Although the association was not as strong as in the previous studies, the findings suggest a temporal association between adolescent cannabis use and anxiety disorders.
One of the most important findings in the study was the significant association between adolescent cannabis and social anxiety disorder. In particular, the association was most pronounced in adolescents with a short serotonin transporter gene. These findings have implications for the broader psychiatric community. Moreover, the study also indicates that cannabis use is related to social anxiety in some subgroups.
One possible explanation for this effect is that adolescent anxiety symptoms impede the development of an endogenous cannabinoid signaling system. This system plays a key role in stress regulation. Therefore, deficiencies in this system may lead to stress-related psychiatric problems in the future.
More studies should investigate the life course effects of cannabis on anxiety disorders. Future investigations should include larger sample sizes, more comprehensive substance use assessments, and adequate assessment of confounders. Further investigations should also consider whether the directionality of the association between cannabis and depression is as good as the findings of these studies.
Finally, researchers should also study the impact of adolescent anxiety and depression on adolescent marijuana use. Previous studies have shown a modest increase in anxiety disorder among adolescents who smoked cannabis. However, these findings are insufficient for conclusive conclusions.
Overall, this study was a positive step toward furthering our understanding of the potential link between anxiety and depression and cannabis use. It provided a sample size of 6325 individuals, including 352 adolescent participants and 583 adults. Furthermore, it allowed for a robust analysis of the relationships between multiple variables of interest.
Of the 6325 participants, 352 reported using cannabis at least once until they reached adolescence. After controlling for sex, cannabis use and anxiety symptoms were correlated. Only 16 of the 256 participants that were excluded from the analyses reported using cannabis.
