Cannabis and the brain

In Progressives Should Just Say No to Legalizing Drugs (US News), Carrie Wofford writes, “There’s a good reason drugs are illegal: They’re dangerous”.

She explains:

Drugs kill. They turn talented, intelligent people into impulsive animals. They destroy marriages. They deprive children of emotionally healthy parents. There’s a good reason drugs are illegal: They’re dangerous. Products that kill do not belong on drugstore shelves.

After reminding the reader of Philip Seymour Hoffman’s tragic overdose (whose heroin addiction was the result of legal drugs prescribed to him for pain), Wofford brings Cannabis into the argument by citing its deleterious effects on brain tissue: Continue reading

Alcohol damaged teens’ brain tissue; marijuana did not (study)

From Alternet

Some new science demonstrates that marijuana may not have the harmful effects critics claim. In fact, while pot had no measured impact in a new study, the very legal and very lucratively-marketed substance alcohol actually has a worse health impact on young users. Continue reading

Study finds no long-term negative cognitive effects from marijuana

From Raw Story By Eric W. Dolan
Wednesday, July 11, 2012

While cognitive performance is negatively affected by cannabis use, the negative effects appear to completely wear off within a month, according to research published in the Experimental and Clinical Psychopharmacology in late June.

“With the number of cannabis users both illicitly and licitly increasing, the question of any potential lasting impact from cannabis use is increasingly important,” Amy M. Schreiner and Michael E. Dunn of the University of Central Florida wrote in their study.

Numerous studies have found that cannabis use affects memory, attention, perceptual-motor tasks, and other cognitive processes, but studies on how long these effects last has been inconsistent. The studies were complicated by the fact that psychoactive compounds in marijuana can linger in the body for days.

In hopes of better understanding the long-term, lasting effects of cannabis use, the researchers used a meta-analysis, a statistical procedure that allows researchers to mathematically summarize the results of a number of different studies.

Schreiner and Dunn’s study included two of these meta-analyses. The first was comprised of 33 studies that examined the cognitive effects of cannabis use after intoxication had worn off. The second was comprised of 13 studies that also examined the cognitive effects of cannabis use after intoxication had worn off, but this group of studies tested users after at least 25 days of abstinence.

The study found that cannabis use caused small impairments in attention, learning, and other cognitive processes that persisted after intoxication. However, the researchers said it was unclear if these minor impairments “translate[d] into practical impairments in functioning.” But the second meta-analysis suggested that these minor impairments don’t last longer than a month.

“While the first meta-analysis revealed a small significant negative effect for general performance and a number of cognitive domains, the clinical significance remains unclear,” Schreiner and Dunn explained. “A second meta-analysis focusing on studies with longer abstention periods was conducted and indicated no lasting residual effects on neurocognitive performance as a result of cannabis use… Whether differences seen in the initial days or weeks of abstinence are due to drug residue effects or withdrawal effects, after approximately 1 month these effects do not persist for the moderate to heavy user.”

Chronic High Doses of Cannabinoids Promote Hippocampal Neurogenesis

– By Bryan Perkins (Source AP)  “The recent discovery that the hippocampus is able to generate new neurons throughout a human’s lifespan has changed the way we think about the mechanisms of psychiatric disorders and drug addiction,” says Wen Jian and colleagues in a study published in the Journal of Clinical Investigation in 2005.

It appears that cannabinoids are able to modulate pain, nausea, vomiting, epilepsy, ischemic stroke, cerebral trauma, multiple sclerosis, tumors, and many other disorders.

Cannabinoids act on two types of receptors, the CB1 receptors (found mainly in the brain) and the CB2 receptors (found mainly in the immune system). The CB1 receptor is one of the most abundant G protein coupled receptors in the mammalian brain and it accounts for most, if not all, of the centrally mediated effects of cannabinoids. Cannabionoid receptors are evolutionarily conserved among various vertebrates and invertebrates which have been separate for 500 million years.

Hippocampal neurogenesis is suppressed following chronic administration of the major drugs of abuse (including opiates, alcohol, nicotine, and cocaine). However, CB1-knockout mice display significantly decreased hippocampal neurogenesis, suggesting that CB1 receptors activated by endogenous, plant-derived, or synthetic cannabinoids may promote hippocampal neurogenesis.

Wen Jiang and colleagues have given the first evidence suggesting that both embryonic and adult hippocampal neural stem/progenitor cells (NS/PCs) express CB1 receptors. Cannabinoids can regulate the proliferation of hippocampal NS/PCs by acting on CB1 receptors. They found that both the synthetic cannabinoid HU210 and the endocannabinoid anandamide profoundly promote embryonic hippocampal NS/PC proliferation.

Chronic, but not acute, HU210 significantly increases the number of newborn hippocampal neurons in adult rats by promoting NS/PC proliferation. These promoting effects are not the outcome of hippocampal neuronal death, as no neuronal loss or dying hippocampal neurons were detected following chronic HU210 injection. A significant increase was observed in the hipoppocampal newborn neurons of mice following twice-daily HU210 injection for 10 days.

It has been shown that acute, high doses of cannabinoids produce anxiety-like effects in rats and depression-like effects in mice. But chronic administration of high, but not low, doses of HU210 exerts anxiolytic- and antidepressant-like effects. This suggests that cannabinoids are the only illicit drug that can promote adult hippocampal neurogenesis following chronic administration. “This increase in hippocampal neurogenesis underlies the mechanism of anxiolytic- and andtidepressant-like effects produced by a high dose chronic HU210 treatment.”

Source: Jiang W, Zhang Y, Xiao L, Cleemput JV, Ji S-P, Bai G, & Zhang X (2005). Cannabinoids promote embryonic and adult hippocampus neurogenesis and produce anxiolytic- and antidepressant-like effects. Journal of Clinical Investigation, 115, 3104-3116

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