THC exposure has long-term effects on the dopamine levels in the brain. The post below from MedicalNewsToday.com, and it reviews a study that shows a link between long-term marijuana use and mental illness. [1]“ A review offers further insight into how long-term marijuana use might have a negative impact on mental health, after finding "substantial evidence" that the drug alters the brain's reward system to increase negative emotions and decrease motivation.[2]
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The study says there is sufficient evidence to suggest marijuana, or cannabis, reduces levels of dopamine in the brain - a neurotransmitter that plays a key role in learning, movement, motivation, emotion, and reward.
Low dopamine levels have been associated with mood changes, fatigue, depression, and lack of motivation; dopamine deficiency is present in a number of neurological conditions, including Parkinson's disease and attention deficit hyperactivity disorder (ADHD). Study leader Prof. Oliver Howes, of the Medical Research Council (MRC) Clinical Sciences Center at Imperial College London in the United Kingdom, and team recently published their results in the journal Nature. According to the 2014 National Survey on Drug Use and Health, there are around 22.2 million marijuana users in the United States, making it the most commonly used illicit drug in the country. Long-term marijuana use has been linked to a number of mental health conditions, including schizophrenia, anxiety, and depression, but the mechanisms underlying this association have been unclear.
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Given the increased legalization of marijuana for medicinal and recreational purposes, researchers are keen to learn more about how the drug affects the brain. For this latest study, Prof. Howes and team conducted a review of numerous studies investigating how the primary psychoactive compound in marijuana - tetrahydrocannabinol (THC) - affects the brain.
THC Exposure Has Long-Term Effects on the Dopamine System
According to the researchers, there is now "substantial evidence" in animal and human studies that long-term exposure to THC leads to a decrease in levels of dopamine. ‘The available evidence indicates that THC exposure produces complex, diverse and potentially long-term effects on the dopamine system,’ the authors explain. ‘These include increased nerve firing and dopamine release in response to acute THC, and dopaminergic blunting associated with long-term use.’
The team believes this effect may explain why people who engage in long-term marijuana use are at increased risk for mental health problems. In animal models, current research shows that marijuana use initially raises dopamine levels, fueling a sense of reward, which the team says may offer an explanation for why some users become addicted to the drug. However, the authors point to some limitations in this area. ‘Fundamentally, animal studies are too short, and don't give cannabis repeatedly or in combination with other substances,’ notes Prof. Howes.
Addressing the Gaps in Marijuana Research
The researchers also noticed some other gaps in research, such as studies assessing what happens to the dopamine system when marijuana use is ceased. What is more, the team notes it is important to learn more about how marijuana use affects brain development, as some women may use the drug in early pregnancy, before realizing they are expecting. ‘Given the increasing use of cannabis, particularly in young people and women who may be pregnant, animal studies are needed to understand the effects of long-term cannabis use on the developing brain in a controlled way that is not possible in human studies,’ says Prof. Howes.
‘These studies also need to use techniques that can be translated into human studies, and to better represent human patterns of use.’ While further investigation into the effects of marijuana is clearly warranted, the researchers believe their current study helps broaden our understanding. ‘The changing patterns of cannabis use, including 'cannavaping' and edible products, mean it's vital that we understand the long-term effects of cannabis on the brain. This new research helps to explain how some people get addicted to cannabis, by showing that one of its main components, called THC, alters a delicate balance of brain chemicals.’”
Co-author Dr. Michael Bloomfield, Clinical Sciences Centre, Imperial College London
What About CBD and Dopamine Levels?
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The research into THC’s effect on dopamine levels is still in the early days of exploration, but even further behind it is the study of CBD oil on our dopamine system. At the moment there is little research into if CBD may have some influence over our dopamine levels. Does it trigger similar changes in the “delicate balance of brain chemicals” that scientists are now associating with THC consumption?
Considering the role that dopamine plays in many serious diseases, such as Parkinson’s, Alzheimer's and schizophrenia, there is interest in exploring alternative therapies which interact with our dopamine system. Cannabidiol has already shown promise as a mesolimbic dopamine system modulator, which could have implications for treatment of schizophrenia and other neuropsychiatric disorders, but could there be more applications for this?[3]
There are a few interesting avenues of investigation regarding CBD oil and dopamine levels, including:
- Sleep regulation and wakefulness cycles [4]
- Atypical alternative to haloperidol, an antipsychotic agent [5]
- As a neuroprotectant against dopamine toxicity in Parkinson’s patients [6]
The science of the human dopamine system and its complicated relationship with many neurological disorders is just getting started. On top of this, researchers have only scraped the surface of CBD’s interaction with dopamine receptors. It will be very interesting to see just where the research takes us in its exploration of CBD oil and dopamine.
Sources:
[1]https://www.medicalnewstoday.com/articles/314222.php
[2]http://www.nature.com/nature/journal/v539/n7629/full/nature20153.html
[3]https://www.ncbi.nlm.nih.gov/pubmed/28185872
[4]https://www.sciencedirect.com/science/article/pii/S0024320511000336
[5]https://link.springer.com/article/10.1007/BF02244189
[6]https://www.ncbi.nlm.nih.gov/pubmed/15837565
