Virginia Thornley, M.D., Neurologist, Epileptologist
May 8, 2018
Cannabinoids are being more and more widely used in a variety of neurological conditions. This always leads to the questions of side effects and will it interacts with other medications? Because this is wholly unchartered territory, in order to answer these questions, it is necessary to understand the underlying mechanisms.
Cannabinoids can cause tachycardia
Phytocannabinoids, when ingested, can induce tachycardia. The metabolism of cannabinoids by cardiomyocytes likely impacts the side effects elicited in cardiac cells. CYP2J2 is the most significant cytochrome p450 which metabolizes endocannabinoid anandamide (AE) into the cardioprotective epoxides. 6 phytocannabinoids were studied in one paper including delta-9-tetrahydrocannabinol, cannabinol, cannabidiol, cannabigerol, and cannabichromene. These were found to be metabolized more quickly compared to anandamide. The cannabinoids may potentially inhibit the metabolism of anandamide by CYPJ2 such that its effects are still circulating in the system. The most significant inhibition was from delta-9-tetrahydrocannabinol. It follows a non-competitive inhibition model such that the cardioprotective epoxides are not formed as abundantly as they should by the cytochrome p450 CYP2J2 (1).
The cytochrome P450 system has a significant impact on the metabolism of cannabinoids. Tetrahydrocannabinol is metabolized by CYP2C19 and CYP3A4. cannabinol is metabolized by CYP2C9 and CYP3A4. Synthetic cannabinoids include JWH-018 which is metabolized by CYP1A2 and CYP2C9 and AMC2201 which is metabolized by CYP1A2 and CYP2C9.
The cytochrome P450 enzymes are also thought to be involved in the metabolism of tetrahydrocannabinol. CYP2C9 greatly influences the metabolism of tetrahydrocannabinol. Cytochrome P450 3A4 is important in the metabolism of THC and CBD (2).
Cannabinoids in relation to hyperemesis syndrome
Once abdominal pain has been explored regarding medical etiologies, and there is a presence of 1-year history of cannabis use usually weekly, this diagnosis comes to mind. It usually involves cyclical vomiting associated with nausea. The mechanism is thought to be related to dysregulation by the endocannabinoid pathway in relation to the gastrointestinal tract. The CB1 receptor by which THC or tetrahydrocannabinol exerts it actions is also present in the GI tract. Exogenous cannabinoids may dysregulate the normal endocannabinoid pathway thereby affecting the GI tract through the down-regulation of the normal CB1 receptors so that it is no longer sensitive to endocannabinoids which regulate the system. This results in a dysfunction of the GI tract clinically manifested as cyclical nausea and vomiting. A disruption of the cannabinoid receptors may occur resulting in slowed motility of the gut. Relief can occur with use of hot water which influences the TRPV receptor a G-related coupled protein
- Arnold, et al, “Cross-talk of cannabinoid and endocannabinoid metabolism is mediated via human cardiac CYP2J2,” J. Inorganic. Biochem., 2018, Apr., 7(184):88-99 doi: 10.1016/j.jinorgbio.2018.03.016. (Epub ahead of print)
- Stout, et al, “Exogenous cannabinoids as substrates, inhibitors, and inducers of human drug metabolizing enzymes: a systematic review,” Drug Metab. Rev., 2014, Feb., 46(10:86-95.
- Lapoint, et al, “Cannabinoid hyperemesis syndrome: public health implications and a novel model treatment guideline,” West J Emerg Med, 2018, Mar., 19(2):380-386.
Virginia Thornley, M.D., Neurologist, Epileptologist
May 6, 2018
There is a well-known correlation of use of cannabis whether it is medical or recreational to the onset of schizophrenia. It unclear if this could be to a direct correlation and disinhibition of the genetic component or the behavior of using it is a prodrome leading up to schizophrenia. This review seeks to elucidate the mechanisms in the correlation of the use of cannabis and onset of schizophrenia.
Mechanisms related to the underlying genetic composition
Schizophrenia may be linked when some of the normal pathways become disrupted with an introduction of THC. There are 4 genes that were described after a lifetime use of cannabis including KCNT2 which were THC responsive, NCAM1 and CADM2 are significant in functioning in post-synapse. With THC in the system, there are more post-synaptic density genes (1).
Mechanisms related to other neurotransmitter pathways influenced by cannabinoids
In one study, because of the alarming rate of potent synthetic cannabis used recreationally which was found to leave long-lasting schizophrenia disorder in recreational users, this has accelerated research into the pathophysiology. Because cannabinoids work on the CB1 receptor, it is likely that it plays a modulatory role on the other neurotransmitters that can give rise to schizophrenia including dopaminergic, glutamatergic and serotonergic pathways. These pathways are well-established as playing a role in a pro-psychotic state. High efficacy synthetic cannabinoids which are manufactured for recreational purposes are highly more potent compared to natural organic cannabinoids and there is an alarming increase in the correlation of schizophrenia in these users (2).
In one study it is thought to be due to the hypofunctioning of the glutamate system which is directly affected by THC. Exposure to tetrahydrocannabinol appears to reduce the activity at the level of the glutamate receptor as well as deregulate genes for synaptic function(1).
Susceptibility is related to the development of schizophrenia
In one animal model, the set-up tried to mimic a more real state seen where not all adolescents exposed to synthetic cannabinoids react by developing schizophrenia, there are some studies where all animals develop schizophrenia with exposure. In this animal model, they provided a model that resembles the human model more closely and found that exposure to synthetic cannabinoids in schizophrenia-prone animals caused hyperfunctioning of dopaminergic pathways compared to the control group who were not susceptible at the same dosages. There may be underlying genetic or environmental factors that cause certain individuals to become more prone (2).
THC can cause anxiety and behavioral disorders but can be prevented with CBD
In one animal study, it was found in a rat study that THC can induce anxiety and behavioral disorders. With THC administration object recognition was impaired in adolescent rates. The studies support effect on the developing brain in relation to cognitive impairment in the animal model. In addition, when rats were exposed to THC there was increased marble burying behavior which in scientific research is thought to signify anxiety or obsessive-compulsive type behavior usually ameliorated with serotonin reuptake inhibitors or benzodiazepines(4).
It was found, however, that a combination of CBD and THC or cannabidiol alone was administered, these behaviors were not produced or produced only minimally. The thought is that CBD is an allosteric competitive inhibitor at the CB1 receptor so that one sees less of the toxic undesirable effects of THC if administered alone (4).
Cannabinoids have a similar profile to atypical anti-psychotics and may be a possible adjunctive treatment in the treatment of psychotic events (5).
There is historical evidence that exposure to THC can give rise to schizophrenia in those individuals that are susceptible accounting for the fact that it does not happen to everybody exposed to it. This is related to its influence on serotonergic, dopaminergic and glutamate pathways. THC can induce anxiety, repetitive behaviors which are ameliorated by CBD. CBD may be a useful adjunctive treatment for psychotic disorders. However, the elucidated mechanisms are based on scientific research based on animal models which may not translate into humans.
- Guennewig, et al, “THC exposure of human iPSC neurons impacts genes associated with neuropsychiatric disorder,” Transl. Psychiatry, 2018, Apr., 8(1):89.
- Fantegrossi, et al, “Pro-psychotic effects of synthetic cannabinoids: interactions with central dopamine, serotonin and glutamate systems, Drug Metab. Review, 2018, Jan, 50(1)
- Aguilar, et al, “Adolescent synthetic cannabinoid exposure produces enduring changes in dopamine neuron activity in the rodent model of schizophrenia,” Int. J. Neurpsychopharmacol., 2018, Apr., 31 (4):393-403.
- Murphy, et al, “Chronic adolescent delta9-tetrahydrocannabinol treatment of male mice leads to long-term cognitive behavioral dysfunction which is prevented by concurrent cannabidiol treatment,” Cannabis Cannabinoid Res., 2017, 2(1):235-246.
- Deiana, et al, “Medical use of cannabis: a new light for schizophrenia?” Drug Test Analysis, 2013, Jan., (5)1:46-51