Introduction to THC and its mechanism of action

Tetrahydrocannabinol, a major substance in marijuana, is attributed to causing the "high" experienced by users. The effect of this compound is mainly psychoactive, influencing the mood, perception, and cognition of its users, and it is very widely used for both recreational and medicinal purposes.¹

This article attempts to describe how THC functions within the body, with special attention focused on its mechanism of action within the endocannabinoid system - the complex network composed of a myriad of receptors and molecules responsible for a wide array of physiological and psychological processes. THC acts primarily through CB1 receptors, found in high concentrations in the brain. This action inhibits and enhances the release of neurotransmitters like dopamine and serotonin.² Such interaction changes mood, perception, and motor control, very often resulting in euphoria, depression, relaxation, or one of the many other altered mental states. Understanding the mechanism of THC illuminates probable effects, use in therapy, and implications within mental health.

Effects of THC on mood regulation

THC can have a deeply complex effect on mood, one that can range from euphoric effects to a potential for mood instability. At low levels, THC is usually a mood elevator in effect, partly due to its release of dopamine.³

Higher doses of THC are associated with more inconsistent effects on mood, contributing to irritation, anxiety, or even dysphoria. It has been suggested that individual factors, including sex and emotion regulation, modulate how THC impacts mental health. For example, a study has indicated that adolescent female cannabis users had a significantly higher rate of reporting more depression, anxiety, and stress as compared to their male counterparts. This could be due to more emotional reactivity and reliance on cannabis as the first source of managing stress and mood regulation. In women, emotional dysregulation (ED) related to cannabis use mediated the association between cannabis use and mental health problems. Those who have higher ED might find their mood disturbance more exaggerated at higher concentrations of THC, perhaps using it to try to alleviate the negative emotions impulsively.⁴

Another study of those with high emotion dysregulation indicates that they are at an increased risk for problematic cannabis use under stress, as they might likely use cannabis to help soothe stress-induced negative feelings rather than directly handle the stressor. Such results suggest that the effects of THC on the mood are dose-dependent and that there may be interactions between such effects and the coping style of an individual and their ability to regulate emotions.⁵

THC’s role in anxiety

The effects of THC on anxiety are somewhat complex and often dose-dependent. At low doses, it acts as an anxiolytic; in other words, it calms the mind and reduces perceived stress while inducing a state of relaxation. It is believed that a low level of THC stimulates endocannabinoid receptors in a manner that balances neurotransmitters related to mood regulation, such as serotonin and dopamine, and so, in some users, it will have a calming effect.

However, at high concentrations, THC tends to reverse this effect and instead increases anxiety levels. Here, at such doses, THC might stimulate the amygdala excessively, which is a critical part of the brain responsible for processing fear. This might result in effects like paranoia, palpitations, and panic attacks. This biphasic effect is interesting as high doses may saturate the endocannabinoid receptors, which in turn could create a disruption of the feedback role of these receptors and might cause an overreaction in the brain's response to stress.⁶

Individual variability may also affect the effects of THC on anxiety. Body chemistry, genetics, and even the condition of the user's mental state at the time could all significantly affect how this substance influences mood and the experience of anxiety. Someone with a predisposition towards anxiety disorders or less tolerance of THC may have greater odds of adverse reactions to lesser doses. However, some chronic users will realise that small amounts are sufficient for them to have a feeling of alleviation with no concomitant risk of increasing anxiety, thus requiring individual consideration in the use of THC, especially for therapeutic purposes.⁷

THC’s short-term vs. long-term impacts on anxiety and mood 

Short-term impacts

THC directly interacts with the endocannabinoid system within the brain, and its effect on CB1 receptors within areas such as the amygdala, hippocampus, and even the prefrontal cortex directly integrates into emotional processing and anxiety regulation. The effects may be hereditary since polymorphisms in the CNR1 gene, which codes for CB1 receptors, appear to influence individual susceptibility to the effects of THC by increasing susceptibility to THC-induced anxiety or psychosis.

Long-term effects

Chronic exposure to THC might induce several neurobiological changes, mainly in predisposed individuals to anxiety disorders or other psychiatric diseases. Chronic exposure to THC results in the desensitisation of the CB1 receptor and may, therefore, compromise the appropriate functioning of the endocannabinoid system during mood and stress responses. Prolonged exposure might also reduce the potential for dopamine synthesis, an event that might be implicated during the development of mood disorders such as depression. Epigenetic alterations whereby modifications to gene expression regarding stress and mood regulation potentially occur with prolonged exposure to THC appear relevant. In this regard, it has been proposed that the effects of THC on certain genes associated with serotonin receptors, such as HTR1A, may increase susceptibility to anxiety and mood disorders.

Genetically, individuals with specific polymorphisms in genes like AKT1 and COMT that modulate dopamine signaling pathways might be more susceptible to the psychotic or anxiety symptoms that have been associated with long-term THC exposure. Changes in cortisol production over time due to THC may also amplify stress responses, creating a positive feedback that enhances sensitivity to stress. Whereas the acute effects of THC appear primarily dose-dependent, the long-term effects might represent changes on a deeper biochemical and genetic level of anxiety and mood pathways.⁸

Balancing THC with CBD for anxiety and mood regulation 

The non-psychoactive compound in cannabis, CBD, is a well-documented compound with anti-anxiety properties and the potential to counteract some effects of THC. Whereas THC directly binds to CB1 receptors in the brain, where it can enhance anxiety or paranoia at more substantial doses, CBD has different mechanisms. Acting mainly on the 5-HT1A serotonin receptors, CBD indirectly affects the modulation of the CB1 and CB2 receptors, and consequently, anxiety levels tend to decrease. Research shows that CBD reduces symptoms across a range of anxiety disorders, including PTSD, GAD, PD, OCD, and SAD, with minimal sedative or addictive liabilities. CBD may also be useful in the alleviation of the acute fear responses that develop following learning by enhancing extinction and interfering with the reconsolidation of fear memory through the action of endocannabinoids.⁹

THC/CBD ratios

The ratio of THC to CBD in marijuana determines the balance in the effect on mood and anxiety. More stable, balanced effects, with reduced possibilities of developing anxiety due to the potency of THC, are those strains or products with a high ratio. Its anxiolytic and anti-psychotic properties will be effective at reducing the hazards of anxiety, paranoia, or stress responses caused by THC in products containing a low concentration of it. In addition, its low potential for abuse and safe profile make it an exciting candidate for medical use, especially in individuals who get anxious or those who need a more stable mood without psychoactive side effects. However, more research is needed to elicit the proper ratios of THC/CBD to be used in specific anxiety disorders, as well as the patient profile, as much depends on the individual's personal genetics and tolerance.¹⁰

Current Research and Controversies  

Current studies of reports on using cannabis for the treatment of anxiety as well as mood disorders reported mixed results, where several studies reported positive outcomes while other studies reported negative effects. For some users, THC, the primary psychoactive compound in cannabis, may help relieve anxiety and improve mood in some cases; however, in others, especially at larger doses, THC may induce states of anxiety, paranoia, and agitation. Variability in this respect would require more research to pin down the exact conditions, dosage, or percentages of cannabinoids that benefit the patients to whom it has been administered to treat a condition like anxiety or mood.¹¹

Even more, with the ready availability of cannabis at dispensaries and coffee shops, there is yet another added layer of complexity. For self-administered cannabis without appropriate dosing or information on cannabinoid content, the end effect can be very inconsistent because products are not standardised. Furthermore, variability in local laws and regulatory obstacles forms a barrier to uniform quality control processes that could make it easier for both patients and healthcare providers to decide whether to use cannabis appropriately. 

Moreover, the pharmacokinetics of cannabis (how it is metabolised in the body) are very poorly understood, and appropriate titration of doses of THC and CBD is a research gap that remains largely unsolved. Without greater accuracy regarding these factors, cannabis remains a contentious and unpredictable treatment for anxiety and mood disorders. Until such clinical studies are available, there is reason to exercise caution with its use for mental health.¹²

Conclusion

Studies on THC and the resulting changes in mood and anxiety levels display a highly complex, individualised relationship. Low doses might have mood-elevating and anxiolytic effects for some, but at higher doses, they can initiate feelings of anxiety, paranoia, and discomfort in vulnerable individuals. Interaction between THC and CBD, one other key player in the system, appears to complicate this overall picture since CBD antagonizes the anxiogenic effects of THC; thus, their balance might critically influence therapeutic results.

Promising findings still lie at the early stage of research, and many studies report mixed findings. Individual variability for THC response, differences in dosages, and mixed product formulations do not make conclusions even more definitive. Regulatory hurdles, lack of standardisation in cannabis products, and limited clinical trials all contribute to the current uncertainty. Further large-scale, well-controlled studies will be necessary for a better understanding of how safe and effective THC, and cannabis itself, can be used to treat both anxiety and mood disorders.