Effects of thc
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Effects of THC: A Comprehensive Overview
Introduction to THC and Its Impact
Delta-9-tetrahydrocannabinol (THC) is the primary psychoactive component of cannabis, known for its wide-ranging effects on the human body and mind. As cannabis use becomes more prevalent, understanding the multifaceted impacts of THC is crucial. This article synthesizes recent research on the behavioral, cognitive, psychological, and physiological effects of THC.
Behavioral Effects of THC
Impulsivity and Behavioral Measures
THC has been shown to influence various forms of impulsive behavior. In a study involving recreational marijuana users, THC increased impulsive responding on the Stop task, which measures the ability to inhibit a prepotent motor response. However, it did not affect performance on the Go/no-go or Delay discounting tasks, indicating that THC may selectively impact certain types of impulsivity while leaving others unaffected1.
Cognitive and Psychomotor Effects
THC's impact on cognitive and psychomotor functions is dose-dependent. Higher doses of THC (up to 69.4 mg) have been associated with slower response times and increased errors in tasks requiring attention and memory. These effects suggest that high-THC cannabis can significantly impair cognitive and motor control, posing public health and safety concerns9.
Cognitive Effects of THC
Memory and Learning
THC impairs episodic memory and learning in a dose-dependent manner. Infrequent cannabis users exhibited significant impairments in explicit memory tasks at peak plasma concentrations of THC, while working memory remained largely unaffected. These cognitive deficits were most pronounced at higher doses and persisted for several hours post-ingestion3.
Long-Term Cognitive Impact
Chronic THC use, especially during adolescence, can have lasting effects on cognitive performance. In adolescent nonhuman primates, daily high doses of THC impaired cognitive task performance and reduced motor activity, although tolerance to these effects developed over time. Co-administration of cannabidiol (CBD) did not mitigate these cognitive impairments6.
Psychological and Psychiatric Effects
Stress and Mood
THC's effects on stress and mood are dose-dependent. Low doses (7.5 mg) can reduce subjective distress and negative mood in response to acute stress, aligning with the common use of cannabis for relaxation. Conversely, higher doses (12.5 mg) can exacerbate negative mood and impair stress response, highlighting the importance of dosage in therapeutic contexts5.
Psychotic Symptoms
Acute administration of THC can induce psychotic and other psychiatric symptoms, including delusions and hallucinations, with significant effect sizes. These symptoms are more pronounced with higher doses of THC, and there is no consistent evidence that CBD moderates these effects. This underscores the potential psychiatric risks associated with THC use7.
Physiological Effects
Autonomic Nervous System
THC affects autonomic cardiac activity, increasing heart rate and decreasing parasympathetic cardiac control. These physiological changes are dose-dependent and correlate with subjective experiences of intoxication and anxiety. Notably, these effects are more pronounced in women, who are underrepresented in clinical cannabinoid research4.
Dopamine System
THC interacts with the dopamine system, which is crucial for its reinforcing effects. Acute THC administration increases dopamine release and neuron activity, while long-term use is associated with a blunting of the dopamine system. This dual effect highlights the complexity of THC's impact on brain chemistry and the need for further research into its long-term consequences10.
Conclusion
THC exerts a wide range of effects on behavior, cognition, psychology, and physiology. Its impact is highly dose-dependent, with higher doses generally leading to more pronounced impairments and adverse effects. As cannabis use continues to rise, understanding these effects is essential for informing public health policies and therapeutic practices. Further research is needed to explore the long-term and developmental impacts of THC, particularly in vulnerable populations such as adolescents and women.
Sources and full results
Most relevant research papers on this topic
Effects of THC on Behavioral Measures of Impulsivity in Humans
THC may increase certain forms of impulsive behavior while not affecting other impulsive behaviors, suggesting impulsivity is an assemblage of distinct components rather than a unitary process.
RCT
Highly CitedThe effect of five day dosing with THCV on THC-induced cognitive, psychological and physiological effects in healthy male human volunteers: A placebo-controlled, double-blind, crossover pilot trial
Repeated THCV administration for five days in healthy male volunteers showed a protective effect on delayed verbal recall and inhibited THC-induced increased heart rate, while potentiating memory intrusions.
RCT
Very Rigorous JournalHighly CitedCognitive and subjective dose-response effects of acute oral Δ9-tetrahydrocannabinol (THC) in infrequent cannabis users
Oral 9-THC impairs episodic memory and learning in a dose-dependent manner, while sparing perceptual priming and working memory in infrequent cannabis users.
RCTHighly CitedAcute effects of oral delta-9-tetrahydrocannabinol (THC) on autonomic cardiac activity and their relation to subjective and anxiogenic effects.
Oral THC increases heart rate and decreases high frequency heart rate variability in healthy adult women, with these effects affecting subjective drug experience and potentially increasing risk factors for cannabis use.
RCTVery Rigorous JournalDose-related effects of delta-9-THC on emotional responses to acute psychosocial stress.
A low dose of THC reduces subjective stress and increases positive mood, while higher doses may increase negative mood and impair performance in a stress test.
RCTHighly CitedEffects of daily Δ9-Tetrahydrocannabinol (THC) alone or combined with cannabidiol (CBD) on cognition-based behavior and activity in adolescent nonhuman primates.
Daily high doses of THC impair cognitive performance and reduce activity in adolescent primates, with tolerance developing within weeks.
Psychiatric symptoms caused by cannabis constituents: a systematic review and meta-analysis
THC alone can induce psychotic, negative, and other psychiatric symptoms in healthy individuals, while CBD shows no consistent evidence to induce symptoms or moderate their effects.
Meta-Analysis
Rigorous JournalHighly CitedBiphasic effects of THC in memory and cognition
THC can improve memory and cognitive function in old animals when chronically administered at low concentrations, promoting neurogenesis and preventing neurodegeneration in Alzheimer's disease models.
Rigorous JournalHighly CitedCognitive and psychomotor effects in males after smoking a combination of tobacco and cannabis containing up to 69 mg delta-9-tetrahydrocannabinol (THC)
Higher THC doses in cannabis cigarettes lead to slower response time and worse motor control impairment, potentially posing a public health and safety concern.
RCTRigorous JournalHighly CitedThe effects of Δ9-tetrahydrocannabinol on the dopamine system
THC, the main psychoactive ingredient in cannabis, can cause acute dopamine release and neuron activity, but long-term use may blunt the dopamine system.
Rigorous JournalHighly Cited