THC

The main psychoactive cannabinoid in cannabis. Shows up in this corner of the world for sleep, appetite, pain and recovery claims — and because so many people tracking their health are already using it and want to know what it does to the rest of their protocol.

THC is the cannabinoid responsible for intoxication, and it works by binding CB1 receptors in the brain — the same receptors the body's own endocannabinoids use to modulate appetite, pain perception, memory and mood. Because CB1 receptors sit densely in the hippocampus and prefrontal cortex, the memory and executive effects are not side effects of the high, they are the same mechanism. It also binds CB2 receptors in immune tissue, which is the basis of the anti-inflammatory claims, though those are much less established.

Real evidence for chemotherapy nausea, some chronic-pain states, and spasticity in MS. For sleep — the common biohacker use — the picture is worse than assumed: it shortens sleep latency but suppresses REM, and rebound insomnia on stopping is well documented. For recovery/inflammation claims, human evidence is weak. Regular use measurably blunts motivation in a dose-dependent way in some users.

• STRONG for two narrow approved uses: synthetic THC products are approved for chemotherapy-induced nausea and vomiting, and for appetite stimulation in AIDS-related weight loss.
• MODERATE for chronic pain — reviews find modest benefit with substantial adverse effects, and the effect sizes are smaller than the cultural conversation implies.
• LIMITED for sleep: it shortens time to sleep but suppresses REM sleep, and tolerance to the sleep effect develops quickly, which is why long-term use for sleep tends to stop working.
• The psychiatric evidence is the serious part. Cannabis use is associated with psychosis and schizophrenia risk, most strongly with early, frequent and high-potency exposure — and a personal or family predisposition is not a prerequisite for that association, though family history changes individual risk further. Causality is debated; the association is consistent and large.
• Cannabis use disorder is real, and the figures need their denominators stated. CDC summarises that about three in ten people who report cannabis use have the disorder; national survey data put past-year cannabis use disorder at 7.1% of the whole US population aged 12 and over. The familiar "one in ten" comes from an older lifetime-transition estimate and mixes metrics.

Delayed onset is the practical hazard worth knowing: when intoxication arrives later than expected, accidental over-consumption follows, and that leads to medical emergencies. THC is fat-soluble and accumulates in tissue, so detection persists long after effects end. Potency in modern products is substantially higher than in the cannabis most epidemiology was based on.

Dependence is real (~9% of users; higher starting young), and cannabis-use disorder is the most common reason people seek help for any illicit drug. Impaired driving, anxiety/paranoia at higher doses, cannabis hyperemesis syndrome with heavy chronic use, and in adolescents/young adults an association with psychosis in the predisposed. Smoked forms carry respiratory harm; unregulated vape carts have their own contamination history. On a tracked protocol: it confounds sleep data and appetite signals more than almost anything else people take.

• The formal contraindication on the approved prescription product is hypersensitivity to dronabinol or to sesame oil. Everything below is a strong avoidance recommendation or a risk-benefit consideration rather than an absolute bar.
• Anyone with a personal or family history of psychosis, schizophrenia or bipolar disorder
• Adolescents and young adults, where the psychiatric associations are strongest
• Anyone pregnant or breastfeeding
• Anyone with significant cardiovascular disease, or a seizure disorder
• Older adults, who face increased neuropsychiatric and fall risk
• Anyone taking interacting central nervous system or cardiac medication
• Anyone driving or operating machinery, where impairment outlasts the subjective high

• Alcohol and other sedatives, where impairment is additive.
• CYP2C9 and CYP3A4 inhibitors or inducers, which can change THC exposure — the direction is that other drugs alter THC, and interactions need assessing product by product.
• Warfarin — a potential interaction requiring clinical review rather than a confirmed one.
• Any psychiatric medication — this belongs in a conversation with the prescriber rather than a decision made alone.
• Driving, where impairment is established and lasts longer than most users estimate.

• Frequency, honestly — daily use is the strongest predictor of dependence and of the psychiatric associations.
• Any psychotic symptoms, paranoia that persists after intoxication, or a family history of psychosis, which changes the risk calculation entirely.
• Cyclical vomiting, which is a recognised syndrome in heavy long-term users and is frequently misdiagnosed for years.
• Cardiovascular symptoms — it raises heart rate acutely, and myocardial infarction has been reported in the hour after use.

Withdrawal after regular use is real and was added to the diagnostic manuals for a reason: irritability, anxiety, sleep disturbance with vivid dreams, appetite loss and low mood, typically starting within a day or two, peaking in the first week and easing over two to four weeks. Sleep disruption can last longer. It is not dangerous in the way alcohol or benzodiazepine withdrawal is, but it is unpleasant enough to be a major reason people do not stop, and knowing it is time-limited is the useful part.

US: federally Schedule I, legal for adults in many states — the state/federal split is unresolved. Employment drug testing does not care what your state legalized.

Papers about this compound, not proof of the claims above. A title says what was studied, which is sometimes a negative result or a different question entirely.

• Cardiovascular risk associated with the use of cannabis and cannabinoids: a systematic review and meta-analysis
  Heart, 2025
• Cannabis and sleep architecture: A systematic review and meta-analysis
  Sleep Med Rev, 2025
• Effects of Cannabis in Parkinson's Disease: A Systematic Review and Meta-Analysis
  J Parkinsons Dis, 2022

• Tetrahydrocannabinol (THC)2026
• The Utility of THC Cutoff Levels in Blood and Saliva for Detection of Impaired DrivingCannabis Cannabinoid Res · 2023
• Delta-8-THC: Delta-9-THC's nicer younger sibling?J Cannabis Res · 2022
• Review of delta-8-tetrahydrocannabinol (Δ(8) -THC): Comparative pharmacology with Δ(9) -THCBr J Pharmacol · 2022
• "Residual blood THC levels in frequent cannabis users after over four hours of abstinence: A systematic review."Drug Alcohol Depend · 2020
• Mechanisms of Action and Pharmacokinetics of CannabisPerm J · 2020
• Recent advances in electrochemical sensor technologies for THC detection-a narrative reviewJ Cannabis Res · 2022
• Tolerability of High-Dose Oral Δ(9)-THC: Implications for Human Laboratory Study DesignCannabis Cannabinoid Res · 2024
• Toxicogenetic analysis of Δ9-THC-metabolizing enzymesInt J Legal Med · 2020
• Experimenter administered Δ(9)-THC decreases nicotine self-administration in a rat modelPharmacol Biochem Behav · 2023
• Commercial Delta-8 THC Products: an Analysis of Content and LabelingJ Med Toxicol · 2024
• THC and gabapentin interactions in a mouse neuropathic pain modelNeuropharmacology · 2019