THC and CBD are different cannabinoids
THC and CBD are the two cannabinoids most often named on prescribed cannabis products. THC activates CB1 receptors and can cause intoxication and impairment. CBD does not produce the same intoxicating effect, but it is pharmacologically active and can cause side effects or medicine interactions.
Calling CBD “medical” and THC “recreational” hides more than it explains. Licensed medicines exist in the UK for purified CBD, nabilone and nabiximols, each with a defined formulation and indication. The evidence for one medicine cannot be transferred to every oil, flower or mixed extract containing the same cannabinoid.
How their effects differ
THC’s effects change with dose, route, previous exposure and the amount of CBD or other compounds in the preparation. Impairment, anxiety, faster heart rate and short-term memory problems are among the effects reported with THC.
CBD has a different receptor profile. At prescription doses it can cause diarrhoea, reduced appetite, tiredness and liver-enzyme changes. The Epidyolex product information also records clinically important interactions, including with clobazam and medicines affected by liver enzymes.
A controlled laboratory study by Bhattacharyya and colleagues found different brain and symptom responses after THC and CBD. That study does not show that adding an arbitrary amount of CBD reliably cancels THC’s unwanted effects in a prescribed product.
Formulation matters more than the initials
A label should be read as a whole:
- THC and CBD amount per dose, not only the ratio
- oil, flower, capsule or oromucosal spray
- other active ingredients
- the prescribed amount and timing
- batch and dispensing details
Two products described as “balanced” can deliver different absolute doses. A CBD-dominant product can still contain THC, while a high-CBD prescription can involve doses far above those in retail supplements.
Evidence by medicine and condition
NICE guidance deals with specific cannabis-based medicinal products and specific conditions. It does not treat THC or CBD as interchangeable general remedies. Purified CBD has evidence and licensing for particular severe epilepsies. Nabiximols contains both THC and CBD and is licensed for MS spasticity under defined circumstances. Nabilone is a synthetic cannabinoid used for chemotherapy-related nausea and vomiting when standard treatments have not worked.
Those examples show why the product, condition and outcome matter. A cannabinoid name alone does not establish that another preparation has the same evidence.
Driving and daily life
THC is covered by UK drug-driving law. A prescription may support the statutory medical defence when the medicine is taken as directed, but it does not permit driving while impaired. CBD is not treated in the same way, although a product described as CBD-dominant may still contain THC.
Gaps in direct comparisons
Large head-to-head trials comparing THC with CBD across most conditions do not exist. Much of the useful evidence concerns a named pharmaceutical preparation rather than the isolated question “THC or CBD?”. Product formulation, absolute dose and the condition studied are therefore more informative than a simple cannabinoid preference.
Read next
- THC:CBD ratios explained for prescribed patients
- THC
- CBD
- Medical cannabis side effects and interactions
Sources
- NHS. Medical cannabis (cannabis-based medicines). NHS guidance
- NICE. Cannabis-based medicinal products, guideline NG144. NICE guidance
- Bhattacharyya S, et al. Opposite effects of delta-9-tetrahydrocannabinol and cannabidiol on human brain function and psychopathology. Neuropsychopharmacology. 2010. Study record
- Electronic Medicines Compendium. Epidyolex Summary of Product Characteristics. Medicine record
- GOV.UK. Drugs and driving: the law. UK guidance
