Properties, benefits and side effects

What is THC and what is it used for?

Delta-9 tetrahydrocannabinol (THC) is a phytocannabinoid that is found in the Cannabis sativa plant. The two main phytocannabinoids are THC and cannabidiol, or CBD, and both can be used in medicinal cannabis preparations.

THC has far-reaching physiological effects. It can help to provide pain relief due to its pain-modulating effect. It can also have a positive effect on mood, stress response, energy regulation, appetite and the immune system.1

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THC properties

Research has found THC to be associated with a number of properties. These include:1,2







Effects of THC on health

Evidence suggests that THC may potentially help to relieve a wide range of symptoms and diseases.

For example, THC has already shown promising potential in:2,3

  • Decreasing anxiety (when taken at lower doses)
  • Stimulating appetite
  • Relaxing tight or stiff muscles
  • Providing pain relief
  • Improving sleep quality
  • Side effects of THC – is it safe to use?

    Medicinal cannabis containing THC can help to improve the lives of millions of patients and it can legally be prescribed for medical use.3,4,5 When medical cannabis containing THC is taken under medical supervision, it has a good safety profile and can improve the quality of life of the patient.3,5

    • Children

    There is limited research around the effects of THC on children. As a result, THC is not recommended for use in this patient group.

    Is THC addictive?

    THC has a good safety profile when taken at the recommended dosage and under medical supervision. In addition, the World Health Organisation’s Expert Committee on Drug Dependence has stated that there have been no reports of public health problems as a result of pure THC being taken.6

    Does THC affect driving?

    This is an area of research where few studies have been carried out, but it appears that the higher the concentration of THC, the greater the level of risk of driving impairment.7

    How long does THC remain in bloodflow?

    With occasional use, studies have shown that THC is typically undetectable in blood serum after four hours.7,8 This suggests that THC remains in the blood for only a very short period.

    For those using medicinal cannabis that contains THC on a regular or more frequent basis, studies have found that THC concentrations in blood serum remain higher for a longer time. It’s estimated that for frequent users, high residual levels could remain for several days.8


    1 Atakan Z. Cannabis, a complex plant: different compounds and different effects on individuals. Ther Adv Psychopharmacol. 2012;2(6):241-254. doi:10.1177/2045125312457586

    2 National Academies of Sciences, Engineering, and Medicine. The health effects of cannabis and cannabinoids: The current state of evidence and recommendations for research. Washington, DC: The National Academies Press. Published 2017. Accessed August 2022.

    3 National Institutes of Health. Cannabis (marijuana) and cannabinoids: what you need to know. Updated November 2019. Accessed August 2022.

    4 National Health Service. Medical cannabis (and cannabis oils). Published 2022. Accessed August 25, 2022.

    5 Nutt D, Bazire S, Phillips LD, et al. So near yet so far: why won’t the UK prescribe medical cannabis? BMJ Open 2020;10:e038687. doi: 10.1136/bmjopen-2020-038687

    6 World Health Organisation. Critical review reports on cannabis – 41st ECDD 2018: Delta-9-THC. Published 2018. Accessed August 25, 2022.

    7 Balíková M, Hložek T, Páleníček T et al. Time profile of serum THC levels in occasional and chronic marijuana smokers after acute drug use – implication for driving motor vehicles [Czech]. Soud Lek. 2014;59(1):2-6.

    8 Sharma P, Murthy P, Bharath MM. Chemistry, metabolism, and toxicology of cannabis: clinical implications. Iran J Psychiatry. 2012;7(4):149-56. PMID: 23408483