CBD and Mental Health: What the Research Does and Doesn't Show
Search for "CBD and mental health" and you will find bold promises: CBD for anxiety, CBD for depression, CBD instead of medication. An earlier version of this article, published here in 2023, was too optimistic too. We have rewritten it to give you the honest picture: what scientists have actually tested, in whom, at what doses, and what that does and doesn't mean for an ordinary person thinking about trying CBD.
Because of the subject, this page does not promote or link to any product.
First, what is CBD?
Cannabidiol (CBD) is one of more than a hundred natural compounds found in the hemp plant. Unlike THC, the compound in cannabis that causes a "high", CBD does not cause intoxication. It is sold in Ireland mainly as oils, gummies, capsules and creams.
One important point before we go further: CBD and cannabis are not the same thing. High-THC cannabis has been linked in research to a higher risk of psychosis, especially in young people and heavy users. Some of the interest in CBD comes from researchers asking whether CBD behaves differently, but nothing in this article is about cannabis use.
Why the research is hard to apply to everyday CBD products
Three things to keep in mind as you read any CBD study:
- Dose. Most human studies on mental health used large single doses or daily amounts of hundreds of milligrams, often 300mg to 800mg or more, given under medical supervision. A typical consumer product contains far less per serving. You cannot assume a result seen at 600mg will happen with a much smaller amount.
- Study size and design. Many studies are small (sometimes a few dozen people or fewer), short, or have no placebo group. Results from small studies often shrink or disappear in larger ones.
- Preclinical vs human. A lot of the research is in cells or animals. That tells scientists where to look, not what will happen in people.
Anxiety: what researchers observed
Anxiety is the most studied area, and the results are the most interesting, but they are still limited.
- Public speaking tests (human, small). In a 2011 study of 24 people with social anxiety disorder, those given a single 600mg dose of CBD before a simulated public speaking test reported less anxiety than those given a placebo. A 2019 study in healthy men found that 300mg reduced anxiety during a similar test, but 150mg and 600mg did not, suggesting the effect may depend on dose in ways that aren't well understood.
- Repeated use (human, small). A small 2019 study in Japanese teenagers with social anxiety gave 300mg a day for four weeks and observed lower anxiety scores than placebo.
- Clinic case series (human, no control group). A 2019 report from a US clinic followed 72 adults given CBD alongside their usual care. Anxiety scores fell in many patients in the first month, but without a placebo group it is impossible to know how much was due to CBD.
What this means: there is a genuine scientific question here, and larger trials are under way. But the evidence comes from small studies at doses well above typical consumer products, and CBD is not a treatment for anxiety disorders. Proven treatments, including talking therapies and, where appropriate, medication, are available through your GP.
Depression: mostly early research
Most of the research on CBD and low mood is preclinical, in animals. Some of those studies observed effects that researchers describe as "antidepressant-like", possibly involving the brain's serotonin system. Good-quality human trials are lacking.
What this means: there is no reliable evidence that CBD helps depression in people. Depression is a serious, treatable illness. Please don't use CBD instead of speaking to your GP, and never stop prescribed medication without medical advice.
Sleep
People often ask about CBD and sleep. In the 2019 clinic case series above, sleep scores improved in some patients in the first month but fluctuated afterwards. Other small studies have produced mixed results. Poor sleep is often linked to stress, pain, caffeine, screens or an underlying condition, and those are worth looking at first. Persistent insomnia is worth discussing with your GP.
PTSD
Research on CBD and post-traumatic stress disorder is at a very early stage. A 2019 report described 11 patients at a US psychiatric clinic who were given CBD alongside their usual treatment and whose symptom scores fell over eight weeks. That is a small retrospective case series with no comparison group. Animal research has looked at how CBD might affect fear memory, but this has not been confirmed in people.
What this means: PTSD needs specialist support. Trauma-focused therapies have strong evidence and are the place to start.
Psychosis and schizophrenia
This is a medical research area, not a self-help one. In a 2012 trial, 39 people in hospital with schizophrenia received either CBD (up to 800mg a day) or an antipsychotic medicine for four weeks, and both groups improved by similar amounts. A 2018 trial of 1,000mg a day added to existing medication observed modest improvements in some measures. Another 2018 study, using 600mg a day, found no meaningful benefit.
What this means: these were supervised clinical studies at very high doses in people already under specialist care. They do not support anyone using CBD products for psychosis, and anyone experiencing symptoms should get medical help straight away.
Safety: what to know before trying CBD
- Medication interactions. CBD is processed by the same liver enzymes as many medicines, including some antidepressants, anti-anxiety medicines, blood thinners and anti-epileptic drugs. It can change how much of a medicine stays in your system. Always check with your GP or pharmacist first.
- Don't stop prescribed medication. Stopping some mental health medicines suddenly can be harmful. Any change should be planned with your doctor.
- Side effects. Reported side effects include tiredness, diarrhoea, changes in appetite and, at high doses, changes in liver tests.
- THC. Some products sold as CBD contain THC, which can worsen anxiety or paranoia in some people. In Ireland there is no legal tolerance for THC in finished CBD products. Only consider products with an independent batch lab report showing THC "not detected".
- Not for young people, pregnancy or breastfeeding. CBD products are for adults, and should be avoided during pregnancy and breastfeeding.
A more useful way to think about it
Mental health is shaped by many things at once: sleep, relationships, money, work, physical health, alcohol, exercise, and whether you have someone to talk to. No supplement changes all of that. If you are curious about CBD as part of a general wellbeing routine, that's a personal choice for an adult to make with good information, ideally after a chat with a pharmacist. But if you are struggling, the most effective step is to talk to someone.
Where to get support in Ireland
- Emergency: 112 or 999
- Samaritans: freephone 116 123, 24 hours a day
- Text support: text HELLO to 50808, 24 hours a day
- Your GP, who can refer you to counselling and mental health services
- HSE mental health information: hse.ie/mental-health
The bottom line
Researchers are asking real questions about CBD and mental health, especially anxiety, and some small studies have observed encouraging results at high doses. But the evidence is early, the doses studied are far higher than in everyday products, and CBD is not a treatment for any mental health condition. Treat confident claims online with caution, check with your GP or pharmacist before trying CBD, and if you are struggling, reach out for support.
Studies referred to: Bergamaschi et al., Neuropsychopharmacology (2011); Linares et al., Brazilian Journal of Psychiatry (2019); Masataka, Frontiers in Psychology (2019); Shannon et al., The Permanente Journal (2019); Elms et al., Journal of Alternative and Complementary Medicine (2019); Leweke et al., Translational Psychiatry (2012); McGuire et al., American Journal of Psychiatry (2018); Boggs et al., Psychopharmacology (2018).
Related reading: CBD gummies in Ireland: a plain-English guide · Where to buy CBD in Ireland: a buyer's checklist
Frequently asked questions
Can CBD treat anxiety or depression?
No. CBD is not a treatment for any mental health condition. Some small studies have observed reduced anxiety at high doses, and depression research is mostly in animals. Talk to your GP about proven treatments.
Is CBD the same as cannabis?
No. CBD is one compound from the hemp plant and does not cause a high. Cannabis containing THC is different, and high-THC cannabis has been linked to a higher risk of psychosis.
Can I take CBD with antidepressants?
Only after speaking to your GP or pharmacist. CBD can affect how some medicines, including some antidepressants, are processed by the liver.
Should I stop my medication and use CBD instead?
No. Never stop prescribed medication without medical advice. Stopping some mental health medicines suddenly can be harmful.
What doses were used in the studies?
Most human mental health studies used hundreds of milligrams of CBD, often 300mg to 800mg or more, under medical supervision. That is far more than a typical consumer serving.
Can CBD make anxiety worse?
CBD itself is not known to cause anxiety, but products that contain THC can worsen anxiety or paranoia in some people. Only use products with a batch lab report showing THC not detected.
Where can I get mental health support in Ireland?
Call Samaritans free on 116 123, text HELLO to 50808, contact your GP, or call 112 or 999 in an emergency.