This scientific study was written by David Heal PhD, DSc, FRSC, FBPhS, co-founder and Executive Director of DevelRx. Find out more about our team of scientific advisors
CBD has been clinically tested and approved as a medicine for treating two rare, severe types of epilepsy of epilepsy called Dravet’s syndrome and Lennox-Gastaut syndrome in patients from 2 years of age. It is also approved in children and adults as an add-on treatment for seizures in tuberous sclerosis. These forms of epilepsy often do not respond to typical medications.
CBD has also been tested in clinical trials for other health disorders (see below).
CBD has been clinically proven to reduce seizure frequency in three rare and severe types of epilepsy in patients aged 2 years and above. These are Dravet’s syndrome, Lennox-Gastaut syndrome and tuberous sclerosis. Treatment of these forms of seizures needs much higher daily doses of CBD than those recommended in CBD food products or CBD oils. The efficacy of CBD to treat other forms of epilepsy has not been proven.
Seizures occur when nerves in the brain signal repetitively and uncontrollably. Epilepsy drugs prevent seizures either by reducing this repetitive nerve signalling at the point where the seizure starts, or by preventing the spread of the seizure to other areas of the brain. These are powerful events and as a proven epilepsy drug, CBD controls the excitability of the brain when it is neurologically dysfunctional during seizures.
The psychotropic (mood altering) effects of THC results from it locking into specific proteins (CB-1 receptors) in the brain. This action produces its intoxicating, emotional, perceptual and hedonic effects (the “high”) and its adverse impact on attention, learning, memory, motor (movement) and cognitive performance. In contrast, CBD has no effect on these CB-1 receptors and does not produce the mood altering effects of THC that are the cause of its abuse and misuse. This is also why ingestion of CBD does not have a negative effect on attention, learning, memory, motor or cognitive performance.
Numerous clinical studies have investigated the potential of CBD for abuse and also its effects on attention, learning, memory and motor performance. In one study, there were no psychological and neurological adverse effects of CBD at single doses of up to 4,500 mg (60 mg/kg) and multiple daily doses up to 750 mg (10 mg/kg). These doses are 10x to 60x higher than the recommended maximum daily intake of CBD as a novel food or food supplement.
Similarly, several studies in cannabis-using humans have demonstrated that CBD does not produce perceptual, emotional or sensory effects in humans and does not impair attention, learning, memory or motor function.
There is good evidence from controlled clinical trials to show that CBD has an effect to reduce stress and anxiety.
Brain imaging has shown that CBD decreased anxiety in patients with generalized social anxiety disorder. In a study in patients with Parkinson’s disease, acute administration of CBD reduced anxiety and stress-induced tremors caused by a simulated public speaking task, which many people find to be an extremely stressful task. In another clinical study, short-term administration of CBD reduced the drug craving and anxiety in drug-abstinent, heroin-dependent subjects.
It is important to note that most of these studies used CBD at doses far in excess of those permitted as a daily intake in foods. However, one study in patients with anxiety or sleep problems used a low dose of 25 mg/day (about one third of the CDB dose that is recommended from food or CBD oils). A though a minority of subjects did experience a worsening of their symptoms, the majority of subjects (80%) had a reduction of their anxiety and more than 55% of people reported improved sleep.
CBD can reduce inflammation when taken orally or applied topically to the skin. This effect of CBD has been demonstrated in placebo-controlled clinical trials in human volunteers.
The possible benefits of CBD in osteoarthritis have also been demonstrated in a veterinary study in dogs. Daily treatment with CBD improved the dogs’ mobility and reduced their level of pain.
Since osteoarthritis occurs in humans and dogs, this is an important finding and suggests that more studies in humans with this painful condition are warranted.
Preliminary findings in a clinical trial have shown that CBD may reduce inflammation in the gut. Further studies are needed to determine whether CBD may be of value for treatment of disorders associated with increased gut permeability, such as inflammatory bowel disease.
Some types of pain may be helped by taking CBD. For example, neuropathic pain, which can occur after suffering from shingles (post-herpetic neuralgia), or it may be caused by nerve trauma or by a trapped nerve. This type of pain is frequently unresponsive to conventional painkillers.
Lower-back pain is a different type of painful condition, which is often successfully treated with conventional painkillers such as aspirin, paracetamol and codeine. When CBD was given to patients in combination with these painkillers it did not increase their pain relief over taking the conventional painkillers alone.
CBD has shown therapeutic potential in reducing neuropathic pain and inflammatory pain (see question on inflammation above), but it is not a conventional painkiller.
There are contradictory reports of the effect of CBD on heart function in human studies. Some studies show no effect of CBD on the heart, while another recent study showed that 600 mg CBD reduced resting blood pressure and stress increased blood pressure, at the same time as increasing heart rate (also see question on tachycardia below).
More clinical investigations are needed to determine whether CBD may be beneficial for treating high blood pressure conditions.
People with epilepsy that is resistant to medical treatment have a very poor quality of life. Such patients who took CBD for a year in a clinical study found an improvement in their quality of life, which was not related to any changes in the frequency or severity of their seizures. This suggests that CBD has a beneficial effect on the wellbeing of these epilepsy patients that is not directly related to its ability to prevent their seizures.
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