Cannabidiol (CBD) is emerging as a promising therapeutic for a variety of health conditions, but research is still in early stages.
Here are some key facts on purified CBD:
- Purified CBD is showing positive results in clinical trials for anxiety, psychosis, schizophrenia, PTSD and substance abuse. Evidence is strongest in these neurological and psychiatric conditions.
- Doses of 300-800mg per day for multiple weeks seem most effective based on clinical trials so far. Single doses of 160-600mg can produce benefits.
- CBD is not yet proven effective for pain relief, cancer, or COVID-19 symptoms despite promising preclinical studies. More research is needed.
- Side effects are generally mild but can include diarrhea, fatigue, appetite changes. CBD can interact with some medications.
Source: J Cannabis Res. 2023
Understanding Purified vs Full Spectrum CBD
CBD is one of over 100 active compounds found in the cannabis plant.
It can be purified into an isolated extract or kept in a full spectrum extract along with other cannabis components like THC.
Purified CBD allows researchers to specifically study effects of the CBD molecule itself.
Full spectrum CBD may have benefits from the “entourage effect” of multiple compounds working together, but it’s hard to attribute results specifically to CBD.
Most research so far has focused on purified CBD, especially an FDA-approved epilepsy drug called Epidiolex.
As purified CBD shows promise in clinical trials for various conditions, we’re starting to understand its therapeutic potential as a standalone compound.
Current Evidence of Effectiveness
Anxiety Disorders
The most robust evidence for purified CBD is in treating anxiety disorders.
Multiple clinical trials in patients with social anxiety and healthy volunteers indicate CBD reduces acute anxiety.
In generalized social anxiety disorder, single doses of 400-600mg reduced anxiety compared to placebo.
Other trials found 4 weeks of daily 300mg CBD decreased anxiety symptoms.
Functional brain imaging shows CBD alters activity in limbic and paralimbic areas of the brain involved in emotional processing and fear memory when given acutely.
This suggests some of CBD’s anti-anxiety effects may come from modulating these regions.
Chronic dosing studies also indicate CBD can reduce anxiety in substance abusers and PTSD patients when confronted with drug cues or trauma reminders.
This points to a potential role in managing substance use and trauma-related disorders.
Overall, results are promising for CBD relieving anxiety states acutely via brain network modulation.
Results are mixed regarding how much repeated CBD dosing helps generalized anxiety disorder. Larger long-term studies are still needed.
Schizophrenia & psychosis
Smaller scale studies provide initial evidence that CBD may improve symptoms of psychosis, schizophrenia and bipolar disorder.
In schizophrenia, 6 weeks of CBD treatment led to modest improvements in cognitive functioning and psychiatric symptoms in one trial.
Other studies found single doses of CBD could alter brain activation patterns in regions implicated in psychosis.
While not definitive, results hint CBD may help normalize dysfunctional brain activity in psychiatric disorders. Larger studies are underway.
Post-Traumatic Stress Disorder (PTSD)
A handful of small trials indicate single doses of oral CBD can dampen the psychological and physical effects of trauma reminders in PTSD patients.
Other studies found multi-week CBD treatment reduced PTSD symptoms in a subset of patients.
These promising results need to be replicated but suggest a potential role for CBD in PTSD management.
Combining CBD with first-line trauma therapies could boost treatment responses.
Substance Use Disorders
Preclinical research indicates CBD may help reduce drug cravings and relapse. A few small clinical trials support this.
In heroin users, 3 days of CBD administration reduced drug cue-induced craving and anxiety.
Other research found CBD lowered cannabis and tobacco use over 4 weeks compared to placebo.
The anti-addictive effects of CBD need more study but initial findings are positive for a variety of substance abuse disorders.
Movement Disorders
CBD has shown neuroprotective and anti-inflammatory effects in preclinical models of Parkinson’s and Huntington’s disease.
Small uncontrolled human studies hint at benefits too.
However, placebo-controlled trials in Parkinson’s patients showed no difference between CBD and placebo for common motor and non-motor symptoms.
The exception was reduced anxiety with single CBD doses.
Despite promising animal research, there is currently minimal evidence that CBD improves movement problems in these disorders.
Dosing may have been too low in clinical trials so far.
Sleep & Insomnia
Many people take CBD to improve sleep, but clinical research is lacking.
While uncontrolled studies and case reports have noted sleep improvements with CBD, placebo-controlled trials did not find differences in sleep outcomes between CBD and placebo.
Changes in sleep may be secondary to CBD’s effects on other symptoms like pain or anxiety.
But there is currently little direct evidence CBD acts as a sleep aid.
Pain Relief
Despite strong preclinical evidence, virtually all placebo-controlled trials found purified CBD had no acute analgesic effects in healthy volunteers or chronic pain patients.
The one exception is moderate reductions in neuropathic pain symptoms with 4 weeks of high dose sublingual CBD spraying.
Topical CBD also improved pain outcomes for 2 weeks in studies of arthritis and neuropathy patients.
This suggests localized administration may be more effective than systemic.
But overall, oral CBD has not shown pain-relieving potential in clinical trials despite promising preclinical results. This could be due to insufficient dosing.
Conditions Needing More Research with CBD
Cancer
Robust preclinical evidence indicates CBD exhibits anti-tumor effects in cell and animal models of cancer.
CBD appears to inhibit cancer cell growth and metastasis via several mechanisms.
But no controlled trials have directly tested effects of CBD on cancer outcomes in actual patients.
Case reports suggest possible benefits but clinical research is sorely lacking.
Given the strength of preclinical findings, there is a pressing need for controlled CBD trials in cancer patients. Initial case reports justify such research.
COVID-19
A recent placebo-controlled trial found 2 weeks of CBD treatment did not improve symptoms or outcomes in patients with mild COVID-19.
This was the first clinical trial testing CBD for COVID-19 based on preclinical rationale that it may help reduce inflammation and disease severity.
The trial did not find benefits from CBD in mild COVID cases.
Further research could examine effects in severe COVID, but current evidence does not support CBD for COVID-19.
Chronic Pain
As noted above, clinical studies show purified CBD does not help acute pain despite positive animal research.
But few trials have tested effects on chronic pain.
Small studies found some reductions in cancer neuropathy pain with short-term CBD treatment as well as improved arthritis pain with topicals.
But larger scale research is still lacking for effects of sustained CBD use on chronic pain patients.
This will help clarify if CBD may be a viable option.
Inflammatory Bowel Disease
Preclinical studies indicate CBD may reduce intestinal inflammation and improve gut barrier integrity based on interactions with the endocannabinoid system.
But placebo-controlled trials found 8 weeks of oral CBD did not improve Crohn’s disease activity or IBS symptoms compared to placebo.
Doses may have been too low.
Clinical data is lacking to support CBD for inflammatory bowel conditions despite theoretical rationale.
Higher dosing studies in IBD patients are warranted.
CBD Dosage: How much is optimal?
Single doses of CBD from 160-600mg appear most effective for acute effects like anxiety reduction based on clinical trials.
These single doses led to blood levels around 150 nanomoles.
Daily doses between 300-1200mg for multiple weeks have shown efficacy for conditions like schizophrenia and PTSD.
Doses under 300mg generally did not improve any outcomes.
Higher blood CBD levels around 150 nanomoles seem necessary to produce therapeutic effects.
But optimal doses likely vary by condition. More dose-ranging studies are needed.
CBD Safety and Drug Interactions
CBD is generally well tolerated but can cause side effects including diarrhea, fatigue, and decreased appetite.
CBD may alter metabolism of certain drugs by inhibiting cytochrome P450 enzymes.
Checking for drug interactions and starting with low doses is advisable.
Talk to your doctor before starting CBD.
Conclusions: Pure CBD
In summary, purified CBD shows early promise for a variety of neuropsychiatric conditions including anxiety, PTSD, psychosis, and addiction based on small clinical studies.
Larger trials are underway.
CBD has not yet shown effectiveness for pain, movement disorders, cancer, or COVID in controlled trials – more research is justified and needed.
While not definitive, current evidence points toward CBD having therapeutic potential beyond epilepsy once effective dosing and delivery methods are optimized.
References
- Study: The therapeutic potential of purified cannabidiol
- Authors: Saoirse Elizabeth O’Sullivan et al. (2023)
