CBD: general

CBD, or cannabidiol, is one of the naturally occurring cannabinoids in cannabis plants [1]. Pure CBD does not produce THC-like intoxication [2]. It's also reported to lack the psychotropic effects of THC while retaining analgesic and anti-inflammatory activity [3][4].

The clearest thing to know: CBD is not risk-free just because it isn't intoxicating [2]. It can cause side effects including dry mouth, low blood pressure, diarrhea, decreased appetite, mood changes, light-headedness, and sleepiness [5]. At low doses it most likely won't do anything therapeutically [6], and at high doses side effects are likely to become more pronounced [6].

CBD has been shown effective in treating epilepsy in several clinical trials, with one pure CBD product having completed Phase III trials, and treatment of certain seizure disorders is the only use currently recognized as safe and effective [1][5]. Beyond that, it's reported to have broad pharmacological effects on pain, inflammation, epilepsy, and anxiety [7]. It does not seem to interact with specific cannabinoid receptors, but has been reported to interact with around 56 molecular targets [7]. This is reported rather than established at the same level as the epilepsy data.

There's no evidence to date of recreational use of pure CBD or of public health problems tied to it [1]. As with cannabinoids generally, interactions with other drugs metabolized by the same liver enzymes (including warfarin and valproate) have been identified — worth knowing if you're on other medication [8].

References

1. CANNABIDIOL (CBD) — World Health Organization
2. Cannabidiol: Science, Marketing, and Legal Perspectives — NCBI Bookshelf
3. cannabidiol | Ligand page | IUPHAR/BPS Guide to PHARMACOLOGY — IUPHAR
4. Molecular and Cellular Mechanisms of Action of Cannabidiol — MDPI
5. Cannabidiol (CBD) - Special Subjects - Merck Manual Consumer Version — Merck Manuals
6. The Essential Medicinal Chemistry of Cannabidiol (CBD) — Journal of Medicinal Chemistry (ACS)
7. The Polypharmacological Effects of Cannabidiol — PMC / MDPI (journal article)
8. Systematic review of drug-drug interactions of delta-9-tetrahydrocannabinol, cannabidiol, and Cannabis — Frontiers in Pharmacology