Glossary

Terms used on study pages, in the order a reader is likely to meet them. Study designs are explained in more depth on how to read a study.

Study designs

Randomised controlled trial (RCT). Participants are assigned to treatment or comparison by chance. The strongest single-trial design, because chance assignment balances the groups.

Placebo. An inactive look-alike given to the comparison group. Some trials use an active comparator instead, such as ibuprofen in Marini 2012. Some “placebos” contain active ingredients; Di Stadio 2022 used a multivitamin.

Double-blind. Neither participants nor the people assessing them know who got what. Single-blind: only one side is unaware. Open-label: everyone knows.

Crossover. Each participant takes both treatments in turn, separated by a washout period. Used in Strobbe 2013 and Rao 2025.

Controlled trial. A comparison group exists but assignment was not random, or the paper does not say.

Open-label study. Everyone received the treatment and knew it. Improvement over time cannot be separated from expectation or the natural course of the condition.

Observational study. The researchers recorded what happened under ordinary care rather than assigning treatment.

Case series. A description of a group of treated patients, with no comparison group.

Meta-analysis. A statistical pooling of results from several trials. Systematic review: a review that searched for and selected studies by a stated method. Narrative review: the authors’ own summary, without a fixed method.

N-of-1 trial. One person alternates between treatment and placebo several times, so each person is their own experiment. Germini 2017.

Multiple baseline design. A small-group design where treatment starts at staggered times. Taye 2026.

Reading results

n. The number of participants. Trials often report the number enrolled and the smaller number who completed.

p value. The chance of seeing a difference this large if there were no real difference. Below 0.05 is the usual threshold. A small p value in a small study can still be a fluke; a large trial can show a tiny difference with a small p value.

Confidence interval (CI). The range within which the true effect probably lies. A wide interval means an imprecise estimate.

Standardised mean difference (SMD). A pooled effect size used when trials measured pain on different scales. Roughly: 0.2 small, 0.5 medium, 0.8 large.

Heterogeneity (I²). How much the pooled trials disagree with each other. Above 75% is high; several PEA meta-analyses report over 90%.

Number needed to treat (NNT). How many people must be treated for one extra person to benefit. Lower is better.

Intention to treat. Everyone randomised is analysed in their group, whether or not they finished. Per protocol analyses only completers, which flatters treatments people stopped.

Primary outcome. The one measure the trial was designed to test. Secondary outcomes and sub-group results are weaker evidence.

Post hoc. An analysis decided after seeing the data.

Outcome scales

VAS. Visual analogue scale, a 0 to 10 line for pain. NRS. Numerical rating scale, the same idea in numbers.

WOMAC. A questionnaire for knee and hip osteoarthritis with pain, stiffness and function sections.

Roland-Morris (RDQ). A back-pain disability questionnaire.

TDI. Sniffin’ Sticks threshold, discrimination and identification: a smell test scored out of 48.

MoCA, FAB. Cognitive screening tests. YMRS. Young Mania Rating Scale. PANSS. Schizophrenia symptom scale.

MNSI, TSS, NPSI. Neuropathy symptom questionnaires.

Owner-reported. In animal studies, the owner scored the animal’s pain or behaviour. No vet examination unless the page says so.

Mechanism terms

Fatty acid amide / N-acylethanolamine. The chemical family palmitoylethanolamide belongs to, with anandamide.

PPAR-alpha. A receptor inside cells that regulates inflammation and fat metabolism. The best-supported target of palmitoylethanolamide, per Rankin and Fowler 2020.

Mast cell. An immune cell that releases histamine and other mediators. Much of the animal and cell work measures mast cell degranulation. Search: mast cell.

Endocannabinoid system. The body’s own cannabinoid signalling. Palmitoylethanolamide does not bind cannabinoid receptors directly; the proposed link is the entourage effect, where it raises the level or effect of anandamide.

FAAH, NAAA. Enzymes that break down palmitoylethanolamide and anandamide.

TRPV1, GPR55. Other receptors with some evidence of involvement.

Glia, microglia. Support cells in the nervous system involved in inflammation.

Neuroinflammation. Inflammatory activity within the nervous system. Often invoked as the mechanism in the pain and brain studies.

LICI, SAI, LTP-like plasticity. Measures of brain cortex physiology taken by magnetic stimulation. Versace 2023.

Pharmacokinetics. How a compound is absorbed, distributed and cleared. Bioavailability: the fraction of a dose that reaches the blood. Unknown for palmitoylethanolamide; see absorption studies.

Product terms

Micronised, ultramicronised. Ground to smaller particles. See micronised and ultramicronised.

Co-ultramicronised. Two compounds ground together, as in PEA-luteolin.

Dispersion form. A coating that helps the powder mix with water. See Levagen.

Palmidrol. The international non-proprietary name for palmitoylethanolamide. PEA-m, PEA-um, um-PEA, PEALut. Abbreviations used in Italian papers.

Food for special medical purposes. The category under which some products are sold in Italy; a food classification, not a drug approval.

AUST L. The number on an Australian listed medicine. See status in Australia.

Regulators

TGA. Therapeutic Goods Administration, Australia, for human medicines. APVMA. Australian Pesticides and Veterinary Medicines Authority, for animal products. FEI. International equestrian federation, which lists palmitoylethanolamide as a controlled medication. WADA. World Anti-Doping Agency, which does not prohibit it. See status and rules.