Chamomile: what the trials looked at, and what they found

Chamomile has been an evening drink for so long that most people assume nobody ever bothered to study it. Several groups have, and the results are more interesting than either the marketing or the scepticism suggests.

The short version: the anxiety trials are the stronger ones, and the sleep trials are mixed.

The plant

Chamomile is the dried flower head of a small daisy. It has been drunk in the evening across Europe, North Africa and western Asia for centuries, which is a long-running observation rather than evidence, but it is why the plant was studied at all.

The anxiety trials

The clearest result comes from a placebo-controlled trial of adults with mild to moderate generalised anxiety disorder. Fifty-seven were randomised to a chamomile extract or placebo for eight weeks, and the chamomile group showed a greater reduction in total anxiety score (Amsterdam et al., Journal of Clinical Psychopharmacology, 2009, PMID 19593179).

A larger and longer study followed a different design. One hundred and seventy-nine adults with moderate to severe generalised anxiety took chamomile extract openly for twelve weeks. The ninety-three who responded were then randomised to continue on chamomile or switch to placebo for twenty-six weeks. Relapse was lower on chamomile, 15.2% against 25.5%, but that difference did not reach statistical significance. What did hold was that anxiety symptoms stayed significantly lower in the chamomile group across the period (Mao et al., Phytomedicine, 2016, PMID 27912875).

Reported honestly: chamomile beat placebo on anxiety scores in the eight-week trial, and in the longer study it kept symptoms down without proving it prevented relapse.

The sleep trials, which are mixed

This is where the folklore runs ahead of the data, and it is worth knowing before you buy anything on the strength of it.

A twenty-eight day placebo-controlled trial in thirty-four adults with chronic primary insomnia found no significant difference on any sleep diary measure. There was a modest, non-significant advantage on daytime functioning (Zick et al., BMC Complementary and Alternative Medicine, 2011, PMID 21939549).

A later study in sixty nursing-home residents aged sixty and over did find better sleep quality scores after twenty-eight days of chamomile extract, though that study was single-blind rather than double-blind, which is a weaker design (Adib-Hajbaghery and Mousavi, Complementary Therapies in Medicine, 2017, PMID 29154054).

What is missing

Two things, and both matter.

No trial of chamomile for sleep or mood in children was found. Every study above is in adults, most of them adults with a diagnosis. Adult results are not evidence about a seven-year-old.

And the amounts varied enormously between studies, using extracts of unstated strength. That makes comparison between one product and another, or between a product and a trial, much harder than a citation on a box implies.

The fair summary

Chamomile is one of the better-studied evening plants, with real placebo-controlled trials showing an effect on anxiety scores in adults, and a mixed record on sleep. It is a plant with genuine research behind it and a research record that does not stretch as far as the tradition does.