Aromatherapy for Post-Dural Puncture Headache: a seemingly rigorous study turns out to be useless

Who does not like a nice fragrance?

Who would object to aromatherapy?

Nobody, I suppose.

But, if its called THERAPY, we surely must ask whether it is therapeutic. And is aromatherapy therapeutic? Let’s see:

This randomized, placebo-controlled clinical trial tested whether patients with post-dural puncture headache (PDPH) caused by spinal anesthesia would benefit from aromatherapy. A total od 50 patients received 15-minute inhalations of either lavender oil or liquid paraffin as placebo. The severity of headache was scored before (baseline) and after the intervention – immediately, 30, 60, 90, and 120 minutes after – using a visual analog scale. In addition, the dosage and frequency of the pain killers as well as adverse effects of the intervention were recorded.

Both groups showed a reduction in headache scores post intervention. However, the headache scores between the groups was significantly different immediately after the intervention in favor of lavender oil (difference: 1.60 ± 0.63, P = .015). Furthermore, it was observed that the mean changes of the headache scores compared to the baseline were significant at each time interval in favor of the placebo group (P < .05), except immediately after the intervention. No significant difference was observed in Diclofenac intake between groups (P = .440), and no adverse effects were noted.

The authors concluded that aromatherapy with lavender oil was observed to reduce the severity of PDPH only immediately after the intervention, while only minimal effects were observed at successive time intervals. However, it is noted that the study was likely underpowered and further studies are recommended to better understand the effects of lavender oil on PDPH and compare its effects to other herbal products or pharmacological agents commonly used for managing headaches.

I find it laudable that some researchers conduct clinical trials even of so-called alternative medicines (SCAMs) which many of us might view as trivial. I find it more laudable that they try to do this rigorously by adding a placebo control group to the study. And I would find it even more laudable, if they did this adequately.

Considering parafin oil to be a placebo in a study of lavender oil inhalation can hardly be called adequate. Placebos are used in clinical trials mostly to account for the expectation of patients. This means that, whenever possible, patients need to be blinded to the group aloocation and the placebo must be indistinguishable from the verum. In the present trial, the patients could obviously tell the difference between the smell of lavender and the absence of any smell in the control group. Thus, their expectation could easily suffice to bring about the findings observed in the study. This means that the trial does not neccessarily demonstrate the effects of armoatherapy, but might (and most probably does) merely show the power of expectation.

How can one design such a trial more rigorously? you will ask.

There are several options. For instance, for the control group, one could use an artificial fragrance not made from natural lavender. Alternatively, one could include only patients who are unfamiliar with the smell of lavender and use a similaryly pleasant fragrance from a different plant as the control intervention.

As it stands, the study – even though aimed at testing the hypothesis that aromatherpy with lavender has specific effects on pain – tells us next to nothing.

… except, of course that it is always worth thinking very carefully about the adequate way to conduct a clinical trial.