Footnotes

• Handling editor Ellen J Weber

• X @pilarortegamd

• Contributors PO confirms sole responsibility for conceptualising and designing the content, preparing the manuscript and creating the figures.

• Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

• Competing interests PO receives textbook author royalties from Elsevier.

• Provenance and peer review Not commissioned; internally peer reviewed.