Did you know?

Click any word in a definition or example to find the entry for that word


noun [uncountable]

a method of treating an illness which takes into account the body's natural rhythms and patterns of rest or activity


noun [countable]



'Doctors are becoming increasingly interested in the science of chronotherapy – aligning medical treatment to our circadian rhythms.'

BBC News 13th May 2014

'Several of the drugs … have a 'best' time of day: give the drug at the right moment, and you can take a smaller dosage, get a greater benefit and have a lower risk of unpleasant side effects … Much more, no doubt, remains to be discovered, and it may, in fact, be a while before a chronotherapist opens an office near you.'

New York Times 22nd December 2009

'Further areas that have matured are … chronotherapeutic delivery … in which drug delivery is designed for known daily cyclic needs of the patient.'

Pharmaceutical Technology Magazine 2nd June 2014

I've always thought of myself as a 'lark' rather than an 'owl' – awake fairly early in the morning, definitely at my best before lunch, and often having trouble keeping my eyes open by 10 in the evening. This is something I'm not always happy about, frequently finding myself envious of the 'owl' members of my family who can enjoy watching a late-night movie and know how it ended!

though still an area at the fringe of medicine, chronotherapy is gaining ground as more doctors realize the importance of the body's natural rhythms

It's fair to say that most people have a reasonably good idea of whether they belong to the 'lark' or 'owl' camp, and possibly adapt their lives accordingly, but in a principled approach to medical treatment known as chronotherapy, an individual's body clock takes on far more significance than their daily patterns of sluggishness or liveliness.

Chronotherapy is the principle of aligning the treatment of illness with a patient's body clock or circadian rhythm – the more formal term for the biological processes which regulate the body over a period of 24 hours. Research has revealed that an individual's natural body rhythms can influence how they experience a medical condition, so that any treatment of this condition is most effective if it's administered according to a schedule that corresponds to those rhythms. Asthma, for example, is worse in the early hours of the morning, when steroid hormones in the body are at their lowest levels. Research suggests that if drugs are taken mid-afternoon, they're optimally effective in the small hours at exactly the time when the condition is worst.

In an approach sometimes known as preventative or precautionary chronotherapy, drugs are taken when they are most necessary, such as, for example, taking hypertension drugs just at the time of day when blood pressure is on the rise. A surge in blood pressure after waking is thought to be the reason why so many heart attacks occur first thing in the morning, so drugs with a delayed reaction can be taken last thing at night so that they're effective several hours later when they're most needed.

It's also been revealed that chronotherapy can help with side effects caused by some drugs, effectively reducing their toxicity. Cancer patients undergoing chemotherapy have been found to experience significantly reduced symptoms if their treatment is administered at a time of day which respects their body clock.

Though still an area at the fringe of medicine, chronotherapy is gaining ground as more doctors realize the importance of the body's natural rhythms. It also has applications in non-clinical settings – in the workplace, for example, it can be used to improve productivity and performance by considering the times of day when employees are most likely to be at their best.

Background – chronotherapy

The term chronotherapy dates back to the 1970s, but remained pretty obscure until the early 2000s, when it began to appear more widely as medical experts understood more about its potential benefits. The word contains the combining form chrono-, originating from the Greek khronos meaning 'time', and occurring in more familiar words like the adjective chronological. Chronotherapy also has an alternative sense connected with the treatment of sleep disorders.

The technical term circadian is also a relative newcomer to the English language, first attested in the 1950s and based on Latin circa (meaning 'about') in combination with dies ('day').

by Kerry Maxwell, author of Brave New Words

For teachers

Would you like to use this BuzzWord article in class? Visit onestopenglish.com for tips and suggestions on how to do just that! This downloadable pdf contains a student worksheet which includes a 'find the information' exercise, comprehension activities, and a focus on verb and noun collocations and phrases with prepositions.

Last week …

Read last week's BuzzWord article. Protologism.

This article was first published on 4th November 2014.

Open Dictionary


a form of location that involves the underwater detonation of a bomb which causes sound waves that are picked up by ships

add a word


A must for anyone with an interest in the changing face of language. The Macmillan Dictionary blog explores English as it is spoken around the world today.

global English and language change from our blog