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Durham University

Durham Infancy & Sleep Centre

Cortisol & Sleep in Infancy (CoSI)

What is the study about?

This project examines salivary cortisol development in infants. We are especially interested in finding out how this hormone develops in breastfed babies who sleep next to their parent/s. We would like parents to take part who are happy to sample saliva from their babies during the day, and before and during sleep. The aim of the study is to describe how cortisol develops in babies during the first 6 months of life.

Who can take part in the study?

We would like to recruit families living in the North-East of England, who are: expecting a baby, or have a baby aged less than 4 weeks at the time of entry into the study. intending to breastfeed. intending to have baby sleep close-by (same room or same bed as parent/s) until baby is 6 months of age.

What will I need to do if I take part?

You will collect saliva* from your baby, using a special swab, four times over the course of 24 hours every 4 weeks when your baby reaches 4, 8, 12, 16, 20 & 24 weeks.

On each occasion you will collect a sample at bedtime, one after your baby falls asleep, one when your baby wakes the next day, and one mid-afternoon) during the course of 24-hour period. You will also fill out a questionnaire and log sheet at each time-point. In case you need it, you will receive individual support from research staff throughout your involvement in the project. Samples will be stored in your freezer. They won’t take up much room, and we will provide you with packaging and instructions.

When you have collected all the samples one of the research team can visit you to collect them.

A thank you!

As a thank you for taking part, you will recieve a £20 High Street Gift voucher on completion of the study.

*Why saliva samples?!

Saliva samples are used as a less invasive alternative to blood samples. They allow us to study hormone development and function in babies, without subjecting them to the stress of having samples taken by a stranger, or being taken out of their home environment. This video shows the swab, and how to obtain a sample

What else should I know?

All information gained from this project is confidential, and will be stored securely. We will not identify you or your baby in any publications. The samples you will provide will be anonymised, analysed for the hormone cortisol, and not used for any other purpose unless you provide us with further permissions. All saliva will be stored securely and disposed of appropriately. You do not have to take part in this project if you do not want to, and even if you consent to take part and then change your mind, you can withdraw at any time without giving a reason.

Get in touch!

If you would like to take part, wish to discuss the study, or if you have any questions or concerns please contact us at

This study has been approved by Durham Anthropology Department Ethics committee.


CoSI Consent Form

CoSI Participant Information Sheet

CoSI Enrolment Form

CoSI Sample collection tool / Log Book