.

Cortisol awakening response (CAR) research relies upon self-collected saliva sampling during the post-awakening period. It is unknown how the CAR protocol is perceived and how they may affect typical routines relevant to CAR methodology. CAR assessment is sensitive to state variables, suggesting that CAR measurement may be affected by research participation. This is the first qualitative study to explore motivation and experiences of participation in CAR research. Interviews were conducted with a sample of 20 participants (males/females: 4/16) aged 46-82 years following their participation in CAR research in the domestic setting. Responses were transcribed verbatim and thematically analysed. Participants were motivated to take part in CAR research for altruistic reasons and the apparent convenience of undertaking the study at home. Participants experienced the study as arduous describing apprehension and the cognitive burden it placed on them leading to disruptions to sleep and morning routines. Participants also struggled to identify the moment of awakening and there was uncertainty surrounding the timing of the first awakening sample. Disruptions were lessened with habituation to sampling on repeated study days. There was apprehension about taking part in CAR research, affecting mood, cognition, and sleep; state variables known to influence the CAR. Findings inform ways to optimise CAR 'ecological validity' and obtain typical CAR characteristics. The 'moment of awakening', was not universally understood, leading to hesitancy in deciding when to collect saliva samples. Researchers need to include a specific discussion of the commonly experienced ambiguity surrounding awakening to increase awareness, lessen anxiety and highlight its importance.