Longitudinal qualitative research design: experience over time

In this paper I examine time in qualitative researchdesign. I focus on a study design that is almost absent from the literature, inwhich qualitative data are collected repeatedly and prospectively from a cohort of individuals over a long period. I will refer to this design as longitudinal qualitative research, and argue that it carries risks and benefits. It heightens the need for ethical clarity, particularly in respect to repeated participation. Unless the aim is to examine a trajectory of experience, longitudinal design may diminish a study's explanatory power by making the sampling less purposive: commitments to long engagement must be honoured, and the participants selected may, over time, become less informative than expected about the issue under study. Conversely, longitudinal design benefits from the development of a history between the researchers and participants, offers unique access to the actions of, and interactions with, time in the experience under study, and helps to guard against epistemological naiveté on the part of the researcher. Qualitative research isoften blind to time, and I conclude that the greatest contribution of longitudinal qualitative research may be its sensitisation of researchers to the importance of time in social life.