Was your most recent study conducted with your clients? Or with a cohort of your surgeon's patients? Or perhaps this study only include the subjects who were admitted to a local emergency department. We all want to correctly identify those wonderful people who voluntarily agree to be part of a research study, but there seems to be some confusion about how we refer to them. Just like the rest of you, I have heard both stolid arguments and passionate pleas supporting some specific preferred terminology. Just as frequently, however, I have heard the counterarguments refuting those passionate pleas. With so much disagreement-does it matter?
First, the question of ownership. No. Stop. Don't.
Possessive pronouns and possessive adjectives are tricky. Nobody should own another human. With good reason, it raises the hair on many necks when a new young resident starts ranting: "I don't want anyone ordering anything on MY patient without talking to me first." Fortunately, a short round of corrective communication tends to resolve this conflict. I also recognize that there is a subtle distinction that occurs when using possessive adjectives to describe a relationship. My son. Your mother. Her spouse. I know that I have said things like "I was just talking to your patient and she thinks you are amazing." Fortunately, scientific writing rarely has need for this particular form of relationship, and I think we can agree to avoid possessive pronouns when referring to other humans.
The harder question surrounds style and intent. Patients are people who are receiving medical care. So, if the human in the study is a patient, it seems like you could use patient. Client arises from psychology literature. Where a patient seeks medical care, a client is in the driver's seat to determine, along with expert advice, the best therapy to aid them. So if the research is subject driven, it seems like you could use client. Subjects are objects of a study. So if the object of the research is the individual, as with a case study or qualitative research, it seems like you could use subject. Participants are those who actively engage. So, if you have a study that requires persons to actively participate, it seems like you could use participant. Volunteer implies that the choice of participation was self-initiated. So if you have a flyer recruiting volunteers, it seems like you could use volunteer. There are good and reasonable arguments to support each term. As the author, you must decide which one works best for each manuscript.
Honestly, as the editor for the Journal of Neuroscience Nursing, I am not highly critical about which term you use. It is, however, important to pick only one. It is difficult for the reader to follow sentences like "We recruited 100 volunteers as subjects. Fifty-four percent of the patients were male. The median age of the participants was 63 years, and all of the clients had at least 1 seizure before enrollment." Whichever term you select, have a reason, be consistent, and please submit your work to the Journal of Neuroscience Nursing.