What's said in a subject line? Framing the email subject lines in health messages sent to university students.

To examine whether manipulating the frame used in email subject lines affects open or click-through rate. Students (N = 38,538) at a Midwestern university received emails from their health clinic about a stress management program (September - December 2017). Three subject lines (Action Instruction only, Gain Frame plus Action Instruction, Non-loss Frame plus Action Instruction) were used. Each student randomly received one subject line in the first two months and one in the next two months. Email open and click-through rates were measured. Emails with the Action Instruction only subject line were more likely to be opened; there was no difference in open rate between the two framed subject lines, and no effect on click-through rates. This study supports the benefits of action instructions to encourage behavior change but calls for further research on the effects of frames and action instructions in email subject lines.