Why do people report better health by phone than by mail?

Past research shows that fewer health symptoms are reported by phone than by mail.

We sought to examine whether interview mode-dependent differences in health symptom reporting are the result of socially desirable responding or to expending less cognitive effort when formulating responses, a behavior known as satisficing.

Participants were randomly assigned to telephone interview only or to mail interview followed 2 weeks later by telephone interview.

Participants were American veterans from the Gulf War Registry (n=719).

Our main outcome measure was the number of mild, moderate, or severe symptoms reported (of 48 possible).

Veterans reported an average of 5 more symptoms via mail than via telephone, F (1, 709) = 32.50, P < 0.001. The difference was mainly the result of symptoms reported by mail as mild but not reported at all by phone. Veterans with higher social desirability scores reported fewer symptoms by phone and mail, F (1, 709) = 10.11, P = 0.001, but social desirability scores did not interact with interview mode. Furthermore, embarrassing symptoms such as genital complaints were no less likely to be reported by phone.

Reporting of better health in phone surveys is the result of fewer mild symptoms reports but not of socially desirable responding. The findings are consistent with phone interviews encouraging satisficing by limiting the recall of less severe health states. Researchers should handle mild symptom reports with some skepticism.