Diaries for observation or intervention of health behaviors: Factors that predict reactivity in a sexual diary study of men who have sex with men

Background: Behavioral diaries for observation of healthrelated behaviors assume absence of reactivity (i.e., change in behavior resulting fromobservation), while self-monitoring diaries maximize reactivity for behavior change. Little is known about when and for whom behavioral diary studies become self-monitoring interventions. Purpose: This study evaluated the moderating effects of social cognitive variables on reactivity in sexual risk behavior and risk appraisals in a diary study of men who have sex with men (MSM). Methods: One hundred forty-three MSM completed weekly online sexual diaries for 3 months. Analyses were conducted with hierarchical linear modeling. Results: There was no evidence of reactivity for the sample as a whole. Social cognitive variables (e.g., risk reduction motivation, condom use intentions, and social norms) moderated reactivity in study outcomes. For example, more highly motivated MSM experienced declines in serodiscordant unprotected anal intercourse over time. Conclusions: Effectiveness of behavioral self-monitoring strategies may vary depending on social cognitive domains.