Out of sight, out of mind? Intersession experiences as protective and risk indicators of suicidal ideation in the context of outpatient treatment

OBJECTIVE: Suicidal ideation is a central clinical risk in psychotherapy. Patients' engagement with therapy between sessions, captured by intersession processes (ISP), may be particularly informative for understanding risk and resilience. This study examined associations between ISP and suicidal ideation, distinguishing between-person vulnerabilities from within-person crisis dynamics. METHOD: = 73, 2,586 total sessions), including an eight-item short version of the Intersession Experiences Questionnaire (IEQ-S) and the PHQ-9 suicidal ideation item. Multilevel logistic mixed-effects models treated suicidal ideation as a binary outcome, disaggregated between- and within-person effects, and included linear, quadratic, and cubic terms. RESULTS: At the between-person level, more frequent problem-focused application of therapeutic insights was associated with a lower likelihood, whereas higher levels of negative emotional ISP were linked to a higher likelihood of reporting suicidal ideation, following nonlinear trajectories. At the within-person level, increases in positive emotional engagement and problem-focused application co-occurred with a lower likelihood, whereas increases in imagining therapeutic dialogue and negative emotions were related to a higher likelihood of reporting suicidal ideation. CONCLUSION: ISP reflect the internalized therapeutic alliance and clinically meaningful cognitive-affective processes, signaling crisis escalation, but also pointing to mechanisms of change. ISP may be valuable monitoring targets.