Associations of prior treatment, waiting time, symptom severity, and session frequency with symptom change in CBT for depression and anxiety in primary care

Overview

This study examined associations between prior treatment history, waiting time to treatment, baseline symptom severity, and session frequency with symptom change among primary care patients receiving routine cognitive behavioral therapy (CBT) for depression and anxiety. Analyses tested whether baseline severity, total number of attended sessions, rate of attendance (sessions per unit time), and delay to treatment onset predicted symptom trajectories, and whether prior treatment exposure moderated outcomes. Primary findings indicate that higher baseline severity was associated with larger absolute symptom reductions, improvement correlated with the total dose of attended sessions rather than attendance rate, waiting time did not systematically predict poorer outcomes, and prior treatment history identified individuals with more persistent or treatment-resistant symptom patterns.

Methods and approach

Observational analysis of routine-care CBT cases in a primary care setting. Symptom severity was quantified using standard continuous measures for depression and anxiety at baseline and across sessions. Independent variables included baseline severity, cumulative attended sessions, attendance rate (sessions per calendar time), waiting time from referral to treatment onset, and prior mental health treatment history. Multivariable longitudinal regression models estimated associations with symptom change, adjusting for confounders such as demographic covariates and baseline symptom profiles. Interaction terms tested moderation by prior treatment history and baseline severity. Sensitivity analyses assessed robustness to alternative model specifications and potential attrition bias.

Results

Higher baseline symptom severity predicted larger absolute reductions in symptom scores over the treatment course, indicating substantial benefit among more severe cases. Total number of attended CBT sessions was positively associated with symptom improvement independent of baseline severity. In contrast, the rate of attendance (sessions per unit time) did not predict greater symptom change once total sessions were accounted for. Waiting time from referral to treatment onset showed no consistent negative association with outcomes across models; effects varied by specification and were not robust. Prior treatment history was associated with attenuated improvement trajectories, consistent with greater persistence or partial treatment resistance among previously treated individuals.

Implications

Findings support maintaining equitable access to CBT regardless of initial symptom severity, since higher-severity cases derive substantial absolute benefit. Service planning can prioritize maximizing total session dose over enforcing higher session frequency, permitting flexible scheduling without expected compromise of symptom outcomes. Assessment of prior treatment history can inform case formulation and escalation planning, as previously treated patients may require alternative or intensified approaches given their association with more persistent symptom courses. Differentiation between client-initiated and system-driven delays is warranted when interpreting waiting-time effects; routine waiting periods alone do not uniformly predict poorer outcomes and should not be assumed to necessitate expedited treatment in every case.