Psychology and Psychotherapy: Theory, Research and Practice

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Volume 90 Issue 3 (September 2017), Pages 245-509

The effect of length, duration, and intensity of psychological therapy on COREglobal distress scores (pages 389-400)


This study explores whether improvements, as measured by the CORE‐OM/10, as a result of psychological therapy were related to length of treatment in weeks, number of treatment sessions, or treatment intensity, as well as any effect of diagnostic group.

Methods and Design

Pre‐ and post‐therapy CORE‐OM/10 scores were extracted from the clinical records of all secondary care adult psychological therapy team patients who undertook psychological therapy between 2010 and 2013 in one mental health trust. Of the 4,877 patients identified, 925 had complete records. Length of therapy was divided by the number of sessions to create ‘treatment intensity’ (sessions per week). Nonparametric analyses were used, initial score was controlled for, and diagnostic group was explored.


No relationship was found between change in score and the number of sessions, therapy length, or treatment intensity; however, change in score was positively correlated with first‐session score. Patients with higher initial scores had longer therapies; however, treatment intensity was similar for patients with lower pre‐therapy distress. There were differences in treatment length (weeks) between diagnostic groups. Demographic differences were found between patients with and without complete records, prompting caution in terms of generalizability.


These findings are consistent with the responsive regulation model (Barkham et al., 1996) which proposes that patients vary in their response to treatment, resulting in no associations between session numbers or treatment intensity and therapeutic gain with aggregated scores. Patients with higher CORE scores at the outset of psychological therapy had longer not more intensive therapy. There was variation in treatment intensity between diagnostic clusters.

Practitioner points

  • Number of sessions, length of therapy (in weeks), and treatment intensity (the number of sessions per week between the first and last therapy sessions) were not related to therapeutic gains.
  • These results fit with a responsive regulation model of therapy duration, suggesting an individualized approach to therapy cessation as opposed to therapy session limits as the number of sessions a patient experienced was not generally associated with outcome.
  • We found that clients with a diagnosis of a behavioural syndrome (F50‐59) had less ‘intensive’ therapy; they experienced the same number of sessions over a longer time frame. Despite this, there were no associations between diagnosis category and change in score.

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