Investigating the dose-response effect in open-ended psychotherapy

Area of Science:

• Psychology
• Psychotherapy Research
• Clinical Psychology

Background:

• Previous psychotherapy research suggests most improvement occurs early in treatment, with diminishing returns over time.
• This pattern was primarily observed in short-term treatments, leaving its applicability to long-term, flexible psychotherapy unclear.
• The optimal 'dosage' of psychotherapy for severe psychopathology remains an area of investigation.

Purpose of the Study:

• To investigate the relationship between psychotherapy duration and treatment outcomes in a real-world, routine-care setting.
• To examine whether the pattern of improvement observed in short-term psychotherapy applies to longer, flexible treatment durations.
• To assess the impact of psychopathology severity on treatment length and overall benefit.

Main Methods:

• Analysis of data from 362 patients receiving open-ended psychotherapy under routine-care conditions.
• Average treatment duration was 52 sessions (SD=59, range=1-364).
• Correlation between treatment duration, severity of psychopathology at intake, and degree of improvement.

Main Results:

• Degree of improvement was linearly associated with time spent in psychotherapy.
• Treatment outcomes were contingent upon the initial severity of psychological problems.
• Less severe cases showed faster change but smaller overall benefits; more severe cases received longer treatments with slower change but greater overall benefits.

Conclusions:

• The linear association between psychotherapy duration and improvement suggests that treatment duration is a critical factor, particularly for severe psychopathology.
• Previous models of psychotherapy dosage may not adequately capture the needs of patients with moderate to severe psychological distress.
• Flexible, long-term psychotherapy can yield substantial benefits, challenging the notion of diminishing returns in all treatment contexts.