title: Therapist effects and moderators of effectiveness and efficiency in psychological wellbeing practitioners: A multilevel modelling analysis.
abstract: OBJECTIVE
  The study investigated whether psychological wellbeing practitioners (PWPs) working within the UK government's Improving Access to Psychological Therapies (IAPT) initiative are differentially effective (i.e., therapist effect size) and differentially efficient (i.e., rate of clinical change), and the moderating effect of demographic and process factors on outcomes.
  
  
  METHODS
  Routine clinical outcome data (depression, anxiety, and functional impairment) were collected from a single IAPT service. A total of 6111 patients were treated by 56 PWPs. Multilevel modelling (MLM) determined the size of the therapist effect and examined significant moderators of clinical outcomes. PWPs were grouped according to below average, average, and above average patient outcomes and compared on clinical efficiency.
  
  
  RESULTS
  Therapist effects accounted for 6-7% of outcome variance that was moderated by greater initial symptom severity, treatment duration, and non-completion of treatment. Clinically effective PWPs achieved almost double the change per treatment session. As treatment durations increased beyond protocol guidance, outcomes atrophied. Treatment non-completion was particularly detrimental to outcome.
  
  
  CONCLUSIONS
  PWPs appear to be differentially effective and efficient despite ostensibly delivering protocol driven interventions. Implications for services, training, and supervision are outlined.
authors.affiliation: Clinical Psychology Unit, University of Sheffield, Western Bank, Sheffield S10 2TN, UK. Electronic address: nick.firth@gmail.com.
authors.forename: Nick
authors.initials: N
authors.lastname: Firth
authors.affiliation: Clinical Psychology Unit, University of Sheffield, Western Bank, Sheffield S10 2TN, UK; Centre for Psychological Services Research, University of Sheffield, Western Bank, Sheffield S10 2TN, UK.
authors.forename: Michael
authors.initials: M
authors.lastname: Barkham
authors.affiliation: Centre for Psychological Services Research, University of Sheffield, Western Bank, Sheffield S10 2TN, UK; Sheffield Social and Healthcare NHS Foundation Trust, UK.
authors.forename: Stephen
authors.initials: S
authors.lastname: Kellett
authors.affiliation: School of Health and Related Research, University of Sheffield, Regent Court, 30 Regent Street, Sheffield S1 4DA, UK.
authors.forename: Dave
authors.initials: D
authors.lastname: Saxon
mesh_terms: D000293:Adolescent; D000328:Adult; D001007:Anxiety / Q000628:therapy; D015928:Cognitive Behavioral Therapy; D003863:Depression / Q000628:therapy; D005260:Female; D006297:Health Services Accessibility; D006801:Humans; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D055361:Multilevel Analysis; D010043:Outcome and Process Assessment, Health Care / Q000706:statistics & numerical data* / Q000639:trends; D011570:Psychiatry / Q000379:methods* / Q000592:standards / Q000706:statistics & numerical data; D011613:Psychotherapy; D015203:Reproducibility of Results; D016896:Treatment Outcome
keywords: Effectiveness; Efficiency; Improving Access to Psychological Therapies (IAPT); Low intensity; Multilevel modelling; Psychological wellbeing practitioners; Stepped care; Therapist effects