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Empirical Support for
Person-Centred/Experiential
Psychotherapies:
Meta-analysis Update 2008
Robert Elliott & Elizabeth Freire
University of Strathclyde
Supported by a grant from the British Association
for the Person-Centred Approach
Main References:
Elliott, R., & Freire, B. (in press). Person-Centred/Experiential Therapies Are
Highly Effective: Summary of the 2008 Meta-analysis. Person-Centred Quarterly.
Elliott, R., Greenberg, L.S., & Lietaer, G. (2004). Research on Experiential
Psychotherapies. In M.J. Lambert (Ed.), Bergin & Garfield‘s Handbook of
psychotherapy and behavior change (5th ed.) (pp. 493-539), New York: Wiley.
PCE Therapy Meta-Analysis Project
• 1992-93: Greenberg, Lietaer & Elliott invited
to contribute a chapter on humanisticexperiential therapies for Bergin & Garfield’s
Handbook of Psychotherapy & Behavior
Change
• Undertook a meta-analysis of all research on
PCE therapies
• Fortunately…
…We are living in the Golden Age of
PCE Therapy Research
• Available outcome research has tripled in past 15 years
• German-language studies
• New versions of PCE therapy have emerged since the late
1980’s
• Focusing-Oriented, Process-Experiential/Emotion-Focused for
individuals & couples
• Much research on these
• Latest development: Large-scale mental health services
research on Person-Centred Counselling/therapy (e.g., King,
Stiles studies)
Experiential Therapy
Meta-Analysis Project
Authors
Year
N of studies
1. Greenberg, Elliott & Lietaer
1994
37
2. Elliott
1996
63
3. Elliott
2002
86
4. Elliott, Greenberg & Lietaer
2004
112
5. Elliott & Freire
2008
186 (82 new studies;
67 studies since 2000)
Scope of Analysis: Converging
Lines of Evidence
• 1. Pre-post studies
•
•
•
•
“Open clinic trials” & effectiveness studies:
Addresses question of whether clients change over therapy
191 studies; 203 research samples
14,235 clients
• 2. Controlled studies
•
•
•
•
vs. waitlist or nontreatment conditions
Addresses question of therapy causes change
63 research samples; 60 studies, including 31 RCTs
2,144 clients; 1,958 controls
• 3. Comparative studies
•
•
•
•
vs. non-PCE therapies (e.g., CBT, treatment as usual)
Addresses question of whether which therapies are most effective
135 comparisons; 105 research samples; 100 studies; 91 RCTs
6,097 clients
Inclusion Criteria
• Exhaustive search: attempt to find all existing
studies:
• Therapy must be labeled as Client-/Personcentred, (Process-)Experiential, Focusing, or
Gestalt; or described explicitly as empathic and/or
centering on client experience
• 2+ sessions
• 5+ clients
• Adults or adolescents (12+ years)
• Effect size (Cohen’s d) must be calculable
Type of PCE Therapy
(Pre-post effects)
Freque
ncy
Percent
Person-Centred Therapy (PCT)
Nondirective supportive
(NDSup)
Emotion-Focused Therapy
(EFT)
Other experiential (e.g., Gestalt,
Psychodrama)
82
40%
33
17%
34
17%
43
21%
Supportive-expressive
10
5%
Study Characteristics
Length of Therapy
(sessions)
(pre-post effects)
M = 20; Median = 12
Range = 2 - 124
Sample Size (clients)
(pre-post effects)
M = 70; Median = 22
Range = 5 - 2742
Pro-PCE Researcher
Allegiance
87% (pre-post effects)
31% (comparative effects)
Non bona fide
(i.e., placebo)
13% (pre-post effects)
19% (comparative effects)
Effect Size (ES) Calculations:
m m
Change E.S.
 pre post
sd
(pooled
)
•Allows use of largest number of studies
•Used Hedge’s d for pre-post differences
•more conservative, controls for small sample bias
•Averaged across subscales within measures; then
across measures; then across assessment periods
Frequency
Pre- v s post- therapy
Post-PCT
Pre-PCT
SD
Psychological Distress
Mpost
Mpre
EFFECT SIZE
(SD units)
1.0
0.9
LARGE
0.8
0.7
0.6
MEDIUM
0.5
0.4
0.3
SMALL
0.2
0.1
0.0
Overall Pre-Post Effect Sizes (Hedge’s d)
ASSESSMENT POINT
N
Mean
SD
Post
186
.95
.62
Early Follow-up (< 12 months) 78
1.08
.67
Late Follow-up (12+ months)
50
1.14
.66
Unweighted
203
.97
.61
Weighted
14235
1.01
.50
Overall:
Frequency
Post-PCT v s pre-
Pre-therapy
Post-PCT
84%
Psychological wellbeing
Controlled & Comparative
Study Analyses
• Calculate difference in pre-post ES between:
• PCE therapy, and
• No-treatment control or non-PCE treatment
• Coded effects:
• +: experiential better outcome
• -: experiential poorer outcome
• Allows "equivalence analysis" to support no
difference findings
Are PCE Therapies More
Effective than no therapy?
• Also: Do PCE therapies cause clients to
change?
• Better: Do clients use PCE therapies to
cause themselves to change?
Controlled Effect Sizes
(vs. waitlist or untreated clients)
N
Mean
SD
Untreated clients
pre-post ES
54
.19
.32
Controlled:
Unweighted
63
.81
.62
2144
.78
.44
Weighted by N
Are Other Therapies more
Effective than PCE Therapies?
• Government wants to know which
therapies are most effective
• Note: Most people in our culture
assume that CBT is more effective than
other therapies, include PCE therapies.
• Is this true or is it a myth?
Comparative Effect Sizes
(vs. non-PCE therapies)
Unweighted
Weighted by N
N
Mean
SD
135
-.02
.53
10378
-.00
.26
Equivalence Analysis: Proving the
Null (no-difference) Hypothesis
• From biomedical research (Rogers, Vessey &
Howard, 1993):
• 1. Set minimum clinically-relevant difference:
E.S. = +/-.4 sd (Elliott, Stiles & Shapiro, 1993)
• ~4% of variance
• Between .5 sd[=“medium”] & .2 sd[=“small”])
• 2. For comparative studies, find:
• mD (m difference in ESs)
• sdD (sd of differences in ES)
Equivalence Analysis - 2
• 3. Calculate 1-group t-test for absolute value of
mean difference E.S. (|mD|) using .4 sd as test
value [=t(.4)]
• 4. If p < .05, conclude treatments clinically
equivalent
• 5. If significantly also different from 0 [=t(0)],
conclude difference is present but clinically
trivial
Equivalence Analyses
Comparison
PCE vs.
non-PCE
N
mD
sdES
t(0)
t(±.4)
Result
135
-0.02
0.53
-0.34
8.38***
Equivalent
Equivalence Analyses
Comparison
N
mD
sdES
t(0)
t(±.4)
Result
PCE vs.
non-PCE
135
-0.02
0.53
-0.34
8.38***
Equivalent
PCE vs.
non-CBT
59
0.2
0.54
2.79**
2.89**
Trivially
better
Equivalence Analyses
Comparison
N
mD
sdES
t(0)
t(±.4)
Result
PCE vs.
non-PCE
135
-0.02
0.53
-0.34
8.38***
Equivalent
PCE vs.
non-CBT
59
0.2
0.54
2.79**
2.89**
Trivially
better
PCE vs. CBT
76
-0.18
0.47
3.37**
4.09**
Trivially
Worse
Equivalence Analyses
Comparison
N
mD
sdES
t(0)
t(±.4)
Result
PCE vs.
non-PCE
135
-0.02
0.53
-0.34
8.38***
Equivalent
PCE vs.
non-CBT
59
0.2
0.54
2.79**
2.89**
Trivially
better
PCE vs. CBT
76
-0.18
0.47
3.37**
4.09**
Trivially
Worse
NDSup vs.
CBT
37
-0.36
0.45
4.77**
0.60
Worse
PCT vs. CBT
22
-0.09
0.29
-1.49
4.99***
Equivalent
EFT vs. CBT
6
0.60
0.49
3.02*
1.00
Better
10
-0.14
0.30
-1.53
2.76*
Equivalent
Other Exp.
vs. CBT
What is “Nondirective/
Supportive” Therapy?
• Nondirective/supportive:
• 87% studies carried out by CBT Researchers
(negative researcher allegiance; 40/46)
• 65% explicitly labelled as “controls” (30/46)
• 52% involve non bona fide therapies (24/46)
• 76% of researchers are North American (35/46)
• 61% involve depressed or anxious clients (28/46)
Researcher Allegiance (RA)
• Tendency to find results that support your
approach or orientation
• Consistent finding:
• E.g., Luborsky et al., (1999) RA predicts results at
r = .86
• Applies to drug research also
• Many possible explanations, e.g.:
• Using non bona fide versions of therapies
• Suppressing negative results
• Researcher/ therapist enthusiasm
What Predicts PCE therapy
Effects?
Negative
Researcher
Allegiance
Bona fide-ness
Labelled as
control
RCT vs. not
Pre-Post ES Cont. ES
(n = 203)
(63)
-.08
-.29*
Comp. ES
(134)
-.49**
.13+
.25*
.17*
--
--
-.31**
--
-.15
-.08
More Predictor Analyses
Pre-Post ES
(n = 203)
-.22**
Cont. ES
(63)
-.05
Comp. ES
(135)
-.31**
Therapy length
-.03
-.08
.06
Sample size
.02
-.03
.01
Year
.10
.14
-.02
Client age
-.02
.05
-.02
T experience
Controlling for Researcher
Allegiance (RA) Effects
• Strong, statistically-significant RA effect in
comparative treatment studies (“horse
races”)
• => Ran analyses controlling for RA
• Regression analysis: Used RA to predict
Comparative ES, calculated residual scores
• Ran analyses again, using residuals (what RA
didn’t predict)
Allegiance-Controlled
Equivalence Analyses (tent.)
Comparison
N
mD
sdES
t(0)
t(±.4)
Result
PCE vs. CBT
78
-0.06
0.41
-1.38
7.28***
Equivalent
NDSup vs.
CBT
38
-0.07
0.45
-1.00
4.52***
Equivalent
EFT vs. CBT
7
-0.14
-0.52
0.73
-1.30
Equivocal
What about “Gold Standard”
studies (RCT’s)
• Selected randomized studies only from
comparative outcome data set:
• N=110
What about “Gold Standard” studies
(RCT’s)?
= Essentially the Same Results (tent.)
Comparison
N
mD
sdES
t(0)
t(±.4)
Result
PCE vs.
non-PCE
110
-0.01
0.52
-0.28
7.75***
Equivalent
PCE vs.
non-CBT
47
0.19
0.56
2.28*
-2.62**
Trivially
better
PCE vs. CBT
63
-0.16
0.46
-2.95**
4.28***
Trivially
Worse
NDSup vs.
CBT
33
-0.29
0.42
3.98***
1.45
Worse
CCT vs. CBT
18
-0.09
0.32
-1.19
4.12**
Equivalent
EFT vs. CBT
4
0.55
0.62
1.77
0.48
Equivocal?
Other Exp.
vs. CBT
7
-0.07
0.22
-0.83
4.07**
Equivalent
Main Conclusion:
Previous versions of metaanalysis replicated with an
independent sample of new,
recent studies:
Person-centred/ experiential
therapies appear to be effective.
Summary of General Results:
Pre-Post & Controlled Effects
• First line of evidence: PCE associated with
large pre-post client change
• Posttherapy gains also maintained over early &
late follow-ups
• Second line of evidence: Clients in PCE
show large gains relative to untreated
groups
• = Causal inference ticket: Therapy causes
client change
Summary of General Results:
Comparative Effects
Third line of evidence:
• 1. PCE therapies in general are statistically equivalent
when compared to non-PCE treatments in general
• 2. PCE therapies in general are slightly but trivially less
effective than CBT (ES: -.18sd)
• May be due to researcher allegiance
• 3. This small effect appears to be predominantly due to the
use of so-called “Nondirective/Supportive” therapies,
which have substantially worse outcomes (ES: -.35sd)
• But this may be due to researcher allegiance
Summary of General Results:
More Comparative Effects
• 4. For the first time in these analyses, pure PCT appears to
be statistically equivalent in effectiveness to CBT (ES: .09sd)
• Even without controlling for researcher allegiance
• 5. Also, new in this analysis: Process-Experiential/
Emotion-Focused Therapy for individuals or couples
appears to be more effective when compared to CBT (ES:
.35)
• But this may be due to researcher allegiance (sample too small)
Other Converging Lines of
Evidence
• These three lines of supportive
evidence complement lines of two
additional evidence:
• Relation of empathy to outcome (Bohart et
al., 2002)
• Client treatment preference data indicating
a substantial number of clients prefer a
PCE approach to therapy
Policy Implications
• In general, Person-Centred/Experiential
therapies are empirically supported by
multiple lines of scientific evidence
• Including “gold standard” RCTs and
RCT-equivalents (e.g., Stiles et al.,
2006, 2007)
• NICE/SIGN/Matrix Guidelines need to
be updated
Policy Implications, cont.
• Taken together, the body of evidence
clearly indicates that PCE therapies
should offered to clients in primary
care, NHS, and other mental health
settings.
• Relying on multiple lines of evidence,
such as provided in the present study,
provides a sound basis for establishing
public mental health policy.
• Beth Freire: [email protected]
• Robert Elliott: [email protected]