Studies using quantitative methodology:

Compiled and written by Dr Evelyn Gibson _{(this is an original piece of work commissioned by South Wales CAT Training and should not be copied without permission)}

CAT is not recommended for any specific mental health intervention in the NICE guidelines; however, it is mentioned in a case example as a potential approach for working psychotherapeutically with carers of people with dementia (National Institute for Clinical Excellence, 2018). Matrics Cymru evidence tables (National Psychological Therapies Management Committee, 2017) identify CAT as a potential treatment for borderline personality disorder (BPD) but highlights that this is based on a lower quality study than the other therapies that are recommended for BPD. CAT is also mentioned as a possible intervention for depression in later life and personality disorders later in life, but both of these recommendations are based on the lowest quality of evidence base identified by the Matrics (i.e., evidence from case series studies and widely held expert opinion). The Scottish Matrix evidence tables (NHS Education for Scotland, 2014) for adult mental health indicate that there is some evidence for the use of CAT with anorexia nervosa. This is based on the lowest quality of evidence used in the guidelines (i.e., at least two well conducted case control or cohort studies with a low risk of confounding or bias).

A Note on Study Designs

Whilst there is some traditional research that has been published into the effectiveness of CAT (e.g., randomised controlled trails [RCTs], pre- and post-intervention outcomes etc.), many of the more recent studies are single case reports which use single-case experimental designs (SCED).

SCEDs focus on individual clients and their idiosyncratic problems by analysing responsivity to treatment on idiographic measures (Barlow, Nock & Hersen, 2009). SCEDs involve a rich description of a case with a detailed exploration of relationships between an independent variable and behaviour (Cohen, Feinstein, Masuda & Vowles, 2014). This methodology has been described as a key strategy for individualising medicine (Lillie, Patay, Diamant, Issell, Topol & Schork, 2011). In contrast, traditional methods report the average group response to the intervention by administering nomothetic outcome measures (i.e., measures that are psychometrically validated with community and clinical norms) at specified time points. This obscures the responsivity of individual clients and ignores the idiosyncratic problems that clients bring to therapy.

The defining features of SCEDs are:

(1) repeated and very intensive sampling of ideographic measures that always start with a baseline period against which intervention phases are then compared;

(2) manipulation of one or more independent variables whilst controlling for sources of bias;

(3) demonstration of stability within and across levels of imposed independent variables

(Kratochwill et al., 2013).

SCEDs use a combination of both nomothetic and ideographic. CAT is particularly well matched to the single case method, as the therapist names target problems and target problem procedures that underpin the presenting problem (Ryle & Kellett, 2018). These can be easily translated into ideographic outcome measures. Single case methods are a scientifically valid and clinically practicable alternative to compliment mainstream clinical research methods (Morley, 2017). They are a time- effective, cost-effective alternative to other methodologies, offering high internal and external validity (Rizvi & Nock, 2008). These studies generate practice-based evidence, as the primary level of analysis is the individual client; this is congruent with the natural focus of psychotherapy (McMillan & Morley, 2010). Withdrawal SCED designs (Hersen, 1990) include the withdrawal of treatment and the reintroduction of treatment; however, it is questionable whether psychotherapeutic treatments, once delivered, can be removed. Although treatment can be halted, some degree of learning is still likely to have occurred. There are also ethical implications to be considered with the withdrawal of a psychological intervention.

An adaptation of the SCED methodology is the hermeneutic single-case efficacy design (HSCED). HSCEDs are a mixed quantitative and qualitative design which first aim to identify causal links between therapy and outcomes and then consider non-therapy explanations for change (Elliott, 2002). This methodology involves the development of a rich case record in which detailed evidence, not collected as part of a traditional SCED, is utilised (Spence, Kellett, Totterdell & Parry, 2019). A further“adjudicated” form of HSCED has also been developed; this mimics a legal process, involving teams of researchers who argue for or against therapy as the explanation for change (Elliott, 2002).

Anxiety and Depression

Early studies indicated that, following CAT intervention, there are statistically significant improvements in depression, anxiety and interpersonal functioning (e.g., Dunn, Golynkina, Ryle & Watson, 1997).

Brockman, Poynton, Ryle & Watson (1987) conducted a randomised controlled trial (RCT) comparing the outcomes of 16 sessions of CAT or of interpretative therapy (Mann & Goldman, 1982). Both therapies produced improvements in depression and general mental health, with CAT clients also experiencing a significantly improved view of themselves. At follow-up, CAT clients demonstrated further improvements in depression scores; however, their general wellbeing deteriorated between end of therapy and follow-up.

Marriott and Kellett (2009) benchmarked short-term (16 session) and medium-term (24 session) CAT against short and medium-term CBT and person-centred therapy (PCT) in routine clinical practice. The results indicated that all modalities were effective in reducing distress across a number of measures. Recovery rates were significantly higher during short-term CBT, but equivocal across medium-term therapies.

CAT has been shown to be effective in reducing anxiety and depression in specific populations and brief interventions. Hamilton, Saxon, Best, Glover, Walters and Kerr (2021) conducted an RCT pilot study comparing CAT for pregnant women with anxiety and depression against treatment as usual (TAU). The results demonstrated the safety, acceptability and potential efficacy of a 16 session CAT intervention in all stages of pregnancy. The majority (90%) of clients completed therapy (i.e., attended at least 12 sessions). This is a high retention rate for a psychological treatment and is line with the finding of other authors (Calvert & Kellett, 2014; Hallam, Simmonds‐Buckley, Kellett, Greenhill & Jones, 2021). The high acceptability of CAT has been attributed to the high levels of early feedback enabled by the narrative and diagrammatic reformulations (Ryle & Kerr, 2002). The majority of clients provided positive feedback and no adverse events or safety issues were reported. The study was under-powered resulting in a lack of statistically significant results; however, there were positive trends that suggested a clinically important reduction in anxiety.

Williams and Craven-Staines (2017) evaluated the efficacy of CAT in reducing symptoms of depression and anxiety in adults aged 65 years or over. The results indicated that CAT was effective in reducing signs of depression and anxiety. Furthermore, following the intervention, participants had a greater sense of integration of the self and showed improvements in interpersonal relationships. No changes in overall psychological distress were found.

Wakefield, Kellett, White and Hepple (2021) investigated an eight session CAT protocol developed for IAPT services. They used a case-controlled study to evaluate anxiety and depression outcomes for clients who were referred to the high intensity step of an IAPT service. These outcomes were compared to clients who received Cognitive Behavioural Therapy (CBT) in the same service1. The eight session CAT model emphasises early mapping of reciprocal roles and procedures, with the narrative reformulation element being integrated (in reduced form) into the goodbye letter. It has been shown by that this adaption does not impair the outcome of therapy (Kellett, Stockton, Marshall, Hall, Jennings & Delgadillo, 2018). In the initial unmatched sample, all baseline symptom measures significantly differed between CAT and CBT, with clients with more severe symptom presentations being allocated to CAT. In order to create a fair comparison between CAT and CBT cases, a case- control sample was derived (Rosenbaum & Rubin, 1983). Overall, no significant differences were found for depression, anxiety or functional impairment between the two interventions after eight sessions. Sessional change trajectories were similar. Significant differences in dropout rates were found between the therapies, with the CAT dropout rate being 13% less than the dropout rate for CBT. The authors concluded that eight session CAT and CBT yielded highly similar treatment outcomes despite the CAT clients being more clinical complex and suggested that CAT is a time-efficient and effective high intensity therapy for clients with trauma histories and associated complex interpersonal issues.

Power, Kellett and Gaskell (2022) used a SCED to investigate the effectiveness of CAT for anxiety and depression in the context of borderline personality traits. The nomothetic and ideographic outcomes showed a partially effective intervention, with significant improvements being found on ideographic outcomes but not on nomothetic outcomes.

Bipolar Disorder

The evidence of CAT for bipolar affective disorder is limited. Kerr (2001) reported on a case series (n = 4) in which two of the clients had a good qualitative outcome. Evans, Kellett, Heyland, Hall and Majid (2016) conducted a pilot RCT for clients with bipolar disorder who were in remission. They compared 24 session CAT with TAU. Clients in the CAT group reported no adverse events and eight out of nine clients completed treatment. At the end of the CAT intervention, two of the nine clients were categorised as “recovered” suggesting a marked improvement in their level of psychological distress. The Personality State Questionnaire (PSQ; Pollock, Broadbent, Clarke, Dorrian & Ryle, 2001) has been devised to measure deficits in personality integrity and is based on the Multiple Self-States Model (MSSM) of CAT, which conceptualises identity disturbances in personality. The results on the PSQ suggested that CAT clients were reporting less state-switching at follow-up compared to the TAU clients. Qualitative data indicated that the most common helpful event during CAT was recognition of patterns in mood variability.

Kellett, Alhadeff, Gaskell and Simmonds-Buckley (2022) conducted a SCED study of CAT for bipolar affective disorder with a withdrawal experimental design. Overall, the results suggested a partially effective intervention. This conclusion was based on the prevention of the manic relapse in response to workplace bullying during the follow-up phase.

Personality Disorders

Ryle and Beard (1993) published a case study of treating a client with a diagnosis of BPD with CAT. The authors suggested that CAT was associated with improvements in interpersonal functioning, reduced global distress and dissociation. These changes were maintained at follow-up. Ryle and Golynkina’s (2000) study also indicated that clients with a diagnosis of BPD showed an improvement in symptoms following CAT intervention. These results were maintained at six-month follow-up. Wildgoose, Clarke and Waller’s (2001) case series measured dissociation, personality fragmentation, global distress and interpersonal functioning in five clients with a diagnosis of BPD. The results indicated that, at nine-month follow-up, all participants had reduced BPD symptoms and four of the clients were considered to have recovered. Kellett, Bennett, Ryle and Thake (2013) used a mixed- method repeated measures design to evaluate CAT with 17 people with a diagnosis of BPD. In this study, four clients experienced clinically significant and reliable change, three clients showed a reliable improvement and one reliably deteriorated. Analysing outcomes at the group level showed statistically significant reductions in risk, dissociation and psychological distress. Dasoukis et al. (2008) conducted an evaluation of CAT intervention for people with a diagnosis of BPD or personality disorder NOS with predominant borderline traits. At two-month follow-up, there was a statistically significant improvement on the majority of outcome measures compared to baseline scores.

Kellett, Gausden and Gaskell (2021) used an SCED design that involved a treatment withdrawal phase. The withdrawal design was indicated due to a fear of abandonment or rejection sensitivity being a key target problem. Overall, the results suggested a partially effective intervention with idiographic measures indicating that self-to-self measures were more responsive to treatment than the emotions or self-to-other measures. CAT appeared moderately effective in terms of reducing self-hate. The results also suggested that the treatment was highly effective for improving “sense-of-self”. Only one nomothetic measure (severity of general psychiatric symptoms) recorded a reliable and clinically significant change from baseline assessment to the end of follow-up.

Livanos et al. (2008) evaluated the effectiveness of 16 sessions of CAT on anhedonia, depression and anxiety in 57 clients with a diagnosis of BPD or personality disorder not otherwise specified (NOS) with predominant borderline personality traits. At two-month follow-up, there was a statistically significant improvement in depression, anhedonia and anxiety scores. Similarly, Kosti et al. (2008) investigated the impact of CAT on anhedonia in clients with a diagnosis of obsessive-compulsive personality disorder (OCPD) or personality disorder NOS with predominant obsessive-compulsive personality traits. At two-month follow-up, there was a statistically significant improvement in depression, anhedonia and anxiety scores compared to prior to the intervention.

Protogerou et al. (2008) investigated the outcome of CAT in 64 clients with a diagnosis of obsessive- compulsive personality disorder (OCPD) with and without an additional axis-1 diagnosis. At two- month follow-up, there was a statistically significant improvement in the majority of clinical scales compared to prior to the intervention.

Kellett (2007) employed a single-case time series experimental design to evaluate the effectiveness of a CAT intervention with clients with a diagnosis of Histrionic Personality Disorder (HPD). The PSQ results indicated that the intervention was clinically effective in terms of initial integration of thepersonality and a reduction in depression and general mental health symptoms. There was no clinically significant change in interpersonal functioning with the client remaining prone to histrionic responding; however, she reported being more mindful of her need to be noticed; being able to tolerate not being the centre of attention; and, interacting in a more adult and rational manner. Nomothetic measures indicated over 40% reduction in histrionic tendencies during intervention. The author concluded that CAT was partially effective with HPD.

Kellett and Hardy (2013) completed a mixed-method SCED of a client with a diagnosis of Paranoid Personality Disorder (PPD) who received 24 sessions of CAT. Results indicated significant reductions in suspiciousness and anxiety and a significant increase in problem solving ability. The client was also independently interviewed with the Change Interview (Elliott & Rodgers, 2008) providing subjective evidence that the changes achieved were attributed to CAT. Of the six target problems, five were extinguished during treatment, although the majority of these changes were not clinically significant. Progress was maintained over the six-month follow-up period.

Kellett and Lees (2020) evaluated the effectiveness of 24 sessions plus four follow-up sessions of CAT for a client meeting diagnostic criteria for dependent personality disorder (DPD). The results provided partial evidence for the effectiveness of CAT for DPD as there was a significant effect of the intervention on reassurance seeking (i.e., reduced emotional dependency; McClintock & McCarrick, 2017); a reliable improvement in self-confidence; and, clinically significant improvement in interpersonal problems. These improvements were maintained at follow-up. There was no change in emotional reliance; assertion of autonomy; and, symptoms of depression.

Mace, Beeken and Embleton (2006) published the results of a controlled study that compared CAT with Brief Psychodynamic Therapy (BPT). CAT and BPT produced similar statistically significant improvements, although the CAT clients were significantly more distressed at assessment and twice as many clients allocated to CAT were diagnosed with a personality disorder. It should be noted that outcome measures were only administered at assessment and three-month follow-up, thereby reducing the validity of attributing change to the interventions.

Clarke, Thomas and James (2013) reported on an RCT comparing the efficacy of 24 sessions of CAT for clients with a broad range of personality disorders with TAU. The results indicated that CAT can be an effective intervention for the self-management and interpersonal difficulties associated with personality disorders. At post-therapy, 33% of the clients completing CAT no longer met diagnostic criteria for any personality disorder. In the TAU group, all clients continued to meet criteria for at least one personality disorder, with 53% showing evidence of continuing personality deterioration. Reliable change scores in the CAT group indicated that 42% had either improved or recovered. Group analysis indicated that CAT participants showed significant improvements in interpersonal functioning and significant reductions in symptomatic distress, in comparison with TAU participants. CAT did not have an impact on healthcare utilisation post-intervention; however, this was probably because participants with chronic self-harming behaviour were excluded from the study, resulting in a floor effect. Participants in the CAT intervention reported being more satisfied than those receiving TAU.

Psychosis

Taylor et al. (2019) published a case series examining the acceptability and safety of CAT for psychosis. Attendance rates indicated that the majority of people with psychosis could engage in CAT and at least reach the end of the reformulation phase of therapy. No serious adverse events were noted and adverse experiences were minimal. The qualitative interviews supported the acceptability of CAT, with participants perceiving the therapy to be helpful, particularly with regard to reducing social isolation and increasing capacity to talk with friends and family about their experiences of psychosis. There was little evidence of change in psychotic symptoms; however, there were trends of improvement in terms of perceived recovery and personality integration. There was also a deterioration in occupational and social functioning. Overall, the results of this study suggested that CAT was partially effective for psychosis.

Eating Disorders

A pilot RCT by Treasure, Todd, Brolly, Tiller, Nehmed and Denman (1995) compared CAT with educational behavioural treatment for people with adult-onset anorexia. No significant differences in outcomes were observed between treatments at one-year follow-up; both resulted in an average weight gain of 6.8kg with 30% of treatment completers maintaining weight gain, although participants in the CAT condition subjectively reported greater improvement.

Dare, Eisler, Russell, Treasure and Dodge (2001) conducted an RCT which compared focal psychoanalytic psychotherapy (FPP), family therapy (FT), CAT or TAU for clients with eating disorders. The results showed that there were no significant differences in engagement rates between the active therapies and more non-completers in the TAU condition. Results at one year follow-up showed that, across active therapies, one third of clients no longer met diagnostic criteria compared with only 5% of the TAU group. Intention-to-treat analysis indicated that CAT was superior to TAU, but that FPP and FT achieve better outcomes than CAT. However, these results should be interpreted with caution because sample sizes were small and therapist competence may have biased findings because FPP and FT were delivered by trained, experienced clinicians, whereas CAT was delivered by non- accredited therapists supervised by an experienced CAT clinician.

Survivors of Childhood Sexual Abuse (CSA)

Two small scale, practice-based studies of CAT for survivors of CSA have been published. Clarke and Llewelyn (1994) investigated the impact of CAT on female CSA survivors. Following the intervention, five of seven clients demonstrated reliable improvement in global functioning; however, only two scored below the clinical cut-off at end of CAT. Scores also indicated improvements in depression, self-esteem and reduced self-blaming beliefs/self-harming behaviour. These changes were maintained over the three-month follow-up, although there was some indication of deterioration in mood. No change was found in interpersonal constructs. Clarke and Pearson (2000) replicated the study with male survivors of CSA, with all participants demonstrating a reduction in self-blaming beliefs about their early abuse experiences and reduced depression scores. Overall, levels of global distress reduced, but two participants reported increased psychological distress following termination of CAT. It has been suggested that 16 session CAT maybe too brief to effect change for clients with highly complex emotional difficulties (Mace et al., 2006; Wildgoose et al., 2001).

Dissociative Disorders

Graham and Thavasothy (1995) described a very brief (five session) CAT intervention for a client with dissociative psychosis. The client showed a reduction in the frequency and severity of dissociative experiences and this was maintained at two-year follow-up.

Kellett (2005) published a SCED with a client diagnosed with Dissociative Identity Disorder. The results indicated that the client experienced a reduction in the intensity of dissociation and increased awareness of identity shifts. Specific changes in dissociative variables were associated with specific CAT interventions and change was maintained over the follow-up period. Reliable and clinically significant improvements in global functioning, depression and personality integration occurred over the course of treatment.

Morbid Jealousy

It has been suggested that CAT is a potential intervention for obsessional morbid jealousy (OMJ) because this disorder contains strong relational elements (e.g., fear of abandonment; Kingham & Gordon, 2004).

Kellett and Totterdell (2013) used matched SCED designs to compare CAT with CBT for the treatment of OMJ. Five experimental jealousy measures were rated throughout baseline, intervention phase and follow-up phases. Clients’ partners also returned contemporaneous daily ratings of two target difficulties. Reliable and clinically significant pre-post improvements were demonstrated in levels of global functioning, depression and interpersonal difficulties for the CAT client and these were maintained at three-month follow-up. For the CBT client, there was evidence of mood deterioration at follow-up. However, whilst there were significant improvements in jealousy, hyper-vigilance, anxiety and self-esteem following CAT, there was an improving trend in the baseline measures of the CAT client. This suggests that the results may not be attributable purely to CAT. The partner of the CAT client did not report any significant subjective improvements in their behaviour.

Curling, Kellett, Totterdell, Parry, Hardy and Berry (2018) conducted an adjudicated HSCED evaluation of a 16 session CAT intervention for OMJ. Following the intervention, the expert judges determined that evidence for efficacy of CAT was “beyond reasonable doubt”; however, there was no evidence that CAT helped the client to reduce their compulsive observation of their partner or to increase time spent socialising in the follow-up period. The changes experienced during CAT were reported by the client to be unexpected; unlikely without the therapy; and, important in terms of changing jealousy. There was also evidence of reduced state-shifting due to treatment suggesting that a degree of integration in states occurred over the course of therapy.

Kellett and Stockton (2021) investigated the effectiveness of the impact of eight session CAT on OMJ via a mixed-methods single-case methodology. The results indicated that the client was less jealous during treatment compared to baseline and that these gains were maintained over the follow-up period. On the primary nomothetic outcome measure, jealousy reduced from moderate at assessment to mild at follow-up with no evidence of deterioration over the follow-up period. The qualitative outcomes suggested that therapy had been experienced by the client as being helpful and that the changes achieved were attributed to the intervention.

Hypersexuality

Kellett, Simmonds-Buckley and Totterdell (2016) utilised a SCED to evaluate the effectiveness of CAT in hypersexuality disorder. The results suggested that CAT was effective because the recovery criterion was met on the primary nomothetic outcome measure. Significant reductions also occurred on ideographic measures, indicating that change was not solely due to therapist contact. Across the ideographic and nomothetic measures there was little evidence of relapse, with some evidence of continued positive change during follow-up.

Systematic Reviews

Marriott and Kellett (2009) compared active psychological interventions for a range of presenting problems and found that CAT, CBT and person-centred therapy were effective and equivalent.

A 2014 systematic review of CAT outcome studies concluded that, although the evidence base is relatively small, there is growing evidence for the utility of CAT in routine clinical practice across a range of presenting difficulties (Calvert & Kellett, 2014). A consistent finding across studies is the model’s acceptability to clients leading to a low rate of early disengagement from therapy in comparison with other psychotherapies (Ryle et al., 2014).

A recent meta-analysis found that CAT led to improvements in global functioning and interpersonal problems and reductions in depression symptoms in clients with a range of presenting problems (Hallam et al., 2021). The findings showed that clients who undergo CAT experience improvements across a range of clinical difficulties, seeing moderate to large pre-post reductions in global symptoms, interpersonal difficulties and depression and small to moderate beneficial effects compared to comparators. These outcomes were maintained at medium to long-term follow-up. Dropout rates were low (15%) suggesting that CAT is acceptable to clients. It should be noted that this meta-analysis used standardised nomothetic measures to assess general psychological functioning but it did not evaluate how useful CAT is for target problems (i.e., idiographic change).

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