Mentalization based treatment for borderline personality disorder: a pragmatic trial but with statistical uncertainty


While personality disorders, particularly borderline personality disorder (BPD), have traditionally been viewed as untreatable, recent longitudinal studies have suggested that symptom resolution may not be uncommon, although a persistent disruption of interpersonal relationships and quality of life has been noted (Zanarini, 2012).

Reflecting the new found optimism for treatment, a range of psychological therapies have been developed to target the symptoms of BPD, primarily the emotional instability and acts of self-harm. A recent Cochrane review however found that while there was no shortage of therapeutic modalities there was a lack of high quality research, and repeat studies of treatment effect are rare (Stoffers, 2012).

One such therapy is Mentalization Based Therapy (MBT); a psychodynamically informed therapy that conceptualises BPD as emerging from disordered attachment experiences, leading to activation of maladaptive means of coping. Therapy is provided through individual and group meetings and initial studies have suggested it to be efficacious (Bateman, 2001 and 2009).

In a recently published study, Bales and colleagues sought to assess the efficacy of MBT in comparison to other psychological therapies (OPT) commonly provided for BPD in the Netherlands (Bales, 2014).

Mentalization, or reflective capacity, refers to the ability to recognise emotions and motivations in ourself and others

Mentalization, or reflective capacity, refers to the ability to recognise emotions and motivations in ourself and others.


The authors used a matched control study methodology (Rose, 2009) to address their research question of mentalization based treatment for borderline personality disorder:

  • The cohort in question was derived from referrals to a day hospital unit providing MBT based interventions
  • Control cases were found from a study assessing the cost effectiveness of psychological therapies in the treatment of BPD
  • MBT clients and controls were matched according to baseline characteristics using a technique known as Propensity score matching
  • MBT was delivered for 18 months with a further 18 months of supportive follow up
  • OPTs were of varying lengths and in both inpatient and outpatient settings, all were approved for the treatment of BPD in the Netherlands
  • Psychiatric symptom severity and level of personality functioning were assessed at baseline, 18 and 36 months for both cases and controls
Matched case-control study designs are commonly used in public health research

Matched case-control study designs are commonly used in public health research


  • A total of 29 participants were recruited to the MBT arm of the trial
  • MBT participants were more likely to have received inpatient treatment, or to be not in paid work or full time study than for OPT
  • These differences appeared to be successfully controlled for through the control matching methodology
  • Psychiatric symptom severity decreased for both MBT and OPT
    • MBT effect size -1.06 at 18 months and -1.42 at 36 months
    • OPT effect size -0.35 at 18 months and -0.57 at 36 months
  • Statistical significance was implied in the paper, but I could not see a formal test of this
  • Level of personality functioning improved by a similar effect size for each of the domains measured e.g.
    • Identity integration
      • MBT effect size 1.23 at 18 months and 1.30 at 36 months
      • OPT effect size 0.35 at 18 months and 0.38 at 36 months
  • MBT was found to outperform the OPT cohort for each measure, with the exception of relational functioning at 36 months where no difference could be demonstrated between cohorts
MBT outperforms the control group, but this can not be taken as being indicative of superiority

MBT outperformed the control group, but this cannot be taken as being indicative of superiority.


The authors concluded:

The present matched control study, executed by an independent research institute outside the UK, demonstrated the effectiveness of day hospital MBT in a highly inclusive and severe group of BPD patients, beyond the benchmark provided by a mix of specialized psychotherapy programmes. Interpretation of the (large) between condition effects warrants cautionary caveats given the non- randomized design, as well as variation in treatment dosages.


This study can be commended for its pragmatic approach to the research question. The use of a case matched control methodology provides an interesting way of addressing perennial problems with differences between day-to-day clinical practice and the beauty of academic clinical practice. However, as the authors acknowledge, the methodology cannot eliminate unmeasured differences between cohorts and is therefore not as robust as a randomised control trial for example.

Differences were apparent between cohorts; for example in the length of therapy received and also the likely integrity of the therapy methods used in the OPT cohort, where no quality control measures were utilised to ensure faithful replication of therapeutic methods.

The biggest difficulty with the study however is the very small sample size. Only 29 participants were included in each arm of the trial. Thus while the authors claim that the effect size for MBT was large the variation in outcome between participants also appears to have been large. The authors primarily make use of an effect size measure (mean difference divided by sample variation) to present their findings. However I could see no statistical measure being taken to ensure that the estimated change in symptom severity and personality functioning was statistically significant. Such a calculation is used to compare between groups but not between baseline and follow up. As a result I found the results difficult to interpret.


Personality disorder represents a complex, not uncommon and controversial diagnostic grouping (Charland 2006). As the recent Cochrane review demonstrated, a range of psychological approaches have been developed, but studies in this field are plagued by wide ranging outcome measures and lack of replication of findings. It is heartening to see work such as that described here, and the use of pragmatic approaches to clinical research, however a greater body of strong, client informed, research is, as always, required.

We badly need research to support evidence-based treatment choices for personality disorders

We badly need research to support evidence-based treatment choices for personality disorders


Bales DL, Timman R, Andrea H, Busschbach JJV, Verheul R, Kamphuis JH (2014). Effectiveness of Day Hospital Mentalization-Based Treatment for Patients with Severe Borderline Personality Disorder: A Matched Control Study. Clinical Psychology & Psychotherapy, n/a–n/a. doi:10.1002/cpp.1914 [Abstract]

Zanarini MC, Frankenburg FR, Reich DB, Fitzmaurice G. (2012). Attainment and stability of sustained symptomatic remission and recovery among patients with borderline personality disorder and axis II comparison subjects: a 16-year prospective follow-up study (PDF). American Journal of Psychiatry 169(5), 476–483.

Stoffers JM, Völlm BA, Rücker G, Timmer A, Huband N, Lieb K. Psychological therapies for people with borderline personality disorder. Cochrane Database of Systematic Reviews 2012, Issue 8. Art. No.: CD005652. DOI: 10.1002/14651858.CD005652.pub2.

Tomlin A. New Cochrane review points to best psychotherapies for borderline personality disorder. The Mental Elf, 31 Aug 2012.

Bateman A, Fonagy P. (2001). Treatment of borderline personality disorder with psychoanalytically oriented partial hospitalization: an 18-month follow-up. American Journal of Psychiatry, 158(1), 36–42. [PubMed abstract]

Bateman A, Fonagy P. (2009). Randomized controlled trial of outpatient mentalization-based treatment versus structured clinical management for borderline personality disorder (PDF). The American Journal of Psychiatry, 166(12), 1355–1364. doi:10.1176/appi.ajp.2009.09040539

Rose S, van der Laan MJ. Why Match? Investigating Matched Case-Control Study Designs with Causal Effect Estimation. Int J Biostat. Jan 1, 2009; 5(1): Article 1. Published online Jan 6, 2009. doi:  10.2202/1557-4679.1127

Charland LC. (2006). Moral nature of the DSM-IV Cluster B personality disorders (PDF). Journal of Personality Disorders, 20(2), 116–25 doi:10.1521/pedi.2006.20.2.116

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