I mainly teach in our advanced psychotherapist program with a psychodynamic orientation. Among other assignments, I'm course manager of "supervised psychotherapy", "complex cases" and "Introduction course". I also teach at our undergraduate psychologist program as well as supervise student in their master thesis work.

My main research interest is process and outcome of psychodynamic psychoterapies. I'm currently involved in two large research projects at the department evaluating online interventions for adolescent depression as well as "medically unexplained symptoms" (see below). You can find links to some of my publications below and a full list of publications on this page. 

A selection from Stockholm University publication database

• The Efficacy of Experiential Dynamic Therapies: A 10-Year Systematic Review and Meta-Analysis Update

  2025. Peter Lilliengren (et al.). Clinical Psychology and Psychotherapy (3)

  Article

  There is a growing interest in clinical interventions targeting emotion regulation difficulties across mental health conditions. Experiential dynamic therapies (EDTs) are transdiagnostic, affect-focused, short-term psychodynamic therapy models that emphasize in-session emotional processing. This review provides a 10-year update on the efficacy of EDTs for mood, anxiety, personality and somatic symptom disorders in adults and children/adolescents. A comprehensive search identified 57 randomized controlled trials (n = 4330) conducted in Western (k = 38; n = 3178) and non-Western countries (k = 19; n = 1152) between 1978 and 2024. Random-effects meta-analyses on primary outcomes indicated large, significant effects for EDTs compared to inactive controls at post-treatment (Hedge's g = −0.96; k = 41) and follow-up (g = −1.11; k = 20). Compared to active controls, effects were small and non-significant post-treatment (g = −0.17; k = 27) but became significant at follow-up (g = −0.40; k = 19), suggesting a potential modest long-term advantage of EDTs. Despite substantial heterogeneity (I2 > 75%), results remained robust in sensitivity analyses. Moderator analyses revealed few significant findings, indicating relative consistency across diagnostic groups, treatment formats and active comparators. Non-Western and lower quality studies reported larger effects compared to inactive, but not active, controls. While cautious interpretation is warranted due to unexplained heterogeneity, findings support EDTs as efficacious transdiagnostic interventions for emotional disorders, with sustained benefits over time. Future research should prioritize large-scale, methodologically rigorous trials that explore mechanisms of change, optimize treatment delivery and identify moderators of long-term outcomes.

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• Internet-Delivered Affect-Focused Psychodynamic Therapy for Adolescent Depression: Treatment Principles and Clinical Application in the ERiCA Project

  2024. Jakob Mechler (et al.). Journal of Infant, Child, and Adolescent Psychotherapy 23 (2), 123-141

  Article

  Internet-delivered, therapist-guided, self-help programs are novel ways to deliver psychotherapeutic interventions adapted from established therapy models. Such programs can be easily accessed online and may offer an important treatment option for patients who struggle with barriers to seeking out and engaging in face-to-face psychotherapy, including depressed adolescents. While there are evidence-based Internet-delivered self-help programs based on cognitive-behavioral therapies (i.e. ICBT) for adolescent depression, a program based on psychodynamic principles (i.e. IPDT) has so far been lacking. In this article we describe the IPDT program developed within the ERiCA project, which has so far been evaluated in two randomized controlled trials (RCTs). We further provide a case example from one of the trials to illustrate the treatment process and therapeutic interaction in detail. Given the novelty of the approach, we will particularly highlight and discuss how a psychodynamic understanding of adolescent development and depressive dynamics as well as affect-focused treatment principles inform the treatment, including the therapist’s role, tasks, and choice of interventions. The potential implications and utility of IPDT for regular clinical practice are elaborated as well as potential research directions for the future.

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• A comprehensive overview of randomized controlled trials of psychodynamic psychotherapies

  2023. Peter Lilliengren. Psychoanalytic Psychotherapy 37 (2), 117-140

  Article

  Randomized Controlled Trials (RCTs) are currently considered ‘gold standard’ for evaluating psychosocial interventions, including psychodynamic psychotherapies (PDTs). The aim of this review is to summarize all available RCTs involving PDTs. A thorough search yielded 298 studies published between 1967 and 2022. The number of studies has increased over time with 123 (41.2%) published in the last 10 years. Most studies have been conducted in western countries, evaluating PDTs of brief duration (<40 sessions) for adults with mood (k = 67, 22.5%), psychosomatic (k = 38, 12.8%), anxiety (k = 35, 11.7%), or personality disorders (k = 29, 9.7%). The studies have utilized comparative (k = 233, 78.2%), additive (k = 33, 11.1%), parametric (k = 30, 10.1%) and dismantling designs (k = 2, 0.7%) and includes a total of 374 comparisons. Categorization of outcomes suggests that PDTs typically outperforms inactive controls, while comparisons with active treatments, inclugding Cognitive-Behavior Therapy (CBT), typically indicate no statistical difference. While the evidence-base for PDTs is growing, there are still major limitations and many research questions yet to be addressed. There is a pressing need for disseminating the existing research for PDTs to policy makers and the general public, as well as integrating findings in psychodynamic training curriculums.

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• Intensive Short-Term Dynamic Psychotherapy for generalized anxiety disorder: A pilot effectiveness and process-outcome study

  2017. Peter Lilliengren (et al.). Clinical Psychology and Psychotherapy 24 (6), 1313-1321

  Article

  The objective of this study was to evaluate the clinical- and cost-effectiveness of Intensive Short-Term Dynamic Psychotherapy (ISTDP) for generalized anxiety disorder (GAD). We further aimed to examine if a key clinical process within the ISTDP framework, termed the level of mobilization of unprocessed complex emotions (MUCE), was related to outcome. The sample consisted of 215 adult patients (60.9% female) with GAD and comorbid conditions treated in a tertiary mental health outpatient setting. The patients were provided an average of 8.3 sessions of ISTDP delivered by 38 therapists. The level of MUCE in treatment was assessed from videotaped sessions by a rater blind to treatment outcome. Year-by-year healthcare costs were derived independently from government databases. Multilevel growth models indicated significant decreases in psychiatric symptoms and interpersonal problems during treatment. These gains were corroborated by reductions in healthcare costs that continued for 4years post-treatment reaching normal population means. Further, we found that the in-treatment level of MUCE was associated with larger treatment effects, underlining the significance of emotional experiencing and processing in the treatment of GAD. We conclude that ISTDP appears to reduce symptoms and costs associated with GAD and that the ISTDP framework may be useful for understanding key therapeutic processes in this challenging clinical population. Controlled studies of ISTDP for GAD are warranted.

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• Intensive Short-Term Dynamic Psychotherapy Trial Therapy Effectiveness and Role of Unlocking the Unconscious

  2017. Allan Abbass (et al.). Journal of Nervous and Mental Disease 205 (6), 453-457

  Article

  This study examined the effects of trial therapy interviews using intensive short-term dynamic psychotherapy with 500 mixed sample, tertiary center patients. Furthermore, we investigated whether the effect of trial therapy was larger for patients who had a major unlocking of the unconscious during the interview compared with those who did not. Outcome measures were the Brief Symptom Inventory (BSI) and the Inventory of Interpersonal Problems (IIP), measured at baseline and at 1-month follow-up. Significant outcome effects were observed for both the BSI and the IIP with small to moderate preeffect/posteffect sizes, Cohen's d = 0.52 and 0.23, respectively. Treatment effects were greater in patientswho had a major unlocking of the unconscious comparedwith thosewho did not. The trial therapy interview appears to be beneficial, and its effects may relate to certain therapeutic processes. Further controlled research is warranted.

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• Patients’ Affective Processes Within Initial Experiential Dynamic Therapy Sessions

  2016. Katie Aafjes-van Doorn (et al.). Psychotherapy

  Article

  Research has indicated that patients’ in-session experience of previously avoided affects may be important for effective psychotherapy. The aim of this study was to investigate patients’ in-session levels of affect experiencing in relation to their corresponding levels of insight, motivation, and inhibitory affects in initial Experiential Dynamic Therapy (EDT) sessions. Four hundred sixty-six 10-min video segments from 31 initial sessions were rated using the Achievement of Therapeutic Objectives Scale. A series of multilevel growth models, controlling for between-therapist variability, were estimated to predict patients’ adaptive affect experiencing (Activating Affects) across session segments. In line with our expectations, higher within-person levels of Insight and Motivation related to higher levels of Activating Affects per segment. Contrary to expectations, however, lower levels of Inhibition were not associated with higher levels of Activating Affects. Further, using a time-lagged model, we did not find that the levels of Insight, Motivation, or Inhibition during one session segment predicted Activating Affects in the next, possibly indicating that 10-min segments may be suboptimal for testing temporal relationships in affective processes. Our results suggest that, to intensify patients’ immediate affect experiencing in initial EDT sessions, therapists should focus on increasing insight into defensive patterns and, in particular, motivation to give them up. Future research should examine the impact of specific inhibitory affects more closely, as well as between-therapist variability in patients’ in-session adaptive affect experiencing.

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• Secure attachment to therapist, alliance, and outcome in psychoanalytic psychotherapy with young adults

  2015. Peter Lilliengren (et al.). Journal of counseling psychology 62 (1), 1-13

  Article

  Using a novel approach to assess attachment to therapist from patient narratives (Patient Attachment to Therapist Rating Scale; PAT-RS), we investigated the relationships between secure attachment to therapist, patient-rated alliance, and outcome in a sample of 70 young adults treated with psychoanalytic psychotherapy. A series of linear mixed-effects models, controlling for length of therapy and therapist effects, indicated that secure attachment to therapist at termination was associated with improvement in symptoms, global functioning and interpersonal problems. After controlling for the alliance, these relationships were maintained in terms of symptoms and global functioning. Further, for the follow-up period, we found a suppression effect indicating that secure attachment to therapist predicted continued improvement in global functioning whereas the alliance predicted deterioration when both variables were modeled together. While limited by the correlational design, this study suggests that the development of a secure attachment to therapist is associated with treatment gains as well as predictive of post-treatment improvement in functioning. Future research should investigate the temporal development of attachment to therapist and its interaction with alliance and outcome more closely. To ensure differentiation from patient-rated alliance, observer-based measurement of attachment to therapist should be considered.

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• Exploring therapeutic action in psychoanalytic psychotherapy: Attachment to therapist and change

  2014. Peter Lilliengren.

  Thesis (Doc)

  The overall aim of this thesis was to explore therapeutic action in psychoanalytic psychotherapy from different perspectives (patient, therapist, observer), using different methodological approaches (qualitative and quantitative). Study I explores patients’ views of therapeutic action with grounded theory methodology. The results indicated that talking openly in a safe therapeutic relationship led to new relational experiences and expanding self-awareness. Hindering factors included difficulties “opening up” and experiencing something missing in treatment. Study II investigates experienced therapists’ views of therapeutic action. The development of a close and trusting relationship was perceived as the core curative factor. Patients’ fear of closeness hindered treatment from the therapists’ perspective. Study III involves the development and psychometric examination of a new rating scale for patient-therapist attachment (Patient Attachment to Therapist Rating Scale; PAT-RS). Inter-rater reliability was good for three of the subscales (Security, Deactivation, Disorganization), but poor for one (Hyperactivation). Patterns of correlations with other measures suggest construct validity for the reliable subscales. Study IV examines the relationships between secure attachment to therapist, alliance, and outcome. Linear mixed-effects models, controlling for therapist effects, treatment length and patient-rated alliance, indicated that secure attachment to therapist relates to outcome. Further, the unique variance associated with secure attachment to therapist predicted continued gains in functioning during follow-up. The results of this thesis suggest that the development of a secure attachment to the therapist is a central mechanism of therapeutic change. The results are discussed in relation to established notions of therapeutic action in psychoanalytic psychotherapy. Two tentative process models that may be useful for clinical practice and future research are proposed. 

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Show all publications by Peter Lilliengren at Stockholm University