• The ReAttach studies presented in this thesis contribute to the practice-based evidence of ReAttach, a transdiagnostic intervention for patients with mental health problems. The next paragraphs summarize the ReAttach studies' findings and describe the steps taken from the continuous practice-based research until today. Especially nowadays, in the context of the COVID-19 pandemic an accessible, mild, and rapid intervention such as ReAttach might help overcome psychological crises. The results suggest that ReAttach may be successful in improving stress-resilience and thereby valuable in creating favorable learning conditions for subsequent therapy.
• Chapter 1 concerned a general introduction in which we positioned ReAttach within transdiagnostic psychiatry. Using literature research, we described the active ingredients that ReAttach shares with other proven effective interventions and how ReAttach distinguishes itself from these therapies. We then introduced the central research question of this thesis.
• In chapters 2 and 3, we investigated the effect of five ReAttach sessions on dysfunctional beliefs and coping strategies of adults and children with (sub)clinical psychological problems.
  In chapter 2, we measured dysfunctional beliefs in terms of adults' early maladaptive schemas with the Young Schema Questionnaire (YSQ3), before and after five ReAttach sessions. We found a significant reduction in total YSQ scores in adults with a variety of psychological complaints, suggesting that ReAttach may change cognitive biases quickly. This reduction was found in all schema domains in adults with a wide range of mental health problems indicating that ReAttach might be a new form of schema therapy that needs further investigation.
• In chapter 3, we measured the dysfunctional behavior of children with the Child Behavior Checklist (CBCL) in terms of internalizing and externalizing symptomatology of mental health problems in children. Compared to these children's baseline assessments, we found a significant reduction of all (sub)clinical scores on the CBCL after five ReAttach family sessions. The transferability of the intervention to ReAttach child-therapists met our expectations. The data suggest that children with internalizing and externalizing behavioral problems thus with a wide variety in (sub)clinical symptomatology, may benefit from the ReAttach (family)intervention. It remained unclear if these positive behavioral changes measured with the CBCL were actual changes in the behavior of the children or, instead, differences in the cognitive biases of the parents who filled in the CBCL forms. The impact of ReAttach on the parent-child relationship, for specific clinical groups, should be studied in more advanced design in controlled settings, including follow-up studies.
• Chapter 4 describes the further exploration of ReAttach in reducing problems in the daily life functioning of children and adults with Autism Spectrum Disorders (ASD). We used the Autism Treatment Evaluation Checklist (ATEC) to compare mean problem scores before and after five ReAttach sessions. We found a significant reduction of problems in daily life functioning in all subtests of the ATEC: Communication, Sociability, Sensory and Cognitive Awareness, and Health and Behavior. These findings suggest a good transferability of ReAttach for this group of therapists and patients. But even more important: we found a symptom reduction across all ATEC domains, which supports the premise of ReAttach optimizing (pervasive) developmental conditions in individuals with ASD. Besides, we have learned from this study that patients with ASD can participate in ReAttach if only the therapist offers sufficient reassurance and predictability.
• A growing interest in sensory modulation and affect regulation was the inspiration to develop W.A.R.A.: Wiring Affect with ReAttach. As described in chapter 5, we assessed the effect of Wiring Affect with ReAttach (W.A.R.A.) on negative affect. W.A.R.A. is a stand-alone exercise used by ReAttach therapists to help patients with chronic pain or emotional dysregulation to process negative affect. At first, we evaluated if W.A.R.A. effectively reduced negative affect, and secondly, we compared the effect of W.A.R.A on negative affect with distraction. W.A.R.A. showed a significantly larger reduction of negative affect compared to distraction. Why W.A.R.A is more efficient than a distraction in reducing negative affect remains unclear. A possible explanation of the difference in effectivity may lie in the patient's physical contact. During W.A.R.A., there is physical contact by tapping on the hands of the patient. Without focusing on trauma, rescripting (imagery rescripting), or neutralizing (EMDR) traumatic memories, W.A.R.A. uses associative memory formation to wire the negative effect to a group of positive concepts. All in all, W.A.R.A. is a very gentle intervention, without exposure, and therefore more accessible than either imaginary rescripting or EMDR. Also, W.A.R.A. can easily be applied to patients who have no idea what causes their negative feelings. W.A.R.A. may be an effective, accessible, and ultrafast transdiagnostic intervention reducing negative affect.
• Chapter 6 describes a pilot study conducted in the context of the current COVID-19 outbreak. Due to the COVID-19 epidemic, there was an increasing demand for online psychological support without violating social restrictions. We provided free W.A.R.A. online training for professionals and explored the transferability of W.A.R.A. remote therapy. This study aimed to compare

W.A.R.A. remote therapy with W.A.R.A.-face-to-face provided by a therapist. We found that the W.A.R.A. remote therapy provoked a significant reduction of negative affect. However, it was less effective than face- W.A.R.A. face-to-face. The findings suggest that the online transfer of W.A.R.A. seems to lead to an inevitable loss of efficacy. W.A.R.A. remote therapy might be beneficial as a first-aid psychological intervention and self-regulation technique. However, W.A.R.A. cannot solve more severe psychopathology. The accessibility, rapid transferability, the mildness of the intervention, and efficiency of W.A.R.A. remote therapy in decreasing negative affect are promising. Patients can learn remote W.A.R.A. as a self-regulation tool, which will enhance patients' autonomy and self-control in times of psychological distress.