The "Common Factors, Responsiveness and Outcome of Psychotherapy" (CROP) study is a naturalistic observational study at the University of Copenhagen (UCPH) carried out in cooperation with psychologists in the Danish practice sector or in private practice. The study aims to examine the contribution of client, therapist and treatment characteristics, as well as the role of therapists' responsiveness, on the process and outcome of psychotherapy. Participating psychologists and clients fill out background questionnaires prior to initiating therapy, and process data for each course of treatment is collected weekly and after each session while outcome data is collected at end of treatment and at three months follow-up. The psychologists are reimbursed DKK 1,000 per client that contributes to the study with at least three session questionnaires, which corresponds to the hourly salary of a psychologist in Danish private practice. All data is collected through an automated, online database to ensure appropriate anonymization and data management, and all participants give informed consent prior to participation. The CROP study has been approved by the UCPH's Department of Psychology's ethical review board and the Danish Data Protection Agency.

The aim of the Common factors, Responsiveness and Outcome in Psychotherapy study (CROP) is to determine client and psychologist characteristics and therapeutic processes associated with the outcome of psychotherapy delivered by psychologists in the Danish practice sector or in private practice. The study addresses two main questions. First, how are specific characteristics of clients and psychologists related to the outcome of therapy and do these characteristics moderate the outcome of different psychotherapeutic approaches? Second, to what extent do therapists adapt their approach to client characteristics and preferences and how does such responsiveness impact the process and outcome of therapy? The results from the study are directly relevant to psychologists and will be disseminated nationwide during and after the end of the study.

The study is a naturalistic, observational study carried out in collaboration with psychologists in the Danish practice sector or in private practice. Self-report data is collected on the participating psychologists and their participating clients before psychotherapy, during psychotherapy (weekly and post-session) and after psychotherapy (at end of treatment and three months follow-up). The data is analyzed using multilevel modeling and structural equation modeling approaches.

The study design and data management procedure have been approved by the Research Ethics Board of the Department of Psychology, University of Copenhagen, and the Danish Data Protection Agency. All data are fully anonymized and stored in agreement with the Danish Act on Processing of Personal Data. All parts of the study are based on the principles of informed consent and clients are informed that they can terminate their participation in the study at any time without consequences to their treatment. The findings of the study will be presented in articles in international, peer-reviewed journals as well as to psychotherapy practitioners across Denmark.

Inclusion Criteria:

• Above 18 of age and in individual psychotherapy

Exclusion Criteria:

• severe psychoticism or other severe mental health issues.

Male, female, other

All clients in individual psychotherapy aged 18 or older are eligible for the study, meaning that in principle all client diagnoses and referral reasons may be represented in the sample. However, in Denmark, reimbursement for psychological treatment in the practice sector is only provided for clients referred by their general practitioner for one of the 11 referral reasons and diagnoses presented below. Thus, clients meeting these characteristics are likely to be overrepresented within the sample.

No participant data is planned to be shared with other researchers besides the CROP research team members.