Quality of Life (QoL) is a multidimensional construct that encompasses the functioning and subjective well-being in various important areas of life (including health). The World Health Organisation (WHO) emphasises that health is "a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity" [1]. It is assumed that a person's QoL is influenced by the individual (health) situation and medical treatment. With the subjective reflection of health, the assessment of QoL has become one of the central patient-reported outcome (PRO) measures [2]. Due to the many advances in medicine from which people with a severe psychotic disorder also benefit through the further development of e.g. antipsychotic medication, long-term thinking in care is becoming increasingly important. Thus, outcome parameters are shifting and QoL is becoming more and more important as a relevant PRO to address satisfaction and well-being in a broader way than just being measurable by the presence or absence of (positive) symptoms [3,4,5].

As such, QoL has become an important issue in the care of people with (severe) mental disorders. Major reasons, beside the acceptance as an important criterion for treatment success, include the increasing community-based and patient-centered care, the importance of subjective well-being [6]. Although there is no universal definition of QoL, it is generally accepted that it contains both objective (e.g., mental and physical health) and subjective (e.g., feeling of well-being and satisfaction) dimensions [7]. Work on personal recovery (PR) also points to a subjective process in the course of (mental) diseases and incorporates various concepts such as connectedness, hope, identity, meaning in life, and empowerment (CHIME framework) [8, 9].Severe mental illness (SMI) is defined as the presence of a mental disorder, which cause severe episodic and/or chronic mental symptoms and thereby, severe impairment of social, personal, family and occupational functioning [7, 10]. This group of SMI thus also includes psychosis diagnoses, even in the early stages of the illness[11].

Patients with psychotic disorders, especially those diagnosed with schizophrenia exhibit an objectively severely reduced QoL at all stages of the disease. Compared to healthy controls, systematic reviews and meta-analyses have shown that patients in the early and late prodromal stages have a significant poorer QoL in all domains. This also applies to the early phase of the disease (early course) and in the long-term phase [12, 13]. The reduced QoL is expressed throughe.g. poor mental and physical health, problems in social relationships, and environmental domains such as living circumstances or finances [13]. Earlier results indicate the critical role of depression in determining QoL among early psychosis patients by demonstrating that greater baseline depressive symptom severity prospectively predicted poor QoL [14]. In addition, patients with psychotic disorders, who experience psychotraumatisation at an earlier age are known to report a poorer QoL compared with patients without a traumatic experience [15].

Evidence-based care including evident care models (e.g. Assertive Community Treatment (ACT)) and evident treatment components (e.g., pharmacotherapy, cognitive-behavioral therapy, social and somatic interventions) often led to an improvement in QoL [11, 16,17,18]. In view of the large number of risk factors for a poor course of the disease on the one hand and for discontinuous treatment on the other, special care models were developed for the early detection (Early Psychosis Services [16]), acute (Crisis Resolution Team [19]), as well as continuous (ACT) [20] treatment of patients with psychosis and specifically for those with SMI. However, studies on ACT as the only long-term care model for severe psychotic diseases show that patients treated with ACT often stabilize better than in standard care. In most cases they do not completely remit and still frequently interrupt or discontinue drug treatment as well as overall treatment [21].

Based on this overall situation, the improvement of patients' QoL is of particular importance. The QoL comprises a subjective measure of satisfaction with the individual circumstances of life and is, from a clinical point of view, an essential measure of the quality and success of treatment of patients and their relatives. Previous studies have often only targeted the defined cohort of first-time psychosis patients [22]. Results from long-term data in people with severe psychotic disorders are still scarce; whereby this would make a critical contribution for structuring, implementing and operating effective and efficient integrated care models and for promoting satisfaction with care, service engagement and adherence.

This study aims (I) to systematically assess the long-term course of self-reported QoL over a period of 5 years in a large sample of patients with severe psychotic disorders, fulfilling established criteria for SMI, (II) to compare data to a healthy norm and (III) to identify relevant variables influencing the course of QoL during the treatment period. A special focus will be placed on the early course of treatment, 6 weeks (42 days) after admission to the integrated care model, since we know that the lengths of stay (LoS) in psychiatric inpatient units varied from 17.9 days to 55.1 days in the European Union [23] and recruitment took place primarily through screening of inpatient admissions.

The ACCESS integrated care model for people with non-affective and affective severe psychotic disorders incorporates therapeutic assertive community treatment (TACT) within a multi-sectoral and interdisciplinary care network of inpatient and outpatient services from the adult and child and youth psychiatry of the University Medical Center Hamburg [11, 18, 24]. The effectiveness and efficiency of the ACCESS model was assessed within three studies: the ACCESS I study assessed the implementation of the model [25]; the ongoing ACCESS II study assesses all patients entering the model (approval by health insurances in Germany [18, 24]; the ACCESS III study evaluated the effectiveness of the expansion of the model to adolescents (from the age of 12 years) and young adult patients in the early stage of the illness [11]. In this evaluation, data from ACCESS II were used.