Quality of life in psychiatry: a systematic contribution to construct validation and the development of the integrative assessment tool "modular system for quality of life"

The aim of the present study is to contribute to an ongoing validation proc ess of the Quality of Life (QoL) construct in the clinical field by investi gating its intemal structure. Eight (inter)nationally validated questionnai res have been analyzed by an integrative approach in a multicenter study. D ata has been collected in a mentally healthy (n = 479), a depressed (n = 17 1) and a schizophrenic (n = 139) sample. Apart from conventional psychometr ic criteria a similarity structure analysis (SSA) within a facet analytic m ethodology has been applied. A dimensional structure of the resulting integ rative questionnaire "Modular System for Quality of Life" (MSQoL) could be generated that consists of one "G-factor" (life in general) and six specifi c dimensions (physical health, vitality, psychosocial relationships, materi al resources, affect, leisure time). This basic structure represents a core module measured by 47 items which is sufficiently valid for all three samp les. The empirical structures of healthy depressed and schizophrenic sample s fulfill the first law of attitude and share a common variance of 95%. In addition, there are four specific modules (demography, family partnership, profession). No specific modules could be identified for the psychopatholog ical subgroups. The conclusion can be drawn that QoL is construed very simi lar by all three investigated populations which is the base for searching f or quantitative differences and profiles. The MSQoL integrates the non-redu ndant components of eight QoL-instruments, is psychometrically able to asse ss the basic structure and can be completed within a cumulative research de sign by items specific for a particular setting.