Objective – The paper discusses conceptual, methodological and clinical issues of comorbidity from the perspective of more recent epidemiological studies. Further the potential causal and pathogenic role of temporally primary disorders for the onset of secondary disorders is evaluated. Results – The available data suggest so far that comorbidity (a) is not an artefact of assessment strategies, sampling or design features, (b) is specific in different disorders, (c) is particularly frequent in anxiety and affective disorders, (d) affects systematically the course of the comorbid conditions and (0 might be related to symptom progression models. Conclusions – Furthermore, evidence is presented that specific forms of primary anxiety disorders affect the risk for secondary depressive disorders, increase the likelihood of non-remission as well as the number of subsequent depressive episodes.
