The occurrence and clinical significance of thought disorder, as measured by general abstraction ability and idiosyncratic abstractions, remains a complex and ambiguous area of inquiry. We studied 49 subjects in a longitudinal design in which the effects of general psychopathology and depression on abstraction function were assessed. Results indicate that a) depressive patients have a generalized abstraction dysfunction not limited to specific content areas, b) some depressive patients have a residual abstraction deficit on discharge from the hospital, c) idiosyncratic abstractions are a characteristic but not pathognomonic marker for schizophrenia, and d) across all subjects, abstraction difficulties represent a seemingly state-dependent “final common pathway” that significantly correlates with general psychopathological impairment rather than level of depression.