Both diseases were diagnosed using a non-hierarchical diagnostic structure. Thus, an individual could have both schizophrenia and bipolar disorder, conditioned on that the person has been diagnosed at least twice in each disease. To avoid possible misclassification between schizophrenia and bipolar disorder, admissions with the diagnoses of schizoaffective disorder (ICD codes 295.7, 295H, F25.X) were not considered; 3,563 individuals were excluded because of this.
