Preceding diagnoses to young adult bipolar disorder and schizophrenia in a nationwide study.

Background: The aim of this comparative study was to investigate the type and frequency of diagnoses preceding adult bipolar disorder (BD) and schizophrenia (SZ).

Methods: A follow-back study of all preceding diagnoses in all patients aged 21-34 years with a primary, first time diagnosis of BD (N = 784) or SZ (N = 1667) in 2008 to 2010. Data were taken from the Danish Psychiatric Central Research Register (DPCRR) including ICD-10 and ICD-8 diagnoses.