Clinical staging in bipolar disorder: focus on cognition and functioning

OBJECTIVE Clinical staging has increasingly been considered suitable for psychiatric disorders such as bipolar disorder. A staging model of bipolar disorder could help clinicians understand the mechanisms underlying the course of the illness and guide prognosis and therapy. This study aimed to investigate differences in functional status and cognitive functioning in patients in different clinical stages of bipolar disorder. METHOD Subjects who met DSM-IV criteria for bipolar disorder (n = 54) were recruited from the Bipolar Disorders Program at Hospital de Clinicas de Porto Alegre (Brazil) from October 2012 to October 2013. All patients had been in remission (score < 7 on the 17-item HDRS and the YMRS) for at least 1 month before assessment. They were classified into 4 clinical stages according to the model described by Kapczinski et al and compared to 43 healthy controls. Functional status was assessed by using the Functioning Assessment Short Test (FAST). Neuropsychological measures were performed to investigate cognitive functioning. RESULTS Significant differences in functional status were found between patients in all stages compared to controls (F = 33.014, P < .001), except for stage I (P = .104). Additionally, a very strong linear association was found between FAST scores and clinical stages, with FAST scores increasing from stage I to IV (F = 149.55, P < .001). In the bipolar group, stage I was associated with better occupational functioning than stage II (F = 48.344, P = .003). Stage IV patients experienced greater impairment in autonomy than stage III patients (F = 26.646, P = .004), and stage III patients experienced poorer autonomy than those in stage II (P = .004). With regard to cognitive measures, patients in late stages (stages III and IV) were more impaired than healthy controls (P < .001). A similar performance was found between patients in early stages (stages I and II) and healthy controls. DISCUSSION This study showed progressive functional changes from stage I to stage IV of bipolar disorder, with a greater impairment in patients in later stages of the illness. FAST scores seem to have a good discriminant ability to distinguish between patients in early versus late stages of bipolar disorder and could therefore contribute to the development of a bipolar disorder staging system.