Clinical characteristic of prodromal symptoms between bipolar I and II disorder among Chinese patients: a retrospective study

Background This study aimed to identify the clinical characteristic of prodromal symptoms in Chinese patients with bipolar disorder (BD), prior to the first affective episode. It further aimed to characterize the prodromal traits between bipolar disorder type I (BD-I) and type II (BD-II). Methods 120 individuals with BD-I (n = 92) and BD- II (n = 28) were recruited to the study. Semi-structured interviews were then administered to evaluate prodromal symptoms in patients, within 3 years of BD onset, by using the Bipolar Prodrome Symptom Scale-Retrospective (BPSS-R). Results In the prodromal phase of the first depressive episode, patients with BD-II experienced more prodromal symptoms (p = 0.0028) compared to BD-I. Additionally, more frequent predictors were reported in patients with BD-II than BD-I including educational and occupational dysfunction (p = 0.0023), social isolation (p < 0.001), difficulty making decisions (p = 0.0012), oppositionality (p = 0.012), and suspiciousness/persecutory ideas (p = 0.017). There were also differences in the duration of the precursors. The duration of "weight loss or decrease in appetite" (p = 0.016) lasted longer in patients with BD-I, while "obsessions and compulsions" (p = 0.023) started earlier in patients with BD-II and occurred during the pre-depressive period. The prevalence and duration of each reported prodrome, preceding a first (hypo) manic episode, showed no difference between patients with BD-I and BD-II. Conclusions Specific affective, general, or psychotic symptoms occurred prior to both affective episodes. The characteristic of prodromal symptoms were key predictors for later episodes of BD including attenuated mania-like symptoms, subthreshold depressed mood, mood swings/lability, and anxiety. In the pre-depressive state, when compared to BD-II, BD-I presented with more prodromal symptoms in nonspecific dimensions, which indicated the substantial burden of BD-II. In conclusion, this study extends the understanding of the characteristics of prodromes of BD-I and BD-II.