Mood instability in bipolar disorder type I versus type II-continuous daily electronic self-monitoring of illness activity using smartphones

•Patients with BD often remain symptomatic in inter-episodic periods.•A smartphone-based monitoring system was used by patients with BD.•Patients with BD II experienced lower levels of mood compared to BD I.•Patients with BD II experienced less time euthymic compared to BD I.•This emphasizes the need for improving treatment strategies for BD type II.

BackgroundA substantial proportion of patients with bipolar disorder remain symptomatic during inter-episode periods, and mood instability is associated with high risk of relapse and hospitalization. Few studies have investigated long-term daily illness activity and none has compared bipolar type I and II using daily data. The objectives were to investigate differences in daily illness activity between bipolar disorder type I and II.MethodsA smartphone-based system for self-monitoring was developed. A total of 33 patients treated in a mood clinic used the system for daily self-monitoring during a median period of 310 days [IQR 189; 437]. Data presented summarize over 8500 observations.ResultsPatients with bipolar disorder type II (n=20), compared to patients with bipolar disorder type I (n=13), experienced a significant lower mean level of mood on a scale from −3; +3 (−0.54 (95% CI: −0.74; −0.35) versus −0.19 (95% CI: −0.35; −0.02), p=0.02), less time euthymic (51.0% (95% CI: 36.4; 65.7) versus 74.5% (95% CI: 62.4; 86.7), p=0.03) and a higher proportion of time with depressive symptoms (45.1% (95% CI: 30.6; 59.5) versus 18.8% (95% CI: 6.9; 30.7), p=0.01). The proportion of time spent with (hypo)manic symptoms did not differ (2.7% (95% CI: 0.1; 5.5) versus 5.5% (95% CI: 3.1; 7.8), p=0.17).LimitationsPatients received different types, doses and combinations of psychopharmacological treatment.ConclusionEuthymia was obtained for a substantial proportion of time in patients with bipolar disorder type I, but despite on-going treatment only for half of the time for patients with bipolar disorder type II. This emphasizes the need for improving treatment strategies for bipolar disorder type II.