Irritability in the Mix: An Exploratory Study of the Role of Irritability in Characterising Mood Disorders

OBJECTIVES: To examine the relationship between irritability and mixed states in bipolar disorder to determine how subjective irritability and mixed symptoms of mania and depression manifest in patients with bipolar disorder over a period of 18 months. METHODS: This exploratory analysis examined longitudinal data from a randomised controlled trial of a psychological intervention for patients with bipolar disorder. Scores of subjective irritability and mood morbidity were analysed from data sampled over ten timepoints over the trial from 82 patients. RESULTS: Significant associations were found between the presence of irritability and mixed symptoms (F(1, 684) = 20.468, p < 0.001). This relationship remained significant throughout the duration of the study and the administration of a psychological treatment which reduced both ratings of mood and irritability. Notably, when mixed symptoms are absent, irritability nevertheless remained for nearly half the time. CONCLUSIONS: Irritability and mixed symptoms are phenomenologically linked. The persistence of this link, regardless of the existence of mixed symptoms, suggests that irritability permeates bipolar disorder and is core to its phenomenology. Future studies should interrogate the tethering of mixed symptoms and irritability in the context of bipolar disorder as this may lead to a deeper understanding of the core characteristics of the illness-both clinically and in terms of its neurobiology.