Affective modulation of emotional reactivity in euthymic patients with bipolar disorder

Affective modulation of startle reflex (AMSR) is a widely used experimental tool for assessing emotional reactivity. Previous research has shown inconsistent findings of emotional reactivity in amplitude in bipolar patients (BP). This study examined emotional reactivity (ER) in euthymic BP compared to healthy controls using both subjective and objective measures. This study compared ER between 33 euthymic BP (I and II) and 35 healthy controls. Subjective experiences, valence, and arousal scores were assessed using the Self-Assessment Manikin. Objective measures included startle reflex parameters - amplitude, area, and latency - from the orbicularis oculi muscle via electromyography. To assess the AMSR, pictures of varying emotional valences from the International Affective Picture System were used during acoustic stimulation. A significant picture category effect was observed in the subjective picture evaluation; however, no substantial group effect or picture category-group interaction was detected. In the controls, picture categories exerted a significant effect on amplitude, but did not in euthymic BP. A linear pattern of startle amplitude across different picture categories was evident in the control group but not in patients. Analyses of the area did not reveal significant group differences. Onset latency was also similar between groups. This study indicates impaired emotional processing in euthymic individuals with bipolar disorder, as shown by altered startle reflex measurements. Future research with larger samples and consideration of bipolar disorder subtypes is needed to explore these findings further. •Bipolar patients show different affective modulation startle reflexes than controls.•Startle reflex changes suggest emotional processing problems•Biomarkers from emotions could aid early diagnosis of bipolar disorder.