Repeated catecholaminergic stimulation, by stressors, stimulants, or, potentially, mania, may lead to persistently enhanced motor and motivational responses to catecholamines (Drouin et al., 2002) and this may underlie the recurrent course of bipolar disorder. Behavioral sensitization is a potential mechanism by which a recurrent course of bipolar disorder, or bipolar disorder complicated by stressors or substance use disorders, could lead over time to more severe impulsivity even outside of manic episodes and in the euthymic state (Dienes et al., 2006). Therefore, sensitization to the effects of catecholamines may increase impulsivity. Altered noradrenergic function may also underlie the inability to sustain attention in the euthymic state that might itself constitute a vulnerability marker in affected individuals (Clark et al., 2002).
