Problems with impulsive behavior in bipolar disorder also extend to delay-discounting. Using the Single-Key Impulsivity task (SKIP), a free-operant-responding task where participants are rewarded for delaying responses, individuals with bipolar disorder made more responses than controls, and had a shorter maximal inter-response delay. These characteristics appear to be independent of affective state or treatment (Swann et al., 2009b). This deficit was also found to be increased in a group of manic patients and in a group with both manic and depressive symptoms when compared to controls (Strakowski et al., 2009). Probit analysis of the dataset showed that rapid responding on the continuous performance task and rapid responding on the SKIP (at the expense of reward) were associated with the number of manic or depressive episodes, and with history of a substance- or alcohol-use disorder. This suggests that impulsivity is indicative of a sensitized course of bipolar disorder; or that impulsive characteristics could precede illness, as part of a predisposition to severe bipolar disorder (Swann et al., 2009b).
