Subjects have a certain act or belief that they must engage in a certain activity that comes into their mind. This can be kleptomania, pyromania, sexual exhibitionism, etc. They feel a sense of building anxiety whenever they are prevented from engaging in this behavior for an extended period (usually several times a day to weekly, depending on the impulse) and will often attempt to engage in this behavior at inconvenient or inappropriate times. This is different from OCD in the sense that OCD is usually a single contained behavior that must be engaged in to reduce anxiety. Impulse control disorder is a variety of behaviors and can be virtually any sort of highly inappropriate action.
Due to the lack of meaningful sleep, insomniacs should suffer from blanket penalties to perception related tasks or anything requiring concentration or prolonged fine motor abilities.