Modvigil is not something I would like to be able to tolerate. I find myself irritable, angry, and anxious at the slightest provocation. But insomnia can cause more than irritated feelings and rages. Even if the insomnia is temporary, it can cause daytime impairments. A short-term insomnia that lasts more than a week, but less than three consecutive weeks, can lead to daytime impaired functioning.