When insomnia lasts a short amount of time, it’s called acute. And when it lasts a long time, it’s chronic. Acute insomnia can last up to 3 months and often has a cause like stress. Insomnia is chronic when a person has sleep trouble at least 3 nights a week for a month or longer.
Insomnia can come and go, with periods of time when a person sleeps fine. And it can last for years if you don't treat the cause.