Insomnia is a catch-all type of sleep disorder. The name literally means “not-sleep,” so the condition is actually more like a simple description of what you’re experiencing rather than a medical state with well-defined causes and outcomes.
Insomnia can be primary, which means it occurs on its own, while secondary insomnia is caused by another condition. Insomnia is also divided into onset insomnia and maintenance insomnia. In onset insomnia, you have trouble falling asleep. In maintenance insomnia, you have trouble staying asleep. You can have both types.
Often, primary maintenance insomnia is actually sleep apnea that’s been misdiagnosed. You wake up at night not for no good reason, but because your air supply is cut off because of sleep apnea.
Note: Having another sleep disorder could interfere with the accuracy of a home sleep study. If you don’t actually have insomnia, this isn’t an issue, but if you do have insomnia, it might make the sleep study inconclusive.