Insomnia is a sleep disorder, which causes the person to not be able to fall asleep easily, or if they manage to fall asleep, they wake up several times during the night. This disorder can occur in specific periods of time, or be continuous. In the latter case, it can cause long-term problems for the person.
Difficulty sleeping can cause a person to have trouble concentrating, irritability, sleepiness during the day, and many other problems in their day-to-day life. To find a solution in this regard, the person should consult with their GP.