Firstly, the most important cause of insomnia is stress that affects us negatively. It is inevitable that we can escape from the stressor .Even daily hassles can be stressor in our life for instance waiting in the line may be a stressor for us and all of stressors might lead to insomnia. When you have a problem, you always think that problem and you can not sleep comfortless. For example, unemployed people may not sleep well on the grounds that they have many economical problems. They always think about these problems so this leads to stress. Also students can have insomnia. before the exam week they may not sleep well because of stress.