One symptom of Internet addiction is excessive time devoted to Internet use. A person might have difficulty cutting down on his or her online time even when they are threatened with poor grades or loss of a job. There have been cases reported of college students failing courses because they would not take time off from Internet use to attend classes. Other symptoms of addiction may include lack of sleep, fatigue, declining grades or poor job performance, apathy, and racing thoughts. There may also be a decreased investment in social relationships and activities. A person may lie about how much time was spent online or deny that they have a problem. They may be irritable when offline, or angry toward anyone who questions their time on the Internet.