Derealisation and depersonalisation go hand in hand, and combined, whether chronic or episodic, are very emotionally upsetting. Bouts of this disorder can last hours, days, weeks, and sometimes even months. In some people, these episodes of unreality might turn into ongoing issues, which may get better or worse at times. However, studies have shown many people have passing feelings of one or the other, and are not a cause for any concern. Ongoing feelings though, should not be ignored, as it could be a sign of another mental health or physical condition. It is always best to visit a doctor if you are concerned about anything.