When is an appointment with a psychiatrist absulutely a must?

If you notice big changes around you whose cause cannot be explained, e.g. the environment well-known to you seems different, alien or even hostile, the people dear to you seem to have turned their back on you, and your life seems empty, unsatisfying and inert, you should certainly consult a psychiatrist. Generally, it is easier for other people to notice changes in your behaviour, so if one of our loved ones has become unjustifiably distrustful, suspicious, sad, thoughtful or absent-minded, and has changed or given up his interests, has sleep problems, has ceased to carry out his daily duties, has begun to reveal bizarre interests or has changed his preferences, then an appointment with a psychiatrist is absolutely necessary.