What are the common factors that indicate a mental health issue? Any sudden change of behavior or attributes in a person that are unusual to them is most commonly the first red flag. These changes can range from a lack of interest, mood swings, excessive substance abuse, lack or excess of eating and sleeping, emotional outbursts, etc. In short, if you find yourself or a close person change their inherent nature for more than a period of 2 weeks, it is time to intervene