PMS: Mood Swings Mood Swings and mood serotonin drops when your period starts depression (and its awkward, unwanted cousin anxiety) extremely depressed a week or two before your period http://www.everydayhealth.com/pms/mood-swings.aspx residual mood swings that come from premenstrual syndrome https://www.everydayhealth.com/pms/mood-swings.aspx These can include http://www.everydayhealth.com/pms/mood-swings.aspx