Bad breath can be a problem that involves oral health, as well as overall physical and mental health. First of all, gum diseases, and/or tooth cavities can cause bad breath. If these two factors are eliminated, you may look for other factors. People taking a myriad of medications that cause decreased salivary flow will often experience bad breath. These medications include some antidepressants, psychiatric drugs, blood pressure pills, antihistamines etc. It is estimated that at least 400 prescription medications are linked to dry mouth. Dry mouth can also be related to a variety of diseases and medical disorders. People with stomach upset or ulcers or acid reflux problem also suffer bad breath. Sometimes, bad breath can be a mere psychological belief in some patients.