Effective drugs for mental disorders have been found by serendipitous findings not supported by knowledge of psychopharmacology. Drug are assigned labels, such as "antidepressant" without knowledge that such a label delimits the utility of such agents. Many double-blind controlled studies have shown that imipramine effectively ameliorates panic attacks and agoraphobia. Epidemiological data show a relationship between Panic Disorder and Depression. Relatives of probands with Major Depression plus an Anxiety Disorder were at greater risk for both Major Depression and for an Anxiety Disorder. Panic Disorder, as a subcategory of Anxiety Disorder was associated with the greatest increased risk. Intravenous sodium lactate reliably produces anxiety attacks clinically indistinguishable from those occurring in Panic Disorder, in subjects with that disorder. Panic Disorder is characterized by response to imipramine, an epidemiological link to Affective Disorder, and is similar to panic induced by infusion of sodium lactate.