Treating mental illness using orthomolecular principles is as old as the discipline itself. Biochemist and psychiatrist Abram Hoffer began treating his schizophrenic patients with niacin and other vitamins in the 1950s. Dr. Carl Pfeiffer continued his work, treating not only schizophrenic patients but also those with bipolar disorder. Pfeiffer and his colleagues claimed that many of these patients had abnormal levels of trace metals as well as high basophil levels (a type of white blood cell that increases with allergic reactions) and high histamine levels (compounds that trigger inflammatory responses to foreign agents like allergens).
The latter two findings led Pfeiffer and other orthomolecular psychiatrists to believe that many mental illnesses are caused by food allergies and can be treated by identifying and omitting the food in question, which is typically dairy, wheat or meat. Other potential causes include heavy-metal toxicity (allegedly due to metal dental fillings) as well as hypoglycemia (low blood sugar).
Orthomolecular psychiatrists have also diagnosed psychiatric patients with conditions not recognized by the mainstream medical community. These include histadella, which is the name for high histamine and basophil levels. Dr. Pfeiffer believed that histadella caused depression, and he treated patients with this condition using megadoses of vitamin B-6 and methionine, an essential amino acid. Pyroluria is a broader condition, which supposedly can cause everything from alcoholism to autism. It's a biochemical imbalance caused by an abnormality in the way the body makes hemoglobin (the protein that maintains iron levels in red blood cells). Practitioners claim that pyroluria leads to a deficiency in zinc and vitamin B6, so supplements of these are used in treatment along with other supplements.
Weaning psychiatric patients completely from their traditional medications is the goal of orthomolecular psychiatrists. Many of them quote Dr. Pfeiffer's Law, which states that "for every drug that benefits a patient, there is a natural substance that can achieve the same effect" [Source: Orthomolecular.org]. However, most believe that orthomolecular treatments can be used in conjunction with traditional medication, maintaining that once the biochemical imbalance is corrected, patients will probably be able to reduce or completely stop their medications.
As you might imagine, orthomolecular medicine in general is very controversial among the mainstream medical community. In turn, advocates of orthomolecular medicine claim that their findings have been suppressed. Next, we'll see why some mainstream doctors claim that orthomolecular medicine is dangerous.