Frostigs and Tom Spies—according to Cleary and Cleary—described more specific psychological symptoms of pellagra as:

Psychosensory disturbances (impressions as being painful, annoying bright lights, odors intolerance causing nausea and vomiting, dizziness after sudden movements),
Psychomotor disturbances (restlessness, tense and a desire to quarrel, increased preparedness for motor action), as well as
Emotional disturbancesIndependently of clinical symptoms, blood level of tryptophan or urinary metabolites such as 2-pyridone/N-methylniacinamide ratio <2 or NAD/NADP ratio in red blood cells can diagnose pellagra. The diagnosis is confirmed by rapid improvements in symptoms after doses of niacin (250–500 mg/day) or niacin enriched food. Pathophysiology
Pellagra can develop according to several mechanisms, classically as a result of niacin (vitamin B3) deficiency, which results in decreased nicotinamide adenine dinucleotide (NAD). Since NAD and its phosphorylated NADP form are cofactors required in many body processes, the pathological impact of pellagra is broad and results in death if not treated. The first mechanism is simple dietary lack of niacin. Second, it may result from deficiency of tryptophan, an essential amino acid found in meat, poultry, fish, eggs, and peanuts that the body uses to make niacin. Third, it may be caused by excess leucine, as it inhibits quinolinate phosphoribosyl transferase (QPRT) and inhibits the formation of niacin or nicotinic acid to nicotinamide mononucleotide (NMN) causing pellagra like symptoms to occur.Some conditions can prevent the absorption of dietary niacin or tryptophan and lead to pellagra. Inflammation of the jejunum or ileum can prevent nutrient absorption, leading to pellagra, and this can in turn be caused by Crohns disease.
Goldberger experimented on 11 prisoners (one was dismissed because of prostatitis). Before the experiment, the prisoners were eating the prison fare fed to all inmates at Rankin Prison Farm in Mississippi. Goldberger started feeding them a restricted diet of grits, syrup, mush, biscuits, cabbage, sweet potatoes, rice, collards, and coffee with sugar (no milk). Healthy white male volunteers were selected as the typical skin lesions were easier to see in Caucasians and this population was felt to be those least susceptible to the disease, and thus provide the strongest evidence that the disease was caused by a nutritional deficiency. Subjects experienced mild, but typical cognitive and gastrointestinal symptoms, and within five months of this cereal-based diet, 6 of the 11 subjects broke out in the skin lesions that are necessary for a definitive diagnosis of pellagra. The lesions appeared first on the scrotum. Goldberger was not given the opportunity to experimentally reverse the effects of diet-induced pellagra as the prisoners were released shortly after the diagnoses of pellagra were confirmed. In the 1920s, he connected pellagra to the corn-based diets of rural areas rather than infection as contemporary medical opinion would suggest. Goldberger believed that the root cause of pellagra amongst Southern farmers was limited diet resulting from poverty, and that social and land reform would cure epidemic pellagra. His reform efforts were not realized, but crop diversification in the Southern United States, and the accompanying improvement in diet, dramatically reduced the risk of pellagra. Goldberger is remembered as the "unsung hero of American clinical epidemiology".