Skin test A blunted response of dermal erythema to niacin has been widely reported in schizophrenia, and it is possible that this response might predict clinical response to niacin treatment. All patients will have the Horrobin niacin patch test (Smesny et al., 2003) on admission to the study and it will be repeated after 6 months of continuous therapy. Niacin is applied simultaneously in four dilutions (0.1, 0.01, 0.001, 0.0001M) of 50microl each (approximately one drop of a standard eye-dropper) to the skin at the inner side of the forearm using chambered plaster for epicutaneous testing. After 90 seconds the plaster is removed. Skin reaction is quantitated at 3 minute intervals up to 21 minutes starting 90 seconds after removal of the plaster.