Nutritional Links to Depression and Mental Illness. Andrew Saul, PhD discusses the benefits of Vitamin B3/Niacin and how he used it to treat an acute case of depression.
Everyone's body is different so dosages can vary.
The side affect you want to avoid is "flushing". Flusing is when the body feels hot or itchy.
As is always the case with nutrients, each individual must determine their own optimum level. With nicotinic acid this is done by increasing the dose until the flush (vasodilation) is gone, or is so slight it is not a problem.
One can start with as low a dose as 100 mg taken three times each day after meals and gradually increase it.
Some start with 500 mg each dose and often will start with 1 gram per dose especially for cases of arthritis, for schizophrenics, for alcoholics and for a few elderly patients. However, with elderly patients it is better to start small and work it up slowly.
For case studies and more info go to the source link.