B complex comprises of a number of vitamins like vitamin B1, vitamin B3, vitamin B5 and vitamin B6 to name a few. Research has found that these vitamins are crucial to a person's mental and emotional health. Vitamin B1 or thiamine is used by the brain to help convert glucose into fuel, without which an individual will feel fatigued. This can lead to and heighten feelings of anxiety, depression, irritability, and at times thoughts of suicide. A deficiency can also result in memory problems, insomnia, loss of appetite and gastrointestinal disorders.
Pellagra, which is responsible for dementia and psychosis, among many symptoms has been found to be brought on by vitamin B3 deficiency. The disease has reduced significantly today, but smaller deficiencies of the vitamin can contribute to anxiety and depression.
answered by M W