Thiamin deficiency causes confusion, uncoordinated movements, depressed appetite, irritability, insomnia, fatigue, personality changes, memory and cognition impairment, shortened attention span, impaired ability to work or learn, and depression.
Riboflavin deficiency causes depression, hysteria, psychopathic behavior, lethargy, and hypochondria evident before clinical deficiency is detected.
Niacin deficiency causes irritability, agitated depression, headaches, sleeplessness, memory loss, emotional instability, and mental confusion progressing to psychosis or delirium.
Vitamin B6 deficiency impairs neurotransmitter synthesis, causes irritability, insomnia, weakness, depression, abnormal brainwave patterns, convulsions, the mental symptoms of anemia (described below), fatigue, and headaches.
Folate deficiency causes the mental symptoms of anemia (described below), tiredness, apathy, weakness, forgetfulness, mild depression, abnormal nerve function, irritability, headache, disorientation, confusion, and inability to perform simple calculations.
Vitamin B12 deficiency causes degeneration of the peripheral nervous system, anemia, and neuropsychiatric damage.