Monoamine research is discussed in terms of association of catechol/amine metabolism to aggression & cerebrospinal fluid 5-hydroxyindol acetic acid’s relation to depression, suicide & aggression. Hormone research is discussed in terms of dysregulated cortisol secretion & thyroid-stimulating hormone response to thyrotrophin-releasing hormone. Methodological flaws are discussed. Evidence suggests a link between suicidal behavior & diminished central nervous system 5-hydroxytryptamine metabolism.