Abstract
The possible involvement of both the neurotransmitter serotonin and certain personality variables, especially harm avoidance, to the susceptibility to alcoholism are considered. Four separate investigations were undertaken. The first study examined whether alcoholics could be easily and reliably distinguished from controls on the basis of diminished serotonergic activity using urinary serotonin metabolite ratios. The second and third investigations tested the reliabilities and validities of the Tridimensional Personality Questionnaire and the Temperament and Character Inventory respectively within British populations. Both questionnaires are designed to measure various personality traits, including novelty seeking, harm avoidance and reward dependence. The final study was designed to examine the effects of an acute ethanol challenge on tryptophan metabolism in normal healthy humans. In addition, possible differential neurochemical effects of alcohol on individuals with different personality structures was explored. The first study showed that decreased urinary serotonin metabolite cannot be used reliably to differentiate alcoholics from controls. It also suggested that a diminished serotonergic functioning may not be universal amongst alcoholics. The second and third studies raised doubts about the validity of both the TPQ and TCI amongst British populations. Only the harm avoidance scale on the TPQ seemed to be adequately reliable. Amongst the seven TCI dimensions, only harm avoidance, novelty seeking and self-transcendent were found to be reliable and consistent. The final study demonstrated that acute alcohol consumption decreased circulating tryptophan and influenced serotonin synthesis, possibly by enhanced tryptophan pyrrolase activity. It also indicated that individuals with different personality structures experienced different neurochemical changes following the acute alcohol challenge. Finally it is concluded that more inter-disciplinary research is needed to determine how various neurobiological factors, such as defective serotonergic transmission, and psychosocial factors including specific personality traits, might interact to influence susceptibility to alcohol dependence.