Smoking, nicotine and psychiatric disorders: evidence for therapeutic role, controversies and implications for future research

Researchers interested in investigating the possible therapeutic effects an d the mechanisms of action of nicotine in neuropsychiatric disorders face a social-scientific-ethical dilemma. This dilemma comprises three components : (1) the known addictive potential of nicotine makes careful evaluation of the therapeutic potential of this compound socially unattractive; (2) the potential misuse of scientifically determined data by the tobacco 'lobby' c reates ethical concerns; and (3) the possible confusion between the differe ntial effects of nicotine in human smokers versus non-smokers creates diffi culties in study designs in voluntary human subjects. Therefore, it is impe rative that, at the onset of this review, the authors stress that they do n ot advocate cigarette-smoking as a route of nicotine intake under any circu mstances on the basis that controlled dosing of nicotine may be of potentia l benefit in some neuropsychiatric disorders. In this article, we review th e psychopharmacology of nicotine and its effects in a variety of neuropsych iatric disorders including schizophrenia, depression, anxiety and Tourette' s syndrome. Possible mechanisms of action of nicotine directly or indirectl y via its interaction with other neurotransmitter systems (i.e. serotonin, dopamine and noradrenaline) in relation to its potential role in these diso rders are discussed. It is postulated that new drugs may need to be develop ed that selectively interact with nicotinic receptors without addiction pot ential.