Interest has been renewed into the association between cigarette smoking and psychiatric illnesses, as shown by Alexander Glassman and colleagues' report (June 16, p 1929)1 of smokers with a history of major depressive disorder. Those who achieved abstinence had a significantly higher risk of developing a new depressive episode. Despite 24% of the initial study group being lost to follow-up, these workers provide new and important evidence into the link between smoking and psychiatric illnesses.

We wish to make the following observations. It is not uncommon to encounter individuals, who have long histories of psychiatric illnesses and nicotine dependence, relapsing after abrupt cessation of smoking. Although many earlier studies focused on the relation between smoking and schizophrenia, thought to be due to nicotine cholinergic dysfunction,2 data reveal a link between smoking and major depressive disorder, bipolar mood disorder,2 and severity of psychotic symptoms associated with bipolar disorder,3 and suggest that nicotine abstinence might be a common mechanism underlying the relapse process of mental illnesses.

Dopamine transmission has been implicated in much of the recent data as a common link between schizophrenia, bipolar disorder, and smoking and nicotine addiction,2 supported clinically by the successful use of bupropion, a dopamine-uptake inhibitor, for smoking cessation.

In view of these reasons patients with any psychiatric illness, not necessarily those with major depressive disorder, should be judged at a higher risk of relapse after abstinence from cigarette smoking than before.

Although our understanding of the pathophysiological processes linking cigarette smoking and psychiatric illnesses remains limited, we suggest that treating clinicians should not be too enthusiastic in encouraging smoking cessation in psychiatric patients, and that if patients wish to stop smoking, they should be more closely monitored, as outpatients, than non-psychiatric patients during the initial period of abstinence.

3 Corvin A, O'Mahoney E, O'Regan M, et al.
Cigarette smoking and psychotic symptoms in bipolar affective disorder.
Br J Psychiatry 2001; 179: 35-38. [PubMed]

We assessed 43 people for changes in nicotine abuse behaviour on developing major depression. 18 (42%) stopped or reduced their tobacco intake after developing depression. 13 (30%) individuals increased tobacco abuse on developing depression. Patients who had been depressed for longer periods or had been abusing tobacco for a longer duration were more likely to stop or reduce the abuse than those who had a shorter history of depression or had been abusing tobacco for less than 1 year.

This finding defies the well known increase in smoking on development of depression. 3-5 Probable reasons for this unusual finding are pressures from family, the media's highlighting of the risks of smoking, or a cross-cultural variation, which need to be investigated. *Rakesh K Chadda, Som Nath Sengupta