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Smoking cessation treatment and risk of depression, suicide, and self harm in the Clinical Practice Research Datalink: prospective cohort study

BMJ 2013; 347 doi: http://dx.doi.org/10.1136/bmj.f5704 (Published 11 October 2013) Cite this as: BMJ 2013;347:f5704

Re: Smoking cessation treatment and risk of depression, suicide, and self harm in the Clinical Practice Research Datalink: prospective cohort study

Clearly Thomas and colleagues have made a major contribution to this topic with such a sizable sample. Three points suggest that the issue of whether these drugs lead to Psychiatric symptoms is not yet settled.

Firstly, the confidence intervals for both suicide and self-harm are too wide to conclude that there is no link with suicidal behaviour.

Secondly, its doubtful that lack of prescription of an antidepressant excludes significant depressive symptoms (or more importantly perhaps, significant dysphoric mood while taking the drugs). The data sheet and patient information leaflet for varenicline for example warn about the possibility of Psychiatric side effects, and recommend that patients experiencing them stop the drug immediately. The likelihood in such a situation is that the patient would discontinue the treatment rather than immediately receive an antidepressant.

Thirdly, significant psychiatric effects not amounting to a diagnosis of depression, such as agitation, insomnia or even Psychosis (which is theoretically possible with Dopamine Agonists such as Bupropionin) for which an antidepressant would not be indicated, can not be excluded by this methodology.

While clearly these drugs are helpful to many who want to stop smoking, we can not on the basis of this study withdraw cautionary advice that some individuals may experience significant Psychiatric side effects from them.

Competing interests: No competing interests

28 October 2013
Stephen P Davies
Consultant Psychiatrist
ABM University NHS Trust
Dept Psychological Medicine Morriston Hospital, Swansea
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