Carbon monoxide blood levels and reported cessation of smoking.

The carboxyhemoglobin (COHb) level was estimated in patients attending an anti-smoking clinic. A surprisingly large fraction of patients that reported "no smoking" were found to have abnormally high COHb. We believe that this discrepancy is due to the patients not reporting their smoking habits correctly. This phenomenon is further evidence that smoking should be regarded as a form of drug addiction in some persons. Some early relapses in stop-smoking programs can apparently be explained by the patient's admitting previously concealed smoking. For scientific purposes the results of stop-smoking cures should be evaluated by other means than the patient's own reports.