On 2016 Oct 24, Peter Hajek commented:

The title and the conclusion are misleading because they imply that the study followed up everyone who tried e-cigarettes (EC) to stop smoking. In fact, it only followed up people who tried but failed. Only people who tried e-cigarettes but reverted to smoking were included at baseline, successful quitters were no longer smokers and so were excluded.

Here is an analogy: Football scouts go round 100 schools and remove talented kids. Some time later they go round the same schools and also 100 new ones. The old schools now produce significantly less talent than the new ones. This is not because the earlier scout visit somehow damaged talent, but because talent was simply removed, in the same way successful quitting with EC removed good quitting prospects here.

The conclusion does not mention that the same effect applied to past use of stop-smoking medications, that result is also predictable for the same reasons.

On 2016 Oct 24, Peter Hajek commented:

The title and the conclusion are misleading because they imply that the study followed up everyone who tried e-cigarettes (EC) to stop smoking. In fact, it only followed up people who tried but failed. Only people who tried e-cigarettes but reverted to smoking were included at baseline, successful quitters were no longer smokers and so were excluded.

Here is an analogy: Football scouts go round 100 schools and remove talented kids. Some time later they go round the same schools and also 100 new ones. The old schools now produce significantly less talent than the new ones. This is not because the earlier scout visit somehow damaged talent, but because talent was simply removed, in the same way successful quitting with EC removed good quitting prospects here.

The conclusion does not mention that the same effect applied to past use of stop-smoking medications, that result is also predictable for the same reasons.