I read with great interest this article by Johnson et al. and have the following comment.

As mentioned in this section, by selecting participants from Lyme Disease support forums you may only be finding the sickest individuals. But, due to condition of study and the methods employed, individuals with underlying psychological issues may also be more likely to be identified and sampled. The subjective nature of the HRQoL makes this a potential explanation for the observed results. reference Specifically, one could alternatively interpret this study as showing that individuals self-identified as Chronic Lyme Disease patients perceive a reduced quality of life and greater symptom burden. Hence, the principal findings may be more a consequence of the sample identified than reflecting the actual role of Lyme Disease in these processes. Such bias would also greatly affect the comparisons made with other populations.

I feel that the potential role of this different kind of selection bias should have been included in the limitations section.

Thank You