A patient's mother comes to you with a prospective cohort study linking autism to the...

Recruiting participants from an autism seminar introduces selection bias. This non-random selection increases the likelihood of overestimating associations due to pre-existing beliefs or exposures in that subgroup.

Toronto Notes 2023 – Epidemiology:

“Selection bias occurs when participants are not representative of the general population, as in recruitment from disease-specific support groups.”

MCCQE1 Objectives (Population Health > 65-2: Study Design and Appraisal):

“Candidates must recognize sources of bias in epidemiologic studies, including selection bias due to non-representative recruitment.”

Recall bias (D) is more of a concern in retrospective studies. Sponsorship (B) may create perception bias but is not a flaw in methodology itself. Standard error reporting (A) is normal. Not accounting for confounders (E) matters but recruitment source is more directly biasing.

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