PURPOSE: Requiring parental consent may result in sampling biases that confound scientific conclusions and stifle the representation of children most at risk for adverse outcomes. This study aims to investigate whether active parental consent, compared with passive parental consent, creates a bias in response rate, demographic makeup, and adverse outcomes in adolescent samples.

METHODS: A meta-analysis was performed on peer-reviewed articles and unpublished dissertations from 1975 to 2016 in five computerized databases ERIC, PsycINFO, MEDLINE, PubMed and ProQuest. Quantitative studies were retained if they included the following keywords: active consent (or informed consent or parental consent), passive consent (or waiver of consent), risk behavior, adolescen*.

RESULTS: Fifteen studies were identified with a total number of 104,074 children. Results showed (1) response rates were significantly lower for studies using active consent procedure than those using passive consent procedure (Z = 3.05, p = .002); (2) more females, younger participants, and less African-Americans were included in studies using active consent procedures than studies using passive procedures (Z = -2.73, p = .006; Z = -12.06, p < .00001; Z = 2.19, p = .03, respectively); (3) studies with passive consent procedures showed higher rates of self-reported substance use than studies using active consent procedures (Z = 3.07, p = .002).

CONCLUSIONS: Requiring active parental consent can lead to a systematic bias in the sample where the population under study is misrepresented. Institutional review board committees should collaborate with researchers to find solutions that protect minors without silencing the voice of high-risk youth in the literature.