Table 1.

Summary of selected applications using negative controls for detection of confounding bias

Reference	Exposure	Outcome	Negative control exposure	Negative control outcome
[42]	Maternal smoking	Low birth weight	Paternal smoking
[43]	Maternal smoking	Sudden infant death syndrome	Paternal smoking
[44]	Maternal smoking	Offspring height, ponderal index, body mass index	Paternal smoking
[45]	Maternal smoking	Offspring blood pressure	Paternal smoking
[47]	Maternal distress	Offspring asthma	Paternal distress
[46, 48]:	Maternal smoking, alcohol use or dietary patterns	Offspring development	Paternal smoking, alcohol use, or dietary patterns
[51]	Air pollutant	Asthma	Future air pollutant, air pollutant elsewhere
[54•]	Mammography-screening participation	Death from breast cancer	Dental care participation	Death from causes other than breast cancer and from external causes such as accidents, intentional self-harm, and assaults
[14]	Influenza vaccination	Mortality and pneumonia/influenza hospitalization		Outcome before and after influenza season; injury/trauma hospitalization
[55]	Air pollutant	Asthma hospitalization		Appendicitis hospitalization
[56–59]	Smoking	Mortality from lung cancer		Other causes of death
[60]	Psychological stress post earthquake	Deaths from cardiac events		Other causes of death, e.g. cancer
[52, 53]	Screening sigmoidoscopy	Mortality from distal colon tumor		Mortality from proximal colon tumor (above the reach of the sigmoidoscopy)