In United States law, epidemiology alone cannot prove that a causal association does not exist in general.

The study later was criticized as methodologically flawed, and later studies failed to establish such a causal device-disease association.

In addition, data from recent smallpox vaccinations have been found to be consistent with a causal association between vaccination and myopericarditis.

These studies tend to suffer from representative issues, and an inability to tease out causal associations in the face of other (possibly unknown) intervening factors.

"Many of the allegations against vaccines," Halsey said in one interview, "are based on unproven hypotheses and causal associations with little evidence."

It was the first strong evidence of a causal association with neurological impairment.

However, the authors do state: 'This could not be interpreted as an evidence of causal association.'

The link between levels of folate and altered mental function is not large, but is sufficient enough to suggest a causal association.

Whether this is a causal association is unclear.

This hazard descriptor is used when there is convincing epidemiologic evidence of a causal association between human exposure and cancer.