About 12 percent of children in the U.S. lived with at least one parent who was dependent on or abused alcohol or an illicit drug last year, according to a new report from the Substance Abuse and Mental Health Services Administration (SAMHSA).

Researchers found that approximately 7.3 million children lived with a parent who was dependent on or abused alcohol, and 2.1 million children lived with a parent who was dependent on or abused illicit drugs.

The report, Findings for Children Living with Substance-Dependent or Substance-Abusing Parents: 2002-2007, looked at children between the ages of 12 and 18 and covered the period 2002 to 2007.

"The research increasingly shows that children growing up in homes with alcohol- and drug-abusing parents suffer -- often greatly," said SAMHSA acting administrator Eric Broderick. "The chronic emotional stress in such an environment can damage their social and emotional development and permanently impede healthy brain development, often resulting in mental and physical health problems across the lifespan. This underlines the importance of preventive interventions at the earliest possible age."