The link between mold and depression remained strong even after researchers from Brown University in Providence, Rhode Island, took into consideration physical illnesses that may be caused by the mold, and a homeowner’s feeling of helplessness in controlling his environment. This surprised the authors, who said they set out to prove that other factors beyond the mold itself may be responsible for the connection.

“We were surprised that we found we cannot explain all of the association between mold and depression by those two elements alone,” said Edmond Shenassa, an assistant professor of epidemiology Brown and the study’s lead author, in a telephone interview today.