A new study found that even though it's been more than 20 years since the 9/11 terror attacks, the mental health of first responders still needs to be monitored.

According to a study by the Stony Brook World Trade Center Health and Wellness Program, researchers found some responders may be experiencing cognitive issues earlier than the general population. Researchers also say that PTSD may be associated with cognitive problems and physical illness.

"Down at the World Trade Center site many times we kind of think of the exposure there, including the dust and all the different toxins very often what we think of his cancer but many of those toxins also potent neurotoxins," says Benjamin Luft, of the Stony Brook Center Health and Wellness Program.

Researchers say additional studies are needed to delve further into investigating the brain status of responders.