The voluntary registry includes rescue and recovery workers, Lower Manhattan residents, area workers, commuters and passers-by.
An estimated 400,000 people were heavily exposed to the disaster.
Overall, half of those in the registry reported being in the dust cloud from the collapsing towers; 70 percent witnessed a traumatic sight, such as a plane hitting the tower or falling bodies; and 13 percent sustained an injury that day.
The new data suggests that 35,000 to 70,000 people developed post-traumatic stress syndrome and 3,800 to 12,600 may have asthma.
"The consensus among physicians is that when it comes to physical health, not everybody felt symptoms right away, though the vast majority felt them the first year," said Lorna Thorpe, the deputy commissioner for epidemiology at the New York City Health Department. "Some people developed symptoms years later. And in some cases, it's hard to tell whether they're World Trade Center-related or a result of allergies or existing conditions."
The post-traumatic stress disorder rate was highest among injured, low-income and Hispanic study volunteers. In general, minorities and low-income respondents experienced higher rates of mental and physical problems, as did women.
The study was conducted by the Health Department and the federal Centers for Disease Control's Agency for Toxic Substances and Disease Registry. It was released in the Journal of Urban Health.
