There's a good chance Hurricane Harvey will leave behind higher rates of PTSD, and an increase in problem drinking.

A man looks out on a flooded road during the aftermath of Hurricane Harvey on August 29th, 2017, in Houston, Texas. (Photo: Brendan Smialowski/AFP/Getty Images)

Like the storm itself, the impact of Hurricane Harvey on Houstonians' mental health promises to linger.

Although specific estimates vary widely, the results of numerous research studies suggest residents who suffered a profound personal loss due to the storm are at significantly elevated risk of post-traumatic stress disorder.

"A large body of research conducted after disasters in the past decades suggests that the burden of PTSD among persons who were exposed to disasters is significant," a research team led by psychiatrist Yuval Neria of Columbia University Medical Center wrote in 2008.

Most often associated with combat veterans and rape victims, PTSD is a mental condition in which a traumatic event continues to plague the victim for months or years. Common symptoms include nightmares, flashbacks, depression, and anxiety.

"There are fairly consistent estimates of PTSD that can be expected in the first year after (it is triggered)," the researchers write. "Specifically, the prevalence of PTSD among direct victims of disasters ranges between 30 and 40 percent."

One group of workers is rebuilding homes, another band of professionals will be busy diagnosing and treating the traumatized.

They report it is more likely to strike victims who suffered major injuries, felt their life was in danger, endured the death or major injury of a loved one, or suffered severe property destruction.

"The range of PTSD prevalence among rescue workers is lower, ranging between 10 and 20 percent," they add. But that number can be higher: One study found 22 percent of firefighters who responded to Hurricane Katrina in 2005 suffered from PTSD two to three months after the event.

Another subset of the population—residents who aren't directly affected by the disaster—are also at some risk. Their rates of PTSD are "expected to be between 5 and 10 percent," the researchers write.

The research does contain some good news for storm survivors: In a post-Hurricane Sandy follow-up report, Naria noted that "the prevalence of PTSD is generally lower after natural disasters compared with human-made and technological disasters." Perhaps we are more resigned to—and therefore less triggered by—"acts of God" than by atrocities committed by our fellow humans.

He also pointed out that "many individuals with early trauma-related symptoms of PTSD tend to recover over time, and regain normal functioning. Across all disaster types, a significant majority of the population experiences minimal mental health effects, instead displaying resilience, positive coping, and effective adaptation of the adverse circumstances."

That said, disasters are particularly tough on people already suffering from mental-health issues such as addiction. A 2011 study looked at data on 697 people directly affected by one of 10 disasters (a list that included several floods).

It found that, while 19 percent of the sample had a drinking problem, only a tiny number—0.3 percent—"developed an acute new post-disaster alcohol use disorder." However, among people in recovery, an astounding 83 percent reported drinking after the disastrous event.

Other evidence suggests an increase in problem drinking may not be limited to those previously identified as alcoholics.

"Evidence from survivors of Hurricane Katrina indicates elevated rates of alcohol problems," writes a research team led by Katherine Keyes of Columbia University. "Increases in binge drinking were found among those most exposed to the hurricane."

And further north, "seven months after the Mt. St. Helens volcano eruption, alcohol center referrals and liquor-law violations had increased compared to the pre-eruption period." It would not be at all surprising to find similar increases in Houston.

So while one group of workers is rebuilding homes, another band of professionals will be busy diagnosing and treating the traumatized. For many residents, recovery—internal as well as external—will be a long, difficult process.