Sgt. Bowe Bergdahl survived five years of captivity before he was freed in a prisoner swap with the Taliban this weekend. But many experts say the days, months -- and even years -- ahead of him will pose some of the greatest challenges of his life.

The military and the public, as well as Bergdahl's family, still know very little about the treatment he received during the time he was held, or what impact it may have had on his psychological state.

To help Bergdahl, the 28-year-old soldier is taking part in the military's reintegration program, a three-phase program designed to help with the physical and mental healing process of returnees.

Bergdahl completed the first and shortest phase at a military base in eastern Afghanistan, where he was taken immediately after his rescue. Following a medical evaluation, he was flown to the U.S. military's Landstuhl Regional Medical Center in Germany for the second phase of the reintegration process.

Officials say there is no pre-determined length of time for his stay at Landstuhl. "The Landstuhl staff is sensitive to what Sgt. Bergdahl has been through and will proceed with his reintegration at a pace with which he is comfortable," stated a press release on Sunday.

A statement issued today by the facility said officials currently are focusing on evaluating his physical health, such as his dietary and nutritional needs, which may have been unmet during captivity.

Staff at Landstuhl will assess when he is physically and psychologically equipped to travel on to the states. Medical personnel are also determining the type of assistance Bergdahl will need once he is transported to his next stop, Brooke Army Military Medical Center in San Antonio, Texas.

This will be the third phase of the reintegration process, where much of the difficult psychological counseling will begin, says Arwen Consaul, U.S. Army South public affairs officer. Army South plans and leads all reintegration efforts throughout the military and has reintegrated seven military personnel since 2007.

"They're going to assess the situation and determine what specific needs we'll need here in San Antonio to help him with his reintegration," Consaul told CBS News. This team will includes a military Survival, Evasion, Resistance and Escape (SERE) psychologist.

Joseph Troiani, associate professor of clinical psychology and founder of the military psychology program at the Adler School of Professional Psychology, told CBS News that in order for mental health professionals to provide him with the best care, they'll need to learn more information about how he was living during the time he was held captive.

"The first question is what level of treatment was afforded to him," Troiani said. "Was it extreme or harsh?"

Experiences of POWs vary widely, said Troiani, who is also a retired commander for the U.S. Navy. In captivity, some are held in isolation, cut off from any human contact. They may experience sensory and food deprivation, harsh interrogation or physical abuse.

The aftermath is also not always the same. Some move on with their lives with relatively few challenges, while others never recover. Troiani said some former prisoners can even experience Stockholm Syndrome, a psychological phenomenon in which a prisoner starts to bond with their captor and may miss the person and the environment once they've been freed.

"He's going through the adjustment after five years. It has got to be a real shock to his system," explained Troiani. "It's going to take time for him to process. I would assume one of the big things he's experiencing is sleep deprivation."

Once Bergdahl arrives at Brooke, he will undergo thorough psychological testing -- but slowly, said Troiani. By doing so, medical personnel will hope to determine first and foremost if he is at risk for suicide, as well as to evaluate him for other psychological issues such as post-traumatic stress disorder, anxiety and depression.

• Full coverage: Bowe Bergdahl and Taliban prisoner exchange

Brooke is a medical training facility and the largest military inpatient hospital in the country. The center not only cares for and rehabilitates members of the military, in service and retired, but also offers housing and support services to families while their loved one undergoes treatment.

Troiani speculates Bergdahl could remain at Brooke for three months, if not more.

After the initial psychological evaluation is completed, military personnel will most likely begin their "debriefing" process, in which they sit down with Bergdahl so he can recount his experiences. For some POWs, debriefing can be traumatic, forcing the individual to relive the events, while others find it brings a sense of closure to the experiences. "Emotionally that could be pretty charged but there's also a piece of it that, that's another way of processing what went on," said Troiani.

Before he returns home to Idaho, Bergdahl will also be given a period of decompression to allow him time to reflect and sort out his experiences, says Troiani. This can be done through talking with professionals and peers, through writing, journaling, drawing, meditation or prayer, depending on the individual's preference. Some POWs even choose to do so in isolation.

But Bergdahl may also have subsequent psychological challenges once he learns more details about efforts to secure his freedom. Former members of Bergdahl's unit have taken to the airwaves, Web and social media alleging other soldiers were actually killed while searching for him. "Once he gets knowledge of that he might have some guilt and negative feelings about that," notes Troiani.

But Troiani says the POWs of today have a higher chance of successful recovery than those who endured and survived captivity during other wars such as Vietnam, since much more is known today about the psychology of war and terrorism.

"The thing that I realized once I got out is that my normal was no longer the real normal," he said. "What I'd been living in was really an unusual world and really not the typical world that you'd experience here in America."