Medications like Seroquil, used for depression, can increase appetite. "It makes people feel like they are pregnant and it is impossible for them to stop eating. People can gain 50 percent of their body weight."
"Pardoxically, it can worsen the condition," said Galynker.
Those with bipolar disorder prior to bypass surgery also have a high incidence of wound reinfection, according to studies.
"The explanation may be that people with bipolar are not as good at taking care of their wounds or keeping it clean or complying with the regimen," said Galynker. "People with bipolar disorder seem to be distractable and have cognition problems, depending on the degree."
Sometimes bypass surgery, like plastic surgery, can make people "more depressed," he said, especially when patients have "unrealistic expectations" about the results.
"For example, somebody may have been told they couldn't be promoted because of their body image, and then they do the bariatric surgery and lose weight and then gain it again ... They went to all the expense and suffering and things didn't change that much. It's easy to imagine they would be depressed."
Jackson Jr. and others with bipolar disorder are most likely to do better in his recovery with the support of family and friends, according to Galykner.
Already, former Rep. Patrick Kennedy has expressed an interest in visiting Jackson, according to ABC's affiliate in Chicago, WLS-TV. Kennedy was also diagnosed with bipolar disorder, but has since resigned from Congress.
Jackson Jr. won a race against former Rep. Debbie Halvorson earlier this year and was predicted to win a ninth term in November, when he is up for reelection.
Having a bipolar II diagnosis should not stand in the way, according to psychiatrist Galynker, as long as the patient is being treated and on the right medications.
"For all intents and purposes they can be healthy and function well," he said.
As for Jackson's wife's reported concern over his condition, "That's a good thing," according to Galynker.
"Our research shows that patients whose families are anxious do better than those who are not anxious," he said. "The family is concerned and that makes them watch over the patient and provide support. When families aren't worried, they don't do so well."