WASHINGTON, D.C. (NewsNation) — Pennsylvania U.S. Sen. John Fetterman is at Walter Reed National Military Medical Center Friday after he voluntarily sought out treatment for clinical depression earlier this week.

Fetterman was elected senator in November following an arduous campaign, during which he suffered a near-fatal stroke. In the first few months of recovery post-stroke, Fetterman continued to campaign and took the debate stage against Republican challenger Dr. Mehmet Oz, using a closed captioning system designed to help him process what was being said as he dealt with lingering symptoms.

While Fetterman has said he will not be stepping down from his position as U.S. Senator and is expected to receive treatment for at least a few weeks, there are still big questions about his future and what his treatment will look like.

Fetterman has dealt with depression on and off throughout his life, but sources close to the senator told NewsNation it has gotten worse in the last few weeks, and it has “never been like this.” Depression is also a common symptom of a stroke, with one in three stroke survivors developing the condition. It is often caused by biochemical changes in the brain, according to the American Stroke Association.

“I’m not sure we truly understand the science behind it,” said Georgetown School of Medicine psychiatry professor Dr. Elizabeth Hoge. “But there are several medical conditions that can increase the risk for depression. And one of them is stroke, which makes it much more likely.”

So what does that mean for Fetterman’s possible treatment plan?

Typically, a variety of options will be explored, including medication, group and individual therapy and daily individual attention from a doctor or team of doctors. Sometimes this will also include psychotherapy or psycho-education groups and may also include yoga and meditation.

Some patients with severe depression will even undergo electroconvulsive therapy (ECT). It is unclear, however, if that will be an appropriate treatment option for Fetterman. According to the American Psychiatric Association, “ECT involves a brief electrical stimulation of the brain while the patient is under anesthesia.” Sometimes, when medicines and other therapies are ineffective, another option might be transcranial magnetic stimulation (TMS), which uses magnetic pulses to stimulate the brain in a non-invasive way.

Meanwhile, while Fetterman continues treatment, another concern in the next few days is that Pennsylvania’s other U.S. senator, Democrat Bob Casey, is recuperating after surgery for prostate cancer. His office says the surgery went well, but they have not indicated when he will be back to work. With both Democratic senators out, it is likely that the party will not bring up important or close votes during that time.