“Empty” is how Justin Schuster, 19, of Rye Brook, N.Y., describes his brain since he completed treatment for Hodgkin’s lymphoma in April. “My thoughts aren’t processing,” says Schuster, who left Lehigh University last December after discovering a swollen lymph node just above his collar bone. “I can’t find the word, and I forget what I’m trying to say.”

What both Colleary and Schuster describe is often called “chemo brain,” shorthand for a debilitating medical condition characterized by loss of word retrieval, memory and executive function, and an inability to concentrate. Physicians call it cancer-related cognitive impairment (CRCI), and research indicates it affects about 75 percent of cancer patients during treatment, with 35 percent reporting persistent symptoms after treatment ends.

Why some people get the condition and others don’t, and why some have symptoms that persist for years while others’ symptoms are resolved in a few months remain puzzling.

But Arum Kim, director of the Supportive Oncology Program at NYU Langone’s Perlmutter Cancer Center, urges people to communicate with their medical team about cognitive changes.

“Really good, calm communication with your treating oncology team is important because there are things that we can do for it — if we know about it,” she says.

What causes 'chemo brain’?

Jeanne Mandelblatt, inaugural director of the Georgetown Lombardi Institute for Cancer and Aging Research, believes that inflammation plays a part.

“Cancer treatment kills cancer cells, but it also causes damage to cells that can accelerate aging and increase inflammation, including inflammation in the brain. That can affect cognition,” says Mandelblatt, who leads Thinking and Living With Cancer, a 15-year longitudinal study focusing on aging breast cancer patients and cognitive impairment.

But “chemo brain” is a misnomer, she adds, because patients experience cognitive impairment from immunotherapy and hormone therapy as well as chemotherapy. “It is not all one thing, but it is a real phenomenon and people have cognitive problems that interfere with their lives,” she says.

Chemo brain probably also kicks up simply because of the cancer itself.

“When people are going through cancer and recovering, they’re experiencing a lot of other problems that can impact their functioning but don’t necessarily impact their brain. There’s a really high rate of insomnia in this population. There can be high rates of anxiety and depression, there can be major lifestyle changes. And those can make you less effective than you were before,” says Nicolette Gabel, division director of rehabilitation psychology and neuropsychology at the University of Michigan Rogel Cancer Center.

Colleary says the crushing depression she experienced during treatment was even worse than her short-term memory loss.

“It became very clear to me that the chemo drugs had killed every positive hormone in my brain,” she says. “Dopamine, serotonin, oxytocin and endorphins simply did not exist. I became nihilistic at times, thinking ‘What’s the point of life? It’s too dangerous, lonely and sad.’”