‘This Is Us’: What Is Wrong with Rebecca?—It’s Not Alzheimer’s—According to Mandy Moore

Fans are worried about Rebecca (Mandy Moore), and they have good reason to be. In season 1 of This Is Us, we were all dying to find out what happened to Jack (Milo Ventimiglia). How did Jack die? The producers led us on for two long seasons until we witnessed his tragic death.

Now, we want to know why Rebecca is on her deathbed? Why is she getting lost and forgetting everything? Let’s take a look at what Moore revealed about her illness and what else it could be if it’s not Alzheimer’s Disease. 

Mandy Moore
Mandy Moore | Rachel Luna/Getty Images

What happened on ‘This Is Us’ that has fans so worried about Rebecca Pearson?

In the episode titled, “So Long, Marianne,” Rebecca takes a walk to a local park and sees someone who looks like William. She starts yelling his name, and when the person turns around, she realizes it is not William. She must have forgotten that William died. 

Then, she forgets that she went to the store to get something from the bakery. She ends up leaving with flowers instead. 

“I haven’t eaten anything today. I think that’s why my brain’s a little fuzzy,” Rebecca tells the cashier at the grocery store. She then proceeds to leave her cell phone there.

“So she came for a cake, bought flowers and forgot the cake,” summarized one fan on Reddit, “put her card in the wrong way, and left her phone. She deteriorated fast.”

Next, she has a panic attack in a Chinese restaurant when she can’t find her phone. She realizes she does not even have the number to call her son. The police end up escorting her home, and fans find out that the events are a flash-forward nine months into the future.

Back in the present time, she shows up at Thanksgiving and tells Randall (Sterling K. Brown), “I was halfway through the trailer of Cats,” she admits, “when I couldn’t remember what movie I was going to see. I think I need to see a doctor.” Something serious is happening with Rebecca.

Mandy Moore tells fans it’s not Alzheimer’s Disease that’s ailing Rebecca

Since the producers of This Is Us began showing clips of Rebecca’s forgetfulness, fans have theorized that she is in the early stages of dementia. The most recent episode fits in with their theories. However, Moore debunked that theory already.

“As someone who lost a grandparent to dementia,” wrote one Reddit user, “the defensiveness and secrecy hit close to home.”

“I’m so distressed watching Rebecca fade in and out,” added another fan.

“Rebecca’s storyline is breaking my heart,” wrote one viewer. “I’m glad she’s admitted she needs help.”

Although fans are mostly in agreement about that Rebecca’s memory loss could be related to Alzheimer’s Disease and dementia, Moore says otherwise.

“I love how people are sleuths,” she told Glamour of the fan theory that Rebecca has Alzheimer’s. “I love that! That’s a good theory. Not true, but I like it.”

Let’s look at another ‘This Is Us’ Fan theory regarding Rebecca’s illness

If it’s not Alzheimer’s Disease, what could it be? Could Rebecca have Multiple Sclerosis? Fans weigh in.

“What’s with the focus on Rebecca’s fingers/joints?” asked a fan on Reddit.

“MS? It can start with brain fog,” wrote another Redditor.

“No two people have exactly the same symptoms,” according to WebMD. “You may have a single symptom, and then go months or years without any others. A problem can also happen just one time, go away, and never return. For some people, the symptoms get worse within weeks or months.”

The early signs of MS also included cognitive issues and vision problems. Rebecca exhibited both memory loss and a brief problem with her vision when she thought she saw William.

This new fan theory is plausible, considering Moore confirmed that Rebecca’s illness is not related to Alzheimer’s Disease. Find out more when This Is Us returns on January 14, 2020.