Michaela Riley knew something was wrong.

At just 15, she was battling a baffling mix of symptoms: thinning, brittle hair; a missing period; crushing brain fog and fatigue so severe she would fall asleep at her desk in school.

“I was rapidly gaining weight, despite eating super clean and working out six or seven days a week,” Riley told The Post. “It felt like there was a layer of puffy water stuck to my body, kind of like the Michelin man.”

But when she went looking for answers, she hit a wall. Riley said she was repeatedly dismissed by doctors, who insisted she was healthy and suggested the symptoms were all in her head.

Years later, she finally got an explanation: Hashimoto’s disease, an autoimmune disorder in which the body mistakenly attacks the thyroid — the butterfly-shaped gland in the neck that helps regulate metabolism, energy levels and hormones.

The condition is believed to be heavily linked to genetics, but with no family history of the disease, Riley couldn’t help but wonder what else may have set it off.

Looking back, she suspects years of chronic stress may have played a role. Alongside overexercising and under-eating, Riley said she often bottled up her emotions and struggled to establish healthy boundaries.

“I think that sealed my fate for having Hashimotos,” said Riley, now 28 and a board-certified functional nutritionist and the founder of Be Balanced Co. “Women have the mindset that we’re people pleasers — I see it all the time from my clients. They put themselves last and everyone else before them.”

That sentiment has exploded online in recent months, fueled by a viral phrase circulating across TikTok and X: “Women have two options: become a bitch, or get an autoimmune disease.”

Across social media, scores of women have recounted years marked by self-silencing, conflict avoidance and putting others’ needs ahead of their own — and linking those patterns, at least anecdotally, to the onset of illness.

Some even claim to have experienced dramatic improvements in their symptoms after changing their behavior and becoming more assertive.

“Started being a bitch and my eczema was GONE,” one user posted on X.

“Started being a bitch openly and my hair got healthier. Dropped the weirdos that were causing the rage and my tummy has never been more regulated!” another quipped.

“For the past eight years, I’ve been healing from ME/CFS, and it wasn’t until I entered my bitchy villain era that I finally managed to heal,” a woman exclaimed on TikTok.

As is often the case online, the trend packages a complex medical reality into a catchy, simplified narrative — but experts say there’s a kernel of truth behind the tongue-and-cheek phrase.

“When stress and emotions are chronically suppressed, the body can stay stuck in a low-level ‘fight or flight’ state,” said Dr. Erin Hammett, a triple board-certified physician in rheumatology, internal medicine and lifestyle medicine.

“Over time, that can affect stress hormones like cortisol, disrupt sleep, increase inflammation and put extra strain on the immune system,” she explained.

“It doesn’t mean emotions directly cause disease, but chronic emotional stress can influence how the body functions and how symptoms are experienced.”

Autoimmune diseases, in which the body’s immune system mistakenly attacks the body instead of defending it, are rarely caused by a single factor.

Genetics can raise vulnerability, while infections, environmental exposures, chronic stress, sleep patterns, hormones, nutrition, lifestyle habits and mental and emotional health may all play a role in triggering or worsening symptoms.

“If you get stressed or you’re repressing anger, it doesn’t automatically mean you’re going to have an autoimmune disorder, but it’s not helping keep your body in a state of homeostasis,” said Dr. Claire Brandon, a board-certified psychiatrist and medical director of Whole Body Psychiatry, who frequently treats patients with autoimmune disease.

As a result, she added, “environmental factors or other triggers that might have hit you anyway have a better chance of sticking and resulting in a spiral of the immune system.”

In the US, research suggests that about 15 million people, or 4.6% of the population, have been diagnosed with at least one autoimmune disease. Strikingly, women account for about 80% of those affected.

“There’s growing interest in how things like long-term caregiving, perfectionism, bottling up emotions, and ongoing social stress can affect women’s health over time,” said Hammet, the medical director at WellTheory.

“Women already tend to have higher rates of autoimmune disease because of hormonal, genetic and immune system differences, but chronic stress from social pressures may play a role too.”

“I don’t think you have to go straight to bitch mode. Moving your body and getting those emotions out in healthy ways is super helpful.”

Christine McMillan

Experts say stress-related symptom flare ups are commonly reported in autoimmune conditions like rheumatoid arthritis, lupus, psoriasis, inflammatory bowel disease and multiple sclerosis.

The same pattern is often observed in hair-loss conditions such as alopecia areata, where the immune system attacks hair follicles, leading to thinning and bald patches.

“A lot of times people say that they can’t talk about what’s going on in their lives, and they internalize that stress and then their bodies are like, ‘OK, we’re obviously having a crisis,” said Christine McMillan, a board-certified trichologist and the founder of Scalp Garden.

For Riley, the pieces started to come together after detailed lab work revealed she had elevated cortisol, chronic inflammation, metabolic issues, gut infections and thyroid dysfunction.

She believes years of dieting, overexertion and suppressing her emotions only made things worse, fueling stress that contributed to a cascade of symptoms that upended her life.

“One day I finally came to the realization that something had to change,” Riley said.

“I started looking at my relationships, work life balance and asking myself how I can show up for myself better,” she said. “I started setting boundaries with certain people and not putting myself in situations I didn’t want to be in, whether that’s a love interest or friendships or family.”

She also adjusted her approach to exercise, stopped restrictive eating patterns and shifted toward a more supportive way of nourishing her body.

Slowly, things began to improve. Her hair grew back, her energy returned, her menstrual cycle regulated, inflammation eased and her weight stabilized.

“It’s really incredible to see how much better quality of life you can have when you start to put yourself first,” said Riley, who has been in remission for Hashimoto’s for seven years and no longer has to take thyroid medication. “It can have a profound effect on health outcomes.”

Online, that transformation is often boiled down to the idea of simply becoming a “bitch,” but experts say the reality is far more nuanced.

“Something I see a lot in the women in my space is the confusion of advocating for themselves and bitchiness,” McMillan said. “But if a man did it, you wouldn’t call it being bitchy.”

In many cases, Hammett said, what people are actually describing is a shift in lifestyle that prioritizes boundaries, rest and self-advocacy rather than constantly putting their own needs last.

“That shift can reduce nervous system stress, improve sleep and recovery, and lower the physical toll of constant emotional strain,” she said. “It’s usually less about becoming mean and more about becoming less self-sacrificing.”

That sense of control, Brandon added, can be deeply meaningful for patients who often feel their bodies are working against them.

“If you notice that you’re feeling better when you’re releasing these emotions, there are probably ways to do it that are going to be even more helpful for you,” she said. “Because anger itself can promote inflammation and higher cortisol levels, which can create more issues in your life.”

Those healthier outlets can include talk therapy, mindfulness practices, journaling, breathwork or simply stronger social connection. McMillan also encourages clients to incorporate daily “joyful movement.”

“I don’t think you have to go straight to bitch mode,” she said. “Moving your body and getting those emotions out in healthy ways is super helpful.”

“The goal isn’t to become hardened or angry, it’s to create a healthier balance where your own needs and limits are respected too,” Hammett said.

“The most helpful approach for autoimmune diseases is usually one that combines evidence-based treatment with support for mental, emotional and physical health together.”