Most of the time, you can’t tell. Most of the time, she smiles politely and moves about the day with a feigned stoicism.

Only an eye, trained through years of ruined birthday parties, eccentric shopping sprees, and new business ventures can see it, ready to surface without warning.

Sometimes it surfaces when I forget to stay calm and understanding. Reactionary frustration adds a sharp edge to my voice. Her face shifts. Her mouth, like mine, which naturally turns down at the corners, seems to droop even further. Her dark eyebrows, thin from years of over-plucking, rise up to create long thin lines in her forehead. Tears begin to drop as she lists all the reasons she’s failed as a mother.

“You’d just be happier if I wasn’t here,” she screams while collecting items apparently necessary for moving out: a piano songbook, a stack of bills and receipts, lip balm.

My 7-year-old brain entertains the idea of life without Mom. What if she just left and never came home, I think. I even imagine life if she died. But then a familiar feeling creeps in from my subconscious like a cold, wet fog: guilt.

I’m crying, though I can’t tell if it’s genuine because manipulative tears have worked too many times to recognize the difference. “You’re a good mom,” I say quietly. “I love you.” She doesn’t believe me. She’s still packing: a collectable glass figurine, a dirty pair of sloppily hand-cut jean shorts saved for gardening. I’ll have to try harder.

This scenario typically ends one of two ways: my dad leaves work to “handle the situation,” or my charm is effective enough to calm her. This time, my dad is spared an awkward conversation with his boss. Thirty minutes later, we’re sitting on the couch. I stare without expression as she unceremoniously explains the perfectly valid reason that she cut last week’s best friend from her life.

“You’d just be happier if I wasn’t here,” she says. The words circle through my head, but I smile, nod, and maintain eye contact.

My mom has never been formally diagnosed with bipolar disorder. She went to several therapists, but they never lasted long. Some people wrongfully label people with bipolar disorder as “crazy,” and my mom certainly isn’t that. People with bipolar disorder need drugs, and she certainly doesn’t need those, she argues. She’s simply stressed, overworked, and struggling to keep relationships and new projects alive. On the days she’s out of bed before 2 p.m., Mom wearily explains that if Dad were home more, if she had a new job, if the home renovations would ever be done, she wouldn’t be like this. I almost believe her.

It wasn’t always sadness and tears. We’ve made so many wonderful memories. At the time, I didn’t understand that her periods of spontaneity, productivity, and gut-busting laughter were actually part of the illness, too. I didn’t understand that filling a shopping cart with new clothes and candy “just because” was a red flag. On a wild hair, we once spent a school day demolishing the dining room wall because the house needed more natural light. What I remember as the best moments were actually as much a cause for concern as the unresponsive times. Bipolar disorder has many shades of gray.

Melvin McInnis, MD, the principal investigator and scientific director of the Heinz C. Prechter Bipolar Research Fund, says that’s why he’s spent the past 25 years studying the disease.

“The breadth and depth of human emotion manifested in this illness is profound,” he says.

Before arriving at the University of Michigan in 2004, McInnis spent years trying to identify a gene to claim responsibility. That failure led him to launch a longitudinal study on bipolar disorder to develop a more clear and comprehensive picture of the disease.

For my family, there was never a clear picture. My mother’s manic states didn’t seem manic enough to warrant an emergency visit to a psychiatrist. Her periods of depression, which she often attributed to normal life stress, never seemed low enough.

That’s the thing with bipolar disorder: It’s more complex than a checklist of symptoms you can find online for a 100 percent accurate diagnosis. It requires multiple visits over an extended period to show a pattern of behavior. We never made it that far. She didn’t look or act like the crazed characters you see in movies. So she must not have it, right?

Despite all the unanswered questions, research knows a few things about bipolar disorder.

Several years and one therapist later, I learned the probability of my mother’s bipolar disorder. Of course, my therapist couldn’t definitively say having never met her, but she says the potential is “highly likely.” It was simultaneously a relief and another burden. I had answers, but they felt too late to matter. How different would our lives have been had this diagnosis — albeit unofficial — come sooner?

I was angry with my mother for many years. I even thought I hated her for making me grow up too soon. I wasn’t emotionally equipped to comfort her when she lost another friendship, reassure her that she’s pretty and worthy of love, or teach myself how to solve a quadratic function.

I’m the youngest of five siblings. Most of my life, it was just three older brothers and me. We coped in varying ways. I shouldered an enormous amount of guilt. One therapist told me it’s because I was the only other female in the house — women need to stick together and all that. I flipped between feeling the need to be the golden child who did no wrong to being the girl who just wanted to be a kid and not worry about responsibility. At 18, I moved in with my then-boyfriend and swore never to look back.

My mother now lives in another state with her new husband. We have since reconnected. Our conversations are limited to polite Facebook comments or a polite text exchange about the holidays.

McInnis says people like my mom, who are resistant to acknowledge any issues beyond mood swings, is often because of the stigma surrounding this illness. “The biggest misconception with bipolar disorder is that people with this disorder aren’t functional in society. That they rapidly shift between depressed and manic. Often this illness hides below the surface,” he says.

As a child of a parent with bipolar disorder, you feel a variety of emotions: resentment, confusion, anger, guilt. Those feelings don’t easily fade, even with time. But looking back, I realize many of those emotions stem from not being able to help her. To be there when she felt alone, confused, scared, and out of control. It’s a weight neither of us were equipped to bear.

Although we were never given an official diagnosis, knowing what I know now allows me to look back with a different view. It allows me to be more patient when she calls during a depressive state. It empowers me to remind her gently to make another therapy appointment and refrain from relandscaping her backyard. My hope is that she’ll find the treatment that will allow her not to fight so hard every day. That will relieve her of the straining ups and downs.

My healing journey took many years. I can’t expect hers to happen overnight. But this time, she won’t be alone.

Cecilia Meis is a freelance writer and editor specializing in personal development, health, wellness, and entrepreneurship. She received her bachelor’s degree in magazine journalism from the University of Missouri. Outside of writing, she enjoys sand volleyball and trying new restaurants. You can tweet her at @CeciliaMeis.