Yes, even someone as successful as Kate Spade can experience mental illness.

The death of the 55-year-old fashion designer Tuesday morning in her New York apartment was officially ruled a suicide by the city's medical examiner's office on Thursday. Some on social media this week have questioned how Spade, who seemingly had everything, could take her own life.

Spade's husband, Andy, told The New York Times she suffered from severe depression. Mental illnesses are medical conditions. Just like diabetes and heart disease, they can affect anyone — regardless of their income or occupation.

"That (argument) doesn't make any sense to me. That's like saying someone's really successful, I don't know how she got cancer," said Dr. Soroya Bacchus, a psychiatrist. "Mental disorders are an equal opportunity and have nothing do with success, education or where you grow up."

Environment does play a role in triggering underlying mental illness, she said, but it doesn't cause it. At the same time, it doesn't prevent it.

Spade built a fashion empire. She was married and had a 13-year-old daughter. To some, she might have had everything. But how someone's life appears on the outside doesn't necessarily reflect how they're feeling on the inside.

"Success doesn't trump severe depression," said Dr. Ken Duckworth, medical director of the National Alliance on Mental Illness.

That's why, he said, you can never judge someone just by looking at them.

"You can't walk a mile in another person's shoes," Duckworth said. "To me, (her success) arouses more sympathy because this brilliant, talented, person kills herself. What gets her there makes me much more sympathetic to how much pain was in this person."

People who think they may have a mental illness, whether anxiety, depression or something else, should seek treatment if they're feeling symptoms for more than two weeks, Bacchus said. They might not need to worry if they're not feeling right after a stressful day at work, but they also shouldn't wait two years.

She recommends people see a psychiatrist because they can prescribe medication or point them to another type of provider like a therapist.

Reta Saffo, Spade's older sister, told The Kansas City Star, that Spade asked her to attend her funeral even though she hates them. Talk like this can be a warning sign, according to Bacchus. She said if people hear someone talk about suicide or display signs of mental illness, they should ask them questions like whether they're feeling depressed or whether they want to live anymore.

If the person could use help, Bacchus suggests taking their insurance card and finding them a psychiatrist within their network and going with them to their appointment.

"That's the best intervention (people) can do," she said.

To get help: Call the National Suicide Prevention Lifeline at 1-800-273-8255 (TALK), 24 hours a day, 7 days a week for free and confidential support.