Actor and comedian Robin Williams seemed to find comic relief in almost any scenario: a genie shackled to a lamp, a divorced father desperate to see his children, a disc jockey entertaining troops in the thick of war.

But even Williams said it himself in many of his public interviews regarding his private life: depression is no laughing matter.

The actor and comedian was found dead Monday at his home near Tiburon, California, according to the Marin County Sheriff’s Office. He was 63.

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According to Williams’s representative, the actor “has been battling severe depression of late,” and preliminary reports suggest Williams hanged himself.

The comedian reportedly fought drug and alcohol addiction for years, and returned to treatment just a month before his death. He had been seeking treatment for depression.

Watched and adored by millions, Williams was said to have felt alone. But the reality is, he’s not alone.

Like Williams, many Americans who grapple with depression find themselves overshadowed by stigma associated with the disease—everything from its diagnosis to its treatment.

For years, mental health experts who encounter depression often find themselves saying this: “it’s not ‘all in your head;’ it’s not the same as being sad; there is no cure.”

After all, how could Williams look so happy on the outside, when deep down he felt suicidal? How could he mask such a serious struggle?

“He may have also dealt with the same struglgles as everyone else, interpersonal relationship difficulties, and the pressure to continue sucess based on past successes,” Randy Auerbach, an assistant professor in the department of psychiatry at Harvard Medical School told Boston.com.

In reality, major depression is best described by Duke University psychologist Stephen Ilardi as a “debilitating syndrome.” So debilitating, in fact, that it suppresses a key hormone that can damage neurons in the brain in areas critical to maintaining memory and reasoning.

Major depression is one of the most common mental disorders in the US, according to the National Institutes of Mental Health. In 2012, an estimated 16 million adults aged 18 or older in the US had at least one major depressive episode in the past year. A combination of genetic, psychological and environmental factors can trigger depression.

But unlike other major diseases, the process of getting a diagnosis or even finding a root cause is not so clear. Blood tests aren’t as reliable when it comes to diagnosing depression. A conversation is the best diagnostic tool physicians have to diagnose depression. A conversation. That’s it. And that’s why it’s so often passed over by those unfamiliar with the condition as something not as serious as one can see on an x-ray or numbers indicated on blood tests.It often starts with a conversation with a doctor.

Doctors look for specific prolonged feelings and behaviors in a person’s everyday life that could be signs of the disorder. A patient may have to fill out a questionnaire that can help rule out other conditions.

But even receiving a formal diagnosis isn’t enough for some patients to recieve the proper support.

“For when those suffering from depression confide their diagnosis to friends and family, they’re often met with relative indifference, born of the assumption that the patient is afflicted with mere sadness—a condition from which they can quickly and easily recover,” Ilardi wrote in a blog post for Psychology Today. “As a result, depressed patients are often encouraged to snap out of it.”

“No one would dream of offering such cruel and ridiculous ‘advice’ to someone diagnosed with cancer or heart disease; the admonition is equally inappropriate in the case of depression,” Ilardi wrote.

Diet and exercise don’t cure depression. Prozac, Abilify, Celexa, Paxil, Zoloft, and other antidepressants don’t cure it either. For many, it doesn’t get better with time. You don’t just have to “get a grip” or “control your emotions.”

There’s no cure, but treatment matters.

Depression looks and feels differently in each patient, and treatment tactics are just as personal as the diagnosis itself. Mild to moderate cases may involve cognitive or behavioral psychotherapy. Scientific studies suggst combining the therapy with various classes of antidepressant medications seems to be the most effective treatment. More severe unresolved cases might also involve electroconvulsive therapy. The goal of these treatments is to regulate chemical imbalances in the brain, learn coping skills, and help change a person’s mood and outlook.

Untreated depression is the number one cause for suicide, according to Suicide.org.

Although 90 percent of people who die by suicide have an existing mental illness or substance use problem at the time of their death, but a depression diagnosis alone rarely leads to suicide.

As subjective as the path to diagnosis, experts say it’s hard to tell which depression patients will attempt to harm themselves or others.

“How do we identify consistent predictors? Right now we can’t,” said Auerbach.

In fact, many live for decades with the condition and hide it well. Depression is the leading cause of disability among Americans age 15 to 44.

Some conceal their condition by faking their mood, while others turn to substance abuse. Ironically, masking the condition may increase the risk for suicide.

Subtle signs of the condition include memory lapses, fatigue, and prolonged aches and pains. But its hard for loved ones, and sometimes even physicians to connect these signs with to depression. And as many medical treatments available, there’s no tool that can truly measure the pain that someone like Williams felt inside his own mind.

There are many lessons fans can draw from Williams’ life and through his movies. If Williams’ death taught us anything, it’s this: Depression is a lifelong condition that can strike at any age. It can be masked by laughter, and in some cases—unlike Hollywood—there are no happy endings.

To learn more about depression and how to help individuals in suicidal crisis, contact the National Suicide Prevention Lifeline: 1-800-273-TALK (8255)