Depression is often a laborious uphill struggle for the sufferer and their loved ones. Add in living with a disease in which a downhill course is almost guaranteed, and you’re facing an unfathomably steep climb.

That’s what beloved comedian and actor Robin Williams was dealing with when he committed suicide, according to his wife, who says he was in the early stages of Parkinson’s disease. We recently discussed Williams’s battle with depression and the stigma that can surround mental illnesses. But the relationship between Parkinson’s disease and depression is important to understand, especially as so many Americans live with the disease—nearly 1 million, according to the Parkinson’s Disease Foundation.

Whether it’s a family member, friend, or celebrity who has been diagnosed, many of us have heard of Parkinson’s, a degenerative disorder of the central nervous system best known for its movement-related symptoms. Not to be confused with Alzheimer’s or other dementias, Parkinson’s disease is a distinct neurologic entity with a mind of its own. Michael J. Fox, the star of Family Ties and the Back to the Future movies, is a well-known champion of the disease. Fox was diagnosed at age 30, defying many preconceptions of Parkinson’s as a disease of only the elderly, and has wielded his celebrity status as a tool to raise awareness. Other prominent Parkinson’s sufferers include boxer Muhammad Ali and the late country music legend Johnny Cash.

Given that nearly 60,000 Americans are diagnosed each year, an understanding of Parkinson’s disease and its treatments is imperative. The death of a well-defined group of brain cells in the substantia nigra, an area the midbrain, that produce an important brain chemical, dopamine, begin to die in Parkinson’s patients. Although the cause of the death of the cells is unclear, the symptoms and signs of the disease are well known and stereotypic. Early signs are often movement-related, including tremors, stiffness, and problems with walking. Later, cognitive and behavioral problems can occur; dementia is not uncommon.

Of note, depression is a common psychiatric symptom of Parkinson’s disease patients. A recent analysis of depression in Parkinson’s disease found that clinically significant depressive symptoms were present in 35 percent of individuals in the studies. Imagine the mental burden of severe depression coupled with that of an even deeper chemical imbalance—the struggle is real, people. Studies of suicide in Parkinson’s disease sufferers are unclear. Some estimates find that suicide is less common in the general population, while others report the opposite. It is clear that further study is required to reach a definitive conclusion on suicide risk in Parkinson’s patients.

The decline in the physical and then mental health of Parkinson’s patients is torturous for sufferers and their loved ones. As symptoms progress, individuals with this disease may have trouble walking, talking, or completing other daily activities.

To date, no cure for Parkinson’s exists. However, medications and therapies have been developed to relieve symptoms significantly. The drug levodopa can be converted into dopamine, buoying the brain’s reserves of this essential brain chemical in the face of the dying brain cells that once produced it. Other drugs mimic dopamine and can help improve symptoms.

But medications are not the only therapy for Parkinson’s disease. Deep brain stimulation (DBS) has been approved by the U.S. Food and Drug Administration (FDA) for this disease, particularly if medication does not help. The indications vary, but progressive poor response and medication intolerance are a few possible justifications. In DBS, a neurosurgeon implants electrodes in the brain that attach to a “pacemaker” for the brain. This pacemaker works to deliver electrical stimulation to specific parts of the brain to counteract the symptoms of Parkinson’s.

These treatments, for the most part, target only the movement-related problems of Parkinson’s disease and not the mental health aspects of the disease. Part of this is because the precise mechanisms, or pathophysiology, of depression in Parkinson’s disease is not well understood. Indeed, scientists are still searching for the precise mechanism for clinical depression absent Parkinson’s.

Neurologic and mental disorders are devastating in many ways. Separate from cancer, hypertension, or other systemic illnesses, patients with neurologic deficits can’t always advocate for themselves and often lose their voice on the podium. We must take every opportunity to raise awareness about our family members, friends, and community members who aren’t always able to speak for themselves, and hope that we will soon be able to unlock the brain.