Late last year, the federal Centers for Disease Control and Prevention surprised some people by adding “mental health conditions” to the list of risk factors that put people at high-risk of getting very sick from COVID-19.

Along with asthma and heart disease, the CDC reported that mood disorders – including depression – and schizophrenia spectrum disorders made people more likely to be hospitalized or die when they caught the Sars COV-2 virus.

If we were surprised, it’s probably because we don’t know enough about these conditions, even though many of us have either had one ourselves or have seen one in someone close to us. One of the things that COVID should have revealed is the empty distinction between mental illnesses and other illnesses.

It is estimated that one in five Americans will experience a mental illness every year, and one in 25 is living with a serious mental illness such as schizophrenia, bipolar disorder or major depression.

But experts estimate that half of the people with serious disorders – 3.5 million people – never get any treatment and are left to suffer on their own. Untreated mental illness doesn’t just put you in danger of a bad case of COVID, it also increases the risk of unemployment, substance use, homelessness, inappropriate incarceration and suicide.

May is Mental Health Awareness Month, which makes this a good time to consider why so many of us are walking around with treatable, life-threatening illnesses. If we can understand the barriers to treatment, we might be able to remove them.

One is cost. Even though the Affordable Care Act requires insurance plans to cover mental health services, the high-deductible plans most of us have mean there is significant out-of-pocket costs. In most parts of the country, someone can expect to pay $100 a session for talk therapy, and one study found that a case of major depression can result in $10,000 in medical costs in a single year.

Even if you can afford treatment, it’s not always easy to find. According to the Health Resources and Services Administration, 149 million Americans, and 285,000 Mainers, live in areas that lack a sufficient number of mental health practitioners.

And what we don’t know can hurt us. Mental illnesses can be debilitating, but they are often hard to recognize if you don’t know what to look for. Anxiety can come across as excessive worry, depression as laziness. Delusions can feel real.

People will keep symptoms to themselves because there is still a stigma around mental health issues that prevents people from seeking help and makes their friends and family members ignore the warning signs. We don’t think less of people who develop cancer or heart disease, but even though we have long known that mental disorders have a biological basis, we too often treat them as character flaws or weakness.

And there are significant racial and cultural barriers to people seeking and receiving treatment. According to a study published by the National Center for Health Statistics, 19 percent of Americans received mental health services in 2019, but that number doesn’t tell the whole story.

Non-Hispanic white adults (23 percent) were more likely to receive treatment than non-Hispanic Black adults (13.6 percent) or Hispanic adults (12.9 percent). Women of all races were more likely than men to receive treatment, and people who live in or near cities were more likely to get care than those in rural areas. Assuming that mental illness is roughly evenly distributed throughout the population, these figures suggest that people are being left out based on factors beyond their level of need.

This month would be a good time to consider our own mental health needs as well as those of the people in our lives. Is everyone getting the care they need and if not, why not?

As the CDC’s COVID advisory shows, drawing a line between physical illness and mental illness makes no sense – they clearly affect each other. We need to be aware of these conditions and what we can do about them.