Counseling Today, Knowledge Share

Digging into the numbers

By Scott Rasmus February 9, 2017

It has been relatively well-publicized in the media that mental illness typically affects 20 percent of the U.S. population, or about 1 in 5 people, yet the source of this statistic is rarely disclosed. Furthermore, media sources typically discuss mental illness in general terms and don’t address its susceptibility by age or present statistics on the prevalence of mental illness over time. For instance, a basic comparison of mental illness prevalence statistics between children and adults, or in any given year versus over a person’s lifetime, is rarely offered.

Therefore, I wanted to offer a web-based meta-analysis of prevalence statistics for mental illness by including as many reputable sources of mental health information as I could identify. These sources include the Centers for Disease Control and Prevention, the National Alliance on Mental Illness, the American Psychological Association, the American Psychiatric Association, the National Institute of Mental Health (NIMH), the Substance Abuse and Mental Health Services Administration (SAMHSA) and the Office of the Surgeon General. The focus of my research was on the most current web research available, spanning the years 2011 to 2015.

Prevalence data

What are the generally accepted definitions of one-year prevalence and lifetime prevalence for mental illness? The NIMH defines one-year prevalence as the proportion of people who have experienced a mental illness in the past year, whereas lifetime prevalence reflects how many people have experienced an incidence of mental illness at any point in their lives up until the point of assessment. These numbers are typically reported as a percentage of the population. It is important to note that these statistics do not necessarily reflect new cases of mental illness, but rather those individuals who have experienced an instance of mental illness — new, ongoing or otherwise — in a given time period. With these definitions in mind, let’s look at the prevalence numbers.

In reviewing the prevalence statistics from various sources, my web research indicated that the average one-year prevalence for adults with mental illness was 22.2 percent (see Table 1), ranging from 14.5 to 26.2 percent over eight well-accepted sources. The average number trends higher than the general prevalence statistic that is often cited in the media, indicating that mental illness is somewhat more common than what is typically reported. With this in mind, one-year prevalence statistics should be revised and presented to the public to reflect that mental illness affects between 20 and 25 percent of adults in any given year.

For youths, I found data only for those ages 8-18. My research indicated that the average one-year prevalence number for mental illness among youths supported the number that is typically reported in the media — 20 percent (see Table 1). However, whereas I identified eight reputable sources of statistics for prevalence of mental illness among adults, I could identify no more than two such sources for youths. This discrepancy in viable sources suggests that a need exists for better research to identify the prevalence of mental illness among our children and adolescents.

I next refined the study to look at the one-year prevalence statistics for severe mental illness (see Table 2). When investigating this special population that is rarely reported in the media, my research indicated that the one-year prevalence average of severe mental illness among adults was 5.7 percent, ranging from 4 to 9.5 percent over seven sources. For youths ages 8-18, the one-year prevalence for severe mental illness averaged about 14 percent over just two sources, with a wide range from 9 to 20 percent.

Putting these numbers in the context of general mental illness, it implies that among adults, severe mental illness constitutes about a quarter of all cases, whereas among youths, severe mental illness makes up more than two-thirds of cases in any given year. This highlights an interesting difference, but we may infer from these numbers that the prevalence of severe mental illness can differ widely based on the definitions applied to it.

My experience suggests that these definitions tend to be more ambiguous and often are termed “severe mental illness,” “severe mental disorder” or “severe emotional disturbance,” to name a few. In my work over the past several years, I have noticed that the interpretation of the definition for severe mental illness can vary so greatly that it may include as few as five mental illness diagnoses or more than 100. SAMHSA’s National Registry of Evidence-based Programs and Practices identifies 17 related terms for severe mental illness. These terms can vary by state and with the inclusion or exclusion of childhood mental disorders and functional impairment criteria. On top of this variance, mental health professionals understand that there is some subjectivity involved in the diagnosis of mental disorders to begin with, even before the classification of the mental illness is determined as severe or not.

Next, I looked at the lifetime prevalence of mental illness for both adults and youths (see Table 3). Interestingly, I found the number of credible sources for these statistics much more limited than those for one-year prevalence, with only two sources apiece for both adults and youths. For adults, the lifetime prevalence statistics averaged 48.2 percent, with a range from 46.4 to 50 percent. For youths, the lifetime prevalence of mental illness ranged from 13 percent (ages 8-15) to 46 percent (ages 13-18), averaging about 30 percent over the full 8-18 age range. Given that youths have had fewer years to experience mental illness, it makes sense that their lifetime prevalence rates are lower than the lifetime prevalence rates of adults.

Finally, when considering the lifetime prevalence of severe mental illness (see Table 4), I could find reliable statistics only for youths, with an average prevalence of approximately 21 percent over two sources. I didn’t find enough credible information about the lifetime prevalence of severe mental illness in adults to even report here. Given the scarcity of statistics for both youths and adults related to lifetime prevalence of severe mental illness, this appears to represent a large gap in the research.

Concerning numbers

After reviewing the prevalence data for mental illness, it makes sense to me to consider current research statistics related to how many individuals with mental illness actually receive treatment for their disorders in a given year. My research indicates that the statistics for both youths and adults seem very consistent with age, averaging about 45 percent overall, and ranging over four sources from 39 to 50 percent.

These numbers shocked me somewhat and were very concerning. Such statistics indicate that regardless of age, less than half of the people who experience an episode of mental illness receive the mental health treatment that they need. This statistic begs the question: Why is this the case?

I can only hypothesize about the answer, which likely has many facets, including a general lack of awareness about mental illness, the need for education around it and the powerful influence of stigma related to mental illness. The media associates mental illness with a number of negative outcomes, particularly highlighting its relationship to violence, which in reality is very rare. To better address this misperception, the board for which I serve as the executive director — the Mental Health and Addiction Recovery Services Board in Butler County, Ohio — has adopted a position statement based on multiple sources indicating that only 3 to 5 percent of those with mental illness are violent. Still, let me offer a practical example of how the prevalence numbers and treatment statistics can be applied to the county where I live and work.

Based on the 2010 census numbers, Butler County has a population of about 370,000 residents. Applying the one-year prevalence statistics for mental illness of 20 to 25 percent, this implies that between 74,000 and 93,000 residents in our county experience an incidence of mental illness in a given year. Of those residents, upward of half don’t receive the mental health treatment services that they need. Potentially, that’s more than 46,000 county residents who may not be living their lives in as fulfilling and productive a manner as they otherwise could, especially when we know that mental health treatment largely works. People recover through modalities such as talk therapy, medications, lifestyle changes and other treatment approaches, which often are incorporated in an integrated way. What a challenge we face in addressing the mental health needs not only in my county but in our entire country and beyond. There are so many lives affected and so much productivity lost to what are very treatable illnesses.

Compiling the information I have shared in this article on the prevalence of mental illness related to time, age and treatment has really impressed on me how much work remains to be done to obtain better estimates of the general incidence of mental illness in our country and the world. We especially need more detailed statistics related to the cultural and demographic aspects of mental illness. The bible of mental illness, the Diagnostic and Statistical Manual of Mental Disorders, fifth edition, contains some valuable information related to prevalence and cultural data for specific diagnoses. There remains, however, a need for better research via large random studies that look at mental illness in general, including developmental disabilities and substance use disorders. I often wonder if the published mental health statistics that I review include these categories of mental illness.

Furthermore, as better statistics are researched and reported, mental health prevalence numbers need to be compared with those of well-known physical illnesses such as cancer, heart disease, diabetes, obesity and hypertension. In this way, I believe we can better demonstrate and publicize how common mental illness truly is in our society. Taking these actions will go a long way toward educating the public about its incidence, thus normalizing mental illness and, I hope, reducing the stigma with which it is often associated.




Knowledge Share articles are developed from sessions presented at American Counseling Association conferences.

Scott Rasmus is the executive director of the Butler County (Ohio) Mental Health and Addiction Recovery Services Board. He received his doctorate in counselor education from the University of Central Florida. He is dually licensed in Ohio as a licensed professional clinical counselor-supervisor and as an independent marriage and family therapist. He has presented internationally on mental health topics. Contact him at

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