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Original article
peer-reviewed

# Prevalence and Impact of Diagnosed and Undiagnosed Depression in the United States

### Abstract

Background: The objectives of this study were: 1) estimate the impact and severity of both diagnosed and undiagnosed depression in the general US population 2) explore the demographics of depression based on its common symptoms 3) interpret Patient Health Questionnaire-9 (PHQ-9) scores to improve accuracy in identifying individuals with depression.

Methods: A random sample of 200 individuals was selected from a general US adult population to complete the Patient Health Questionnaire-9 (PHQ-9).

Results: Only 39.4% of respondents indicated that they had a formal diagnosis of depression. In contrast, 53% of participants have considered seeking help from a mental health professional. More importantly, 31.45% of respondents without a formal diagnosis had a PHQ-9 score of over 10 (moderate to severe depression).

Conclusions: The results indicate that undiagnosed depression exists in the US population and suggest that access to mental health services needs to expand across the nation.

### Introduction

Clinical depression is a mood disorder that causes a persistent feeling of sadness and loss of interest that can affect ones thinking and behavior. This condition can lead to a variety of physical and emotional problems and often requires long-term treatment [1]. In a normal brain, neurotransmitters successfully send chemical messages through electrical signals released and received by neuron synapses. Dopamine is responsible for regulating one’s motivation for reward [2]. When comparing the brain of a depressed patient, there are several abnormalities including brain shrinkage (atrophy), a loss of grey matter volume, and reduced functional activity in the hippocampus. There is also a depletion of the neurotransmitters in the central nervous system including serotonin, norepinephrine, or dopamine [3]. Personality traits such as low self-esteem, a family history of depression, childhood depression, or traumatic life events such as sexual or emotional abuse have also been associated with an increased risk for depression. In addition, individuals ages 18-25 years old, those who identify as two or more races, and women are more prone to depression [4]. Several forces interact to cause depression including faulty mood regulation by the brain, genetic vulnerability, and stimuli from traumatic events [5]. As the global coronavirus pandemic took place, depression cases in adults jumped from 8.5% before the pandemic to a staggering 27.8%. Research from the Boston University School of Public Health reveals that elevated depression rates have persisted into 2021, climbing to 32.8%, thus affecting one in three adults [6]. Depression typically occurs in multiple episodes, with signs and symptoms reoccurring often. Some of these symptoms include feelings of sadness and emptiness, frustration, sleep insomnia, lack of energy, reduced appetite and weight loss, anxiety, slow thinking, trouble concentrating, unexplained physical issues, and suicidal thoughts and actions [7]. Three of the more common methods used in depression treatment include cognitive behavioral therapy, which is a psychosocial intervention, interpersonal therapy, a form of therapy to improve interpersonal functioning, and psychodynamic therapy, an approach to facilitate a deeper understanding of one's emotions [8].

The Patient Health Questionnaire-9 (PHQ-9) is a self-administered questionnaire designed to screen, diagnose, and monitor the severity of depression. This assessment was derived from the original PHQ which aimed to address multiple health concerns including depression, panic, anxiety, etc. The PHQ-9 was developed by Spitzer, Williams, and Kroenke under a grant from Pfizer. This self-administered nine-question questionnaire assesses each criterion of depression in the Diagnostic and Statistical Manual of Mental Disorders (DSM) and is commonly administered at therapists’ or doctors’ offices to monitor and evaluates a patient’s mental health [9].

The objectives of this study were: 1) estimate the impact and severity of both diagnosed and undiagnosed depression in the general US population; 2) explore the demographics of depression based on its common symptoms; 3) interpret PHQ-9 scores to improve accuracy in identifying individuals with depression.

### Materials & Methods

#### Design

A cross-sectional study was conducted in July of 2022. Data were collected through an anonymous questionnaire using an online survey platform. A convenience sample of 200 respondents included all adults in the general US population regardless of age, sex, race, or ethnicity. This study was given an exempt determination by our institutional review board (2022-578).

#### Data collection

The survey consisted of three parts: First, it inquired about participants' demographics including their age, gender, level of education, and income. Then the PHQ-9 assessment with a few follow-up questions regarding their diagnosis of Depression. For each of the nine questions on the Patient Health Questionnaire, the respondent was asked: “Over the last 2 weeks, how often have you been bothered by the following problems?” Each question had only four choices including “Not at all” (0 points), “Several days” (1 point), “More than half the days” (2 points), or “Nearly every day” (3 points). The scores from all nine questions were added together to compute a total score. The interpretation of the depression severity is as follows: 0-4 points indicates none-minimal depression, 5-9 indicates mild depression, 10-14 indicates moderate depression, 15-19 indicates moderate-severe depression and 20-27 indicates severe depression. A few follow-up questions were asked regarding whether the patient had been formally diagnosed with depression, thought of seeing a mental health professional, what prevents them from seeing a mental health professional, and a final open-response question allowing them to express any concerns about their depression that hadn’t previously been expressed.

#### Statistical analysis

Statistical analysis was performed using JMP version 16 (SAS Institute Inc., Cary, NC, USA). Parametric tests were used for normally distributed variables and non-parametric tests were used for skewed data. Chi-square testing was performed to assess correlation between a high PHQ-9 score and having a formal diagnosis of depression. A p-value of <0.05 was considered statistically significant.

### Conclusions

Our data suggests depression is ongoing, and under-diagnosed. Increasing access to affordable care may be beneficial in diagnosis, treatment, and prevention. Overall, depression continues to be an ongoing problem in America and across the globe, and healthcare access and innovative solutions are imperative for improving our nation’s mental health and quality of life.

### References

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2. Pathophysiology. Major Depression Case Study. (2018). Accessed: July 11, 2022: https://u.osu.edu/majordepressioncasestudy2018/pathophysiology.
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4. Depression. (2022). Accessed: July 11, 2022: https://www.nimh.nih.gov/health/topics/depression.
5. What causes depression?. (2022). Accessed: July 11, 2022: https://www.health.harvard.edu/mind-and-mood/what-causes-depression.
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9. Patient Health Questionnaire. (2020). Accessed: July 11, 2022: http://www.apa.org/pi/about/publications/caregivers/practice-settings/assessment/tools/patient-health.
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Original article
peer-reviewed

### Author Information

###### Ethics Statement and Conflict of Interest Disclosures

Human subjects: Consent was obtained or waived by all participants in this study. HCA Centralized Algorithms for Research Rules on IRB Exemptions (CARRIE)/ IRB issued approval 2022-578. Based on the information provided and attested as true, the research plan described does not require IRB oversight. This is because the investigators are either a) not engaging in research with human subjects as defined by federal regulations; b) engaging in research with human subjects deemed excluded from IRB oversight per 45CFR46.102(l) OR c) engaging in research with sufficient human subject protections in the design to meet one or more IRB exemption criteria set forth in 45CFR46.104. Animal subjects: All authors have confirmed that this study did not involve animal subjects or tissue. Conflicts of interest: In compliance with the ICMJE uniform disclosure form, all authors declare the following: Payment/services info: All authors have declared that no financial support was received from any organization for the submitted work. Financial relationships: All authors have declared that they have no financial relationships at present or within the previous three years with any organizations that might have an interest in the submitted work. Other relationships: All authors have declared that there are no other relationships or activities that could appear to have influenced the submitted work.

###### Acknowledgements

This research was supported (in whole or in part) by HCA Healthcare and/or an HCA Healthcare affiliated entity. The views expressed in this publication represent those of the author(s) and do not necessarily represent the official views of HCA Healthcare or any of its affiliated entities.

Original article
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