The Fallout of the COVID-19 Pandemic on College Students, Current Psychiatry Reports, 14 March 2025 by articles

The Fallout of the COVID‑19 Pandemic on College Students

Brunhild Kring1 · Ludmila de Faria2 · Alexandra Ackerman3 · Meera Menon4 · Francesco Peluso5 · with the Group for the Advancement of Psychiatry, College Student Committee

Accepted: 28 January 2025

Abstract

Purpose of Review We examine the deleterious efects on emotional development and mental health of college students wrought by the COVID-19 pandemic. In the era of climate change, political polarization, and global pandemics, some students are likely exposed to public disasters either on campus or at home at any given time.

Recent Findings The worsening incidence and severity of mental health symptoms foreshadowed a youth mental health crisis of unanticipated proportions.

Summary Post disaster, the treatment of physical illness typically takes precedence to the exclusion of preventive mental health measures. Even though the mental health efects of mass trauma are more pervasive and last longer than physical symptoms, mental health experts did not have a prominent place at the table of the COVID-19 response teams beyond their traditional role in the care of individual students. We conclude with a review of best practices for psychological frst aid, and highlight the need for disaster response training for psychiatrists

Keywords College students · COVID-19 · Disaster psychiatry · Youth mental health crisis · Transitional age youth · Emotional development of young adults

Introduction

The COVID-19 pandemic has been named a massive trauma for our society, but segments of the population have been particularly vulnerable: these were the elderly who bore the highest risk for medical complications, the economically disadvantaged who lost their jobs and the young who missed

out on efective learning and social connection with peers [1].

* Brunhild Kring brunhild.kring@nyu.edu

1 Student Health Center, Counseling and Wellness Services, Department of Psychiatry, New York University Grossman School of Medicine, New York, NY, USA

2 Director of Residency Training, Department of Psychiatry, University of Florida, Gainesville, FL, USA

3 Private Practice, Department of Psychiatry, New York University Grossman School of Medicine, New York, NY, USA

4 Department of Psychiatry and Behavioral Health, The Ohio State University Medical Center, Columbus, OH, USA

5 Yale Health, Yale University School of Medicine, New Haven, CT, USA

Multiple studies emphasize that the unimaginable loss of life for families, economic devastation of communities, uncertainty about the future and the repeated unpredictable virus surges took an especially heavy emotional toll on the young [2]. Such highly stressful experiences can shatter previously held fundamental benign assumptions about oneself, the world, one’s place in it and one’s hope for the future [3]. Furthermore, the multiple interrelated social, economic, biological and medical factors that are referred to as syndemic interacted and amplifed each other, resulting in increased rates of depression, anxiety, loneliness, substance abuse and suicidality [4, 5].

The United States Surgeon General issued several advisories analyzing the relevant public health threats exacerbated by the pandemic and articulated urgent calls to action [6–8]. He takes a broad biopsychosocial point of view and maps out strategic interventions that young people, families, schools, health care organizations, technology companies, media and government can implement. He further emphasizes that there was an existing youth mental health crisis prior to the advent of the COVID-19 pandemic. For college mental health professionals,

this acknowledgement resonates with our frst-hand experience with the student population and their expanding need for mental health services.

As early as 2017, Twenge presciently described the complex efects that the smartphone had on the emotional wellbeing of teenagers: they were feeling left out, lonely, anhedonic, and sleep deprived [9]. Cyberbullying, a pernicious outgrowth of social media use, was particularly frightening to vulnerable teens. Some of the victims became desperate, questioned the meaning of life, and engaged in suicidal behavior.

In 2024, Jonathan Haidt, a social psychologist, examined the socially corrosive efect of social media on the lives of children and adolescents. In his book, The Anxious Generation, he describes the surge of psychiatric symptoms particularly among members of Generation Z, born between 1997 and 2012 [10]. His analysis prompted him to recommend rather radical interventions: children should not be given smartphones before high school, avoid social media before age 16, attend phone-free schools and sleep in phone-free bedrooms and be allowed to have a play-based rather than phone-based childhood for the beneft of their emotional and social development.

The COVID-19 pandemic resulted in a public mental health emergency among young people, compounded by the increased awareness and visibility of social injustice for people of color, the xenophobic attacks on Asian and Asian American and Pacifc Islander communities, and the looming climate crisis. Many of the key indicators of mental health distress worsened. Some young people who felt compelled to take to the streets distrusted the commitment of their elders to efectively address social inequality and the degradation of the planet wrought by climate change [11, 12].

The disruptive efects wrought by the COVID-19 pandemic in the lives of college students included repeated displacements from campus, isolation from peers, and adjustment to unpredictable learning environments. Even though some students may have benefted from returning to live with their families, there is concern about the potential long-term pandemic consequences for the psychological and educational independence of students.

For years to come colleges will need to support varied developmental trajectories as students move into adulthood. Public health disasters have predictable traumatic efects and likewise, this pandemic will have repercussions not yet seen on students’ ability to mature [13, 14].

Student Emotional Development

Traditional college students often attend school at a fair distance from their families and encounter peers from diferent social backgrounds and cultures. Academic studies and

extracurricular activities expand their educational and interpersonal experience. Hill and Redding’s conceptual model for identity exploration lists these steps for emotional and identity development: deconstructing and letting go of old beliefs and goals and expanding the landscape of possibilities in the context of tolerating angst and discomfort while teetering in the unknown [15]. The college campus inspires students to question long-held beliefs and integrate their new experiences into their emerging selves. However, the campus community was not available as a place to hold the tenuous new selves of this student cohort.

Identity development has been described as a helix of “lifelong tensions between the yearnings for inclusion and distinctness”, a continual process of diferentiation from their parents and simultaneous integration with peer groups [16]. The COVID-19 pandemic disrupted the late-adolescent transition from high school to college. Instead of diferentiating from their parents and actively forging a new sense of self in the stimulating environment of college classrooms and dorms, students were relegated to their adolescent bedrooms. This potentially regressive environment resulted in missed opportunities for exploration and practice.

Intersection Between Brain Development and Psychological Development

To understand what impact the COVID-19 pandemic has had on the emotional development of college students, one must also consider the intersection between the cognitive development of transitional youth and the psychological pressures of the transition to adulthood.

Brain maturation progresses through 25 years of age. It results in inferior and posterior brain regions maturing before superior and anterior ones [17]. This research shows that the transitional age brain is characterized by a mismatch between fully matured reward-seeking and fear-sensing subcortical structures like the nucleus accumbens and amygdala, without the tempering input from emotion-regulating and impulse-controlling cortical networks that have yet to fully develop [18].

This mismatch contributes to minds that are especially reactive to intense emotions and that have not yet developed nuance in understanding and responding to the emotional states of others. For example, the transitional age brain is more likely to misinterpret neutral or inquisitive facial expressions as a sign of anger [18]. An underdeveloped prefrontal cortex is not yet optimized to provide the impulse control, refection and planning necessary to inhibit more automatic, afectively charged responses and fnd the most efective strategy to respond to highly stressful experiences.

This uniquely wired brain may serve to bolster the college student through the challenging developmental task of

distancing themselves from parental infuence and authority to create their own independent identity. While this distancing promotes growth, a sense of loss or aimlessness that may be outside of conscious awareness accompanies the reorganization of internal object relations.

This time of great neurological and psychological malleability poses opportunities that the college environment has historically aimed to enrich by allowing students to experiment with a wide array of new identities, perspectives and relationships. In fact, evidence suggests that the transitional age brain experiences signifcant epigenetic and synaptic shifts that contribute to considerable plasticity, likely to allow new psychological organizations to replace those of childhood [18]. Unfortunately, this malleability also presents vulnerabilities as evidenced by the increased incidence of psychopathology and high-risk activities during this developmental period. The college setting can provide ego-lending support, for example in the form of advisory relationships with coaches and professors or a sense of belonging and efcacy in student clubs and teams.

The measures that were required to keep the pandemic in check have disrupted the ways that colleges have historically supported the psychological development of students. The social isolation and sense of languishing caused by the pandemic is particularly poignant for college students. Their developmental vulnerabilities and the traumas of the pandemic complement each other in ways that may lead to worrisome results without more creative ways to foster adaptation in the setting of global uncertainty.

The New College Experience

According to a blog published online by the Center for Collegiate Mental Health, 94% of over 43,000 surveyed students reported that at least one aspect of life was negatively afected by COVID-19 [19]. However, only about one third (33%) indicated that their reasons for seeking mental health services were related to the COVID-19 pandemic. This discrepancy suggests the difculties students may have had connecting the challenges they were experiencing, such as mental health (72%), motivation or focus (68%), loneliness or isolation (67%), academics (66%), and missed experiences or opportunities (60%), to the pandemic. Black, Indigenous, and people of color or BIPOC students, already less likely to use counseling services, felt an additional burden to contextualize their social, economic, and cultural problems to their white therapists [20].

The availability of psychiatric resources on and of campus had already been outpaced by the escalating mental health needs of students for years prior to the pandemic. In a 10-year period, the percentage of students with a lifetime mental health diagnosis increased from 22% in 2007 to 36% in 2016–2017

[21]. In the 2020 Healthy Minds Study data, 37% of all university students screened positive for depression, 39% screened positive for anxiety disorder, 11% screened positive for eating disorders, 23% endorsed non-suicidal self-injurious behavior, and 13% reported suicidal ideation [22].

Perhaps more concerning than the growing incidence of mental health problems among this population is their increasing severity. The percentage of students prescribed more than one mental health medication increased from 28.2% in 2007 to 40% in 2018–2019 [23]. Despite this, 31.6% of colleges and universities have zero psychiatry hours available on campus [24]. During the 2018–2019 academic year, a primary care provider prescribed 58.8% of psychiatric medications and 36.1% were prescribed by a psychiatrist [23].

Additional troubling themes for students entering college during COVID-19 included lack of social connections and the challenges of managing schoolwork while maintaining focus and fnding a rhythm or groove. Online classes were less engaging and interfered with participation. Students also worried about missing internship opportunities, networking in extracurricular activities and meeting mentors for career development. These reported impacts on student experience may continue to infuence students’ abilities to adjust to the academic and social challenges of college life.

A recent article showed that students just wanted “normal” circumstances to return, e.g. having a social life, going to large gatherings, joining with fans at sporting events, traveling, and making new friends [25]. They were looking forward to simply interacting with others in-person instead of electronically. As one student put it: “it is about experiencing college for what it should be, not the simulated version that they are selling me.”

The new reality during the pandemic afected students' decision to either enroll or withdraw from academic and extracurricular activities [26]. The process of college admissions was profoundly reshaped [25]. Even though the process can be stressful, there are many enjoyable aspects. Unfortunately, pandemic-related restrictions upended inperson visits on campus. Applicants had to decide whether a college was a good ft for them via online information only, and many students chose to enroll. Nevertheless, a subset of students, especially minoritized or low-resourced students, preferred to attend college near home or postpone enrollment altogether, marking a shift in attendance patterns compared to pre-COVID.

Response by Institutions of Higher Education in the Aftermath

The COVID-19 pandemic has stymied the emotional development and maturation of college-age students. It is the responsibility of the greater university community to

implement systemic change to help students get back on track. In preparation for likely future virus surges, staf need to apply the lessons learned and stay nimble in response to medical public health advisories. If another respiratory viral pandemic were to arise in the near future, would college psychiatrists be any better prepared to move beyond their traditional frame of crisis assistance and psychiatric care to individual students? Have we engaged in any tabletop exercises to acquire a frm grasp of the principles of disaster response?

The Center for the Study of Traumatic Stress, on its website (https://www.cstsonline.org/fact-sheet-menu/fact-sheetsearch), has formulated best practices for psychological frst aid for mental health practitioners who are responding to disasters. The principles of disaster management are summarized in brief actionable fact sheets, sometimes in bullet point format, that staf can review on short notice. Helpful references to more resources pave the way for efective intervention. A smart response to an unforeseen public health emergency should include the following: advance planning and preparation, thoughtful communication with the afected student population during the crisis, attention to the wellbeing of the clinical staf to maintain morale in order to avoid overwhelming clinicians and prevent burn out, identifcation of vulnerable subpopulations on campus, as well as support of the emotional well-being of students who do not have any preexisting psychiatric conditions.

To date, the psychological needs of college students have not abated. The adverse mental health consequences of social distancing and quarantining resulted in the isolation of young adults, drove them to neglect in-person interactions with family, peers and mentors, dramatically increased screen time and reliance on computer-mediated communication, which impeded individuation, and identity formation.

A crucial frst step during a disaster is to identify vulnerable subpopulations on campus, because sociopolitical factors infuence the mental health and development of the college student population. International students, students of color, and students who identify as members of the LGBTQ community experienced an increase in violent incidents [27]. Rather than allowing prejudicial rifts to grow between communities of students, intentional programming and outreach to connect students in ways that promote mutual acceptance and facilitate access to mental health services should be implemented. Outreach eforts facilitate help-seeking behaviors in marginalized populations [28]. To meet this demand, the workforce of culturally competent college mental health clinicians must be expanded. Students without stable family support or limited fnances faced the threat of losing their housing with campus shutdowns. The U.S. Surgeon General’s Advisory on Protecting Youth Mental Health emphasized that adverse childhood experiences (ACEs), fnancial and housing instability and food shortages put children and

transitional age youth at risk for developing mental health symptoms (The US Surgeon General's Advisory). For many students, the availability of emergency funds through the Coronavirus Aid, Relief, and Economic Security Act, 2020 or CARES Act and other grants such as the Higher Education Emergency Relief Fund made it easier to aford food, shelter, medications, and healthcare [29, 30].

The availability of such grants continues to be benefcial even as students and their families gradually recover from COVID-19’s massive initial fnancial impact. Growing student loan debt adversely afects retention rates. Students chose not to return to college to prevent adding to their already insurmountable debts as COVID-19 prevented a normal college experience. As a way to improve retention and increase graduation rates among highly educated individuals, several universities are now ofering tuition free education based on family income.

Calls for expansion of mental health services on campus persist. Especially during mass disasters, the provision of resources is rarely adequate for the true needs of the afected population. At times, health experts need to develop creative solutions, engage in out-of-the box thinking, foster self-efcacy so students can learn what they can do to help themselves. From a therapeutic standpoint, students respond well to modalities that improve distress tolerance, such as interventions informed by principles of dialectical behavioral therapy. Group therapy and drop-in-workshops can extend the reach of an understafed workforce and decrease the stigma of accessing services through supportive peer interactions.

During the pandemic, mental health services had to quickly morph to a tele-mental health model made possible by loosening government licensure restrictions [31]. For some students, the switch to tele-mental health added fexibility and convenient access. For others who were technologically disadvantaged and lacked private physical space, this novel modality presented its own challenges. Nonetheless, one should not underestimate the invaluable beneft for students who avoided a hiatus of treatment because college psychiatrists and other mental health clinicians were granted permission to provide crucial mental health treatment across state lines.

While the expansion of mental health services on and of campus is essential, expecting institutions of higher education to carry this challenge alone may be logistically untenable and further infate tuition. Conrad and Riba therefore propose the creation of specialized clinics within academic medical centers to respond to rising student needs and simultaneously provide training for mental health clinicians to care for this population [32].

The trauma of the pandemic did not spare staf or faculty. Many felt overwhelmed by the task of balancing home and work obligations. They lived in fear of contracting or

transmitting the virus, and many lost loved ones. Young adults rely on the ability of their teachers and mentors and health staf to attune to their needs and provide a stable and predictable campus environment in which to grow. Therefore, tending to the emotional and mental well-being of those tasked with cultivating the minds of students should be a priority.

Conclusion

As the acute stress of the COVID-19 pandemic has transitioned to a long post-traumatic phase, we must address the evolving needs of adolescents and young adults as they contend with the fallout from this developmental insult. The factors that allowed certain students to thrive during the pandemic should be carefully examined to aid in implementing strategies to foster population-wide post-traumatic growth. This endeavor will require stakeholders in government, higher education, and mental health to combine their collective strengths and devise creative solutions as challenges emerge. A postvention guide after a public disaster afecting campus communities similar to the existing manuals of the Higher Education Mental Health Alliance (HEMHA, https://hemha.org/) would be a helpful document to improve preparedness for college psychiatry.

Key References

• Haidt J. The Anxious Generation: How the Great Rewiring of Childhood Is Causing an Epidemic of Mental Illness. Penguin Press; 2024

○ This is a data-driven book by a social psychologist who analyzes the youth mental health crisis preceding the COVID-19 pandemic. The college students belonging to GenZ, born 1997 and thereafter, were ill-prepared for the social isolation wrought by mandatory online learning approaches during the pandemic.

• Ofce of the Surgeon General. Social Media and Youth Mental Health. 2023. Available from: https://www.hhs. gov/surgeongeneral/priorities/youth-mental-health/ social-media/index.html

○ In this advisory, the Surgeon General delineates the harmful efects of social media use on the mental health of children and adolescents. He outlines an urgent call to action for policy makers, technology companies, families and young adults themselves to protect youth mental health.

Author Contribution BK, LD, AA, MM, and FP all made substantial contributions to this paper in drafting the outline, performing the literature review, authoring the text, and providing edits.

Data Availability No datasets were generated or analysed during the current study.

Declarations

Conflict of Interest The authors declare no competing interests.

Human and Animal Rights and Informed Consent This article does not contain any studies with human or animal subjects performed by any of the authors.

References

1. Bridgland VME, Moeck EK, Green DM, Swain TL, Nayda DM, Matson LA, et al. Why the COVID-19 pandemic is a traumatic stressor. PLoS One. 2021;16(1):e0240146. https://doi.org/10. 1371/journal.pone.0240146

2. Czeisler MÉ, Lane RI, Petrosky E, Wiley JF, Christensen A, Njai R, et al. Mental health, substance use, and suicidal ideation during the COVID-19 pandemic—United States, June 24–30, 2020. MMWR Morb Mortal Wkly Rep. 2020;69(32):1049–57. https:// doi.org/10.15585/mmwr.mm6932a1

3. Park CL. Trauma and meaning making: Converging conceptualizations and emerging evidence. In: Hicks JA, Routledge C, editors. The experience of meaning in life: Classical perspectives, emerging themes, and controversies. Springer Netherlands; 2013. p. 61–76. https://doi.org/10.1007/978-94-007-6527-6_5

4. Haseltine WA. The covid syndemic: the mental health crisis of mental health workers. Forbes. 2021 Mar 9. https://www.forbes. com/sites/williamhaseltine/2021/03/09/the-covid-syndemic-themental-health-crisis-of-mental-health-workers. Accessed 14 Apr 2021.

5. Mendenhall E. The COVID-19 syndemic is not global: Context matters. Lancet. 2020;396(10264):1731. https://doi.org/10.1016/ S0140-6736(20)32218-2

6. Ofce of the surgeon general. Protecting youth mental health. 2021. Published December 6, 2021. https://www.hhs.gov/surge ongeneral/priorities/youth-mental-health/index.html. Accessed 8 Apr 2022.

7. Ofce of the surgeon general. Social media and youth mental health. 2023. Published May 23, 2023. https://www.hhs.gov/surge ongen eral/ prior ities/ youth- mental- health/ social- media/ index. html. Accessed 10 Nov 2023.

8. Office of the surgeon general. Firearm violence in America. 2024. Published June 25, 2024. Available from: https://www. hhs. gov/ surge ongen eral/ prior ities/ firea rm- viole nce/ index. html. Accessed 15 Nov 2024.

9. Twenge JM. iGen: Why Today’s Super-Connected Kids Are Growing Up Less Rebellious, More Tolerant, Less Happy—and Completely Unprepared for Adulthood. Atria Books; 2017.

10. Haidt J. The Anxious Generation: How the Great Rewiring of Childhood Is Causing an Epidemic of Mental Illness. Penguin Press; 2024.

11. Meyer R. Why greta makes adults uncomfortable. The Atlantic. 2019 Sep 23. https://www.theatlantic.com/science/archive/2019/ 09/why-greta-wins/598612. Accessed 16 Apr 2021.

12. US EPA. Recommendations from youth perspectives on climate change. 2018. Published July 12, 2018. https://www.epa.gov/envir onmentaljustice/recommendations-youth-perspectives-climatechange. Accessed 16 Apr 2021.

13. Messias E. The Phases of a Disaster: Are We Headed Towards Disillusionment? The Doctor Weighs In. 2020 Jun 15. https:// thedo ctorweighs in. com/ phases- of- disas ter. Accessed 12 Nov 2021.

14. Myers D, Wee D. Disaster Mental Health Services: A Primer for Practitioners. Routledge; 2004. https://doi.org/10.4324/97802 03646908

15. Hill NE, Redding A. The End of Adolescence: The Lost Art of Delaying Adulthood. Harvard University Press; 2021.

16. Kegan R. The Evolving Self: Problem and Process in Human Development. Harvard University Press; 1982.

17. Sowell ER, Thompson PM, Holmes CJ, Jernigan TL, Toga AW. In vivo evidence for post-adolescent brain maturation in frontal and striatal regions. Nat Neurosci. 1999;2(10):859–61. https://doi. org/10.1038/13154

18. Chung WW, Hudziak JJ. The transitional age brain:“the best of times and the worst of times. Child Adolesc Psychiatr Clin N Am. 2017;26(2):157–75. https://doi.org/10.1016/j.chc.2016.12.017

19. Center for Collegiate Mental Health (CCMH). Part 1 of 5: COVID-19 Impact on college student mental health, 2021. Published February 2, 2021. https://ccmh.psu.edu/index.php?option= com_dailyplanetblog&view=entry&year=2021&month=02& day=01&id=9:part-1-of-5-covid-19-s-impact-on-college-stude nt-mental-health. Accessed 18 Nov 2022.

20. Brown S. Students of color are not ok. Here’s how colleges can support them. The Chronicle of Higher Education. 2020. Published July 6, 2020. https:// www. chron icle. com/ artic le/ students-of-color-are-not-ok-heres-how-colleges-can-supportthem. Accessed 15 Nov 2022.

21. Lipson SK, Lattie EG, Eisenberg D. Increased Rates of Mental Health Service Utilization by U.S. College Students: 10-Year Population-Level Trends (2007–2017). Psychiatr Serv. 2019;70(1):60–3. https://doi.org/10.1176/appi.ps.201800332.

22. Healthy Minds Study (HMS). HMS-Fall-2020-NationalData-Report. The Healthy Mind Network; 2021. Published in 2021. https://healthymindsnetwork.org/wp-content/uploads/2021/ 02/HMS-Fall-2020-National-Data-Report.pdf. Accessed 15 Nov 2022.

23. Morris MR, Hoefich CC, Nutley S, Ellingrod VL, Riba MB, Striley CW. Use of psychiatric medication by college students: A decade of data. Pharmacotherapy. 2021;41(4):350–8. https://doi. org/10.1002/phar.2513

24. Association for University and College Counseling Centers Directors. 2020–21 Annual survey report public survey. Association for University College Counseling Centers Directors; 2021. Published 2021. https://www.aucccd.org/assets/2020-21%20Annual%20Sur vey%20Report%20Public%20Survey.pdf. Accessed 15 Apr 2022.

25. Musico M. How has COVID-19 changed the college experience? CollegeData. 2021. Published March 26, 2021. Available from: https://www.collegedata.com/resources/covid-19/how-has-covid19-changed-the-college-experience. Accessed 15 Apr 2023.

26. National Center for Education Statistics (NCES). U.S. Education in the Time of COVID. 2022. Published August 2022. https:// nces.ed.gov/surveys/annualreports/topical-studies/covid/?educa tionType=postsecondary-education. Accessed 15 Nov 2023.

27. Flores AR, Langton L, Meyer IH, Romero AP. Victimization rates and traits of sexual and gender minorities in the United States: Results from the National Crime Victimization Survey, 2017. Sci Adv. 2020;6(40):eaba6910. https://doi.org/10.1126/sciadv.aba69 10

28. Broglia E, Millings A, Barkham M. Student mental health profles and barriers to help seeking: When and why students seek help for a mental health concern. Couns Psychother Res. 2021;21(4):816–26. https://doi.org/10.1002/capr.12462

29. US Department of the Treasury. About the CARES Act and the consolidated appropriations act. 2020. Published March 27, 2020. https://home.treasury.gov/policy-issues/coronavirus/aboutthe-cares-act. Accessed 15 Apr 2023.

30. US Department of Education. Higher Education Emergency Relief Fund (HEERF). 2022. Published April 1, 2024. https://www2.ed. gov/programs/heerf/index.html. Accessed 15 Apr 2024.

31. De Faria L, Kring B, Keable H, Menon M, Peluso F, Notman M. Tele-psychiatry for college students: challenges, opportunities, and lessons learned from the pandemic. J Med Regul 109(2):21–8 https://doi.org/10.30770/2572-1852-109.2.21

32. Conrad RC, Riba M. Current opportunities within college mental health. Acad Psychiatry. 2021;45(5):549–51. https://doi.org/10. 1007/s40596-021-01520-0

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