Will COVID-19 Result in More ADHD Cases?

Jennifer Lubell

May 13, 2021

Editor's note: Find the latest COVID-19 news and guidance in Medscape's Coronavirus Resource Center.

Dr Luis Rohde

While it's possible that residual effects of SARS-CoV-2 could lead to an eruption of attention-deficit/hyperactivity disorder (ADHD) cases, a debate at the World Congress on ADHD – Virtual Event underscored the fact that this is still a hypothesis. The bottom line is there needs to be more data, said Luis Augusto Rohde, MD, PhD, cochair of the congress' scientific program committee and moderator of the session, "Residual effects of the 2019 pandemic will mirror the 1918 pandemic: Will we have lots of new ADHD cases?"

Considering the current pattern of the pandemic, there is not enough evidence for this to be a concern, Rohde said in an interview.

James Swanson, PhD, professor of pediatrics at the University of California, Irvine, opined that biological co-effects of COVID-19 are likely to have selective effects in children that may produce symptoms representative of ADHD. Using the 1918 Spanish flu pandemic as a historical reference, he estimated that COVID-19 would produce 5 million individuals with new-onset symptoms related to ADHD. "If these cases meet DSM-5 or ICD-11 criteria, there will be lots of new ADHD cases," he predicted.

David Coghill, MD, a professor of child adolescent mental health at the University of Melbourne, observed that the sums Swanson presented "are based on maxing out the potential rather than looking at the sums more realistically."

Could the 1918 Pandemic Offer Clues?

In a commentary, Swanson and Nora D. Volkow, MD, wrote about "lessons learned" from the 1918 pandemic, and how residual sequelae in that era led to a condition labeled hyperkinetic syndrome in children. "It may be worthwhile to consider the hypothesis that the COVID-19 pandemic may result in a novel etiologic subtype of ADHD that clinicians may recognize in patients in the future," wrote the commentators.

In survivors of the 1918 pandemic, brain inflammation or encephalitis sometimes emerged as residual sequelae, said Swanson. In some adult cases, these symptoms were diagnosed as "encephalitis lethargica" (EL) and were associated with Parkinson's disease. In 1930, based on patients evaluated after 1918, researchers Franz Kramer and Hans Pollnow at Charité Hospital in Berlin described the behavioral manifestation of EL in children as hyperkinetic syndrome, a condition that was characterized by symptoms similar to the properties of ADHD: lack of concentration, insufficient goal orientation, and increased distractibility. "They even reported on autopsy cases that described brain regions that we now know are associated with ADHD from decades of brain imaging studies," said Swanson.

COVID-19 rarely results in severe respiratory problems in children but the absolute number requiring hospitalization has accumulated and is now relatively large, said Swanson. One study of 1,695 severe COVID-19 cases in children and adolescents used MRI and detected neural effects in specific brain regions such as basal ganglia and frontal lobes that previous research had associated with ADHD. Approximately 22% of these rare but severe cases had documented neurologic involvement, and studies of affected children with mild or none of the initial respiratory symptoms of COVID-19 also detected similar selective effects in these brain regions.

A recent survey of medical records of 80 million people that identified 240,000 COVID cases (mostly adults) revealed that a third had neurological and psychiatric sequelae. Swanson also mentioned an article he wrote more than a decade ago on environmental as well as genetic factors that resulted in etiologic subtypes of ADHD, which provided a model for the impact of COVID-19 on specific brain regions that are associated with ADHD.

So far, the COVID-19 pandemic has produced 150 million cases worldwide and there are about 100 million survivors, setting an estimate of a maximum number of cases with residual sequelae. "I think that severe COVID-19 will probably be related to severe residual sequelae, and that mild or asymptomatic COVID-19 may be associated with less severe residual sequelae, which may resemble ADHD" said Swanson. If one-third of the cases manifest in some neurologic or psychiatric systems, this means 27 million would have residual sequelae. If 20% have impaired concentration or brain fog, this could result in about 5 million ADHD cases, he said.

Estimates Aren't Evidence

The Swanson/Volkow commentary contains a lot of references to "might, could, and may," said Coghill. While it's true that COVID-19 could produce a novel etiologic subtype of ADHD, "the point here is at the moment, all of this is based on hypotheses," he said.

The Spanish flu did produce mental health consequences – survivors reported depression, sleep disturbances, mental distraction, dizziness, and difficulties coping at work. In the United States, flu death rates from 1918 to 1920 were directly attributed to suicide rates. Unfortunately, these impacts weren't widely researched, said Coghill.

It also seems clear that the 1918 Spanish flu outbreak was associated with significant neurological consequences, said Coghill. By 1919 and 1920, physicians and researchers in the United Kingdom were reporting increases in a variety of symptoms among some patients recovering from flu, such as neuropathy, neurasthenia, meningitis, degenerative changes in nerve cells, and a decline in visual acuity.

The EL cases Swanson mentioned did coincide with and reach epidemic proportions alongside the Spanish flu. "But still, a causal relationship is far from proven," said Coghill.

Sol Levy, MD, described a "disease of criminals" following the 1918 pandemic, in which patients exhibited a high degree of general hyperkinesis, a difficulty in maintaining quiet attitudes, abruptness and clumsiness, and "explosive motor release of all voluntarily inhibited activities."

However, these impairments suggest a much broader presentation typically seen in ADHD, noted Coghill.

Neurological complications occur more commonly than initially thought in severe COVID-19, with estimates ranging from 36% to 84%. But in a systematic review of neuropsychiatric complications of severe coronavirus infection, researchers found few psychiatric sequelae of these infections. While they did mention impaired concentration and difficulties with emotional ability, it's very important to remember that these conditions "are cardinal symptoms of a wide range of psychiatric disorders," said Coghill.

Overall, more neurological and neuropsychiatric symptoms largely confine to those with severe COVID-19, meaning they're much less likely to occur in children and young adults, he said.

If there are severe effects of COVID-19, Swanson countered that "they might have more ADHD than the complex residual effects [Coghill] described. I hope that he's right, but I do think there will be biological co-effects of COVID-19 that will produce symptoms that are more ADHD than other neurological disorders."

Epigenetic Effects

Researchers are now seeing transgenerational and intergenerational effects of potential infection. "So I certainly back high-quality studies looking at the effects of maternal and paternal infection on offspring," said Coghill. Establishing clinical cohort studies to follow up on this population would be essential in understanding the risks of SARS-CoV-2. "That might be one way we'll see an increase in ADHD," said Coghill.

The reality is COVID-19 hasn't been around for that long, and current knowledge about it is limited, he said. Rapid publications, cross-sectional or retrospective data, and poor methodological quality and rigor make generalizability difficult. In addition, limited testing and detection probably underestimate prevalence of neurological and neuropsychiatric complications.

"If history teaches us anything, it is that we should always be measured in how we glean lessons from the past. So let's not get ahead of ourselves," he cautioned.

An informal, post-discussion survey of session participants revealed that a slight majority – 55%-60% – expected residual effects of COVID-19 to lead to more ADHD, compared to 40%-45% who didn't think this would happen.

Swanson has two patents: (PIXA4), which uses a "time-of-flight" camera to measure growth on infants, and a provisional patent on the mechanism of tolerance to stimulant medication (PATSMTA). Coghill worked for several pharmaceutical companies but had no disclosures relevant to this debate.

This article originally appeared on MDedge.com, part of the Medscape Professional Network.


Comments on Medscape are moderated and should be professional in tone and on topic. You must declare any conflicts of interest related to your comments and responses. Please see our Commenting Guide for further information. We reserve the right to remove posts at our sole discretion.