The COVID-19 pandemic was a crisis that affected everyone of all ages and health statuses. The many uncertainties created by the pandemic, such as fear of infection, isolation from work and family, and the disruption of daily routines, contributed to widespread complaints of insomnia.

A recent meta-analysis of almost 200,000 people affected by COVID-19 found that insomnia was reported more often than depression, anxiety, and psychological distress. COVID-19 worsened the symptoms of those already suffering from insomnia and caused insomnia in people who were normal sleepers before COVID-19. Indeed, insomnia increased by 33 percent among those who were good sleepers before COVID-19. Sleep quality during the COVID-19 did not get worse for everyone. Some people with pre-COVID insomnia experienced an improvement in sleep quality, while most pre-COVID good sleepers experienced worse sleep during and after COVID-19.

A recent large study determined that normal sleepers were at risk of worsening insomnia after the COVID-19 outbreak. Furthermore, having depressive symptoms before the pandemic strongly predicted the increased risk of insomnia. Specifically, pre-COVID suicidal ideation was one of the most predictive variables for insomnia. This finding should not be surprising; depression has long been recognized as a major risk factor for sleep disorders; the pandemic simply made this worse for these individuals. Insomnia during the COVID-19 pandemic was associated with depression-related symptoms, such as worry, negative affect, loneliness, and social dysfunction. In addition, females had a higher risk of developing insomnia during and after having COVID-19 and also reported a significantly higher incidence of brain fog after COVID-19.

Brain Region Connectivity

A detailed functional magnetic resonance imaging (MRI) study identified COVID-19-induced changes in how specific cortical regions communicate with each other. The study found an association between pre-COVID depression and post-pandemic insomnia that involved the left precentral gyrus, right middle temporal gyrus, and right inferior temporal gyrus.

Alterations in the connectivity of these brain regions imply deficits of basic sensory integration and motor control functions. Previous structural and functional MRI studies of depressed patients have found abnormalities in these same brain regions. Structural and functional abnormalities in these brain regions have also been discovered in the brains of insomniacs. Why is there such an overlap in areas affected? It’s thought that the brain regions normally involved in producing depression are particularly vulnerable to the inflammation induced by the virus that causes COVID-19. Long-term brain inflammation plays a critical role in the development of depression.

Information Processing

Additional studies have also suggested that abnormalities in information processing in these brain regions are prevalent in people suffering with both depression and insomnia. These brain regions also receive signals from the neurotransmitters serotonin and norepinephrine that may contribute to depression and insomnia. Both neurotransmitters are common targets of widely used antidepressants and treatments for insomnia. Serotonin controls sensory processing and integration and regulates the transition between sleep stages. Norepinephrine controls arousal; its dysregulation is associated with insomnia.

How did COVID-19 cause these changes? The virus that causes COVID-19—indeed all viruses—has the same goals as humans: survive and procreate. It does not intend to cause pathology in its host. The neurological manifestations in COVID-19 are similar to, although more extreme than, those produced by an influenza infection and include an aberrant interferon response, cytokine storm, lymphopenia, and hypercoagulation (due to the effects of the virus on the endothelium). These are all responses by the brain’s immune system due to the presence of the virus. Consequently, the brain changes its chemistry and how some brain regions communicate with others, all leading to “brain fog,” delirium, cognitive impairment, and insomnia in about one-third of all COVID-19 patients.