The COVID-19 pandemic has had lasting effects, and many individuals are still suffering from post-COVID syndrome (PCS). Patients suffering from PCS can have a wide range of symptoms including fatigue, shortness of breath, heart palpitations, “brain fog”, headache, depression, and/or anxiety. PCS can affect individuals for months or years, and it remains to be seen if some individuals will have life-long effects from COVID-19. Therefore, it is important to understand the underlying pathophysiology of PCS and identify potential therapeutic targets to lessen or resolve the symptoms of PCS.
PCS has marked similarities with chronic fatigue syndrome (listen to the keynote about KP and chronic fatigue syndrome in our latest webinar 5), which drew the attention of Rus and colleagues to look at the hypothalamic-pituitary-adrenal (HPA) axis function and inflammation in PCS patients. Notably, in a previous publication, they determined a similar reduction in the HPA axis function, with reduced glucocorticoid levels in PCS individuals. In this recent publication, they investigate the impact that selective serotonin reuptake inhibitors (SSRIs) have on PCS. This study used self-reported questionnaires from patients diagnosed with PCS before and after SSRI treatment. SSRI treatment decreased PCS symptoms/severity in nearly 64% of the patients. However, the effectiveness of the SSRI treatment fluctuates depending on the symptom, and in this small study they saw the most improvement with brain fog and sensory overload. This study demonstrates that SSRI treatment may improve PCS overall, although this study lacked a control group, so the researchers were unable to rule out a placebo effect.
In our first newsletter (issue 1), we emphasized the dysregulation of tryptophan metabolism in COVID-19 patients and since then many publications have further confirmed KP dysregulation in both those with COVID-19 and PCS. While this study did not specifically look at the kynurenine pathway (KP) metabolite levels, it did highlight the connection between SSRIs, PCS, and the KP. Since both the serotonin and kynurenine pathways stem from tryptophan they can influence each other, suggesting that SSRIs impact the KP in individuals with PCS. Additional research is needed to identify the underlying mechanism of action of SSRIs in individuals with PCS.