**1. Introduction**

The emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) caused a devastating pandemic. COVID-19, which stands for Coronavirus Disease 2019, is an infectious disease that can affect people of all ages in many ways. Most people infected with SARS-CoV-2 develop mild to moderate disease with viral replication confined mainly to the upper respiratory tract. However, acute respiratory distress syndrome (ARDS) can develop when a virus from the upper respiratory tract spreads to the lungs and produces viral pneumonia and lung damage. When severe, it impairs the body's capacity to maintain vital oxygen levels in the blood, which can result in a number of body system failures and even lead to death [1]. Old age, obesity, and being male are well-established risk factors for severe outcomes of the COVID-19. Various preexisting conditions are also associated with an increased risk. For example, common comorbidities associated with an increased risk of death include hypertension, heart failure, cardiac arrhythmia, diabetes, renal failure, and chronic lung disease [1–3].

The aforementioned infectious disease COVID-19 has rapidly affected mortality worldwide. Globally, till today, there have been 632 million confirmed cases of COVID-19, including 6.5 million deaths, reported to the World Health Organization (WHO) [4].

Although most patients who have COVID-19 recover after two to six weeks, research shows that 10–30% of people who have had COVID-19, even with a mild clinical picture, remain with persistent symptoms that have a devastating effect on their quality of life. These symptoms, which most often include fatigue, shortness of breath, chest pain, headache, and cognitive dysfunction, but also others, which generally have an impact on everyday functioning, are recognized as a clinical condition called post-COVID syndrome (long COVID) [5].

In addition to physical disabilities in people recovering from COVID-19, mental health problems have also been observed, including problems with concentration ("brain fog"), anxiety, depression, sleep disorders, and symptoms of post-traumatic stress disorder (PTSD) [6].

In this chapter, we provide a comprehensive review of the current scientific findings identifying post-COVID conditions and the relationship with mental health status.
