# Immersive Phobia Therapy through Adaptive Virtual Reality and Biofeedback
## 2 Phobia Statistics and Therapy Methods  
Nowadays, 1.1 billion people suffer from various mental health disorders, and although they can be treated or prevented, most people do not have access to effective care [1]. Anxiety disorders, such as fear of public speaking, specific phobias, PTSD, generalized anxiety disorder, and OCD, affect 275 million people and rank sixth in global disability [2]. People suffering from anxiety disorders experience fear and avoidance of objects and situations that pose little or no danger at all. The prevalence per country ranges from 2.5% to 6.5%, higher in the US, Canada, and northern Europe [2]. Mental conditions are more prevalent in women. They are affected especially by depression, anxiety, eating disorders, and bipolar disorders. The social isolation caused by the COVID-19 pandemic, the fear of infection, or the fear of illness or death of a dear one led to an increase of 25% in the incidence of depression and anxiety disorders, especially among young people and women [3]. Moreover, the outbreak of monkeypox in May 2022, declared a Global Public Health Emergency by the World Health Organization, led to an increase in activity on social networks concerning recommendations and measures, as well as sharing information about the disease [4]. The Marburg virus threatened epidemiologists in 2022 due to its high global spread and potential for a new pandemic. In order to prevent this undesirable situation, social media may increase awareness concerning the disease and the associated risks [5].  
Approximately 13% of the global population suffers from various phobias, such as social anxiety disorder and agoraphobia, and specific phobias like fear of heights, flying, spiders, snakes, claustrophobia, etc. [6].  
Social phobias (fear of writing or eating before someone, meeting people of higher authority, using a telephone, or speaking before a large crowd) affect people of all ages, but they usually emerge in adolescence. Later in life, 45% of individuals with social phobias develop agoraphobia and anxiety attacks, while 17% develop depression. The majority of them turn to medication, even substance abuse with illegal drugs (nearly 17%) or alcohol (nearly 19%) [7].  
Approximately 15-20% of the world's population experiences specific phobias at least once in their lifetime [7]. Acrophobia (fear of heights) with an incidence rate of 7.5%, claustrophobia (fear of narrow or enclosed spaces), aerophobia (fear of flying), and ophidiophobia (fear of snakes) are the most prevalent. Specific phobias begin during childhood and can persist during the lifetime. If treated, they have only a 20% recovery rate.  
The most popular methods for treating anxiety disorders include medicines (pills) and cognitive behavioral therapy (CBT) in the presence of a therapist, which enables the patient to see the traumatic experience in a different way, through thought and behavior control [8]. Exposure therapy has response rates of 80-90%. It is classified into in vivo, in sensu (in imagination), and in virtuo exposure. In virtuo exposure, where the therapy is conducted using a computer-generated virtual environment, is preferred by patients as they are aware that they are confronted only with a simulation [9]. Virtual reality exposure therapy (VRET) has a strong real-life impact and good stability of results in time, equal to those obtained in CBT therapies, and there is no difference in the dropout rate between VR and in vivo exposure. However, virtual exposure sometimes induces motion sickness, due to a mismatch of information between the simulated movement of the body and other senses. The first study on the use of VR in acrophobia therapy dates back to the 1990s and belongs to [PERSON] [10].