Smartphones are increasingly integrated into people's daily activities, offering a wide range of mobile applications with different purposes: communication, education, internet browsing, and gaming [1,2]. The number of smartphone users has increased in the last decade in many countries, especially among young adults [3]. In the United States, in 2016, 92% of citizens between 18 and 34 years old reported having at least one smartphone. The number goes even higher in Australia, with 95% of the population owning the device [4].

Smartphone addiction is an emerging phenomenon categorized as a behavioral addiction, such as Internet addiction [5]. People with this problem encounter psychological, social, and health problems, including depression, sleep disorders, and musculoskeletal complaints [6-8].

The repetitive use of smartphones and the repeated movement of the hands in a specific posture proved to be the main factors contributing to musculoskeletal symptoms1. Usually, the typical posture when manipulating smartphones involves holding the tool with one or two hands below eye level, looking at the device with flexion of the neck, and using the thumb to touch the screen, embracing a harmful body posture maintained for long periods [9]. The body parts most commonly affected by pain complaints are fingers, wrists, neck, back, and shoulders [10-12].

Many smartphone users experience pain in the thumb and wrist. However, few researchers have evaluated whether those who develop pain are addicted to smartphones. A single study carried out by Baabdullah and colleagues with medical students in Saudi Arabia found a correlation between smartphone dependence and hand pain, indicating that heavy use of these devices can cause subclinical effects on the human hand [13]. Previous studies have shown that the use of electronic devices that involve frequent movement of the thumb leads to an increased load on the thumb and, therefore, to a greater risk of pain in the hand or wrist [10,11,14].

The smartphone's functions represent a great potential for applications in medical education since they allow the access of doctors and medical students to high-quality information materials to support better therapeutic decision-making13. Medicine is constantly changing: different diseases and treatments are discovered all the time, medical knowledge is getting updated frequently, the current primary research source of new information has become the internet, in which articles, video classes, apps, and websites can be more updated than traditional books. Although its benefits, electronic devices users must be aware of the several physical effects, such as musculoskeletal pain, discomfort, and numbness that they can cause [15].

In Brazil, it is not of our knowledge that studies associate smartphone addiction with wrist pain. The present study aims to determine the prevalence of smartphone addiction among medical students in Brazilian universities and investigate the possible association of this dependence with the occurrence of wrist pain, using a questionnaire with internationally validated scales.