Trauma is one of the most common causes of TOS, such as car accidents. In collisions, the body may be suddenly thrown or experience a prolonged crushing sensation or pinning of the shoulder, which can lead to the condition. Repetitive stress is also a primary factor in TOS, for instance, due to work-related tasks such as carrying heavy shoulder loads or participating in sports that require repetitive arm or shoulder movement like baseball, golfing, volleyball, swimming, etc. Other causes include stress or depression, weightlifting, poor posture, sleep disorders, or tumor or large lymph nodes in the upper chest or underarm area.