Panic Disorder or Anxiety-Related Chest Pain: This is the most likely diagnosis given the direct correlation between anxiety and the onset of chest pain. Anxiety can cause significant physiological symptoms, including chest pain and discomfort, often due to hyperventilation or increased muscle tension.

Gastroesophageal Reflux Disease (GERD): GERD can cause chest pain that radiates to the back, and anxiety can exacerbate symptoms of GERD, creating a vicious cycle.
Musculoskeletal Pain: Tension in the chest and back muscles, which can be exacerbated by anxiety, leading to pain.
Costochondritis: Inflammation of the cartilage that connects the ribs to the breastbone, which can cause sharp pains in the chest that may radiate to the back and can be worsened by anxiety-induced muscle tension.

Myocardial Infarction (Heart Attack): Although less likely in younger individuals without risk factors, it's crucial to rule out a heart attack, as it is life-threatening. Anxiety can sometimes be a symptom of a heart attack.
Pulmonary Embolism: A blood clot in the lungs can cause sudden, severe chest pain that radiates to the back and can be associated with anxiety due to the body's stress response.
Aortic Dissection: A tear in the aorta's inner layer can cause severe, tearing chest pain that radiates to the back. It's a medical emergency that requires immediate attention.

Esophageal Spasm: Abnormal muscle contractions of the esophagus can cause chest pain that may radiate to the back, though this is less common.
Pneumothorax: Air in the space between the lungs and chest cavity can cause sudden chest pain that radiates to the back, though typically accompanied by shortness of breath.
Pericarditis: Inflammation of the sac surrounding the heart can cause chest pain that may improve with leaning forward and can radiate to the back, but it's less directly associated with anxiety.