Nexus Letters

What is a Nexus Letter?

A Nexus letter is a document that establishes a connection between a veteran's current medical condition and their service-connected condition or military service, often provided by a qualified medical professional to support a VA disability claim.

Source: Veterans Guardian 

To obtain a medical nexus letter, you need to request one from a qualified and experienced specialist or mental health provider, preferably a military veteran with prior years of experience. Ideally, the physician/provider you choose is a specialist in the field that encompasses your health condition. For instance, it would be best to request a letter from a psychiatrist or licensed psychologist if you are seeking benefits for depression or Post-Traumatic Stress Disorder (PTSD). Depending on your medical condition, you may need to schedule a face to face appointment with the physician/provider.

Source: Veteran Law