In a shoulder-stand it is best if the neck does not actually touch the floor.

This is ideally a type of resistance work. The position is one of having the head ‘downwards’ towards the chest and the neck ‘backwards’ away from the chest. But you should be trying to resist and escape from this position by trying to move the throat ‘forward’ towards your chest and the chin ‘upwards’ away from your chest.

This means that both in the simple bridge with the arms interlocked behind the back, and in the actual shoulder-stand itself, the neck should not touch the floor at all. It is Ideal if only the back of the head, the shoulders and the elbows actually touch the floor.

This can help correct any protrusion deformity of the upper thoracic spine. It can also help relieve neck pain. And it can also relieve tension headaches coming as a result of neck muscle stiffness.

In cases where therapy is needed shoulder-stand itself is generally not recommended and it is better instead to just do the bridge either with the hands interlocked behind the back as described here or the bridge where you actually rest on the base of the back of the neck and the top of the thoracic spine.