stuttering and asthma are two separate things that don’t necessarily overlap. however, anxiety can cause asthma attacks. what’s most likely happening is that the anxiety your friend experiences around their stutter is what leads to asthma. further, the feeling of stuttering or blocking can feel a lot like not being able to breathe, which can then make someone with anxiety and asthma spiral into an asthma attack. so it’s not necessarily the stuttering so much as the anxiety around stuttering that gives your friend asthma attacks.