How many of you think that the predisposition to developing a stutter can be passed on through genes, and whether one develops it depends on environment?

How many of you think that the predisposition to developing a stutter can be passed on through genes, and whether one develops it depends on environment? I just have a general question, just for fun... No right or wrong answer! How many of you think that a certain *type* of stuttering can be developed (or worsened) due to environmental influences ? I noticed that my family is big, and as a child I was often interrupted, and when I would normally speak, I would be negatively reinforced (for example, brothers shutting me down verbally/physically, or parents responding with fear/anxiety)? I notice that when I stutter I often have this general fear/anxiety, of insecurity, or not being accepted by my surroundings (what came first the chicken or the egg??), which could seep into my conscious, periodically, when I notice that my speech is acting up. When I exercise (relieve that stress) or am on other drugs (ex. alcohol) I seem to have a altered state away from social anxiety, and that correlates well with fluent speech. I understand that stuttering is pretty much unknown, and stuttering could be broken down into subgroups, or *types* of stutters depending on severity and triggers. But my question is, for some types (not all) how much of a environmental influence do you think is involved in developing a stutter (whether its in your genes or not)?