It means that stutter impacts the communication via speech you have with people. I'm not sure we'd label that "psychological", inasmuch as it's a rather involved affair to enter into that sort of relation with others. We'd be remiss if we didn't mention stutter variance here, though. It's not necessarily the case that a stutterer can't stutter when alone, and also, it's not necessarily the case that a stutterer stutters when there are others around. So, in short, it's not binary, and we can't use the presence of others to label stutter "psychological". We _definitely_ shouldn't understand it as something we're doing (to) ourselves due to an inability to be around other people in general.