A fascinating new study has found that having two or more siblings may be linked to poorer mental health in American teenagers. Brothers and sisters: can’t live with them, can’t live without them. Whilst their incessant stealing of hand-me-downs and blame games with parents might drive you up the wall, a new study has now found that teenagers have poorer mental health when they have more siblings in both the US and China. Teens with more siblings have worse mental health, new study findsA new study by researchers from Ohio State University has found that teenagers from larger families with mor…