Studies support the theory that there are several causes, instead of a single environmental cause or genetic problem.
VOA: special.2009.01.06
Scientists have believed that S.I.V.did not cause a similar immune system problem for primates.
VOA: special.2009.09.08
Anything you see as a problem can cause stress.
VOA: special.2009.03.24
Stuttering's cause has long been a mystery, but it has frequently been diagnosed as a psychological problem.
VOA: standard.2010.02.11
Engineers discovered the problem during fueling, and worried that any excess hydrogen on the launch pad could cause an explosion during engine ignition.
VOA: standard.2009.03.15
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