There are many effects that were caused by the Vietnam War. These effects were not only in Vietnam, but also in the United States. what caused the Vietnam war and later caused all of these health problems were political causes. The United States had a fear of communism spreading and wanted to stop it. Both President Kennedy and later President Johnson both believed in the Domino Theory, which was the belief that if one country fell to communism, other surrounding countries will do the same. So it was believed that if communist North Vietnam took over non-communist South Vietnam, all other countries would also fall.