The contributors to narcissism are complex. Overvaluing children appears to be one of the causes but there are also genetic and other environmental factors at play that also need to be studied. Some children appear to be are more vulnerable to overvaluing parenting styles. Professor Brad Bushman, one of the study’s authors, indicated that the study had changed his parenting style. Before he began this research in the 1990s, he used to think his children should be treated like they were extra-special. He is careful to avoid doing that now because children believe it when their parents tell them that they are more special than others, which may not be good for them or for society. Rather than overvaluing the child, concentrating on being emotionally warm towards children was linked with better levels of self-esteem, not narcissism. It is important to express emotional warmth to your children because that may promote self-esteem, but overvaluing them may promote higher narcissism.