The advancing understanding of human genetics will increase the importance of this factor. One reason why health psychology has become such an important field in psychology is money. Money makes the world go round, and people in developed nations spend an awful lot of money on their health. If it were possible to influence people to lead healthier lives, it could save a lot of money. Spending millions of dollars on anti-smoking campaigns may be money well spent, if it actually curbs smoking.
Health is a broad concept that includes physical health, mental health, and social welfare.
Experiments can be used to examine the influence of psychological interventions on health behaviors. A few months later, researchers can measure how many individuals in each group used condoms. If more individuals in the group that was exposed to the campaign used condoms, the campaign was successful. If the two groups did not differ, the campaign is ineffective. Experiments have the advantage that they provide easily interpretable results because only the experimentally manipulated variable can explain differences between two otherwise identical groups.