For instance, testing nicotine patches requires multiple samples of a biological fluid. Saliva tests can be used to measure testosterone levels. Higher levels of testosterone have significant health benefits for some middle-aged men. Men with higher testosterone are less vulnerable to high blood pressure, heart attacks, frequent colds and obesity. In addition, they are more likely to rate their health as excellent or good rather than fair or poor.
Studies show self ratings of health correlate highly with physicians' assessments.
Saliva assays can test cortisol levels, too. Cortisol is a hormone linked to stress, anxiety, depression and socially withdrawn behavior. Children who are more socially withdrawn or anxious are more likely to have an increased level of cortisol in their bodies. This is in response to stresses like social conflicts with their parents. Many people look at DHEA as a supplement to enhance aspects of their cognition, mood and health.