Clarence Gravlee and his colleagues carried out research in Puerto Rico, attempting to explain why darker skin pigmentation was associated with higher blood pressure. They found that Puerto Ricans with darker skins and higher socioeconomic status actually experienced higher blood pressure than other Puerto Ricans. How did they interpret this finding?

individuals with darker skins and higher socioeconomic status were likely to experience more intense racism, which contributed to higher blood pressure

Explanation:

The initial finding shows that

Dark skins + darker skins with higher socioeconomic status = higher chance of blood pressure

In plain sight, this might be seen as a genetic correlation (there is something within people in darker skin's genetic that lead to the blood pressure)

But, if we step back and examine more carefully there is also other factors that influence high blood pressure : Stress level.

When people are faced with daily racism, they will feel huge amount of threats due to the aggressive behavior and insults that trowed by other people around them. If this happen constantly within prolonged period of time, it will lead to higher blood pressure within that target group. Especially if they are higher in socioeconomic status. They become more well known to the people and invite more aggressors.