Which of the following could be classified as a moral hazard in underwriting?

A moral hazard in underwriting refers to a situation where an individual's behavior might lead to increased risk, particularly due to a change in circumstances that comes with having insurance coverage. In the context of substance abuse, this behavior can significantly impact the likelihood of claims being made. Individuals who struggle with substance abuse may not take necessary precautions to maintain their health, leading to higher risks of accidents or health issues. As such, insurers need to consider this aspect when assessing the risk profile of an applicant.

Other factors listed, such as age, gender differences, and medical history, while relevant in evaluating risk, do not typically fall under the definition of moral hazard. Age and gender are demographic factors that can be analyzed statistically for predicting risk based on populations. Medical history provides insight into past health behaviors and conditions but does not inherently indicate a change in behavior that could adversely affect future behavior after attaining insurance. In contrast, substance abuse directly suggests a likelihood of future risky behavior, embodying the essence of moral hazard.