To measure anything, a scale or counterweight is needed. The counterweight to a risk is a benefit. For example, every time someone gets into a car or an airplane they are making an unconscious decision that the benefits of rapid transportation outweigh the risk of injury or death. A benefit is something that promotes or enhances well-being. Recreation itself is a benefit, and different people choose different types of recreational activities, depending on their tastes and preferences.
Different people use different drugs and report different benefits.
What determines the weight of a risk. The weight of a risk can be described as the severity of the possible harm that might occur from a given activity multiplied by the probability of the harm occurring. Generally speaking, higher risk activities have higher probabilities of more severe harm, while lower risk activities have lower probabilities of less severe harm. Of course, a harm that one person considers extremely severe another person might not care about very much at all. The risk of death.