Abby Clark mentions that she believes she woke up sooner than the rapist intended because redheads handle drugs differently. Natural redheads get their color from a mutation in the MC1R gene, which is responsible for the production of the skin pigment melanin, in redheads this gene mutations causes them to not produce melanin causing both their hair color and extremely fair skin. Research has shown that this gene is also responsible for how the brain perceives pain, which is why redheads have a higher pain tolerance. It also affects how certain drugs act on their nervous system, how exactly is not yet fully understood. What is known is that the gene mutation makes redheads more tolerant to anesthetics like ketamine (commonly used as a date rape drug) and propofol, anesthesiologists have to give redheads 20% more anesthesia to achieve full sedation. Their gene mutation also makes redheads more tolerant to benzodiazepine sedatives like diazepam (Valium), lorazepam (Ativan), alprazolam (Xanax) and flunitrazepam (Rohypnol: another popular date rape drug). On the reverse the gene mutation causes redheads to be more sensitive to opioids like codeine, hydrocodone, oxycodone, morphine and fentanyl, redheads often need only half the dose that someone their age and weight would normally need. This explains why redheads have a higher pain tolerance because they respond better to their own endorphins, a morphine-like substance produced in the brain that acts as the body's natural analgesic.