The heritability of nicotine dependence across 17 twin studies was found to be .59 for males and .46 for females. This is less than the heritability for heroin or cocaine dependence, about the same as for alcohol dependence and higher that dependence on other drugs of abuse. However, nicotine is thought to be the most addictive drug since it has a higher percent of users that become dependent than other drugs of abuse.