Dopamine D1 receptors mediate desire. The D2 receptors mediate self-control. Addictive drugs downregulate the D2 receptors, inducing the craving and impulsivity of addiction.

The runner’s high is an example of endorphin rush, but it is unclear if it is caused by endorphins or endocannabinoids.

Porn is not addictive. It induces short increases of dopamine and not the sustained ones produced by cocaine and opioids.