My question is about the idea that the relationship is like being addicted to crack or like being upducted by aliens.
Here's a link that describes some of the chemicals and brain interaction.
Brain Chemistry And here is a short quote from it:
"Researchers are using functional magnetic resonance imaging (fMRI) to watch people's brains when they look at a photograph of their object of affection. According to Helen Fisher, a well-known love researcher and an anthropologist at Rutgers University, what they see in those scans during that "crazed, can't-think-of-anything-but stage of romance" -- the attraction stage -- is the biological drive to focus on one person. The scans showed increased blood flow in areas of the brain with high concentrations of receptors for dopamine -- associated with states of euphoria, craving and addiction. High levels of dopamine are also associated with norepinephrine, which heightens attention, short-term memory, hyperactivity, sleeplessness and goal-oriented behavior. In other words, couples in this stage of love focus intently on the relationship and often on little else.
Another possible explanation for the intense focus and idealizing view that occurs in the attraction stage comes from researchers at University College London. They discovered that people in love have lower levels of serotonin and also that neural circuits associated with the way we assess others are suppressed. These lower serotonin levels are the same as those found in people with obsessive-compulsive disorders, possibly explaining why those in love "obsess" about their partner. "
The link to the article above has several pages related to the topic. Hope you find it helpful.