The horrifying thought of a man eating another man’s face leads one to ask: how could someone in his or her right mind do that? Clearly, Rudy Eugene was not in his.

One theory is that he suffered from “cocaine psychosis,” meaning that cocaine caused him to become psychotic and attack the victim, Ronald Poppo. Another theory implicates LSD-like chemicals in bath salts as the cause.

However, simply finding cocaine — or any other drug — in a psychotic person’s system does not mean it led to his or her violent behavior. There are many people who self-medicate their psychological illnesses with alcohol, pain medications or other illicit substances instead of seeking professional help. It is possible that Eugene already had an underlying mental illness before ever using drugs.

Psychosis of any kind involves a loss of reality. During a psychotic episode, people believe things that aren’t true and sometimes see or hear things that are not there. Psychosis is part of several psychiatric illnesses, most commonly, schizophrenia and bipolar disorder.

But, the generalization linking psychosis to violent, horrifying behavior is not representative of all those with the illness.

There are, in fact, examples of people with longstanding psychosis or an acute, “psychotic break” who kill their own families or attack innocent people.

But, there are plenty of people with psychosis who would never dare to do something so gruesome. People in a psychotic state may behave strangely by societal standards, they may become delusional and believe they are superheroes or mob bosses, and they may dress inappropriately in public — yet they never hurt a single person.

Eugene’s behavior brings to mind the cannibalism of Hannibal Lecter in Silence of the Lambs. Interestingly, though, experts who have analyzed Lecter’s behavior have classified him not as psychotic but as a psychopath.

A 2007 Scientific American article points out the difference between the two. Unlike psychosis, psychopaths are usually rational and in touch with reality. They can be charming, manipulative and exploiting, without a sense of guilt or empathy for another person. There’s a strong link between psychopathy and criminal behavior.

However, the drugs in question induce psychosis — not psychopathic behavior like Lecter’s.

Cocaine is abused for its intense pleasurable effects, along with increased energy, feeling more social, a decreased need for sleep and a decreased appetite. However, it can also cause troublesome effects such as anxiety, paranoia, delusions and hallucinations.

Those who use LSD — also known as “acid” — also experience symptoms of psychosis. It’s very common for LSD to cause hallucinations, paranoia and an altered sense of reality. It tends to amplify thoughts that already exist in the person’s mind. And, whereas the high from cocaine can last as short as 20 minutes in some cases, a high from LSD can last up to 12 hours.

A 1991 New York Times article describing the growing trend of LSD also reported how, in the 1960s, “thousands of young people landed in mental hospitals and others were killed after leaping out of windows, believing they could fly, or became involved in other accidents. Some killed people while in psychotic rages induced by the drug.”

This more fitting description may have led to the recent reports that focus more on LSD and the bath salts than cocaine. However, given his death, Eugene’s mental state and possible psychiatric illness cannot be truly examined and diagnosed outside of assumptions and theories.

Dr. Tyeese Gaines is a physician-journalist with over 10 years of print and broadcast experience, now serving as health editor for theGrio.com. Dr. Ty is also a practicing emergency medicine physician in New Jersey. Follow her on twitter at @doctorty.