The Slenderman Stabbing – A rare account of a Folie a deux

The Slenderman is a fictional character who was born in a photo contest for the website Something Awful. His father is the artist Eric Knudsen who posted the photoshopped pictures of children with a tall, slender dark figure in the background.

His creation soon took off. Fans helped to provide the internet with alleged accounts of Slenderman sightings, fueling the modern myth of the faceless figure that lurks in forests and parks. The thrilling web-series Marble Hornets was built around it and the free horror game Slender helped the creation to be known across the world.

On June 5th, 2014, however, the myth of the Slenderman broke the fourth wall and became painfully real. Two girls had tried to sacrifice their friend to the fictional creature. Their crime shocked the world. Naturally, one simple question arises: Why?

A sense of foreboding?

Anissa and Morgan were 12 years old. They were friends. And as friends, they shared common interests and fantasies. Girls at this age often do not totally live in the real world. Usually, they dream about a musician being their first boyfriend and wonder what Hogwarts House the Magical Hat would sort them into. Parents, however, would never see this behavior as being severely out of touch with reality. It is very common for prepubescent girls, after all.

There is a psychiatric term for being out of touch with reality. Psychosis is defined as a disease of the mind that makes the sufferer lose his grip on the reality “normal” humans perceive. He gets lost in his own world, which is filled with strange sounds, voices, the sense of being stalked, the feeling of being controlled from afar and many other sensations. To bystanders, their behavior may seem bizarre. It is rare, however, that a psychotic person kills.

The first episode of psychosis usually develops in early adulthood. If the episodes keep coming back and the individual`s education, career and social status suffer from it, the patient will receive the diagnose of Schizophrenia (=chronic paranoid psychotic disorder). Usually, Schizophrenia runs in the family.

An unlikely Illness

Now, Schizophrenia is a diagnosis that is rarely given before the age of 20. Childhood schizophrenia, however, is so unusual that you hardly learn anything about it in medical training. The core symptoms are the same, but in children, they are harder to spot. I recommend reading this article of the Mayo Clinic, from which I want to pick out the following quote:

When childhood schizophrenia begins early in life, symptoms may build up gradually. The early signs and symptoms may be so vague that you can’t recognize what’s wrong, or you may attribute them to a developmental phase.

During the court proceedings, Morgan was diagnosed with early-onset-schizophrenia. She could not differ between internet fiction and reality. She held on to the magical belief of becoming an accomplice of the Slenderman for killing her friend. It is stated that she had been obsessing over her plan for months. In an interview, her mother stated that she had no idea that her daughter was mentally ill. With the information we have on Childhood Schizophrenia, we can understand why. Furthermore, her father reportedly suffers from Schizophrenia. For him, the illness began when he was 14 years old.

The shared delusion

Morgan, however, was not the only offender. Her friend, Anissa, was trapped in Morgans delusions so much that she took part in planning and executing the intended murder.

When an individual who is not psychotic starts to believe and take part in a loved one’s delusions, psychiatrists call it a shared delusional disorder, or Folie à Deux. This is stated to have happened with the two girls.

A Folie à Deux (FD) is extremely rare and current research on it is scarce. This review by Arnone et. al. (2006) gives an overview of reported FD cases in the literature during the span of 12 years. In this time, there were only 64 cases identified. In the 42 cases the authors examined, the majority of FD occurred between spouses. Scientists also report FD between parent and child. The main criterion that seems to increase the risk of developing FD is the social isolation of the two persons. The review, however, stressed that there often was a history of mental illness in secondaries (=those who take part in the delusions of the primary). The authors conclude that FD is more likely to occur when the secondary has a high risk of developing a mental illness himself.

(I could not find evidence of any mental health issues in Anissa prior to the incidents.)

So, what does Slenderman have to do with it?


First of all, we have an extremely rare condition which is Childhood Schizophrenia in 12-year-old Morgan.  (Bare in mind that among homicidal offenders, only 6% tend to suffer from psychosis). Then, we have an even rarer condition, namely a shared delusional disorder, which caused Anissa to take part in the stabbing.

This crime was unbelievably unlikely. Subtract one aspect, and it might not have happened. But change Slenderman into any other paranormal figure and ask yourself: Would it have made any difference?

I say no.