Folie à Deux


Most people recognise ‘Folie à Deux’ as Fall Out Boy’s fourth studio album.  However the album is named after a rare mental illness. Folie à Deux is french for “shared psychosis”, and in this blog post I’m going to explore what this means, what it involves, and some cases of this strange phenomenon.

Folie à Deux is the mental phenomenon of shared psychosis. It involves an individual who is in a close relationship with someone who already has psychosis, and begins to develop the same symptoms.

But before I go into shared psychosis in detail, I’ll first explain the ins and outs of psychosis. Psychosis is a mental health illness which forces the individual to to perceive things around them differently from others. This can include hallucinations and delusions. However it should not be confused with schizophrenia. Schizophrenia is a mental illness where a symptom can be psychosis, however psychosis or psychotic episodes can occur without a diagnosis of schizophrenia.

As previously mentioned, the two main symptoms of psychosis are hallucinations and delusions. 

Hallucinations affect an individuals senses. Someone experiencing hallucinations can see, hear, smell, taste and even feel things that others cannot, and are essentially not embedded in reality.

Hearing voices is one of the most common hallucinations, as are seeing things. People having hallucinations can hear voices of people from their past, but also voices that they cannot identify. Very rarely are the voices positive ones; they can be demanding, instructive and dangerous – especially if they create suicidal and/or homicidal intentions and thoughts. (Despite this, psychotic individuals are no more dangerous to the public than those without psychosis). Individuals with psychosis have a higher rate of self harm and suicide than those without psychosis, and this may be due to the voices instructing them to harm themselves, or used a coping strategy.

This is also the same of people seeing things – they can see people, machines, perceive objects to be moving when they are not, and even see people who are alive but the individual may believe them to be dead.

Delusions are where an individual has strong beliefs that are not shared by others. For example, an individual may believe that someone is out to hurt them, or they may believe that the FBI are spying on them.

There is no single cause of psychosis. It can be caused by psychotic mental illnesses – as a symptom of schizophrenia, bipolar or severe depression. Other causes of psychosis can be trauma, stress, drug and/or alcohol misuse, or physical conditions such as a brain tumours or high fevers.

Now we have a brief understanding of psychosis, how does psychosis become Foli

Folie à Deux?

It starts with an individual who has an already-established delusion. For example; a young man has psychosis and has delusions that the neighbours are working for the FBI and are spying on him. This young man is what’s called the primary case, or primary partner. His girlfriend may then begin to have the same hallucinations, despite originally being healthy. She will be what’s called the secondary case.

Shared psychosis usually occurs in relationships that are long-term. They can be romantic relationships, or parent/sibling. They usually live together, or are in relative social isolation, and usually the primary case is the more dominant individual of the relationship and the second individual tends to have the more submissive personality. It can also occur within groups; such as a parent having delusions and then these delusions being shared with their partner and their children.

But what are the causes?

As it is with psychosis, there is no single known cause of shared psychosis. However, there are similarities between cases.

  • There are several variables that can affect the influence of the creation of a shared psychosis ; isolation of the people in the relationship, closeness, length of relationship and if a submissive/dominant factor exists in the relationship and the strength of this.
  • Roughly 55% of secondary cases have a relation who also has psychosis or a psychotic disorder, not including the primary case. The secondary case also often meets the criteria for dependent personality disorder – this may explain their submissive personality as they rely on others more than the average person.
  • Generally, if separated from the primary case for a significant amount of time (e.g. 2 weeks), the secondary case usually drops their delusions.
  • In the case of close siblings with shared psychosis, Soriano et al (2009) concluded that shared psychosis can partly be explained by the siblings having a ‘shared past experience and expectations.’


Usual the delusions shared between the two individuals are believable, far less bizarre than those found in schizophrenia. Examples include a mother and daughter believing that the husband/father was poisoning them, a family believing their neighbours are going to come after them and kill them, or a couple believing that they were being harassed by the IRA. However the principle feature is the unwavering, concrete belief the secondary case has in the primary case’s beliefs.

But how is it treated?

Usually the individuals have to be separated for treatment. However, this alone is not enough as when reunited they may relapse. Both the primary and secondary case may have to be treated with antipsychotics to avoid this. Family therapy is also offered to in order to get to the root of the problem, and to identify any submissive/dominant relationships which may be unhealthy.

Little more is known about the phenomenon of shared psychosis. Not enough is known about psychosis when it affects a single individual, let alone when it becomes a social group illness. However it is an interesting concept, and raises the question as to whether other mental illness can affect groups with the same contagious effect?




Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )


Connecting to %s