Shared Psychosis: When Delusions Spread

Psychosis is a mental health symptom involving a disconnect from reality. This disconnect may manifest as symptoms like hallucinations and delusions—and in rare cases, delusions may spread to others as well in a mental health experience known as shared psychosis. Whether you’re experiencing this situation or are observing it in a loved one, it may leave you overwhelmed, scared, and unsure of how to help or move forward. Finding out more about this phenomenon and how it can be treated may help you understand how to proceed. Here, we’ll explain what shared psychosis is, how it’s diagnosed, and key treatment options.

Understanding shared psychosis

The American Psychological Association (APA) defines psychosis as “an abnormal mental state involving significant problems with reality testing,” characterized by symptoms like hallucinations and delusions. Delusions are false, unshakeable convictions that lack a basis in reality and often center on abnormal perceptions and bizarre and/or persecutory ideas. 

Shared psychosis is when two or more people with a close relationship experience this state simultaneously, with shared delusions. Specifically, the APA defines shared psychosis—sometimes referred to as “folie à deux”—as “an identical or similar delusion that develops in an individual who is involved with another individual who already has a psychotic disorder with prominent delusions.” 

This rare disorder is estimated to appear in 1.7–2.6% of psychiatric hospital admissions. It usually affects couples or siblings—but in rare cases, it may affect entire families. In the most recent edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5), shared psychosis is not recognized as a separate disorder from delusional disorder. In the International Classification of Diseases (ICD-10), it’s categorized as induced delusional disorder. It may also be referred to as shared delusional disorder or induced psychotic disorder.

How shared psychosis, or folie à deux, develops

The exact cause of shared psychosis remains unclear. However, research suggests that the condition often starts with:

• A primary individual, who is more dominant and typically has an existing primary illness, often with psychotic features
• A secondary individual, who is more submissive, suggestible, and/or dependent, and has a very close, long-term relationship with the primary individual (such as spouses or siblings)

Over time, the primary partner or dominant person's strong, delusional beliefs influence the more susceptible person, leading to the same delusion and a shared, distorted view of reality. 

Risk factors for shared psychosis

While a mental disorder in the primary individual (like schizophrenia) might be the driving force of the delusion in some cases, shared psychosis can also occur without the dominant person having a separate diagnosis. Stressful life events, social isolation, and limited exposure to diverse viewpoints might sometimes cultivate the environment for false beliefs to take hold and spread between closely connected people. 

Other risk factors for shared psychosis include:

• A cognitive impairment, intellectual disability, and/or untreated mental illness in the secondary individual
• Communication difficulties between the affected individuals
• A significant power imbalance in the relationship
• Untreated psychotic symptoms in the primary individual

An online therapist may be able to help address several risk factors for this and other mental illnesses before they can progress, from helping you develop healthy relationship skills to addressing any underlying conditions.

Recognizing the signs and symptoms of shared psychosis

Only a trained healthcare professional can provide a clinical diagnosis of shared psychosis or another mental illness. That said, becoming familiar with common signs of shared psychosis could help you recognize when the condition may be occurring in loved ones so you can encourage them to seek support.

Symptoms of shared psychotic disorder

Here are some possible symptoms that may manifest in individuals with shared psychosis:

• Unusual beliefs. The individuals express strange, often persecutory ideas that are firmly held and lack any foundation in reality.
• Shared conviction. The delusional belief is embraced by both/all of the individuals involved with seemingly unwavering certainty.
• A close relationship. There's a strong and typically long-term bond between the individuals, often characterized by social isolation or dependence.
• Behavioral changes. You might also observe unusual behaviors, withdrawal from social activities, and/or an intense preoccupation with the delusion.

If separated from the dominant individual, the submissive person's belief might lessen or even disappear. However, the primary person's delusions often persist even without reinforcement.

Diagnosing and treating shared psychosis, or folie à deux (“madness of two”)

The way shared psychotic disorder is treated can vary significantly because of its complexity and because of how unique each situation can be. That said, some common components of treatment may include the following.

Psychiatric assessment 

The diagnostic process for a person showing any signs of a mental health condition begins with the clinical aspects of a psychiatric assessment, which may take place in a clinical practice or psychiatric hospital. The clinician will usually:

• Evaluate each individual’s symptoms against DSM or ICD criteria
• Consider each person’s medical and psychiatric history
• Conduct an interview with each patient if possible
• Administer any necessary psychological tests

A core part of this step is the clinician assessing both individuals for any underlying conditions. For example, they may do an evaluation to determine whether the dominant person is showing signs of a primary psychotic disorder like schizophrenia spectrum disorder or bipolar disorder. They may also request a medical evaluation to rule out other conditions or experiences that may cause or mimic symptoms of psychosis, such as:

• Schizoaffective disorder or another psychiatric disorder
• A mood or affective disorder
• Neurological issues
• Cognitive impairment
• Substance use
• Other medical conditions

If you are struggling with substance use, contact the SAMHSA National Helpline at 1-800-662-HELP (4357) to receive support and resources. Support is available 24/7.

If you’re experiencing signs of stress as a loved one undergoes the diagnostic process, meeting with a therapist yourself may be helpful. An online therapist can offer personalized, convenient support.

Safety evaluation

Another common component of the diagnostic process is the safety evaluation, where the clinician and, in some cases, a social worker or caseworker will aim to determine whether immediate intervention is needed to ensure the safety of both parties. For example, the clinician will often screen the individuals for any self-harming behaviors or suicidal ideation.

Separation considerations

Separation from the dominant person often lessens or resolves the shared delusion for the secondary partner or individual. The care team will usually determine whether separation is feasible for the people involved and, if so, may take steps to support this process.

Mental health treatment for the primary and secondary individuals

Finally, the clinician will determine the appropriate course of treatment for all individuals involved.

• If the dominant person has a psychotic disorder or another diagnosable illness, treatment will usually involve some form(s) of psychotherapy, often in combination with medication like mood stabilizers, antipsychotics, or others. Alternative treatments like electroconvulsive therapy may also be recommended in some cases.
• If the secondary individual has a diagnosable disorder too, therapy and, in some cases, medication may also be recommended. If not, counseling can help them build coping skills, self-esteem, and resilience.

How loved ones can offer support

While shared psychosis requires professional intervention to address, the support of loved ones can be helpful during recovery and beyond. Here are some suggestions for how you might offer support to loved ones experiencing this type of mental health concern while also prioritizing your own well-being:

• Educate yourself. Learning what you can about shared psychosis and mental disorders like schizophrenia, if applicable to your loved one’s situation, can help you approach the situation with knowledge and empathy.
• Keep the lines of communication open. If safe to do so, you might let your loved ones know you're there for them. Gently expressing your concern in a non-judgmental way may open the door for a supportive conversation about seeking help.
• Avoid confrontation. Challenging the delusion directly often backfires. Instead, focusing on listening with empathy and validating their feelings may help build trust and a sense of safety.
• Encourage professional help. Gently encouraging your loved ones to seek an evaluation from a mental health professional can be helpful. Offering to help them find resources or even accompanying them to appointments could reinforce your support.
• Set boundaries. Supporting someone with a mental illness doesn't mean sacrificing your own well-being. According to the American Psychiatric Association, setting boundaries and practicing self-care may help you maintain your own mental and physical health.
• Find a support network. Connecting with support groups for loved ones of people with mental illness—or shared psychosis in particular, if possible—may allow you to share experiences and get support from others who understand.

Also, keep in mind that if there are concerns about harm to self or others, addressing these immediately can prevent potential crises. Having a safety plan in place and seeking professional help if needed can be helpful. Requesting emergency assistance may be necessary in crisis situations.

In addition, if you’re able to, minimizing day-to-day stress for your loved ones may be helpful. A calm, predictable environment may reduce agitation and make delusional symptoms less intense. Avoiding arguments is generally also beneficial, as trying to reason with someone in a delusional state is often unhelpful and can increase distress for everyone involved. Finally, engaging in enjoyable distractions like shared hobbies, listening to calming music, or spending time in nature might help shift focus away from the delusion.

Maintaining hope during treatment for shared psychotic disorder

While shared psychosis might seem overwhelming, successful management and recovery can be possible. You might remind yourself of the power of separation, as the submissive partner’s delusional beliefs often fade once they’re apart from the dominant individual. You might also aim to remember that the long-term benefits of treatment can be significant for the mental health of all the individuals involved in the shared delusion. With time, therapy, and support, they may be able to develop skills to better cope with stress, manage difficult emotions, and improve their mental health.

Seeking support for shared psychosis

Watching loved ones experience shared delusions can be difficult, and the emotional stress of trying to figure out how to help can be intense. Finding a convenient way to connect with a therapist can be useful as you cope with this type of situation, and online therapy can make care more readily available. With a platform like BetterHelp, you can get matched with a therapist and then meet with them via phone, video, or live chat from the comfort of home. They can provide a listening ear, emotional support, and positive coping strategies. 

Note that, in many cases, treatment for individuals experiencing psychotic disorders is most effective in person. However, online therapy may sometimes be an appropriate component of ongoing care once a person with such a disorder has received stabilizing in-person support.

The benefits of online therapy 

A growing body of research suggests that online therapy can often be similarly effective to in-person therapy for treating several types of emotional and mental health challenges. For example, consider a study that indicates that internet-based cognitive behavioral therapy (iCBT) can be effective in reducing stress-related symptoms.

Research also indicates that, in some cases, online therapy can be a useful component of treatment for certain psychotic disorders. For example, some studies report that online sessions can be easier to attend regularly and, therefore, may boost treatment engagement. This consistency could mean faster progress toward a life with improved mental well-being. Keep in mind that even if full recovery isn't possible, shared psychosis can often be managed.