Psychosis is a mental state characterized by a disruption in the way the brain processes information. A person experiences psychosis when thoughts and perceptions interfere with the ability to decipher what is real and what is not.

Although psychosis is often thought of as a type of disorder, it is actually a symptom of several different types of mental illness. It is also linked with certain medical conditions and injury to the brain, as well as substance use.

The causes of psychosis are not completely understood, but scientists are working to find answers to why a person develops psychosis. It is thought a complex link exists between genetics and environmental factors. One thing the experts do know is that certain mental health conditions bring on psychosis.

Mental Health Conditions

When it comes to mental illness, common conditions where psychosis occurs include:

  • Schizophrenia
  • Bipolar disorder
  • Schizoaffective disorder
  • Major depressive disorder with psychotic features (psychotic depression)
  • Delusional disorder
  • Brief psychotic episode

Schizophrenia

Schizophrenia is a serious mental illness involving positive symptoms (meaning they are present rather than absent) and negative symptoms (which take away from a person’s normal life experience). 

Positive symptoms of schizophrenia are considered symptoms of psychosis as well. The three most prevalent positive symptoms of schizophrenia are:

  • Hallucinations (seeing or hearing things that others do not see)Delusions (having false beliefs that are tenacious and continue in the face of evidence that proves these delusions/beliefs are untrue)Disorganized thinking (which leads to disorganized speech)

Negative symptoms of schizophrenia, on the other hand, involve a lack of enthusiasm, a lack of motivation, and the inability to express emotions, to name a few.

A person must have at least one episode of psychosis before a diagnosis of schizophrenia can be made.

Bipolar Disorder

Bipolar disorder is a condition that involves mood fluctuations, ranging from depression (low moods) to mania (high moods). When a person with bipolar disorder is in a depressive or manic phase, psychotic symptoms may also occur, but psychosis is more common during mania.

The exact pattern of psychotic symptoms (such as the length or severity of symptoms) differs from person to person. The psychosis associated with bipolar disorder may involve:

  • Delusions of grandeur: Falsely believing a person is very important or that a person has special powersHallucinations: Seeing things such as people, lights, or other visions that are not real, or hearing voices (auditory hallucinations)Disorganized thinking: Confusing or incoherent thoughts

These psychotic symptoms may be accompanied by a lack of awareness of the illness (anosognosia). Note: Not everyone with bipolar disorder will experience psychotic symptoms. 

Schizoaffective Disorder

Schizoaffective disorder is a serious mental illness involving symptoms of schizophrenia in addition to a mood disorder.

Like schizophrenia, schizoaffective disorder causes a disturbance in a person’s:

  • Perception of realityThinkingEmotionsSocial interactions

Psychotic symptoms in a person with schizoaffective disorder are those that are caused by delusions or hallucinations. The mood part of the disorder can be either major depressive disorder or bipolar disorder.

Depression With Psychotic Symptoms

Some people with major depressive disorder experience psychosis. This distinct type of depressive illness involves a mood disorder accompanied by either delusions, hallucinations, or both.

Some estimates are that up to 18.5% of people with major depressive disorder have psychotic features.

Delusional Disorder

Delusional disorder is the presence of one or more delusions (fixed, false beliefs) present for greater than one month. More than likely, these delusions become lifelong convictions.

People with delusion disorder are not likely to hallucinate. 

Brief Psychotic Episode

As the name suggests, a brief psychotic episode is one that lasts a short period of time, between a day to a month.

The psychosis may or may not be associated with stress. Symptoms of brief psychotic episodes may include:

  • DelusionsHallucinationsDisorganized thinkingBehavior that is odd or out of character

Physical Illness or Injury

In addition to mental health disorders, other medical conditions can also cause psychosis, including:

  • Human immunodeficiency virus (HIV) and acquired immune deficiency syndrome (AIDS)
  • Malaria
  • Malaria medications
  • Syphilis
  • Alzheimer’s disease
  • Lewy body disease
  • Parkinson’s disease
  • Lyme disease
  • Stroke
  • Multiple sclerosis
  • Lupus
  • Brain tumors
  • Hormone disorders

Head injuries and some types of nutritional deficiencies are also known to lead to psychosis.

Substance Use

The recreational use of drugs has been known to trigger psychosis. Common types of drugs linked with psychotic symptoms include:

  • Cannabis (marijuana)AmphetaminesLSDMushroomsKetamineEcstasyCocaine

In rare cases, certain types of prescription medications can also cause psychosis, particularly when the recommended dosage is exceeded.

Drug-Induced Psychosis

Certain types of drug use can cause a person to have symptoms of psychosis. Also, when a person suddenly quits using drugs or drinking alcohol (withdrawal), it can trigger psychotic symptoms.

Emotional Trauma

Medical science is well aware of the impact of overwhelming stress when it comes to post-traumatic stress disorder (PTSD). Researchers are also looking into the relationship between psychosis and PTSD.

According to a 2017 study, lifetime prevalence rates of PTSD in individuals diagnosed with a psychotic disorder have been estimated at 30%, compared with 7.8% in the general population.

The study authors report that in addition to the impact of trauma on the development of psychosis and PTSD, there is evidence that traumatic experiences influence the content of psychotic symptoms, including hallucinations and delusions.

The connection between psychosis and PTSD is said to be very complicated and may involve several different factors, including:

  • Psychosis resulting from childhood adversityTrauma resulting from psychotic symptoms (including involuntary treatment experiences)Psychosis as a component of PTSD, resulting from traumaPTSD retraumatization, resulting in stressors that worsen psychosis

Genetics

Studies indicate that individuals who have a family history of psychotic disorders—such as schizophrenia—have an increased risk of having psychosis. 

A single causative gene has not been identified, but several genes are thought to increase the likelihood of developing psychosis.

Other Causes

Some research has attempted to classify psychosis not just based upon specific symptom patterns, but different measurable brain and body functions (biomarkers) as well. For instance, a 2015 study noted that multiple biological pathways may lead to clinically similar psychotic symptoms.