Psychosis: Everything you need to know


A doctor explains what psychosis is, the common symptoms and causes – as well as how to get help.

By Dr Louise Wiseman MBBS, BSc (Hons), DRCOG, MRCGP

Psychosis is a state that causes the sufferer to experience the world in a different way to those around them. The main symptoms of psychosis are hallucinations and delusions.

Psychosis is not a condition but a symptom that can be caused by many things. The treatment will very much depend on the underlying cause. Many psychiatrists or doctors use the term ‘experiencing psychosis’ rather than giving a patient a specific diagnosis or label.

Dr Louise Wiseman explains what psychosis is, what it feels like, the possible causes and triggers of psychosis and what can be done to treat it.

What is psychosis?

Psychosis occurs when a person loses contact with reality and experiences the world differently to the people around them. This can also be called a ‘psychotic episode’, a ‘psychotic experience’ or ‘psychotic symptoms’. It is thought to be due to problems with functioning in the front part of the brain. The sufferer sees and thinks about the world differently to how they normally would, and may believe things that other people would not.

How long does psychosis last?

Psychosis can be something someone lives with for a long time or you may have short episodes throughout life or only suffer it once.

Psychosis symptoms

The main symptoms of psychosis are hallucinations and delusions.

These can make thoughts and emotions very confused and disorganised in themselves.

There is however a further group of symptoms called ‘disorganised thinking’ (also called ‘formal thought disorder’) that can be a specific type of psychosis in itself.

Less commonly, patients suffer ‘catatonic’ behaviour where they hardly move/speak or react to the world around them.

If you know someone who develops a psychosis you may interpret some of the symptoms as simply a change in personality.

Here we break down the main symptoms of psychosis:


A person sees or hears things that do not really exist outside their mind. This can also extend to feeling, smelling or tasting things that are not there. These feel very real to the person experiencing it.

Examples of hallucinations include:

  • Seeing objects move in unusual ways or that are distorted from normal.
  • Seeing things that others do not (faces, animals, religious figures).
  • Tasting, smelling or having sensations for which there is no cause (e.g. feeling spiders crawling over your skin).
  • Hearing voices that other people don’t (these can be a positive, helpful voice or a voice with a threatening, nasty or hostile tone).


A person has strong beliefs that others do not share. This is not the same as beliefs that are shared by different groups of people (e.g. faith, politics). A delusion is a belief in something that is false and to which there is clear evidence to the contrary.

Examples of delusions include:

  • Feeling you can control things e.g. the weather or other people.
  • Believing you are rich and powerful when it is not true (delusions of grandeur)
  • Believing that someone or something is trying to control you/cause you to harm/poison/kill you when there is no reason to believe this (paranoid delusions)

It is not automatic that everyone finds hallucinations and delusions distressing – many people are able to function in everyday life and live with these experiences.

Disorganised thinking and speech

Doctors use two terms regularly to describe this disordered thinking:

  • Racing thoughts– thoughts go through your head so fast they feel out of control.
  • Flight of ideas– thoughts jump from one idea to another; other people might not see the links between them like you do.

Disorganised thinking can mean you link words together due to how they sound rather than what they mean. This then might not make sense to the person you are talking to – it is sometimes called a ‘word salad’. Disorganised thinking can also mean you speak so quick the words are stumbled, you change topic so fast that others can’t keep up and you can’t pay attention to just one thing. These can also be symptoms of mania or hypomania.

Generally, when suffering psychosis symptoms, cognitive function is impacted. This means patients also suffer problems with memory, concentration and making decisions. This would be true in many states of stress, anxiety and depression as well.

Psychosis causes and risk factors

Causes of psychosis are divided by doctors’ classification into primary and secondary causes.

Primary causes

Doctors may decide in some patients that the cause of psychosis is actually another specific mental health diagnosis. We say that the primary cause of the psychosis is the mental illness. These include

  • Schizophrenia(this can include hallucinations and delusions)
  • Bipolar disorder
  • Severe depression with psychotic symptoms
  • Schizoaffective disorder
  • Postpartum psychosis (happens rarely – 1 or 2 in every 1000 women within 4 weeks of giving birth)

Secondary causes

A secondary cause of psychosis is something that causes psychosis as a side effect or ‘accident’.

Psychosis can be very different for different people and there are many potential causes or triggers. Certain clinical and life scenarios can be risk factors for psychotic symptoms. Psychosis is not always part of a mental illness.

Triggers can include:

  • Abuse or trauma– these scenarios can make psychosis more likely – it could be a one-off traumatic event or long-term. It may be related to events in childhood or adulthood.
  • Extreme stress e.g. bereavementor losing one’s home
  • Extreme lack of sleep
  • Extreme low blood sugar or severe malnutrition
  • Physical illness or infection (deliriumis the name for a state of confusion after an illness or operation)
    • g. high fever, heavy metal poisoning, thyroid problems, Cushing’s syndrome
    • infections that cause brain swelling including some sexually transmitted infections, Epstein-Barr virus, measles, mumps, rabies, certain parasites, malaria, fungal infections
    • Head or brain injury especially to the front of the brain
    • Certain vitamin deficiencies
    • Poisoning from toxins such as weedkillers or fertilisers (delirium is the name for a state of confusion after an illness or operation)
  • Neurological conditions such as MSEpilepsyAlzheimer’sDementiaor Parkinson’s Disease, Fahr’s disease can cause hallucinations or delusions. Hallucinations can less commonly be a presenting symptom of a brain tumour or brain infection. Some rare genetic conditions can cause hallucinations.
  • Some autoimmune conditions in certain people e.g. with inadequate nutrient absorption, such as coeliac disease
  • Recreational drugs (e.g. cocaine, cannabis, amphetamines, PCP, glue, aerosols, nitrites) or alcohol misuse. Some of the effects may only occur at high doses or in withdrawal. Research is ongoing but it seems that drugs like cannabis and LSD can make you more likely to hear or see things and once you have had a psychotic experience certain drugs can make a recurrence more likely.
  • Drug or alcohol withdrawal can trigger symptoms such as hallucinations.
  • Prescribed medication can cause psychotic symptoms as a side effect or whilst you withdraw from them (e.g. anticholinergics, dopamine agonists, steroids, thyroid hormones, herbal remedies containing ephedra, some antibiotics and antivirals (rare) cough and allergy medicines)
  • You can be more likely to experience psychosis if a parent or sibling has experienced similar but doctors are not sure why this happens. It is sometimes difficult to work out what is genetic and what is from upbringing.
  • Some people describe hearing voices or seeing visions as part of a religious worship and this can be seen as a good or bad experience depending on how the person interprets it.

Net Doctor


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