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HealthInfo Canterbury

Overview of psychosis

Distorted figures on a beach Psychosis can happen when your brain function becomes seriously disrupted. You can stop understanding what's real and what's not. This can be extremely distressing for you and for those around you.

When you're experiencing psychosis you might:

There are no tests to show what causes a psychotic mental illness. A psychiatrist will diagnose someone with psychosis after thoroughly assessing them and talking with their family and friends.


If you're concerned about someone's behaviour and think that they might harm themselves or someone else, call the Police on 111.

If you're concerned about someone's behaviour, but you don't think it's immediately threatening anyone's safety, contact your local mental health crisis team on one of these numbers:

If someone has psychosis, it often starts when they're between the ages of 15 and 25. It usually happens as part of a serious mental illness but there are some other causes. One in five people who have psychosis for the first time get better and never have it again.

Causes of psychosis

Serious mental illnesses such as schizophrenia, severe depression, or bipolar disorder can lead to psychosis.

Very rarely, a woman can develop psychosis after giving birth – this is called postnatal psychosis.

Psychosis can also happen as a result of severe stress or drug or alcohol use.

Sometimes a medical condition such as a reaction to a medicine, high fever, a brain condition or dementia can cause psychosis.

Symptoms of psychosis

Psychosis can show in a variety of ways and can range from mild symptoms to severe ones that interfere with daily activities.

The main symptoms are

People who are developing psychosis may not understand that what they think and believe isn't real. They may tell others about their ideas, thoughts and unusual experiences, or they might keep them to themselves. The change may happen gradually, or it may suddenly show in bizarre ways. Each person's experience is different.

It's very rare for a person with psychosis to be violent towards other people. They are more often frightened, confused, or feeling low.

Diagnosing psychosis

When someone first shows signs of psychosis, it can be hard to tell what's going on. They may simply start to withdraw, care less about the people in their lives, and struggle to do their job as well as before, or start to take less care with their appearance. If this happens in teenagers it can be very hard to tell if they are developing a psychotic disorder or just struggling with being a teenager.

When doctors try to find out what's happening to someone with psychosis, they will consider whether there is an underlying temporary cause such as an acute physical illness or reaction. They may need to do tests to check for this.

In young people, it may take a long time of watching to work out what is the most likely cause of the psychosis.

If there's concern that you have a psychotic mental illness, your GP is likely to send you to see a psychiatrist. If you are very unwell you may need to be admitted into hospital. Many people will agree that this is the best way to get care and will go to hospital willingly. However, some people will need to be admitted to hospital against their will, using the Mental Health Act.

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On the next page: Self-care with psychosis

Written by HealthInfo clinical advisers. Endorsed by consultant psychiatrist, Canterbury DHB. Last reviewed December 2020.


Page reference: 146816

Review key: HIPSY-124133