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Schizophrenia changes how a person thinks and behaves.

The condition may develop slowly. The first signs can be hard to identify as they often develop during the teenage years.

With young people, some symptoms can be mistaken for normal adolescent behaviour. For example, becoming socially withdrawn and unresponsive. Or changes in sleeping patterns

People often have episodes of schizophrenia when their symptoms are severe. This is acute schizophrenia. They can then go through periods with few or no symptoms. Thoughts can still be confused or muddled. Even when there are no obvious external symptoms.

Positive and negative symptoms

The symptoms of schizophrenia are usually grouped into the following types of symptoms.

Positive symptoms

Any change in behaviour or thoughts, such as hallucinations or delusions.

Negative symptoms

A withdrawal or lack of function that you would not usually expect to see in a healthy person. For example, appearing emotionless and flat, with confused or muddled thoughts.


Hallucinations are when you see, hear, smell, taste or feel things that don't exist. The most common hallucination is hearing voices.

Hallucinations are very real to the person experiencing them. Even though people around them can't hear the voices or experience the sensations.

Brain-scanning shows changes in the speech area, in the brains of people with schizophrenia, when they hear voices. These show the experience of hearing voices as a real one - as if the brain mistakes thoughts for real voices.

Some people describe the voices they hear as friendly and pleasant. More often they're rude, critical, abusive or annoying.

The voices might:

  • describe activities taking place
  • discuss the hearer's thoughts and behaviour
  • give instructions or talk directly to the person

Voices may come from different places or one place in particular, such as the television.


A delusion is a belief held with very strong conviction. Even though it's based on a mistaken, strange or unrealistic view. It may affect the way the person behaves. Delusions can begin suddenly, or may develop over weeks or months.

You may develop a delusional idea to explain a hallucination you're having. For example, if you hear a voice describing your actions, you may think someone is monitoring you.

You may experience a paranoid delusion. This is when you believe you're being persecuted or harassed. You may believe you're being chased, followed, watched, plotted against or poisoned. Often by a family member or friend.

You may believe people on TV or in newspaper articles are communicating messages to you. Or you may believe there are hidden messages in everyday events or coincidences.

Confused thoughts (thought disorder)

People experiencing psychosis often have trouble keeping track of their thoughts and conversations. Psychosis is a symptom of Schizophrenia. 

Some people find it hard to concentrate and will drift from one idea to another. They may have trouble reading newspaper articles or watching a TV programme.

People sometimes describe their thoughts as "misty" or "hazy" when this is happening . Thoughts and speech may become jumbled or confused. This makes conversation difficult and hard for other people to understand.

Changes in behaviour and thoughts

A person's behaviour may become more disorganised and unpredictable. Their appearance or dress may seem unusual to others.

People with schizophrenia may behave inappropriately. They may become very agitated and shout or swear for no reason.

They may believe that their thoughts :

  • are being controlled by someone else
  • are not their own
  • have been planted in their mind by someone else
  • are disappearing, as though someone is removing them from their mind.

Some people feel their body is being taken over. They may feel someone else is directing their movements and actions.

Negative symptoms of schizophrenia

Negative symptoms of schizophrenia often appear several years before the first acute episode.

These initial negative symptoms are the 'prodromal period' of schizophrenia.

Symptoms during the prodromal period usually appear gradually and slowly get worse.

They include the person becoming more socially withdrawn. They may also lose interest in their appearance or personal hygiene.

It can be difficult to tell if the symptoms are part of the development of schizophrenia. They could be caused by something else.

Negative symptoms experienced by people living with schizophrenia include:

  • losing interest and motivation in life and activities, including relationships and sex
  • lack of concentration, not wanting to leave the house
  • changes in sleeping patterns
  • feeling uncomfortable with people
  • being less likely to start conversations or feel there's nothing to say

The negative symptoms of schizophrenia often lead to problems with friends and family. Symptoms can sometimes be mistaken for deliberate laziness or rudeness.


1st episode psychosis

A first acute episode of psychosis can be very difficult to cope with. It can be difficult for the person who is ill and for their family and friends.

Drastic changes in behaviour can occur. They might become upset, anxious, confused, angry or suspicious of those around them.

They may not think they need help. It can be hard to persuade them to visit a doctor.

Related topic


Content supplied by the NHS and adapted for Ireland by the HSE.

page last reviewed: 15/03/2019
next review due: 15/03/2022

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