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. 

Symptoms such as becoming socially withdrawn and unresponsive or changes in sleeping patterns can be mistaken for an adolescent "phase".

People often have episodes of schizophrenia, during which their symptoms are particularly severe, followed by periods where they experience few or no symptoms. This is known as acute schizophrenia.

Positive and negative symptoms

The symptoms of schizophrenia are usually classified into:

  • positive symptoms – any change in behaviour or thoughts, such as hallucinations or delusions
  • negative symptoms – a withdrawal or lack of function that you would usually expect to see in a healthy person; for example, people with schizophrenia often appear emotionless and flat


Hallucinations are where someone sees, hears, smells, tastes or feels things that don't exist outside their mind. 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.

Research using brain-scanning equipment shows changes in the speech area in the brains of people with schizophrenia when they hear voices. These studies 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, but 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 complete 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.

Some people develop a delusional idea to explain a hallucination they're having. For example, if they have heard voices describing their actions, they may have a delusion that someone is monitoring their actions.

Someone experiencing a paranoid delusion may believe they're being harassed or persecuted. They may believe they're being chased, followed, watched, plotted against or poisoned, often by a family member or friend.

Some people who experience delusions find different meanings in everyday events or occurrences.

They may believe people on TV or in newspaper articles are communicating messages to them alone, or that there are hidden messages in the colours of cars passing on the street.

Confused thoughts (thought disorder)

People experiencing psychosis often have trouble keeping track of their thoughts and conversations.

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 to them. Thoughts and speech may become jumbled or confused, making conversation difficult and hard for other people to understand.

Changes in behaviour and thoughts

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

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

Some people describe their thoughts as being controlled by someone else, that their thoughts aren't their own, or that thoughts have been planted in their mind by someone else.

Another recognised feeling is that thoughts are disappearing, as though someone is removing them from their mind.

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

Negative symptoms of schizophrenia

The negative symptoms of schizophrenia can often appear several years before somebody experiences their first acute schizophrenic episode.

These initial negative symptoms are often referred to as 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 and increasingly not caring about his or her appearance and personal hygiene.

It can be difficult to tell whether the symptoms are part of the development of schizophrenia or 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, and changes in sleeping patterns 
  • being less likely to initiate conversations and feeling uncomfortable with people, or feeling there's nothing to say

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


Schizophrenia is often described by doctors as a type of psychosis.

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

Drastic changes in behaviour may occur, and the person can become upset, anxious, confused, angry or suspicious of those around them.

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

Read more about understanding psychotic experiences.

Page last reviewed: 11/10/2016

Next review due: 11/10/2019