People with a psychosis may display:

• Disorganized or incoherent or strange speech 
• Strange behavior
• Confused thinking
• Strange, possibly dangerous behavior
• Slowed or unusual movements
• Loss of interest in personal hygiene
• Loss of interest in activities
• Problems at school or work and with relationships
• Cold, detached manner with the inability to express emotion
• Mood swings or other mood symptoms

More detailed symptoms are given on the right.

They are often totally unaware that their behaviour is in any way strange, or that their delusions or hallucinations could be imaginary.

A number of substances and medical conditions can cause psychosis, including:

• Alcohol and certain illegal drugs, both during use and during withdrawal
• Brain tumors
• Dementia (including Alzheimer's disease)
• Degenerative brain diseases, such as Parkinson's disease, Huntington's disease, and certain chromosomal disorders
• HIV and other infections that affect the brain
• Some prescription drugs, such as steroids and stimulants
• Some types of epilepsy
• Stroke

Psychosis is also part of a number of psychiatric disorders, including:

• Bipolar disorder (manic or depressed)
• Delusional disorder
• Depression with psychotic features
• Personality disorders (schizotypal, shizoid, paranoid, and sometimes borderline)
• Schizoaffective disorder
• Schizophrenia

Treatment may require investigations  to rule out a disorder in the brain, medicines to bring the symptoms under control, and psychotherapy.

Hallucinations

Hallucinations are sensory perceptions in the absence of external stimuli when the sensory apparatus is intact e.g. seeing a snake which is not there during broad daylight. Hallucinations are different from illusions  which are misperceptions of stimuli when the sensory input is poor and the sensory apparatus is intact e.g. seeing a rope (stimulus) in the dark of the evening (poor input) and mis-perceiving it for a snake.Hallucinations should also be differentiated from sensations perceived because of damage to a sensory apparatus e.g. a buzzing sound in the ear due to damaged hearing.

Hallucinations may occur in any of the five senses and take on almost any form, which may include simple sensations (such as lights, colors, tastes, and smells) to more meaningful experiences such as seeing and interacting with animals and people, hearing voices, and having complex tactile. Someone with psychosis may see colours and shapes, or imaginary people or animals; hear voices that are angry, unpleasant or sarcastic;feel insects are crawling on the skin; experience strange or unpleasant smells or tastes

Delusions

Delusions are fixed, unshakable false beliefs without any basis that can be established, and which are contrary to the personal cultural and religious background e.g. delusions if infidelity, delusions of persecution, delusions of poverty, delusions of loss, delusions of riches, delusions of being the center of reference by others, delusions of thoughts being broadcast over radio, TV etc., delusions of thoughts being removed by external forces, delusions of being controlled by external forces etc.

Thought disorder

Thoughts can only be assessed through speech. Thus thought disorder in reflected in irrelevant talk, incoherent talk, flying from one idea to another, thoughts that are unconnected with each other, talking too fast and / or too much or not talking enough when compared with usual speech etc.

The speech of a person with may become rapid and difficult to understand; the content of their speech may appear random. For example, they may switch from one topic to another mid-sentence or speak in what appear top be different language; their train of thought may suddenly stop, resulting in an abrupt pause in conversation or activity.