Many people feel paranoid at times. 'Is she looking at me strangely? Is he talking about me behind my back?' Sometimes these feelings can be justified.

Paranoia is a state of mind in which a person believes that others are trying to harm them. It could be a feeling of being watched, listened to, followed or monitored in some way. It might be a belief that there is some kind of conspiracy operating against them. Paranoid people sometimes have an increased sense of self-importance, believing that many others are taking notice of them when it is not true.

Mild paranoid thoughts are quite common in the general population and tend to recover naturally. Long-term paranoia can be a symptom of a mental disorder or be caused by recreational drug abuse, dementia or other medical conditions that affect the brain. Paranoia doesn't necessarily come from a mental disorder.

Paranoia is sometimes referred to as a persecutory delusion. A delusion is a fixed, false belief that someone continues to hold even when there is no evidence that the belief is true. Paranoid symptoms can range from a general feeling of distrust and suspicion of others through to bizarre and complicated beliefs such as conspiracy theories about the government, police or aliens.