Mental illness is a clinically significant behaviour or psychological (to do with the mind) disorder that is associated with distress or disability. It is not just the way someone responds to a particular event nor is it limited to the way a person interacts with society.

A mental illness can continuously or intermittently (occasionally) affect our capacity for speech, language, mood, affect, thoughts, perceptions, insight, judgement, cognition (understanding) and volition (ability to make choices). It can limit our ability to function as society would normally expect of us and can put us and others at risk.

Mental illness is therefore, a broad term that covers problems ranging from minor to severe disorders.